t, X

(/

Tree Windbreaks

for the

Central GrBot^lains

m%^

Agriculture Handbook No. 250

U.S. Department of Agriculture • Forest Service
TREE WINDBREAKS

FOR THE CENTRAL

GREAT PLAINS

Ralph A. Read, Research Forester

Rocky Mountain Forest and Range Experiment Station

Forest Service, U.S. Department of Agriculture

Agriculture Handbook No. 250 February 1964

U.S. Department of Agriculture Forest Service

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C., 20402 - Price 50 cents
Contents

Page

Introduction 1

Why plant tree windbreaks 2

How windbreaks affect the environment 3

Effect on wind velocity 3

Effect on air temperatures and humidity 4

Effect on evaporation 4

Effect on soil temperatures 7

Effect on soil moisture and snow drifting 7

Effect on soil properties 8

How windbreaks affect plants and animals 8

Effect on crops 8

Effect on farmsteads and livestock S

How to use windbreaks for protection 10

Single purpose versus many purposes 11

Types of windbreaks and their functions 12

Windbreaks for field protection 12

Windbreaks for farmstead protection 16

Windbreaks for livestock and range protection. 17

Windbreaks for protection of public facilities.. 17

How to select windbreak trees 18

What to consider 18

Select species adapted to planting sites 19

Select species for windbreak characteristics 21

Recommended species 22

How to arrange and space trees in the windbreak.- 25

Growth and development with age 25

Arrangement of species components 27

Spacing between tree rows 27

Spacing between trees in the row 29

How to prepare land for tree planting 29

Why is land preparation needed? 29

Kinds of land preparation practices 30

How to decide which practices to use 31

General practices for all lands 31

Practices depending upon soil and land use 31

Recommended practices 32

When to prepare land 32

Page

How to obtain and handle tree planting stock 33

Where to buy planting stock 34

Specify the seed sources 34

Specify sizes and grades 34

Packing and shipping 37

What to do when trees arrive 38

Storage 38

Heeling-in 38

How to plant windbreak trees 39

When to plant 39

Layout 39

Planting depth 39

Care of trees during planting 40

Machine planting 40

Hand planting 41

How to cultivate and protect windbreak trees 42

Why control of vegetation is important 42

Alethods of control 42

Why protection is important 45

Methods of protection 45

How to manage windbreaks 53

Objectives of management . 53

Relieve crowding 53

Release conifers 53

Add conifers 54

Modify low-level density 54

Reduce width 54

Methods of management 54

Thinning and release cutting 54

Coppicing 56

Interplanting 56

Use of natural reproduction 56

Pruning 57

Appendix 58

Examples of effects of windbreaks on field environment 58

Examples of effects of windbreaks on crops, livestock, and farmsteads 62

Literature cited 65

Additional references 68
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS

By Ralph A. Read, Research Forester*

Introduction

The planting and care of tree windbreaks for

protection against climatic extremes and for the

improvement of living conditions in the Great

Plains of the United States is as old as settlement.

In the 1860's homesteaders in the east«m Plains

planted trees around their homes and gardens and

along their farm boundaries not only to relieve

the monotony of the level, treeless plains, but also

to slow the force of the wind. In fact, tree planting on the Plains was considered so important to

settlement that Congress passed the Timber Culture Act in 187-3 to encourage planting of trees on

all new homestead lands.

B. E. Fernow, Chief of the U.S. Department of

Agriculture's Division of Forestry, the presentday Forest Service, worked with and encouraged

State Agricultural Experiment Stations throughout the Plains during the 1890's in establishing

tree-planting tests to find out which species were

best adapted for plains conditions. The Nebraska

National Forest, established in 1902, was the first

large-scale demonstration of growing trees in the

sandhills. Ranchers and farmers throughout the

sandhills have since followed the practice of tree

planting around ranches and farmsteads, and especially on range areas for winter protection of

livestock. Carlos G. Bates, a pioneer Forest Service researcher, wrote the first comprehensive

Department of Agriculture publication on windbreaks and their influence and values. His bulletin, now out of print, was published in 1911.

Field stations of the U.S. Department of Agriculture's Bureau of Plant Industry, now part of

the Agricultural Research Service, began treeplanting experiments during the period 1910 to

1920 at locations near Mandan, N. Dak., Cheyenne, "Wyo., Akron, Colo., and Woodward, Okla.

Enactment of the Clarke-McNary law in 1924

provided Federal assistance to farmers in obtaining trees at cost, through the State and Extension

foresters, for planting on farms and ranches in

the Great Plains.

The Shelterbelt Project of 1935 to 1942, known

after 1937 as the Prairie States Forestry Project,

*Mr. Read is stationed at Lincoln, Netor., in eooi^ration

with the University of Nebraska Agricultural Experiment Statíon.

was the largest windbreak planting project to date.

In this project the U.S. Forest Service directly

assisted farmers and ranchers in planning and

establishing windbreak systems on croplands in

the eastern Plains in a belt extending from North

Dakota to northern Texas.

Raphael Zon, under whose direction windbreak

research by the Forest Service was conducted in

tlie late 19;30's, strongly advocated windbreaks for

the Plains in the following statement :

Trees grouped together as windbreaks are credited

with the improvement of physical conditions, probably

most tangibly expressed as protection of crops and cropland. Moreover, a vital value that cannot be expressed

in physical terms or realized by those who have not experienced life in the Great Plains region, is the reinforcement of peoples' morale that comes with shelter from the

ever-prevailing winds, shade from the sun's glare, the

improved appearance of the landiscape, a greater pride in

ownership, and a real increase in value of property—all

culminating in a general sense of being at home on the

land. ( Slightly edited from "Possibilities of Shelterbelt

Planting in the Plains Region," 1935.)

In the century since the first homestead near

Beatrice, Nebr., the trial and error experience of

thousands of farmer and rancher tree planters,

and the work of State and Federal agencies, has

provided us with better knowledge of how to

plant trees and windbreaks on the Plains.

This handbook summarizes what is known

about the influences and values of windbreaks

and gives practical recommendations for the

planting and care of tree windbreaks in the central Great Plains. This area includes Nebi-aska,

Kansas, eastern Colorado, and soutliem South

Dakota.

Detailed information on species and special

types of windbreaks for the northern Plains may

be obtained from the U.S. Forest Service research

office at Bottineau, N. Dak., the Agricultural Research Service Field Station at Manclan, N. Dak.,

and from the Soil Conservation Service and State

and Extension foresters in both North Dakota and

South Dakota.

Information for the southern Plains may be obtained from the Agricultural Research Service

Field Station at Woodward, Okla., from the Soil

Conservation Service, and State and Extension

foresters in Oklahoma and Texas.
U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 25 0

Why Plant Tree Windbreaks

Tree windbreaks are good investments on farms

and ranches of the Great Phiins. Wmdbreaks

protect people, farmsteads, gardens, orchards,

soils, field crops, livestock, wildlife, and public

facilities from the extremes of Plains climate

(fig- !)• 1 ^^ u

These extremes include years of low ramtall

and high summer temperatures and years of

scanty snowfall and low winter temperatures.

Such extremes are accentuated by the i)ersistent,

high-velocity winds of Plains climate. Winds are

especially persistent, and strong during the late

fall and early spring when most soils are not protected by growing crops. Wind erosion damages

the structure and fertility of soils. Strong wind

uncovers and blows away freshly sown seed,

causes lodging of grain and corn, degrades fruits

and vegetables, and drifts snow and soil across

country roads.

In summer, hot, dry winds burn crops, decrease

yields, increase water losses during irrigation, and

dry out soils. In winter, cold winds make life

diiticult for people and livestock. Snow drifts

into ra\ines and road ditches, depriving fields of

needed moisture and blocking transportation and

communication systems.

What can tree windbreaks do to moderate the

damaging etl'ects of wind on the Plains? Properly located windbreaks can provide protection

in a variety of different ways. On cultivated fields

they can improve microclimate conditions and

crop production by :

1. Reducing wind velocity and soil erosion.

2. Modifying air and soil temperatures.

?>. Reducing evaporation and transpiration.

4. Improving distribution of snow and soil

moisture.

'<, '%

Figure 1.—Pattern of field and farmstead windbreaks in Oklahoma.

SCS-79481
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS

5. Improving distribution of water in sprinkler

irrigation.

6. Reducing windburn and wilting of crop

plants.

7. Protecting newly seeded crops from blowout.

8. Protecting mature crops from lodging.

On the farmstead, in addition to beautifying

surroundings, windbreaks can:

1. Reduce fuel requirements for house heating.

2. Reduce building maintenance costs.

3. Provide personal comfort in working areas.

4. Control snow drifting in work areas and

driveways.

5. Protect poultry.

6. Protect sensitive garden and orchard crops.

7. Screen farmhouses from highway noise.

On livefitock range, and pasture and feeding

areas, windbreaks can :

1. Reduce mortality during blizzards.

2. Reduce feed requirements throughout the

winter.

3. Maintain productivity and reduce calf losses.

4. Control snow drifting in feeding areas.

5. Improve forage production and quality.

6. Provide shade.

On public facility areas, such as along highway

and railway rights-of-way, windbreaks can :

1. Protect roads and fences from drifting snow

and soil.

2. Protect vehicles from strong, gusty side

winds.

3. Protect camping and recreation areas from

wind and dust.

In all areas of the Plains, trees and windbreaks

can incidentally provide :

1. Beautification and landscaping.

2. Food and cover for wildlife.

3. Small wood products, such as fenceposts and

fuel.

HOW WINDBREAKS AFFECT THE

ENVIRONMENT

In the sheltered zone on the leeward side of

windbreaks, the environment is distinctly different

from that on open unslieltered fields exposed to

wind. Within the sheltered zone, windspeed is

reduced and this causes important changes in air

temperature, atmospheric luunidity, soil moisture,

evaporation, and plant transpiration.

Efifect on Wind Velocity

The amount and extent of wind reduction depends upon the characteristics of the tree barriers.

Height, density, cross-sectional shape, width,

length, and continuity of barriei's all have an important bearing on tlie extent and degree of

protection.

Effect of Height.—Height of trees is probably

the most important characteristic, Ijecause the distance tliat protection extends to leeward is proportional to the height of the windbreak. Tlie distance that protection extends is therefore commonly expressed in windbreak heigiits (H's). For

example, the amount that wind is reduced will

dirt'er at leeward distances of 4, 10, or ¿0 times the

average height of barrier, but the percent reduction at 4 H, for example, is the same regardless

of barrier height (figs. 2 and 3). When wind

direction is at a right angle to the long axis of a

l)arrier, windspeed to leeward is significantly reduced for distances up to 20 times the average

lieight of barrier. Small reductions in velocity

extend to '?>() H. In addition, there is a small reduction in windspeed at 2 to 5 H windward of certain

types of barriers.

Wind direction

-Wind velocity 40% of open ot 80 feet.

L^^i.

Wind velocity 40% of open

at 160 feet.—;

)

Wind velocity 40% of open

ot 240 feet.-^

100 150

Leeword distance (feet)

Figure 2.—Leeward distance of wind protection is proportional

to height of barrier.

Tlie percentage reduction in wind velocity at

any particular H distance fi'om a dense windbreak is relativel}' constant and does not depend

upon how hard the wind blows. A windbreak

that reduces a 20-mil6-per-hour wind to 10 miles

per hour at 8 H, will reduce a 40-mile-per-hour

wind to 20 miles per hour atthe same point ( fig. 3 ).

Although this relationship does not liold for more

permeable type windbreaks, it is given here only

as a rough guide. More important is the ability

of windbreaks to reduce wind to less than 12 to l.^i

miles per hour, which is the threshold velocity

above which soils begin to move.
U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

Wind direction

25 to 50% of open

field velocity

_L

"\ 50 to

\

\

70% 70 to 80%

\

A. 1^^

5H ICH I5H 20H

Open field

velocity (m.p.h.) 5H

20

40

5 to 10

IOto20

Leeword velocity (m.p.h.)at

ICH

10 to 14

20 to 28

I5H

l4tol6

2810 32

Figure 3.—Zones of reduced wind velocity leeward of barrier as percentage of open field velocity. Examples of actual leeward velocities

with open field winds of 20 and 40 m.p.h. Vertical scale exaggerated.

Effect of Density and Width.—Density of a

windbreak also influences the reduction of wind

velocity. Very dense windbreaks reduce windspeed in the 0 to 10 H zone more than open ones,

but the leeward distance of effective reduction is

limited. Moderately dense barriers reduce windspeed over a greater leeward distance than very

dense ones (fig. 4, C). Windbreaks with a very

penneable lower level do not reduce windspeed so

much as dense ones, but the maximiun reduction

occurs at a greater distance leeward (fig. 4, 5).

Open or "loose" windbarriers, very penneable from

top to gi-ound, provide relatively small reductions

near the barrier, and practically none beyond 10 H

(fig. 4, yl). Moderately dense windbreaks, which

act as a filter rather than as a solid barrier, are

generally considered the best. Density of 50 to

65 percent is considered best for field windbreaks

m Denmark, Switzerland, Great Britain, and

Russia. However, in Nebraska and Soutli Dakota,

the greatest gams m com yields were produced

leeward of wmdbreaks having a density of about

80 percent.

Narrow windbreaks of moderate density are as

eñective as wider ones. In fact, windbreaks wider

than 5 H may actually be less effective than narrower ones (fig. 5). It should be kept in mind

however, that suigle rows of one species have no

safety factor, because dead trees may leave o-aps in

a smgle row and seriously reduce windbreak

emciency.

Effect of Cross-Sectional Shape.—Cross-sectional sliape of tree barriers also influences wind

velocities to the leeward. Vertical-side windbreaks

appear to provide greater wmd reduction over a

wider leeward area than windbreaks with inclined

slopes. Because some wind is forced directly

through the barrier, the area of reduced windspeed

IS extended farther to the leeward (fia 6) A

smooth inclined slope is assumed to offer less resistance to wind. However, results of research on

what constitutes the best cross-sectional shape for

greatest windbreak effectiveness are contradictory,

and no definite conclusions can be stated until more

information is available.

Effect on Air Temperatures and

Humidity

Air temperatures are modified in the protected

leeward zone of windbreaks. In the lee (to the

north) of a moderately dense windbreak in central Kansas during July (fig. 7), midday air temperatures 1 to 4 feet above plowed soil in a zone

0 to 4 H from the windbreak were up to 6 degrees

warmer than in the open. But in the 6 to 24 H

zone they averaged *2 to 5 degrees cooler than over

open unsheltered fields. At night, air temperatures near the ground from 0 to 30 H were 1 to 2

degrees warmer than in the open. (See also examples of effects, items 1 to 5, appendix p. 58.)

Air in the sheltered area of windbreaks is generally more humid than on unprotected areas.

Averages of 2 to 4 percent higher relative humidity have been recorded in windbreak-sheltered

areas as compared with open areas in the Plains

of the United States and on the Russian steppe.

In dry, hot weather this effect may extend a quarter of a mile from the windbarrier, depending

upon its height. (See also examples of effects,

Items 8-13, appendix pp. 58-59.)

Effect on Evaporation

Evaporation is greatly reduced in the lee of

^vindbreaks, owing to reduced wind movement and

air temperature, and increased atmospheric

humidity (fig. 8). Evaporation may be reduced
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS

Wind direction -

A All levels very permeoble throughout

82to877oOf\ 87to947o \ 94 to 997o

open field velocity\ \

_A ^

99 to 100%

5H lOH I5H 20H

B Dense upper level ond very permeable lower level

95 to 757o \, 75 to 557

\

\

^. 55 to 907o

^

99tol007e"

\

5H lOH I5H 20H

C All levels moderately dense throughout

22 to 38 7o X 38 to 7 77o

_^

7 7 to 87 7o \ 87 to 90 7o

5H lOH I5H 20H

Figure 4.—Zones of reduced wind velocity as percentage of open field wind (5 feet above soil) leeward of barriers of various density.

Vertical scale exaggerated. (After Soegaard, 1954.)

Wind direction

IH 14% l4 7o

I

24 7o

_J

38% 527o 70%

I

5H lOH Í5H 20 H 25H 30 H

I5H

407o 407o 657o

I

757o

I

807o

I

857o

—I

5H !0H I5H 20H 25H 30H

Figure 5.—Zones of reduced wind velocity as percentage of open field wind lat 0.2 H above surface) to leeward of vertical-face artificial

barriers of different widths in wind funnel. Scale of models exaggeroted. (After Caborn, 1957.)
6

u

.s. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Wind direction

33%

lOH

16%

I

I5H

45%

20 H

60%

25 H

75%

L_

30 H

0

14%

5H

14%

lOH

24%

I5H

38%

I

20 H

52%

I

25H

70%

30 H

Figure 6.-Zones of reduced wind velocity as percentage of open field wind (at 0.2 H above s

^ shaped ortificial barriers in wind tunnel. Scale of models exaggerated. (After Caborn, 1 957.)

urface) to leeward of different cross-sectional

25 r

15

5

(feet)

Ä

/\^ ^ ( Up to

Wind direction (fronn South)

\

) 6 degrees j

1

warmer

0

/L.

Midday

5H

Up to 2 degrees cooler

^2^ to 5 degrees cooler- IliàÉi

lOH I5H 20 H 25H 30H

25

15

5

(feet)

i...i.„,.nÍÉÉÍiMÍMi

Night

Up to 5 degrees cooler

"Pí'^^íTto 2 degrees warmer ;-:í^-^;vi^í-?^

5H lOH I5H 20H 25H 30H

Figure 7.—Air temperoture zones leeward of a 25-foot-tall moderately dense windbreak, compared with open field temperatures. Win

at 14 to 20 m.p.h. with open field temperatures ranging from 86° to 110° F. in Kansas during July. Vertical scale exaggerate .

(After Woodruff et al., 1959.)
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS

Wind velocity 20 m.p.h.

* 80

5 60

\

\

\

\\

Windward

Cottonwood windbreak

with open lower level

/

/ Cottonwood grove with

/ moderately dense lower level

Leeward

2H

Figure 8.—Percent of open field evaporation windward and leeward of cottonwood windbreaks of different structure. (After

Bates, 1911.)

in an area extending 24 H to leeward. Reduced

evaporation conserves water during sj^rinkler irrigation and reduces the loss from reservoirs and

ponds. Evaporation is reduced more under fast

than under slow wind movement. Reduction in

evaporation is proportional to windbreak density,

so that permeable barriers, especially those with'a

sparse lower level, are not so efficient as dense barriers in reducing evaporation (fig. 8). (See also

examples of effects, items 14-20, appendix p. 59.)

Effect on Soil Temperatures

Windbreaks influence the temj^jeratures of soils

near and directly beneath the trees, but differences

at 20-inch depth beyond 1 or 2 H from barriers

are negligible. Nevertlieless, surface soil temperatures are higher in spring and summer, and

lower in fall and winter in the sheltered area than

in open, unsheltered areas. (See also examples

of effects, items 6-7, appendix p. 58.)

Effect on Soil Moisture and Snow

Drifting

Windbreaks conserve soil moisture in their lee

by reducing evaporation and transpiration and by

controlling distribution of precipitation, especially

snowfall. Snow commonly blows off bare open

fields and contributes little to field soil moisture.

Distribution of snow in sheltered areas depends

upon structure of the barrier (fig. 9). Windbreaks

With dense lower levels cause snow to drift deeply

691-791 o—64 2

Windbreak

height

(feet)

60

40

20

60

40

20

ÍN

Wind direction

row cottonwiood 60 feet

tal I and open below

Snov»

depth

( inches)

60

40

20

200 400 600 800

^^ n

1 ] 1- row willow 20 feet

1 \ toll and dense

^] \

60

40

20

200 400 600 800

60

40

20

Multirow (50-100 feet wide)

cottonwood 60 feet tall

\ and open below

60

40

20

200 400 600 800

200 400 600 800

Leeward Distance (feet)

Figure 9.—Profiles of snow depth as influenced by windbrecks

of different width and structure. Vertical scales of tree height

in feet and snow depth in Inches are exaggerated. (After Bates

and Stoeckeler, 1941.)

within or near the leeward edge of barriers.

Barriers with more permeable lower levels cause

60 to 80 percent of the snow to spread out over

leeward fields. Drifting patterns correlate closely

with reductions in wind velocity. Windbreaks

prolong snowmelt on protected fields and thus reduce moisture loss by evaporation. (See also examples, of effects, items 21-25, appendix pp. 59-

60.)

Despite greater water uptake and greater yields

by crops on fields protected by shelterbelts, the

amount of moisture remaining in soil in some areas

has been found to be greater than in unprotected

fields. Effects of windbarriers on soil moisture

in the area of 0 to 2 H, however, are complicated.

Increases due to snow drifting, shading, and reduced evaporation may be offset by moisture utilization by the trees. (See also examples of

effects, items 26-33, appendix p. 60.)

Accumulation of snowdi-ifts within and adjacent to windbreaks results in a larger area of

unfrozen or porously frozen soil than open, unprotected areas where soil freezing is deep. This

soil condition provides for greater water infiltra-
8

U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

tion and consequently reduces water loss and soil

erosion caused by rapid spring runoff. (See examples of effects, item 34, appendix p. 60.)

Effect on Soil Properties

Windbreaks have improved soil properties in

fields as far leeward as .5 to 7 H from the trees.

Improvements have been noted in physical and

chemical properties, including increased organic

matter, penneabilily, porosity, aggregation, infiltration, and depths of A horizon. (See examples

of effects, items 3.5-45, appendix p. 61.)

Typical examples of research on the influences

of windbreaks on air and soil temperature, air

humidity, evaporation, snow distribution, runoff',

soil moisture, and soil structure are listed in the

appendix, p. 58. Omission of any items in the

listings indicates that no data were available.

How Windbreaks Affect Plants and Animals

The sheltered areas produced by windbarriers

are generally moi-e favorable for growth of plants

and animals than an open, unsheltered environment. Windbreaks reduce wind movement, daytime air temperatures, and evaporation, and

increase atmospheric humidity. These modifications of environment reduce transpiration of field

crops and conserve soil moisture. The influences

of a windbreak on plant transpiration in Kansas

during hot, windy July days has been computed

by formula using wind velocity and air temperature data. Transpiration in the lee of the windbreak 0 to 20 H ranged from 79 to 95 percent of

open-field rate. The greatest daytime reduction,

to 79 percent of oçen-field transpiration, was

found at distances ot 2 and 8 H. Beyond 25 H

the reduction was negligible. At night the transpiration rate at 2 H leeward was 69 percent of

open-field rate.

Plant growth proceeds most rapidly when the

cells of gi-owing tissues are full of water. When

cell water drops below full capacity from excessive transpiration, unavailable soil moisture, or

both, the physical and chemical processes of

growth are slowed. At the extreme, plants wilt

under stress of limited moisture, especially when

accompaniecl by wind and high temperatures.

Carbon dioxide, which is essential for plant

growth, tends to accumulate in areas of reduced

wind. Consequently, more carbon dioxide is available for plant growth in the lee of windbreaks

than in the open. Furthermore, more is utilized

by the plants because the stomata of the leaves,

through which the carbon dioxide enters the

plants, remain open longer each day when the level

of moisture in the plants is high.

Effect on Crops

Greater yields of field crops have been found in

the shelter of windbreaks than in the open in

many parts of the world (see examples of effects,

appendix p. 62). The amount of change in yields

varies from test to test because of differences in

structure and location of windbreaks used and in

climates and weather. Short, permeable windbreaks differ in effects from tall, dense ones.

Minimum benefits are to be expected in cool, moist

climates or seasons that have little wind; maximum benefits in hot, dry, and windy climates or

seasons. Despite differences, real benefits have

been found in the shelter of many types of windbreaks in many climates. The general effect of

field windbreak protection on yields of corn and

small grain as derived from data obtained during

1935^1 in the Great Plains region of the United

States is shown in figure 10.

A narrow strip of ground about 1 H wide paralleling tree barriers on both sides is often unfavorable for crops (fig. 11). These strips are occupied

by tree roots which use soil moisture and nutrients.

There is some evidence that this unfavorable effect

may also be related to shading and higher air temperatures. Crop yields may be reduced to nothing in these strips. However, the area affected

unfavorably is relatively small compared to the

area favorably affected by windbreaks (see numbers 3 and 4 of figure 10). Further discussion of

this effect will be found in the section on "Limitations," p. 15.

Effect on Farmsteads and Livestock

Properly located tree barriers can improve the

local environment of farmsteads, where many

daily chores are done. Reduction of winter wind

movement permits homes to be kept more comfortable with less fuel. Windbreaks can control

snow drifting and provide clear working areas

after severe storms (fig. 12, A). Lessened exposure of buildings to the elements reduces maintenance costs for wind damage and paint. Properly arranged and located windbreaks can also

reduce dust and soil movement and improve comfort on the farmstead during hot, dry summer

weather.

Tree windbreaks about feedlots will protect cattle from winter winds and control drifting of snow

(fig. 12, 5). Shelter from the cold blizzard winds

reduces storm-caused mortality, enables the cattle

to maintain better weight with less feed, and reduces calf losses. If snow drifting is controlled,

feed areas can be kept free of drifts.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS

160

140

l?0

n-it

UjO 100 a^

RO

?•" -_i 6Ü

IxJ

3- 40

Uu. 20

>o 0

NÖR*i1ÄL YIELD OF UNPROTECTED FIELD

1 r -i r T r

j L J L

13 14 15 16 17 18 19 20H

DISTANCE FROM WINDBREAK

IN UNITS OF WINDBREAK HEIGHT

( H= 40 feet in this diogram )

LEGEND

EFFECTS ON OPEN, UNPROTECTED FIELDS

© UNPLANTED FIELD BORDERS

(2) NORMAL CROP LOSS AT FIELD BORDERS

(D NORMAL CROP YIELD OF FIELD

ADDITIONAL EFFECTS ON WINDBREAK PROTECTED FIELDS

(D CROP LOSS IN SAPPED STRIP NEAR TREES

(4) CROP GAIN DUE TO WINDBREAK EFFECT

(g)_(D NET WINDBREAK EFFECT

Figure 10. Cross secfion of crop yield on a field leeward of a windbreal<. (After Stoeelceler, 1962.)

Figure 11 .-Unfovorable effect of windbreak on crops shows up on 12 rows of corn in tliis irrigated western Neb«.ska field. Tlie

windbrealc trees are Siberian elm, 45 feet tall. (Photo courtesy of W. T. Bagley, University of Nebraska.)
10 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 25 0

t„:,, Jj^Á

F^53801-408999

Figure 12.—A, Properly located windbreaks protect this farmstead winter and summer. B, Beef cottle and sheep feeding in protected

leeward space behind a tall, wide windbreak.

The influences of windbreak shelter have been

studied in many countries of the world. Results

have differed with kind of crop, pre\ious cropping

history, moisture, weather, density of windbreak,

and other factors. Results of many of these

studies are condensed in the appendix, p. 62. The

results show that in the majority of cases, beneficial efl'ects on crops, livestock, farmsteacls, and

facilities have been demonstratecl under windbreak

shelter protection in windy agricultural regions

throughout the world.

How To Use Windbreaks for Protection

Protection tree plantings on agricultural lands

are long-term investments in soil and water conservation. Although tree windl}reaks will give

some early protection, they normally will require

30 years to reach full protective etl'ectiveness in

the central Plains. Since in most situations they

will remain useful for anotlier -25 to ?>0 years, the

plantnig and care of tliem will span more than a

generation. " ' "" Careful plamiing is therefore essential to protect the investment and to insure

continued long-term benefits. Mistakes in tree

selection, arrangement, spacing, and location can

be costly.

"Windbreak systems can be fully effective only if

used to supplement other soil conservation practices, such as stubble tillage, cover crops, and stripcropping. Windbreak systems are a part of overall farm planning; the soils and topography of
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 11

fields, terraces, waterways, pastures, and other

uses will greatly affect and often limit their location. Therefore, the entire plan of farm land use

must be considered in locatnig permanent structures such as tree barriers. The windbreak system

should be planned and laid out on a lai'ge-scale

aerial pliotograph of the farm or ranch. Using

this method (fig. lo), the adequac}' of windbreak

protection in relation to all land uses can be

visualized.

The o\vner or manager should list the purpose

of windbreak protection for each field <n' unit

of land use. It is essential to decide on purpose

at the outset, because this will determine what

planting specifications are to be used to provide

the windbreak structure that will accomplish

specific objectives.

As emphasized in the first section, the density

of different height levels in windbreaks has an

important influence on pattern of wind velocity

reduction to leeward, and consequently on other

miiToclimatic factors. Windbi'eaks of different

structures are required to satisfy different objecti\es. For e.xanq)le, the wind reduction needed

for a farmstead should be greater but over a

smaller area tJian that requii-ed for a field windbreak. This difference in objectives will require

different kinds and numbers of trees, and different

arrangement and spacing intervals between trees,

rows, and barriers.

SINGLE PURPOSE VERSUS MANY

PURPOSES

Although windbreaks are often planted to serve

several purposes, they cainiot ordinarily serve all

purposes equally well at the same time. As mentioned previously, the patterns of wind reduction

required by one objective are often different from

Figure

SCS-D-2728

13.—Windbreak protection patterns should be planned in conjunction with total land use planning for the farm and ranch
12 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

those required for another objective. Variations

in density, width, and sliape of l)uiriei- are required to obtain different patterns of wind velocity

recUiction and their acconipanyin<i effects on temperature, evaporation, and snow accumuhxtion.

Therefore, if plantings are to provide maximum

benefits, the owner's decisions as to specific kinds

and arrangements of trees to attain major objectives in structure must take precedence over other

considerations.

Multiple-use windbreaks designed to satisfy several objectives have been tried in the past, with

only moderate success. Results of such plantings

after '20 years do not appear to justify the combination of several objectives into one tyi^e of

planting. For example, windbreaks intended for

field protection should not include trees such as

black walnut and apricots, ostensibly for fruit

production. Such trees occupy considerable

space, yet contribute little to windbreak effectiveness. Again, field windbreaks intended for maximum snow spreading on leeward fields should

not include low shrubby species for wildlife food

and cover. The ground level density of shrubs,

in this instance, will defeat the main objective by

creating snowdrifts near the windbreak instead

of spreading it over leeward fields.

"Windbreaks should ordinarily Ije planted with

one primary purpose in mind. This should determine, within limitations of the soil, the species,

their arrangement, and spacing. Variations may

be used to fulfill an incidental or suliordinate objective, provided this does not interfere with

proper functioning for the primai-y objective.

The primary purpose, hoAvever, should have exclusive priority in deciding as to species, arrangement, and spacing that will inflnence windbreak

structure.

Recreational, esthetic, and wildlife values are

nearly always present as incidental values of tree

plantings, regardless of major purposes. Such

mcidental values therefore need not be of primary

consideration in planting field windbreaks, farm"-

stead wmdbreaks, or livestock and road protection

windbreaks. If recreational areas or wildlife

habitats are desired as primary rea,sons for tree

planting, these objectives should be so stated, and

the plantings made for those purposes, and not

for wind protection of fields, homes, etc.

TYPES OF WINDBREAKS AND THEIR

FUNCTIONS

Windbreaks may be classified into four general

types, according to location and objectives of

protection :

1. Field windbreaks, often called shelterbelts—

to protect extensive areas of cultivated fields from

wind erosion and to provide more favorable environment for growing crops.

2. Farmstead windbreaks—to protect a limited

space of living areas in and around the farm home,

barnyards, feedlots, and gardens for greater yearround comfort, conveniencej and productivity.

3. Pasture and range windbreaks—to protect

limited areas in which livestock range and feed,

and to provide more favorable environment for

forage and animal growth over more extensive

areas.

4. Public facility windbreaks—to protect highway and railway travel routes and recreational

areas from strong winds, soil blowing, and snow

drifting.

Field protection may require several kinds of

windbreak structures, depending upon objectives.

For example, a barrier for snow distribution

should have a different density and spacing inter\'al than a barrier intended to protect crops

from hot winds. Moreover, barriers intended primarily for wind erosion control are likely to differ

from either of those just mentioned in density

and spacing intervals.

The structure of farmstead windbreaks, on the

other hand, can be limited to a fairly standard

arrangement. There is usually only one objective—providing the greatest reduction in wind

velocity around the farm buildings. Influence

upon wind and drifting snow over a large leeward

area is usually not important in such plantings.

The structure of pasture and range windbreaks

may vary, as in the field barriers, because of different objectives. Barriers for maximum protection of livestock in feeding areas must be dense

enough to control snowdrifting near them, while

barriers to improve snow distribution over grassland require more permeability. For temporary

livestock shelter during severe winter storms

another type of barrier is needed. Such a windbreak should be very wide in order to accommodate the livestock herd.

The structure of barriers along railways and

highways may be fairly standard because the

major objective is to control snow and soil

drifting.

Windbreaks for Field Protection

Objectives.—Tree barriers on cultivated fields

are usually planted for more specific objectives

than are barriers in other locations. For one

thing, the areas to be protected are larger than

farmsteads or livestock feeding areas. Secondly,

field barriers may be desired for several different

objectives, each requiring a slightly different type

of structure.

Some of these different objectives are :

1. To reduce soil movement and damage to

crops during windstorms.

2. To protect growing crops from extremely hot

and desiccating winds.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 13

3. To provide better retention and distribution

of snow on fields.

4. To reduce evaporation and improve distribution of sprinkler irrigation water.

Pattern and Orientation.—In planning windbreaks for field protection, it is desirable to think

in terms of patterns for complete protection, not

just, isolated windbreaks oriented in one direction.

The best protection requires a pattern or grid consisting of individual windbreaks oriented in several directions and at close enough inter^^als to

protect all fields.

The maximum protected area leeward of parallel barriers at 20 H intervals occurs when wind

blows at right angles to them. A series of such

parallel windbreaks, though not providing a cumulative effect, does create a larger area of stilled air

than the same number of isolated bai-riers spaced

at greater intervals. However, when wind direction changes, the axis of maximmn wind velocity

reduction shifts and the area of protection decreases (fig. 14). Snowdrifting patterns and the

effects upon soil moisture are shifted in relation

to the barriers as prevailing winds change during

snowstonns. The area affected by favorable

change in temperature, humidity, and evaporation

is likewise shifted and reduced in size.

The effect of shifting wind direction can be

minimized by establishing complete patterns of

windbreaks (fig. 15). Thus windbreaks at intervals not exceeding 20 H and oriented in two directions will create a grid or "baffle" within which

the "climate" or environment near the ground is

significantly different from that on an open plain.

Complete patterns are essential for maxiniimi protection because winds blow from nearly all directions sometime during the year.

The establishment of windbreak patterns in

level country presents few problems. Since winds

in Nebraska and Kansas prevail from the south

during the growing season and from the northwest

during fall, winter, and early spring, the basic pattern of barriers should be oriented east-west.

Patterns should be completed with north-south

barriers at 20 H intervals or less to provide maximum protection.

The cardinal directions are given here merely

as examples. Where farm fields are planned for

conservation practices such as stripcropping, the

pattern of windbreaks should conform with the

field margins or subdivisions thereof.

Establishment of patterns in rolling country is

more of a problem. '\^niere slopes exceed 5 percent, windbreaks should follow as closely as possible the contours of rolling topography. Contour

planting will reduce to a minimum the variations

that commonly occur in tree survival and height

growth, when part of the windbarrier is on one

kind of soil and part on another. Since contour

Wind from due South

Wind from West - Southwest

Figure 14.—Comparison of protected areas leeward of parallel

barriers when wind direction changes.

windbreaks will not always be oriented to provide

maximum protection from prevailing winds, the

establishment of supplemental cross barriers

should be considered. Cross barriers to complete

the ¡patterns of contour-planted windbreaks

should not be used on steep slopes, hoAvever, unless special practices are undertaken to prevent

water erosion. Contour windbreaks should always be planned as part of terracing systems so

that trees will have the advantage of extra

moisture from the terraces.
14 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Wind from West - Southwest

Figure 15.—Comparison of protected are<is leeward of a pattern

of barriers when wind direction changes.

Intervals.—Distance intervals between windbreaks in the pattern depends upon the maximum

effective height attainable by the species planted

as the tall component. This interval should not

exceed 2(t times the average height at 20 years, and

for best protection it should be about 15 heights.

Since trees do not grow as tall on upland sites

as on lowland sites, the actual distance (20 H)

between windbreaks on uplands will be less. Intervals between windbreaks on sloping ground

should be slightly less than on level ground.

Generally, the maximum height attainable by

Siberian elm and ponderosa and Austrian pines

on upland soils in central and eastern Nebraska

and Kansas is al)out 45 to 50 feet. Tlie elms attain

this height in '20 years and the pines in -40 years.

This requires a 20 H interval not exceeding 800

to 1,000 feet between windbreaks. In the Avestern

Plains where maximum tree height on uplands is

only 25 to 35 feet, the distance between windbreaks should not exceed 500 to 700 feet.

On lowlands, bottomlands, terraces, and uplands with water table easily accessible to tree

roots, the distance between windbreaks can be as

much as 1,200 to 1,500 feet. Cottonwoods on these

sites will provide effective heights up to 80 feet.

More detailed information on selection of species

for height growtli on various kinds of soil will be

found in the next section.

Where complete protection is wanted before the

windbreak trees reach maximum height, the

spacing interval should be reduced by one-half,

and temporary barriers of fast-growing trees

should be planted in the alternate intervals. These

shoulcl then be renjo\ed when the main windbreaks reach maxinnim height and effectiveness.

Continuity.—If there are gaps in barriers, the

wind will stream through tliem with a jet effect.

Velocity through these gaps is usually higlier than

in the unprotected open fields, but tlie increased

windspeed does not extend far to the leeward

(fig. 16).

Less than 70 Less than 70

Open field wind direction

Velocity 100 percent

Figure 16.—Percent of open field wind velocity through and leeward of a 30-foot gap in a windbreak. (After Nägel!.)

The danger of increased velocity through gaps

and around ends, however, lies in soil erosion and

damage to the acljacent edge trees, which are subjected to greater stresses than those of the interior

stand. This is one of the reasons that shrubs or

conifers are recommended for low-level density at

the ends as well as on both sides of windbreaks.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 15

Good windbreak systems have few gaps in

them. It is important to plan the location of

windbreak patterns to avoid spots of unfavorable

soil where trees may die early or not sur^'ive at all.

Once the plantings are made, it is necessary to

replant gaps or fail spots within the hrst 2 years.

Roadways or lanes through windbreaks wider

than 50 feet should be located at an angle through

the plantings so that prevailing winds will seldom

blow through these gaps ( fig. 17 ). The corners of

windbreak patterns, especially those corners subjected to strong northwest winds, should be

rounded and reinforced with an extra row of

shrubs. Curved rows around a corner are an advantage in cultivation, in addition to maintaining

better continuity. The ends of rows should be

planted to shrubs and conifers in order to provide

low, dense foilage at windbreak ends comparable

to the continuity of the frontal faces.

-Wind direction

Wind direction Wind direction

Figure 17.—Examples of roadway or lane location through windbreaks to minimize effect of gaps.

Dimensions.—Lengih of individual barriers is

not important with complete patterns of windbreaks. The effectiveness of any single windbreak

in a pattern depends on the orientation, interval,

and continuity of others in the system.

Width of field barriers is important only insofar as it affects density. Making windbreaks

wider than is necessary to attain moderate density

will have little direct effect in reducing wind

velocity.

Barriers on cultivated fields, therefore, should

be as narrow as practicable, while containing sufficient tree rows for the required density at all

height levels. If moderately dense foliage is required, barriers need bo only two to three rows

Avide. Where greater density is needed at all levels from ground to maximum height, wider barricTs of five to seA'en rows should be used.

Single rows of trees or combinations cf trees

and shrubs in one row are frequently recommended by the Soil Conservation Service in various areas of the Plains in order to develop complete patterns. When used in patterns at close

intervals, single rows of trees and shrubs may

furnish a moderate amount of protection. However, single rows do not normally produce the

foliage density at all height levels comparable to

that attained by several rows of different species

of trees and shrubs. Moreover, single rows are

moi-e likely to develop gaps that reduce the

effectiveness of windbreak systems.

Limitations.—Patterns of field windbreaks will

naturally restrict use of farm machinery as compared with its normal use in open fields. This is

a limitation only insofar as the landowner wants

it to be. Farming with windbreaks requires modification of some practices, as does farming with

terraces.

Patterns of field windbreaks will result in

strips of land that are unproductive for crops

because of competition for moisture and nutrients

by tree roots and because of shading. This area

must be considered as part of the land devoted to

the trees, in exchange for real en^'ironmental benefits over a much larger area of cropland. These

so-called "sapped" strips may often be used as

field roads, or they may be planted to some earlymaturing crop that will not be affected by

shading and moisture competition.

Field windbreaks should be located Avhere they

will provide greatest benefit, yet not interfere

with other land uses, travel routes, or public

utilities. If they are located too close to road

rights-of-way, they create serious problems such

as snowdrifting on the road, blind intersections,

interference with communication and power lines,

and increased likelihood of damage by wildfire.

Therefore, windbreaks paralleling roads should

be located at least 300 feet from rights-of-way.

The corners of windbreak patterns or the ends of

individual barriers should not be closer than 300

feet from road intersections.

Location and orientation of windbreak patterns

should be planned with as complete a knowledge

of soil conditions as possible. Soils may often be

the limiting factor in deciding Avhat species to

use and where to plant. Location and orientation

pattern should avoid certain soils or other local

691-791 O—64-
16 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

conditions unfavorable for tree growtli. Likewise,

a compromise may be needed to take advantage of

locating windbreaks on the better soils. liyaluation of sites for determining choice of species for

greatest windbreak effectiveness is co\ered in detail in the next section of the handbook.

Windbreaks for Farmstead Protection

Objectives.—Tree barriers adjacent to the farm

and ranch home, about other farm buildings and

feedlots (fig. 18), and surrounding orchard or garden'areas, have as their major objective the control of wind and temperature. ^Maximum reduction of wind velocity will normally control snowdrifting. Some of the objectives are :

1. To prevent snowdrifting on driveways and

work areas.

2. To reduce fuel requirements for house heating.

3. To reduce weathering of paint and other

maintenance expenses.

4. To protect sensitive crops in garden and

orchard.

5. To control snowdrifting in livestock feeding

yards.

6. To provide more comfortable and quiet working conditions.

Orientation.—Since the area of the farmstead,

its miscellaneous buildings, and its garden ai-ea is

usually rather small compared with that of fields,

there is no need for patterns of barriers. Rather

it is the location, orientation, and windbreak

density in respect to these facilities that is of

greatest importance. Main windbreaks for farmsteads in the central Plains should be oriented in

a near north-south direction to the west of, and in

an east-west direction to the north of all buildings. In addition, a more permeable type windbreak should be located to the south of farmsteads

for protection against hot southerly winds. Farmstead windbreaks need not, however, be restricted

to cardinal directions in straight rows, as long as

their placement is such that the buildings to be

protected are well within the leeward area of

winds coming from the north through west to

southwest (fig. 19).

Dimensions.—Considerable leeway in width

and length of windbreak is allowable for farmstead protection in contrast to field windbreaks.

The main requirements are: (1) Adequate lowlevel density to reduce wind velocity and force

snowdrifting close in, (2) adequate height to provide at least 50 percent wind reduction over the

farmstead work area, and (.3) adequate length

to cover most areas as winds shift from north

throug'h west to south. The importance of keeping the size and number of gaps at a minimum

is just as great as with field windbreaks.

Limitations.—AVindbreaks for farmsteads have

often been placed too near houses and other buildings. The consequences have been snowdrifting

in the very areas that should be free of snow, and

oppressive heat during the summer in place of

cooling air movement. Windbreaks for farmsteads should be located at least 100 to 150 feet, but

not more than 300 to 400 feet, distant from the

buildings to be protected.

Figure 18._Conifer windbreaks protect livestock feeding facilities from strong wind and snowdrifting.

P-365445
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 17

Barn Feedlot

North

Permeable barrier

Figure 19.—A suggested plan for windbreak protection of the

farmstead.

Farmstead windbreaks should be long enough

so that the snowdrifting pattern around the ends

of the barrier does not cross driveways or other

access roads from the farmstead to the county

road, or to feedlots and barns.

Windbreaks for Livestock and Range

Protection

Objectives.—There are several objectives in the

planting of tree windbreaks on range and pasture

land. Of greatest importance is that of providing

a protected area for livestock during severe winter storms. One purpose is to provide a haven

where animals can get out of strong wind and

snow, and thus prevent their drifting with the

wind. Another purpose is to maintain an area

relatively free from deep snow where hay and

other feed is easily accessible.

Shade protection in extremely hot, dry summers

may be the objective of some plantings. This is

especially necessary for dairy cattle and hogs.

Like windbreaks for increasing crop yields on

cultivated fields, barriers may be used for improving hay and grass production over large areas of

range, pasture, and meadow land.

Orientation.—As with farmstead windbreaks,

complex patterns of windbreaks are not usually

needed on pasture and range areas. In extensive

areas of grassland range, tree jjlantings should be

in the form of block plantation units located at

strategic places for livestock feeding during the

winter. They should be located to take advantage

of protection by natural topographic features.

Since protection is most needed during severe

snowstorms, the blocks should extend lengthwise

from southwest to nortlieast. Some ranchers have

planted U-shaped blocks with the open end to the

south or southeast, for maximum protection.

The orientation and location of barriers for

range or pasture yield improvement may, however,

take the form of field windbreak patterns with the

objective of gaining better snow distribution.

Dimensions.—The width and orientation is of

most importance in tree plantation blocks intended

specifically for protection from winter Avind and

snow. Barriers similar to farmstead windbreaks

are normally dense and tall enough to protect livestock, provided the plantings are not open to stock.

'\^niere plantations are to be used as wintering

grounds among the trees, the blocks should be several hundred feet wide. The windward north and

west sides should be fenced off from stock. Plantations to be used for summer shading should

likewise be several hundred feet wide, so as to offset thelossof lower foliage by browsing.

Limitations.—Pasture and range windbreaks

for livestock protection should not be located near

summer watering or salting areas. Tree plantations near such areas where livestock congi^egate

will be severely damaged by browsing and trampling, and their protective effect will be reduced.

Fencing against normal livestock use is recommended for all windbreaks on range and pasture.

Access to winter protection plantations by livestock should be provided only during severe

storms. In plantations grown specifically for

summer shading, access should be provided only

after the trees have reached suitable height for

effective shading.

Windbreaks for Protection of Public

Facilities

Objectives.—The objective of tree barrier

planting along roads and other rights-of-way is to

control the drifting of snow or soil so that it does

not interfere w4th the use of the road or railway.

Tree plantings for public recreation use along

higliAvays, on the other hand, may be established

primarily for campers and picnickers. Such areas

can provide temporary shelters against strong, hot

winds away from highway dirt and noise.

Density, especially near the ground, is essential

in structures for snow and soil control. Height is

of less importance, though it should be sufficient to

contain drifts of 8 to 10 feet deep and still serve

as a barrier.

Orientation.—Of coui-se, the direction and pattern of the roads or other rights-of-way to be pro-
18 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 25 0

tected determines orientation of windbreaks.

Generally, the barriers for snow control slionld l)e,

located from 100 to 300 feet north and west of

rights-of-way. In some locations where snowdrifting is difficult to control, a series of two or

three narrow barriere, 50 to 100 feet apart, slioiild

be used. Plantings for reci-eation purposes sliould

be located at least several hundred feet from liighway rights-of-way, and should be oriented to form

an enclosure protected on all sides.

Dimensions.—Structures for snow and soil drift

control need not exceed two or three rows of trees

and can therefore occupy less than 20 feet width.

I^ength depends on specific topogi-aphic conditions.

Locations of windbreaks should normally l)e

limited to segments of rights-of-way where tliere

are deep cuts or extended low areas to the south

and east of higher ground. Recreation area plantings can be long and irregular in shape, but they

should be wide enough to provide space for camping areas.

Limitations.—The most serious limitation appears to be a conflict of land-use objectives. To be

of greate.st value, windbreaks and recreation enclosures must not be too close to rights-of-way;

otherwise they will create rather than solve snow

problems. Tlie requirement for such specific locations as snow fences may often put barriers of this

kind in places where landowners may not want

them. Many landowners do not like to farm

around tree strips or blocks located within cropland fields.

The establislunent of field windbreak patterns

for protection of crops on famil and can normally

serve also to protect roadways and otlier public

facilities in the vicinity if this is considered in

planning their location. Special-purpose barriers

then will not be needed.

How To Select Windbreak Trees

Successful establishment of permanent and effective windbreak systems to fulfill long-term objectives in conservation farming depends a great deal

on the choice of species. In addition to the usually diy and windy climate of the Plains, there

are many different soils and topographic conditions that limit the choice of trees for planting.

Tree species recommendations given in this

handbook apply only to the central Plains area

(fig. 20). Recommendations have been adapted

from several sources: (1) current technical specifications of the Soil Conservation Service; (2) results of a 1954 survey of shelterbelts in Nebraska

and Kansas; (3) results of field testing by Agricultural Research Service field stations at Cheyenne, Wyo., and Akron, Colo.; and (4) past

recommendations of State and extension foresters.

Tree and shrub recommendations for the northern

and southern Plains are given in other publications, some of which are listed in the appendix to

this handbook, page 68.

WHAT TO CONSIDER

Environment of the Plains is such as to test the

hardiest of tree species. Trees growing outside a

forest environment, as in the Plains region, are

constantly subjected to unusual stresses of wind,

temperature, moisture, evaporation, insects, and

diseases. They must be adapted not only to the

climate, but also to soil types and competitive

vegetation much different from that occurring in

naturally forested areas.

Windbreak trees must also fulfill certain functions if they are to be useful in this environment

Survival and growth is not enough. They must

. 10 K L A H /o M :

' SOUTHERN PLAINS / .

'^ E W MEXljcol =^^^^-yi L

L_rFigure 20.—Central area of fhe Great Plains to which species

recommendations apply.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 19

possess other qualities that enable them to associate perfectly with other adapted species, providing windbarriers of the desired structure.

Windbreak trees should also have moderate to

dense crowns, stout boles, good retention of lower

limbs, and fairly uniform rate of height groA\i:h.

Selection of tree and shrub species therefore involves two major questions: (1) "Wliat species are

best adapted to the soil or planting siteí (2) Of

these adapted species, which have the growth characteristics for producing the type« of windbreaks

desired ?

Select Species Adapted to Planting Sites

Farmers and ranchers have, for years, "selected" the soils for their corn, wheat, alfalfa, pasture, and other crops. A farmer knows which

crops grow best on a particular type of soil through

the experience of planting and harvesting over a

short period of years. Measuring the adaptability

and usefulness of tree species on different soils,

however, requires a longer period of years. Furthermore, mistakes made in selection of tree species are not as easily corrected as with annual

crops.

The enviromnent (site) of a planted tree is

made up of climate, soil, topography, and other

living organisms. Trees that are not adapted to

the site will lack vigor, grow poorly, and may die

young. Adapted trees will grow well and thrive

for years. Some species and varieties have shown

superior adaptation to a wide range of Plains

environments, while others are adapted to a very

narrow range of conditions.

Climate.—Climate places severe limitations on

tree survival and growth in the Plains. The

moisture, temperature, and wind environment of

planting sites is determined primarily by the prevailing type of climate. This climate in the central Plains ranges from arid and semiarid to subhumid, with wide and rapid fluctuations in temperature and moisture. Strong and persistent

winds prevail from the south and the northwest

during most of the year. Scanty rain and snowfall, coupled with the high evaporation and transpiration which accompanies strong wind movement, creates great moisture stresses in trees.

Severe winter blizzards and hailstorais do much

mechanical damage by breaking limbs and bark.

Rapid changes in air temperature, such as a droj^

of 40 to 50 degrees in a few hours, frequently

cause dieback and death of trees and shrubs that

are slow to reach dormancy in the fall. Trees

weakened by such climatic stresses are more susceptible to attack by diseases and insects. Spec'^s

such as green ash, Siberian elm, caragana, and

ponderosa pine are well adapted to cold and snowy

locations. Catalpa, locust, tamarix, and shortleaf

pine must be restricted to southern areas of the

Plains for best growth. In addition, certain races

or strains are often better adapted than others of

the same species.

Soil.—Soils i^lace a second limitation on choice

of tree species, for the ways in which climate affects tree growth are often modified by texture

and depth of soil a,nd configuration of the land

surface. Depth, texture, fertility, acidity, and

moisture relations of the soil are all important

factors in tree survival and growth (fig. 21).

Nearly all trees grow well on deep, moist, fertile

soils. Eelatively few species, however, can tolerate alkaline, very acid, or very stiff, impermeable

soils. Some trees grow well on shallow soils for

a short periodof years, then cease growth and die.

Choice of species becomes more limited as soil

conditions become more adverse. Cottonwood and

willows require moist locations and consequently

do well where the water table is close to the surface. They are short lived on upland where water

tables are far from the surface. Junipers, ponderosa pine, and certain broadleaf species can make

respectable growth and live a long time on relatively shallow soils and dry sites. Russian-olive is

probably better adapted than other species for

extremely alkaline or saline soils.

Topography.—Topography places a third limitation on choice of trees, for the lay of the land

greatly influences soil moisture and wind conditions. In a river or creek bottom land, for example, where ground water is close to the surface,

most tree species grow well (fig. 22). On a flat

upland far from the water table, choic« is restricted and all species are apt to grow more slowly.

Uplands are more exposed than lowlands to all

climatic elements, especially wind. On an exposed windy plain, trees grow less well than in a

more protected area of lowland, even though the

soil may be as deep and fertile. Protection by

natural topographic features should be utilized

when possible in planning the location and orientation of tree plantings. Locations to the leeward

of ridges, knolls, and dunes are favorable owing

to extra moisture from snow accumulation.

Other Organisms.—A fourth limitation on

choice of species may be the other living organisms with which trees are associated. Diseases,

insects, animals, other vegetation, and even man

all have a bearing on survival and growth of trees.

This is the only factor than man can readily

modify by taking positive control measures.

Ideally, selection of species or strains should

be limited to those with most resistance to insects

and diseases. However, some species with low

resistance )nay be used because they have other

desirable characteristics. Generally, species that

are highly susceptible to major diseases and insects, sucii as American elm, should be avoided.

Susceptibility to minor pests need not limit choice

of species.
20 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

"Á<;'-'mt.;^U>^,, . .- 'Vs.i^ir.Ä-Ä

'^.^ -, ■■ , ' • M-.«*i«i!ii^^->-j»^;,ijaáfaeit^--':&.

F-485736-783

Figure 21.—Variations in soils have affected survival and height growth of different species in these 16-year-old windbreaks: A, Survival

and growth of tall, fast-growing species in the right half of this windbreak have been reduced by unfavorable soil conditions; conifers

were not affected. B, Small spots of unfavorable soil hove caused gaps to appear in the upper level of this windbreak.

^-:-^><:

-ii. í-&!^'Si^a.iífSí¡ñiXÍ'^ »Älacai£&Siiii.^,iii_; .•-i;aüfci**ia£i¿¿a»astíA*aA2a¿E!iteiij*A'>r.-'-.--. í

r^86773-782

Figure 22.—Topogrophy—upland, lowland, or slope—has affected survival and height growth of different species in these 16-year-old

windbreaks: A, Cottonwoods are 60 feet tall on lowland site (right), but are nearly all dead on higher ground (left). B, Cottonwoods

ana elms Jiave died on the knolls of deep sandy soils on undulating topography. Survival and growth is good in the lower places.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 21

Use of windbreaks as shade and stomp lots for

livestock, surveys have shown, is the principal

factor is reducing the effectiveness and overall

usefulness of tree plantings. Nearly one-third

of the Prairie States shelterbelts are being seriously damaged. Some species more than others

are damaged by trampling, direct browsing, or

nibbling by large animals and rodents. Since

such damage can be controlled, however, proneness to injury by animals should not influence

choice of species.

Select Species for Windbreak

Characteristics

The capacity of a tree planting to furnish protection depends on the sum total of all tree and

shrub foliage making up windbreak height, density, and continuity. Windbreaks ordinarily require several kinds of trees with different growth

characteristics so as to provide foliage density at

various height levels over a period of years. As

trees grow older their form and crown characteristics change. For example, young eastern redcedars provide very dense foliage near the ground ;

but as they grow older the lower limbs die and

density of foliage shifts to a higher level. Fastgrowing cottonwoods provide dense foliage at low

to medium heights when young; but with time,

foliage density shifts to the upper level. Some

fast-growing broadleaf trees develop very loose,

open crowns in middle age, and consequently are

worthless for windbreaks. Shrubs usually retain

dense foliage near the ground throughout their

lifetime, especially if they are cut back periodically.

Maintenance of the sheltering effect of windbreaks over a useful span of years depends on the

relative life spans of the trees and shrubs planted.

Selection of species for their longevity must first

fit the limitations of the planting site.

Height.—Height, the most important of windbreak characteristics, influences the extent of the

protected area. The effect of height on leeward

shelter distance was explained in the first section,

and is generally agreed to be significant for 15 to

20 windbreak heights. Therefore, it is well to

choose trees that grow as tall as the planting site

will allow. For quick effect, fast-growing trees

that reach maximum height in a short time are

the first choice. Since these fast growers are likely to be short lived even on favorable sites, slower

growing tall trees that mature later and remain

effective for a long time should be used also. Examples of fast-growing tall trees are cottonwood,

sycamore, and Siberian elm. Slower growing tall

trees are ponderosa pine and Austrian pine for the

central Plains; shortleaf pine for the southern

Plains.

Foliage Characteristics.—Density or penetrability also influences the extent of leeward protection. This characteristic depends on width of

windbreak, arrangement and spacing of species,

and crown height of the different species at various ages. These determine cross-sectional shape

and foliage density at various height levels in the

windbreak. Such characteristics will naturally

change with time as temporary species die and

more permanent species reach full crown growth

and maximum height.

As explained in the second section, the required

density of various height levels will vary depending upon the objectives of protection. Windbreaks of moderate density at all heights provide

a wider area of protection than those of greater

density. For greatest wind velocity reduction

over the greatest area, therefore, trees that maintain medium density at all height levels throughout the growing season are ideal.

The density of a windbreak composed entirely

of broadleaf species, or in combination with conifers, changes from season to season as the deciduous foliage grows and drops (fig. 23 ). Windbreaks

composed entirely of conifers do not change density and therefore provide the same degree of protection the year around.

Upper level density depends on the crowns of

the tall trees. At least two rows of tall trees are

necessary for adequate upper density, since the

other shorter tree rows do not contribute to this

level.

Middle level density during the first 15 years

depends on the medium to slower growing broadleaf trees. After that, the pines and redcedars

provide most of the middle level density, with the

taller growing pines beginning to form the upper

level.

Lower level density is provided by all rows during the first 15 years. After 20 to 30 years, most

conifers and broadleaf trees will lose their lower

foliage. An exception is eastern redcedar which

retains its lower foliage when not crowded.

Thereafter the low density must be provided by

thick-growing shrubs not exceeding 8 to 10 feet

in height, and preferably less than 5 feet tall.

Continuity.—Continuity of windbreaks also influences the extent of protected area. Gaps or

openings caused by tree failure in any part of a

windbreak destroy uniformity of the structure

and reduce efficiency. Gaps also invite encroachment of herbaceous vegetation into windbreaks,

with consequent competition and weakening of the

entire tree stand.

Protective windbreak systems provide maximum

benefits when fields are completely surrounded by

barriers, so that a minimum of area is exposed

to open field environment. Therefore, the rule

is to choose trees that are so adapted to the particular soils that practically all of them survive
22 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

Â '• îî«^n4*iA.-. ¿'i ¿?';'ÍÄ%Äi*,'- ^î«^*^"'''Ai' '

•' ¿.A^:'ïx

Figure 23. Change in foliage density from summer to winter in a 20-year-old windbreak of conifers and broaüleaf trees: A, Effective

height in summer is 65 feet, B, Loss of broadleaf foliage during winter redjces effective height to 20 feet.

and grow well if given proper care. If there are

several different soil types in the planting area,

the best species for each soil should be selected.

The occurrence of gaps can be prevented by replacing dead or dying trees with the same species the

following season.

Longevity.—Because of the large initial investment in tree planting, the backbone of windbreaks

should be the long-lived tree species that provide

effective protection for at least 50 years. Protection on farms and ranches in the Plains will be

needed just as much 50 to 100 years from now

as within the next decade. Plains environment

tends to shorten the lives of trees, but some species

can live and remain thrifty longer than others.

Since these longer lived species will provide an

effective windbreak for a longer period of years,

they constitute a better investment.

RECOMMENDED SPECIES

Tree and shrub species suitable for windbreaks

on six different kinds of sites in the central Plains

are given in table 1. Expected maximum heights

at maturity, rate of height growth, and longevity

are also given. The three longevity (useful life)

classes in the tables are broad and overlapping.

Short-lived trees may live from 10 to 40 years;

medium from 20 to 60 years; and long-lived trees

from 50 to 80 years or more. Longevity is influenced by site, as well as by inherent species

characteristics, care, and management. Relative

longevity may therefore differ by sites. Other

important characteristics of each species are given

in table 2, and scientific names in table 3. The

section "Why Protection Is Important," page 45.

gives information on insects and diseases likely to

attack different tree and bhrub species.

The kinds of trees in a windbreak should be

kept to a minimum, including only those needed

to provide the structure for the main objective.

For example, if cottonwood is selected as the tall,

fast grower, another tall, fast grower such as

Siberian elm should not be added. From the tables presented here, trees should be selected tentatively for the soil and site condition most similar

to the prospective planting location (table !)•

Then from the tentative list, those species having
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 23

the desired characteristics such as crown density

and drouth resistance should be selected with the

aid of table 2.

Many tree and shrub species not recommended

in this handbook have been tried and tested.

Wliile some of them are without doubt adapted

and useful under certain conditions, they cannot

be generally recommended for the variety of conditions encountered in the central Great Plains.

Other species that have been used extensively in

the past, such as American elm, are not recommended because of impending disease or insect

conditions. Honeylocust is not recommended hecause it has an open crown habit not suitable for

creating maximum foliage density in windbreaks.

TABLE 1.—Recommended tree and shnii species

for six kinds of sites in the central Plains

DEEP, MOIST, PERMEABLE SOILS (EIVER AND CREEK

LOWLANDS)

Mature size and

common name

Tall trees:

Cottonwood

White willow

Siberian elm

Sycamore

Shortleaf pine (south

only).

Ponderosa pine

Austrian pine

Medium trees:

Northern catalpa

Black willow

Golden willow

Green ash

Hackberry

Bur oak

Scots pine

Jack pine

Eastern redoedar

Short trees:

Boxelder

Russian-olive

Diamond willow

Russian mulberry

Osage-orange

Rocky Mtn. cedar

Shrubs:

American plum

Chokecherry

Tamarisk (south

only).

Purple willow

Common lilac

Honeysuckle (north

only).

Caragana (north

only).

Maximum

height

(ieet)

80

50

60

60

60

60

60

40

40

30

45

45

45

45

45

45

25

25

15

20

25

25

10

10

10

10

Height growth

Fast

.__do

.__do

Medium.

...do

Slow.

...do.

Fast

...do

...do

Medium.

...do

Slow _ Medium.

...do

Slow

Fast

do...

Medium.

do...

do..

Slow

Fast

do...

do...

do..

Medium.

do.-

do..

Useful life

Medium.

Do.

Do.

Do.

Do.

Long.

Do.

Medium.

Short.

Do.

Medium.

Do.

Long.

Medium.

Do.

Long.

Short.

Medium.

Short.

Medium.

Long.

Do.

Medium.

Do.

Short.

Do.

Medium.

Short.

Medium.

MEDIUM TO DEEP UPLAND SOILS (SILTY OR CLAYEY LOAMS)

Tall trees:

Siberian elm

Shortleaf pine (south

only).

45

45

Fast.

Slow.

TABLE 1.—Con'inued

MEDIUM TO DEEP UPLAND SOILS (SILTY OR CLAYEY

LOAMS)—continued

Ma.xiMature size and mum Height growth Useful life

common name height

(feet)

Tall trees—Continued

Ponderosa pine 50 do Long.

Austrian pine 45 do Medium.

Medium trees:

Green ash. 35 Medium.. . Do.

Hackberry.. 35 do Do

Bur oak ... ._ 35 Slow Long.

Eastern redcedar . 35 do Do.

Short trees:

Boxelder 25

25

Fast

do

Short

Russian-olive Do.

Russian mulberry 20 Medium Do.

Osage-orange 25 do Long.

Rocky Mtn. cedar 25 Slow Do.

Shrubs:

American plum 10 Fast Medium.

Chokecherry.. 10 do Do

Tamarisk (south 10 do Short.

only).

Common lilac 8 Medium Medium.

Caragana 8 do Do.

Skunkbush sumac 6 Slow Do.

MEDIUM TO DEEP UPLAND SOILS (SANDY LOAMS AND

LOAMY SANDS)

Tall trees:

Cottonwood

Siberian elm

Shortleaf pine (south

only).

Ponderosa pine

Austrian pine

Medium trees:

Green ash

Bur oak

Eastern redcedar

Short trees:

Boxelder

Russian-olive

Russian mulberry

Osage-orange

Rocky Mtn. cedar..

Shrubs:

American plum

Chokecherry

Common lilac

Skunkbush sumac

60

50

50

60

50

30

35

35

20

20

15

20

25

Fast

...do....

Medium

Slow

...do....

Medium

Slow

...do..-.

Fast

...do....

Medium

...do....

Slow

Fast

...do....

Medium

Slow

Short.

Medium.

Do.

Long.

Do.

Medium.

Long.

Do.

Short.

Do.

Do.

Long.

Do.

Medium.

Do.

Do.

Do.

SANDHILL UPLANDS

Medium.

Do.

Tall trees:

Ponderosa pine

Austrian pine

Medium trees:

Scots pine

Jack pine

Eastern redcedar

Short trees: Rocky

Mountain cedar.

Shrub: Chokecherry...

50

40

40

40

30

20

Slow

...do

Medium.

...do

Slow

...do

Medium.

Long.

Medium.

Do.

Do.

Long.

Do.

Medium.

691-791 O - 64
24 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

TABLE 1.—Continued

MEDIUM TO SHALLOW UPLAND SOILS

(Underlain by coarse sand, gravel, impermeable claypan,

or bed rock.)

MaxiMature size and mum Height grovrth Useful life

common name height

(feet)

Tall trees:

Siberian elm 25 Medium Short.

Ponderosa pine 35 Slow Medium.

Medium trees:

Bur oak 30 do Do.

Eastern redcedar 25 do Long.

Short trees:

Osage-orange 20 Medium Medium.

Rocky Mtn. cedar... 15 Slow Long.

Shrubs:

American plum 5 Medium Short.

Tamarisk South 5 do Do.

only).

Common lilac. — 5 Slow Do.

Skunkbush sumac 5 do Medium.

TABLE 2.—Continued

Mature size and

common name

Medium trees—Con.

Eastern redcedar.

Short trees:

Boxelder

Russian-olive

Diamond willow.

Russian mulberry.

Osage-orange

Rocky Mtn

cedar.

Shrubs;

American plum. _

Chokecherry

Tamarisk

Purple willow

Common lilac

Honeysuckle

Caragana

Skunkbush

sumac.

Crown

density

Dense.

...do..

Medium.

...do

Dense

...do

...do

...do

...do

Medium.

...do

Dense

...do

Medium.

Dense

Root habit

Deep.

Medium.

...do

Shallow.

Deep

...do

Medium.

Shallow.

...do

...do

...do

...do

...do

...do

Medium.

Drouth

resistance

High.

Medium.

Do.

Low.

Medium.

High.

Do.

Medium.

High.

Medium.

Low.

High.

Medium.

High.

Do.

VERY WET, POORLY DRAINED SOILS (SALINE OR ALKALINE

UPLANDS AND LOWLANDS)

Tall trees:

45

30

Medium

do

Short.

White willow Do.

Siberian elm 25 do Do.

Medium trees:

Golden willow 20 do Do.

Green ash 20 Slow Do.

Short trees:

Russian-olive 15 Medium Do.

Diamond willow 5 do Do.

Shrub: Purple willow... 5 do Do.

TABLE 2.—Croion, root., and drouth characteristics

of tree and sh7'uh species reconimended for

planting in the central Plains

Mature size and Crown Root habit Drouth

common name density resistance

Tall trees:

Cottonwood Medium Shallow... Lowr.

White willow ...do ...do Do.

Siberian elm Dense Medium Medium.

Sycamore ...do ...do Low.

Shortleaf pine Medium ...do High.

Ponderosa pine.. ...do Deep Do.

Austrian pine ...do ...do Medium.

Medium trees:

Northern catalpa. Medium Shallow Low.

Black willow ...do ...do Do.

Golden willow Dense _. ...do Do.

Green ash Medium. Medium Medium.

Hackberry ...do Deep High.

Bur oak Dense.. ...do Do.

Scots pine Medium... ...do Medium.

Jack pine ...do Medium Do.

TABLE 3.—Common and scientific na.mes of tree

and shrub species I'ecommended for planting in

the central Plains

Mature size and common name Scientific name

Tall trees:

Cottonwood Populus deltoides

White willow Salix alba

Siberian elm Ulmus pumila

Sycamore Platanus occidentalis

Shortleaf pine Pinus echinata

Ponderosa pine P. ponderosa scopulorum

Austrian pine P. nigra

Medium trees:

Northern catalpa Catalpa speciosa

Black willow Salix nigra

Golden willow <S. alba vitellina

Green ash Fraxinus pennsylvanica

Hackberry Celtis occidentalis

Bur oak Quercus macrocarpa

Scots pine Pinus sylvestris

Jack pine P. banksiana

Eastern redcedar Juniperus virginiana

Short trees:

Boxelder Acer negundo

Russian-olive Elaeagnus angustifoUa

Diamond willow Salix missouriensis

Russian mulberry Morus alba tartárica

Osage-orange Madura pomífera

Rocky Mtn. cedar Juniperus scopulorum

Shrubs:

American plum Prunus americana

Chokecherry P. virginiana

Tamarisk Tamarix pentandra

Purple willow Salix purpurea

Common lilac Syringa vulgaris

Honeysuckle Lonicera tatarica

Caragana Caragana arborescens

Skunkbush sumac Rhus trilobata
TKJfllfl WINDBREAKS FOR THE CENTRAL GREAT PLAINS

How To Arrange and Space Trees in the Windbreak

25

Determination of spacings and arrangements of

trees for best growth has been the aim of a number of experiments in the Plains for five or six

decades. These studies have led to recommendations of different spacings and arrangements depending on location within the region, whether

in the arid western or more humid eastern zones.

Most of these studies, however, have dealt with

the effects of space and arrangement on individual

tree growth, rather than the effects on windbreaks

structure.

The Plains tree planter should keep in mind

that windbreaks are not planted simply for the

best growth and development of individual trees.

They are planted for mass effect against the wind.

Therefore, spacings and arrangements recommended solely on the basis of individual tree

growth, with no regard for the type of structure

desired, are of doubtful value in producing effective windbarriers. On the other hand, arrangement and spacing of windbreak trees must often

be a compromise between requirements for individual tree growth and requirements for growing

a stand of trees that will produce the type of structure needed for protection.

One-row windbreaks have free growing space

for trees on two sides and obviously create no

problem of crowding between rows. Eesearch

has shown, however, that single rows of trees do

not provide sufficient density for maximum wind

reductions over extended leeward areas, although

the amount of reduction close to the barrier may

be satisfactory. Single rows of trees have no

safety factor against occurrence of gaps; for example, the failure of several consecutive trees can

seriously impair the continuity of barriers (fig.

24). More than one row of trees is therefore

recommended to produce windbarriers of effective

density and height.

Machine planting and cultivation have greatly

influenced row spacing recommendations. Close

spacings between trees and rows are possible when

hand planting and cultivation are used, but

machine planting and cultivation now require row

spacing of at least 8 feet and ranging up to 24

feet. Widely spaced rows are required to accommodate the large cultivation equipment in common

use on western Plains wheat farms.

GROWTH AND DEVELOPMENT WITH

AGE

It is important to understand the growth

phases of windbreak trees in order to decide on

proper arrangement and spacing of the various

species components. Above all, it should be kept

in mind that the height, density, cross section, and

profile of tree windbreaks changes with time.

These changes will greatly affect the structure

and efficiency of the windbreaks.

Hypothetical examples in development of two

five-row windbreaks composed of different species

•îKsisa

Figure 24 —Atthough single-row windbreaks are fairly easy to establish compared with windbreaks of several rows, they do not provide

the density and continuity required for best protection of cropland.
26 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 25 0

over a 40-year period are given in figures 25 and

26. A significant cliange takes place between tlie

20th and 40th year. In the conifer windbreak

(fig. 25) the slower growing pines and redcedars

reach mature lieight after 30 to 40 years, at which

time the fast-growing elms begin to deteriorate.

This illustrates development of an effective longlived windbreak through use of conifers. In the

HEIGHT

(feet)

20

10

0

CROSS SECTION

/"

windbreak composed exclusively of broadleaf

trees (fig. 26) most species begin to decline and

the windbreak loses its eli'ective height and

density between the 20th and 40th year. Earlier

deterioration of broadleaf species as compared to

conifers has occurred in many plantations

throughout the Great Plains.

PROFILE AGE

5

Years

30

20

10

0 n 4 I á

10

Years

40

30

20

10

O

x^ ^^V^,' -"^v^r-v^V''^>

20

Years

40

30

20

10

0

Shrub Pine Elm

Redcedor Redcedar

Figure 25.—Cro«-scction and profile choracferistics of a five-row

40

Years

conifer windbreak as influenced by growlh and development during

40 years. "^
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 27

HEIGHT

(feet) CROSS SECTION

20

10

0

30

20

10

0

40

30

20

10

0

40

30

20

10

0

0}Ô^(

Q

PROFILE

m.

•ËMa

OíTCV^-V-

,^ ^\ r(

äSM

AGE

5

Years

10

Years

i 20

40

Years

Figure 26.—Cross-secMon and profile characteristics of a five-row

broadleaf windbreak as influenced by growth and development

during 40 years.

Growth and development of windbreak trees

and shrubs can be controlled and modified to

some extent, to produce a barrier with certain

characteristics. Shrubs, for example, may be cut

back to the ground and allowed to sprout, so as to

increase ground level density. Much research is

needed, however, to determine more specifically

how to manage the components of windbreaks by

means of silvicultural cutting practices. With

proper silvicultural care, it may be possible to

prolong the effectiveness of broadleaf windbreaks

such as that illustrated in figure 26. At present,

however, a minimum of two rows of conifers is

recommended for all windbreaks, to provide

longevity and protection against soil blowing in

late fall, winter, and early spring, when broadleaf trees are bare. Pines and junijiers are particularly well suited for this purpose.

ARRANGEMENT OF SPECIES

COMPONENTS

The arrangement and row spacing of different

tree species determines the cross-sectional shape

of a windbreak. With normal survival and

growth of species of known height and crown

growth habits, this shape may be easily predicted

for any age.

Species arrangements which provide a moderately dense lower level are generally better than

very dense or very open barriers. Barriers with

an abrupt or nearly vertical cross section are better than those with a gently sloping cross section.

Species arrangement should therefore provide

not only for the best tree-row development, but

also for moderate density and a fairly abrupt

cross-sectional face. Slower growing species

such as pine and redcedar intended for future

effective height and longevity should not be

placed in a position where they will be overtopped

by fast-growing species.

A tree row should be of one species from end to

end, except where soil differences dictate a change

as described in the previous section. A mixture

of species within tree rows, alternating short and

tall, is not recommended. Failure of one or the

other species will leave within-row openings

along the windbreak axis that weaken the entire

structure. Failure of an entire row is much easier to correct by replanting than scattered failures

within rows.

Arrangement of medium and tall trees may be

varied to some extent. The shrub and pine rows,

however, should always be at least 20 feet distant

from tall, fast-growmg trees. This is necessary

not only for best height growth, but also to maintain crown vigor to the ground level. Both sides

of windbreaks should contain rows of trees or

shrubs that will remain dense near the ground.

Fast-growing but short-lived trees should always

be in the outside rows, where they may be removed

after 20 to 25 years with minimum interference

to the remainder of the wmdbreak.

SPACING BETWEEN TREE ROWS

Very wide spacing between tree rows is believed

by some observers to be necessary for tree survival

in the drier parts of the Plains. There are many

excellent windbreak plantings at row spacings of

20 to 30 feet. On the other hand, there are also

examples of vigorous 20- to 40-year-old conifer

windbreaks in the high Plains at row spacings of

8 to 10 feet.

A windbreak is most efficient when the wind is

blowing from either of the two directions perpendicular to the long axis of the barrier. Therefore,

the profile or frontal view is the most important

aspect to consider in terms of wind reduction effect. Density of this profile is determined primarily by (1) species, (2) spacing between trees

m the roiv, and (3) number of rows.

Distance between tree rows can be varied

considerably without appreciably affecting the

density, height, and continuity of windbreaks.

Variations in row spacing between 10 and 20 feet

have little effect on wind velocity reduction, since

the frontal pace of the windbarrier presents to the
28 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

wind approximately tlie same hei^rlit and density,

regardless of distance between tree rows (fig. 27).

The advantages and disadvantages of close

versus wide row spacing as it aifects tree growth

and windbreak maintenance should lx>. considered.

The chief disadvantage of widely spaced rows is

that plantings must be maintained by cultivation

for an indefinite number of years, because the tree

crowns never close and shade out herbaceous vegetation. Another disadvantage is that widely

spaced rows occupy more land than necessary for

a windbreak of the required density.

An advantage of widely spaced rows is that

larger tree crowns develop and maintain lower

foliage density for many more years than closely

spaced trees. This advantage is not essential,

however, since with proper composition of the

windbreak, low level density can be provided as

well or better with shrubby species. Then too,

large-crowned trees require more moisture and

may be more subject to dieback during drouth.

The advantage of closely spaced rows (not less

than 8 feet apart, however) is early crown closure

and completion of the cultivation job. A disadvantage of closely spaced tree rows is that competition among trees starts very early. Unless thinning and releiuse cuttings are planned and carried

out, the vigor of trees is likely to decline.

Minimum spacing between rows may sometimes

have to be detezTiiined by the size of cultivation

equipment available. The minimum spacing

should be 3 to 4 feet wider than the implement, to

avoid mechanical damage to the trees.

Current tree row spacing recommendations for

eastern Nebraska and Kansas are 10 to 16 feet,

and for western parts of these States 12 to 18 feet.

Across the Nebraska and Kansas line in eastern

Colorado, the recommended row spacing on drylands i-anges from 12 to 20 feet; on irrigated lands

10 to 14 feet. To the north in South Dakota, the

statewide recommendation is 10 to 14 feet, (18

feet by current Soil Conservation Service teclmical

guides) with slightly wider spacings for very

heavy soils and in areas of very low rainfall.

Since a range in spacing between tree rows from

10 to 20 feet is not critical from the standpoint of

producing an effective windbarrier, the landowner

should choose whatever spacing best fits his cultivation equipment and his intentions as to later cultivation, thinning, and management.

HEIGHT

(feel)

40

30

20

10

0

40

30

20

10

0

40

30

20

10

0

Figure 27.—i

CROSS SECTION

Cultivation needed for 5 years

Cultivation needed for 15 years

nL_4i

PROFILE ROW SPACING

10 feet

15 feet

20 feet

Cultivation needed for 25 years

Cross-section and profile characterisHcs of a 25.year-old five-row windbreak as influenced by spacing between rows.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 29

SPACING BETWEEN TREES IN THE

ROW

Whereas variations in row spacing make little

difference in windbreak effectiveness, the spacing

between trees within rows makes considerable

difference.

Spacing between trees in the row directly affects

the frontal and interior density of the barrier (fig.

28). In the low level portion of a barrier the

distance between shrubs determines the density

and continuity of that level. Similarly at other

levels from medium to tall heights, the distance

between trees will at any age añ'e<:t the density of

barrier. Number of tree rows contributing to a

height level, of course, has an additional effect on

density.

Recommended spacing for shrubs or conifers

for low level density is between 3 and 5 feet.

Under most conditions this spacing will provide a

dense barrier from the gi'ound level to 3 or 4 feet

high. Shrubs such as caragana will pro^ade effective height to 10 or 12 feet.

Spacing between the tall, fast-growing trees

such as cottonwood, willows, or Siberian elm

should be from 6 to 12 feet. If the owner definitely intends to thin tree rows after 5 to 10 years,

these tall fast growers can be planted at 6-foot

spacing, in order to provide an effective barrier

during early years. The tall fast growers, however, should be spaced 10 to 12 feet apart if no

thinning is to be done.

Slower growing trees should be planted 6 to 10

feet apart within rows. Pines and junipers both

grow well at this spacing for the first 20 years.

As the pines reach 20 feet in height, they will need

more space. Pines should then be thinned to a

LAYOUT

AVAVAVAVAVAV

^ii: ^t 'X:t -><:t y^t "^t"^

A V A V A V

X :i; ^ )k ->^ ^ -X

ooooo û':>oooooti

A V A

0'^OOCJaC?C?C7C3iiOi

A- Redcedars

PROFILE

Tree spaced 6 feet opart

m the row

Mààiiéâ.

Tree spaced 12 feet apart

in the row

Tree spaced 18 feet apart

in the row

^ - Pines =-Shrubs

Figure 28.—Windbreak profiles at age 15 years with different

tree spaclngs in the row. Shrubs spaced 3 feet and rows 12

feet opart.

spacing of 15 to 20 feet within the rows. This

should be done before the lower limbs begin to die.

Staggering or alternating the position of trees in

adjacent rows is desirable where tree spacing in

the rows is the same. This will not only help to

cover up gaps caused by mortality but will also

provide a more uniform density of windbreak

profile.

How To Prepare Land for Tree Planting

WHY IS LAND PREPARATION

NEEDED?

Preparation of land for tree planting in the

Plains is needed for the same reasons that land is

prepared for any agricultural crop. Land preparation doesthe following :

Increases survival and growth of trees by :

ia) Destroying weed competition.

(b) Reducmg subsequent weed crops.

(c) Increasing soil moisture storage.

Reduces likelihood of wind erosion damage

(a) Providing a growing cover crop.

(b) Maintainmg a rough soil surface.

1

2,

by:

3. Controls the amount of previous plant residues that would otherwise interfere with machine

planting.

Past experience and research in the Plains have

shown repeatedly that- trees survive very poorly

when planted with no prior soil preparation on

land occupied by grass or alfalfa. This is especially true in the drier areas of the western Plains.

Land is plowed and summer fallowed for grain

and other crops in order to store moisture and to

control herbaceous vegetation. This practice is

just as important for trees. E^'en in the sandhills

grasslands where a minimum of soil preparation

is recommended because of their light, unstable

soils, some preparation for trees is necessary and

beneficial.
30 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

Tlie natural vegetation of the Plains is predominantly grass, with smaller amounts of forbs,

including many vigorous weeds. This vegetation

is well adapted to Plains climate and soils. It

naturally has a great advantage o\-er small trees,

at least for the first few years after planting. The

nati^•e grasses and weeds and some very aggressive

introduced weeds grow vigorously on most soils.

The highly vigorous growth of herbaceous

vegetation which characterizes the Plains region

often completely occupies the sites intended for

windbreaks. Available moisture in the soil is

rapidly used by tins vegetation. If there is to be

moisture available for new trees, this vegetation

must be controlled, at least until the tree roots

become established at a depth below roots of natural vegetation. Following are some specific reasons for controlling the competing plants.

1. Young trees, whether bare-root or potted

seedlings and transplants, need plenty of moisture

for the first year or two in the field until roots

have become well established.

2. Moisture must be available in the toj:) 2 to 3

feet of soil.

3. Heavy stands of weeds, grass, or crops deplete

the surface soil of moisture.

4. Young trees weaken and die when competition for available moisture in the surface soil is

too great, as from fast-growing weeds and grasses.

5. Young trees weaken and die when they are

overtopped or heavily shaded by fast-growing

weeds and grasses.

KINDS OF LAND PREPARATION

PRACTICES

Practices of preparing land for tree planting

are all aimed toward more favorable conditions

for tree survi\'al and growth. The following

brief descriptions of land preparation practices

and their purposes will l>e helpful in deciding

which should be used in a particular case.

Contour terracing.—To provide extra moisture

for trees planted on the contour adjacent to or on

terraces. Terraces also reduce water erosion within tree plantings.

Diversion ditches.—To provide for diversion

of runoff water from adjacent fields or road ditches

to the planting area either by spreading or along

the tree rows.

ßnow fence harrier.—To catch and hold snow

on land to be planted the "following spring (fig.

29). This is of greatest importance in dryland

areas where additional subsoil moisture can benefit trees.

Subsoiling.—Loosening of a narrow strip of soil

to a depth of 2 to 3 feet for the purpose of breaking up a hard layer of plowsole or a naturally impermeable subsoil. This practice provides for

deeper penetration of moisture and tree roots into

hea^-y-textured subsoils. Subsoiling has increased

tre« survival on hardpan soils by one-third. It

has increased (1) planting efficiency, (2) height

and root development, and (3) vigor.

' ''imm

'ä^

Figure 29.-Sn»w fencing p„, up ,he previous fall will accumulate snow ,o give exf«, moisture fo, o new windbreok planting.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 31

Summer fallow.—Clean cultivation of soil

throughout a growing season. It accomplishes

two important things: (1) Accumulation of moisture, and (2) accumulation of nutrients. Summer

fallow prevents growth of weeds and grass that

would otherwise deplete surface soil moisture and

nutrients. It allows accumulation of nutrients

from decomposition of organic materials in the

soil.

Stuhhle-mulch or trashy fallow.—An adaptation

of summer fallow in which protective organic

materials are maintained on the soil surface by

use of special tillage implements.

Summier cover crop.—A close-growing grain,

sorghum, or sudan crop planted on sandy land in

late summer prior to tree planting, to remain

through the fall and winter for protection against

wind erosion.

Fall ¡yloioing.—Loosening of soil to provide better reception and holding of moisture tliroughout

the winter, and to bring soil into better tilth for

spring tree planting. It should be deeper for trees

than for crops.

Fall cover crop. — A close-growing crop of oats

or barley planted in the early fall prior to spring

tree planting. The cover protects the soil and

catches and holds snow.

Spring dishing and harrowing.—Smoothing of

the site to facilitate tree planting and to kill earlygerminating weeds and grasses. This should be

done 3 to 4 weeks before ¡Dlanting so that early

spring rains will settle the soil.

Spring cover crop. — A close-growing crop of

sorghum, sudan, or grain planted in early spring

at tree planting time, to provide protection for

trees and sandy soils.

Spring furrow.—The removal of a strip of sod,

11/2 to 2 feet wide and several inches deep, to facilitate planting of trees on light sandy soil which

cannot otherwise be prepared by ordinary clean

cultivation.

HOW TO DECIDE WHICH PRACTICES

TO USE

Preparation of land for tree planting includes

several important steps. All are aimed toward

providing the most favorable soil conditions for

receiving transplants, so that there is the greatest

possible opportunity for young trees to survive

and grow.

The method of preparation will naturally differ

according to :

1. Kind of soil—whether a loose sandy soil subject to blowing, or a silty clay soil somewhat impermeable to roots.

2. Present cropping practice or vegetation

cover.

3. The likelihood of spring rains following

planting, and other factors of climate.

General Practices for All Lands

The following practices should be applied to

most lands for tree planting, as important supplemental measures to improve moisture conditions of

the planting site. Such practices are, for the most

part, permanent conservation practices. They

are here considered as land preparation practices,

because for greatest benefits they should be put

into effect a year or so before tree planting.

Contour terracing.—Whenever terracing is recommended, the planting of windbreaks should fit

the terracing pattern. Contour tree planting,

especially on rolling land where tree sites are likely to be variable, provides additional moisture for

increased and more uniform tree growth.

Diversion ditches.—As with contour terracing,

securing additional moisture from field diversion

will result in increased and more uniform tree

growth.

Irrigation.—If trees can be irrigated, the advantages are similar to those for any crop.

Snow fence harrier.—The increase of moisture

on tree planting areas brought about by snow drift

fences will assure greater tree survival and growth.

Practices Depending Upon Soil and

Land Use

Present land preparation recommendations for

tree planting are similar among States in the

Plains region. Recommendations vary, however,

according to soil texture, erodibility, and land use.

The combination of these factors will likely determine the appropriate land preparation practices.

Kind of Soil.—Practices for sandy soils, especially very sandy textures, must provide a means

for maintaining vegetation cover within and on

the soil surface. Without adequate cover these

lighter texture soils are apt to be damaged severely

by wind erosion. Practices for sandy soil'shpukl

ordinarily cause a minimum of disturbance to

vegetation cover. If cover is inadequate under

previous land use, cover crops should be established.

Medium to heavier textured soils are less subject to wind erosion, but they require more intensive weed control to conserve moisture. The use

of summer fallow should be regarded as a standard treatment for tlie heavier soils, except perhaps on corn land in the eastern areas of the Plains

where moisture availability is not so critical.

Present Crop or Vegetation Cover.—The present use of land to be tree planted naturally determines to a large extent what can be done in the

way of preparation. - Grass and alfalfa land

should be prepared a year in advance, except on

highly erodible soils. However, the presence of

other crops on land to be tree planted frequently

forces land preparation for trees into a rather

tight schedule.

691-791 O - 64 - 5
32 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Gmssland.—Sod on medium to heavy soils

should be plowed deeply and worked until it is well

decomposed. Prepuration of grassland, on all but

loose sandy soils, should begin at least 1 year before planting trees. During very drouthy seasons

2 years of summer fallow after plowing may be

necessary. The roots of natural vegetation completely occupy the site and are highFy competitive

for moisture. When this vegetation is reduced

or destroyed and the organic materials from it

partly decomposed, the soil will be in best tilth

for planting. Soil will be moist and free of fresh

organic matter that would otherwise clog planting machines, and require moisture and nutrients

for decomposition.

In contrast, grassland on light sandy soils cannot be prepared ahead of time because of the risk

of wind erosion. In this case, the vegetation is

scalped and turned over in a narrow strip 1^^ to

2 feet wide at the time of tree planting.

Alfalfa fieldx.—Alfalfa fields should be prepared for tree planting in the same way as grasslands, except on light sandy soils.

On the sandy soils, alfalfa should be plowed 1

year before tree planting, and an annual crop

planted in its place for temporary cover during

the gi'owing season. Trees can then be planted

directly in the stubble with no further preparation.

Small grain fields.—Stubble of small grain normally furnishes aderjuate cover until tree planting

time the next spring. In light, sandy soils trees

can then be planted in stubble with no further

preparation. In heavier soils, however, stubble

should be plowed and disked the fall before

planting.

AVhere stubble is not adequate, or if soil moisture is low, heavier soils should be summer fallowed and seeded to oats in the fall. Sandy soils

should be planted to a late summer cover crop.

Vorn fields.—On heavier soils the only preparation needed is to cut cornstalks and disk in the

fall. Sandy soils, however, should be fall seeded

to grain if the field lacks cover.

Noxious weeds, such as bindweed (creeping

jenny), leafy spurge, thistle, and quackgrass,

should be killed by cultivation and/or chemical

sprays before trees are planted on any lands.

Recommended Practices

Minimum land preparation practices according

to broad soil texture classes and land use are summarized below. The recommendations are adapted

from two sources: (1) Soil Conservation Service

technical specifications for Nebraska, and (2) recommendations of various State and extension foresters m the Plains. It is emphasized that these

recommendations are minimum, practices and intended only as a general guide. Detailed recommendations by specific soil types and difl^erent'

vegetation covers have been developed for most

local areas in the central Great Plains, and these

will be used by soil conservation and forestry

technicians.

RECOMMENDED MINIMUM LAND PREPARATION FOR TREE

PLANTINO ACCORDING TO SURFACE SOIL TEXTURE AND

LAND USE

Sandy to very sandy soils

Grassland Scalp a 20-mch band of sod just

before planting ; plant trees in

narrow furrow.

Alfalfa Plow 1 year before; plant summer annual cover crop ; plant

trees in cover crop stubble.

Small grain I)o not disturb if good stubble;

plant trees in narrow furrow.

Plow if poor stubble; plant

summer cover crop ; plant

trees in cover crop stubble.

Corn Fall disk cornstalks; plant

small grain cover crop ; plant

trees in cover crop stubble.

IMPORTANT After planting, do not cultivate

between the tree rows on any

sandy soils ; just keep the

weeds and grass mowed.

Medium to heavy soils

Grassland Plow 1 year before ; summer fallow : fall seed small grain for

cover ; spring disk and plant

trees.

Alfalfa Same as for grassland.

Small grain Fall plow and disk if good moisture and stubble ; plant trees

in undisturbed soil. Plow

stubble and summer fallow if

poor moisture and stubble ;

fall seed small grain for cover ; spring disk and plant

trees.

Corn Fall disk cornstalks; plant trees

in undisturbed soil.

WHEN TO PREPARE LAND

Preparation of land well ahead of planting is

an essential part, of tree planting know-how in the

Plains.

1. Lay out terraces 1 year before planting.

2. Subsoil areas with tight impermeable layers

1 year before planting.

3. Plow grassland and alfalfa stands, except on

light sandy soils, at least 1 year in advance to

allow for partial decomposition of organic

materials.

i. Summer fallow plowed grass and alfalfa during the growing season before planting.

5. On light sandy cultivated soils, maintain as

much coarse litter as possible on and in the surface the growing season and winter before

planting.

6. If light sandy cultivated soils lack cover,

plant a close-growing temporary crop the summer before and leave stubble undisturbed.

7. Erect snow fence barriers to windward of

area the fall before planting.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 33

8. When planting in spring-seeded grain, cultivate a narrow 4-foot strip for planting.

A time schedule for the various practices, by

kind of soil and present land use, is suggested

in the following checklist.

Sandy soils Medlum to heavy soils

Practice

Grass Alfalfa

Grain Corn Grass AlfalfaGrain Corn

One year before:

Build terraces

Diversion

ditches

Plow... ...

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Subsoil X

(*)

(*)

X

X

Summer before:

Fallow

Stubble mulch

Leave stubble _ X

(*)

(*)

Disk stubble

Plant oats X

Sandy soils Medium to beavy soils

Practice

Grass Alfalfa

Grain Corn Grass Alfalfa

Grain Corn

Fall before:

Leave stubble X X X X

(*)

(*)

(*)

X

X

(*)

X

Plow

Disk (*) 9

(*)

X

X

(*)

(*)

X

X

X

X

(*)

(*)

Plant oats X

X

X

Snow fence X

Spring:

Leave stubble

X X

X

(*)

(*)

X

Disk and harrow X X (*)

Plant oats

Plant trees in:

Firm fresh soil X X (*)

X

(*)

Stubble X X

(*)

X

(*)

X

Grain (*)

Scalped furrow X

*Alternative practice if poor stubble cover or low moisture.

How To Obtain and Handle Tree Planting Stock

Because of the unfavorable conditions for germinating tree seed and tending small seedlings

directly on planting sites in the Plains, the most

practical method of establishing plantings is to

transplant small trees. Large quantities of tree

seedlings are produced in special nurseries (fig.

30) where the small delicate plants may be spaced,

watered, fertilized, and weeded according to their

needs. The 1- to 4-year-old seedlings or transplants are then shipped to the tree planter.

The average landowner tree planter must depend upon these special nurseries for his planting stock. These are operated by private commercial companies or by State and Federal

agencies. Choice of species is therefore limited

to those produced by these nurseries. In some

years nursery failures further limit the kinds of

trees and shrubs available.

Some species can be home grown by the farmer

willing to devote some extra time to the job.

Thus, species not generally available from nurseries may be produced for windbreak planting.

If the farmer has had no previous experience in

raising trees from seed, however, it will probably

not pay him to try it for large quantities of planting stock. The cost of good-quality 1- to 4-yearold tree planting stock is well within the means

of most landowners. For farmers interested in

growing their own stock from seed, the following

publications are recommended :

Woody-Plant Seed Manual.

U.S. Dept. Agr. Misc. Pub. 654. 1948.

Nursery Practice for Trees and Shrubs Suitable

for Planting on the Prairie-Plains.

U.S. Dept. Agr. Misc. Pub. 434,1941.

(Out of print; may be seen in libraries.)

Forest Nursery Practice in the Lake States.

U.S. Dept. Agr., Agr. Handbook 110. 1957.

Planting the Southern Pines.

U.S. Dept. Agr., Agr. Monograph 18. 1954.

Another method of obtaining tree planting stock

is to dig small naturally grown seedlings from

within well-established windbreaks, other plantations, or woodlands. These small wild seedlings,

if top-pruned to balance the size of the root system

excavated, can be transplanted in the same manner

as nursery-grown seedlings. This is a practical

method of obtaining small quantities of stock,

but is not likely to be economical for 500 or more

tree seedlings.

The purchasing and handling of tree-planting

stock must be regarded as equal in importance to

other phases of tree planting. Selection of recommended species will improve chances of success. However, variations in adaptability, growth,

form, and insect and disease resistance will depend upon the parent trees or stands from which

the seeds were collected (fig. 31). Source of seed

materials is second only in importance to species

selection itself. Much improvement in seed sources

is anticipated in the future, but will require time

for selection, breeding, and testing.

Proper handling of stock from the time it leaves

the nursery until it is planted in the field is of
34 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Figure 30.—Tree nursery showing pine and redcedar seedling stands, sprinl<ling system, and snow fences for wind and snow control.

Each fool of row contains about 20 seedlings.

utmost importance. This is the only time during

the life of trees when the roots are exposed to

abnormal conditions of temperature, moisture,

and light. Therefore, with bare-rooted trees,

careless handling even for a few minutes under

dry, windy conditions can easily cause death of

the trees.

WHERE TO BUY PLANTING STOCK

Planting stock for windbreaks is produced in

about 20 nurseries in the Great Plains States. Of

these, 10 are private commercial nurseries and 8

are State or soil conservation district nurseries.

The two U.S. Forest Service nurseries, which also

produce stock for National Forest planting, do

not accept orders directly from landowners; they

supply seedlings through State foresters, extension foresters, or Soil Conservation Districts for

farm and ranch planting.

The common way of obtaining large quantities

of tree-planting stock for windbreaks is through

an agricultural agency. Tree orders are processed

in several ways: (1) Through county agricultural

agents to the extension forester's oíRce, (2)

through district foresters to the State forester's

office, and (3) through Soil Conservation District

offices. These agencies accept orders and consolidate them before sending them to the various private. State, or Federal nurseries. Tree orders can

also be mailed directly to any private commercial

nurseryman.

Specify the Seed Sources

Studies in genetic variation of trees emphasize

the importance of careful selection of seed sources

for successful plantation establishment. Most

tree species have a wide range of genetic variation. Best success may depend largely upon use

of selected stock which has been grown from seed

of parent trees of known adaptability and resistance to insects and diseases.
TREE "WINDBREAKS FOR THE CENTRAL GREAT PLAINS 35

F-508713, 721

Figure 31.—Ponderosa pines of distinctly different crown form, branch angle, and foliage density. These different traits are inherited

from the parent stocks.

Cost of planting stock should not be a primary

consideration in a long-term investment such as

windbreaks. It is better to pay for stock of

known adaptability than to pay less for untried

and poorly adapted stock. The cheaper plant

materials may prove to be expensive in the long

run, because of poor survival.

Special selections of two species recommended

for Plains windbreaks are presently available.

Chinkota elm, a selection of Siberian elm, has

proved to be more winter hardy than the general

run of Siberian elm available in most nurseries.

This selection was developed by research scientists

at South Dakota State College and certified for

use in South Dakota. A selection of cottonw-ood,

known as Siouxland, is faster growing, more vigorous, and more resistant to leaf rust than the

general run of common cottonwood (fig. 32). It

was developed by Dr. C. M. Nagel, a plant

pathologist in South Dakota.

A general recommendation in specifying source

of seed for planting stock is that it should originate within a range in latitude of 100 miles north

and south of the planting site.

Progress is being made toward identifying and

propagating individuals and sources of trees that

have superior characteristics for windbreak use.

Progress will be encouraged if orders for trees

specify where they are to be planted and what is

desired in terms of tree growth rate, form, disease

and insect resistance, and other special characteristics.

Specify Sizes and Grades

In any bed or lot of nursery-grown stock there

are some small, deformed, or damaged seedlings

not suitable for field planting. These should be

discarded by the nurseryman, but sometimes are

shipped out to planters. Planters should discard

all small-grade cull stock. Experience and research have demonstrated that certain sizes and

grades of planting stock are required to obtain

satisfactory survival and growth of trees on
36 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 260

Plains planting sites. These sizes usually average

somewhat larger than is required in stock for the

more humid forested regions.

Caliper or diameter of stem 1 inch above the

grouncl line is a good measure of the ability of

planting stock to survive. Large-caliper stock

gives highest survival in normal to dry seasons.

Slightly smaller caliper stock will do well during

seasons of above-average rainfall in April and

May.

Minimum stem caliper for trees to be ¡slanted

in the Plains should be one-fourth inch for both

conifers and broadleaf species. Two to three

years are required to grow junipers and pines to

this size ; one year for most broadleaf species.

Size of top is of less importance than stem caliper, although many nurseries list their stock by

top size only. Conifers should have tops no less

than 8 inches and no more than 15 inches tall.

Broadleaf seedlings should average between 18

and 30 inclies in height. For most species, the top

size will be correct if the stem caliper is between

Vi and % inch.

Grading of seedlings and transplants provides

tlie greatest assurance of good-quality stock.

Grading takes into consideration not only stem

caliper and top height, but also the ratio of top

to root size, root damage, size of terminal buds,

occurrence of disease, color of foliage, etc. The

use of top-root ratio by weight can make the gradCi-jr-*''-.-:^ < jk. ir*..'- *i>,^-^

Figure 32.—Siouxlond, rust-resistant cottor,wood 40 feet tall at 7 years of age, Lincoln, Nebr''"""
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 37

ing process more accurate and selective, since it

expresses favorable or unfavorable balance. Seedlings having a large root system for an average

or better top will survive better than those with a

small root system. Shearing or cutting back the

top growth of seedlings is often practiced in the

nursery to obtain a more favorable top-root balance. This should be done by the tree planter if

he receives trees that are poorly balanced. For

conifers a 3 to 1 ratio of top to root weight is

desirable ; a 3 to 2 ratio is better.

There are at present no standard grading rules

for any species used in Plains planting. If "g-rading" is being done, it is merely a matter of culling,

rather than sorting trees into small, medium, and

large grades. The mass of evidence, however,

from all regions of this country and the world,

and with most tree species, supports the practice

of gi-ading for best results. The medium and large

grades of stock (fig. 33) consistently give the

highest survival and growth.

F-B0371B

Figure 33.—Specimens of nursery bedrun, 3-yecir-olel ponderosa

pine, showing large (L), medium (M), and small iS) grades of

planfing stock. The small grade trees are culls for Plains

planting. Scale in inches.

PACKING AND SHIPPING

Although packing and shipping will normally

be done by experienced nurserymen or foresters,

the landowner or technician receiving trees should

be aware of proper packing and shipping procedures. He should notify the agencies responsible

of any serious deficiencies in packing methods.

The period of time during which bare-rooted

trees are liept out of the soil is probably the most

critical time for them between germination and

maturity. Conifers are more sensitive to poor

care of the roots than most broadleaf species.

Packing and shipping must therefore be accomplished with little delay and by methods that will

maintain proper moisture and temperature about

the root systems until trees reach their destination. Once tree roots are damaged or become dry,

no amount of watering or care is likely to make

them grow.

Trees are packed in various ways depending on

the preferences of nurserymen and agencies responsible for distribution. Packing is usually

done inside a building that is kept rather cool,

not over 50° to 60° F.

Sphagnum moss and shingletow are the most

commonly used packing materials. This material

is allowed to soak up as much water as it will hold.

It is then spread out in the center of the wrapping

material and trees placed on it with roots to the

center. More moss or shingletow is placed on the

roots and the spread is then rolled into a compact

bundle. Wrapping materials may be ordinary

burlap, burlap-backed paper, asphalt-impregnated paper, or crinklekraft paper. Bundles are

tied with twine, wire, or steel strap.

Some agencies used corrugated paperboard cartons lined with wax to preserve the useful life

of the carton containing the damp packing material. These are closed with gummed tape or large

staples. With wax-lined cartons imier wrapping

paper is not used ; the trees and packing materials

are put directly into the box.

Larger tree orders are often put up in bales

either in the field or packing shed. Such bales

may contain 1,000 to 2,000 trees, and generally

contain a smaller quantity of packing materials

in proportion to tree roots than the smaller bundles. Field baling is not ordinarily done during

hot, windy weather. Bales are usually watered

with a probe if stored for any length of time before shipment. Once dug from the nursery beds,

all conifers whether in bales or loose in field carry

boxes are stored in refrigerated rooms at 40° F.

when not actually being counted, graded, packed,

or transported.

Trees in bales or boxes are shipped 50 to several

hundred miles by various means. Planters living

within 50 miles of the nursery often pick up trees

to reduce the time in transit. Railway parcel post

or express is the predominant mode of tree ship-
38 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

ping, although trucks are increasingly used. Refrigerated trucks are preferred for longer hauls

requiring more than a half day or if freezing

weather is likely. Air freight, available at a limited number of points, provides shipment with the

least delay, though at higher cost. Trees shipped

by air reach their destination in several hours and

are practically as fresh as when shipped.

WHAT TO DO WHEN TREES ARRIVE

When tree planting stock is received at the farm

or ranch, the bale or carton should be opened for

inspection without delay. If trees have been

packed properly to keep roots moist a.nd cool, have

been in transit no more than 2 or 3 days, and have

not been subjected to either freezing or high temperature, they will be in good condition for planting.

If trees are to be planted within 2 weeks from

the time of arrival, they can be left in the box

or bale. They should be watered each day, and

kept in a cool place out of the sun and wind.

In contrast, if roots are dry or barely moist and

noticeably warm or moldy, trees should not be

planted. The office through which the tree order

was given should be notified. The tree-distribution people and nurserymen want to know about

the condition of trees after shipment, and prompt

notification of poor conditions will aid them in

improving packing and shipping methods.

Planting stock should also be inspected for size

and grade. If the shipment contains more than

5-percent cull or very small tree«, the tree-distribution people should be notified. The small trees

should not be planted.

Storage

If moist cold storage at temperatures of 33° to

40°F. is available, trees should be so stored until

planting time. The bales should be opened and the

packing material moistened thoroughly by sprinklmg. The bales should then be retied loosely

and watered often to maintain moderate moisture.

The cold storage will keep trees donnant for several weeks until planting can be done.

Heeling-In

If planting is to be delayed longer than 2 weeks

after arrival of the trees, and if moist cold storageis not available, trees should be heeled-in the soil

m a shady, cool place.

Heeling-in is done by digging a V-shaped

trench (fig. 34) deep enough to accommodate the

Figure 34.—A properly made heel-in trench for temporary storage

of seedlings and transplants.

full spread of tree roots against the bare soil. A

bundle of seedlings is untied and spread out on

the sloping side of the heel-in trench, so that each

tree root system will be in contact with soil. The

trench is then filled with soil, packed and watered

so that.there will be no air spaces among the roots.

Heel-in trenches should be deep enough to accommodate roots without their being bent or

curled upward. Following are detailed directions

for storing seedlings in trenches. Throw in pulverized soil on the first layer of tree roots imtil the

roots are covered by an inch or two of soil. Then

start another layer of trees. No part of the green

tops of conifers should be covered with soil.

Check soil moisture each day and sprinkle if necessary. Trees should be removed from the heelin beds and planted before buds burst and new

growth has started.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAESTS 39

How To Plant Windbreak Trees

Twenty-five years ago most tree planting was

done by hand ; 500 trees per man on Plains sites

was a good day's work. Many plantings-of less

than 500 trees are still planted by hand, and generally this is the cheapest and most eíRcient way

to establish small plantings.

Complete windbreak systems for most farms

nowadays require several tnousand trees. Furthermore, weather conditions and the pressure of other

work at tree-planting time often demand that the

job be done as quickly as possible. Tree-planting

machines are therefore used to do the job quickly

and efficiently. A 3-man crew with planting machine can plant up to 8,000 trees a day.

A word of caution regarding machine planting.

Even with a machine working properly and an experienced crew, it is better to plant fewer trees

and plant them well, than to set a speed record

and later find less than half of them alive, because of a poor job of handling and planting.

WHEN TO PLANT

Trees are best planted in the 3 to 4 weeks of

early spring after the frost is out of the ground,

but before the tree buds begin to swell. In eastern

Nebraska in average years this period falls between April 10 and May 10. Planting in western

Nebraska is usually 1 to 2 weeks later. Tree planting in southern Kansas may begin in mid-March,

2 to 3 weeks earlier than in eastern Nebraska.

Bare-rooted trees should not be field planted

after they have started new top growth, since many

of them will die with such treatment. Potted trees

should likewise be planted before growth starts.

However, if delay in planting is unavoidable,

potted trees can be field planted throughout the

growing season, if they are watered on planting.

Fall planting is not recommended. Experience

has shown that mortality of fall-planted frees is

likely to be high, owing to excessive moisture loss

during winter before trees can establish a new

root system. There is also danger of frost heaving

in heavier soils. Fall-planted trees are apt to suffer higher mortality from rodent damage, since

they lack a well-established root system and hence

the capacity to recover.

Other recommendations concerning techniques

of planting are as follows. Choose calm, cloudy

days for planting, when possible. Plant even during rain on sandy soils where equipment can be

operated in wet weather. Defer planting when

wind velocity exeeds 15 m.p.h. If spring planting

conditions are too unfavorable, i.e., with excessÍA^e

wind, heat, and dry soils, line out trees a foot

apart near the farmstead where they can be irrigated and tended for a season. Dig them before

growth starts the following spring and transplant

by hand or machine to the field location.'

LAYOUT

The District Forester or Soil Conservation District technician will assist in preparing planting

layout plans. Copies of the layout, including

number of rows, species arrangement, spacing, etc.,

are furnished as a guide to the farmer and treeplanting foreman.

The planting layout in the field should be completed before any trees are moved. Distance between rows should be staked with flags or laths.

Then the tractor driver pulling the tree planter

can line up the machine without delay. Sufficient

space for cultivation should be left between tree

rows and existing fences.

Rows should be laid out in advance if a row

marker on the machine is not used. Stakes should

be set close enough (not more than 150 to 200 feet

apart) in each row so that tree rows are parallel.

Crooked and nonparallel rows can cause trouble

in cultivation. Where rows curve or turn comers,

more stakes should be set so that a smooth curve

is made. The most timesaving and accurate

method of making parallel rows is to use a row

marker attached to the tractor or the planter (fig.

35).

In advance, the first stake in each row should be

labeled clearly to identify the species to be

planted. Intermediate stakes where a change in

tree species is required should be similarly labeled.

This is important, to make sure the different species

are planted in the arrangement that was planned.

Obviously, mistakes are not easily corrected after

the trees are planted.

Distance between trees in the rows can be estimated by pacing when hand planting. In machine planting, the proper distance can be governed by speed of the machine and timing of the

planters. A flagged spacing stick can be fastened

to the tail end of the planting machine to help the

planters estimate distance between trees.

PLANTING DEPTH

Trees should be planted in the field at approximately the same depth as they grew in the nursery.

A frequent mistake in present-day plantmg practice is setting trees too deep. This mistake is

sometimes compounded later by close cultivation

which tends to cover the trees even more. Planting too deeply is more damaging to conifers than

to broadleaf species. A good rule is not to cover

any lower branches.

It is also a mistake to plant too shallow unless

a cultivator following immediately will throw soil

toward the trees. Shallow planting is likely to

expose part of the roots to drying and also wall

result in trees being blown over. It is better to
40 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

.•in<f^' .'TÍ^ y-xs''- ■■-t¿-- 'í

- ^-.^"^ :?v* -'r ^V

^^^ * " * w *

If l' -^««K'

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'<;í^

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Figure 35.—Tracfor-drawn tree-planting machine with row marker in carry position. In use, the long bar swings out at a right angle to

line of travel and marks the next row to be planted.

plant at the proper depth in the first place, then

keep cultivation equipment at least a foot away

from the trees.

Conifers and most broadleaf trees will normally

be planted as they come from the nursery.

Shrubs, however, can be top-pruned to fore« low

branching. Broadleaf species and eastern redcedar exceeding 20 inches in top length should also

be top-pruned. This will improve top-root ratio

and assure better growth the first season.

CARE OF TREES DURING PLANTING

Tree roots should never he alloived to dry, even

slightly. On the planting site, all trees excepting

the ones needed for a complete round or pass

through with the planter should be kept wrapped

in cool, moist conclition in the shade of other trees

or beneath a vehicle. If the roots of trees in a

bundle are tangled together, each tree should be

carefully separated so that roots are not stripped

during the fast pace of machine planting.

In both machine and hand planting, trees should

always be carried with their roots in water, moist

moss, sand, or burlap. No delay or interruption

should occur in moving trees from the moist bales

or heel-in beds to planting containers.

MACfflNE PLANTING

The very speed that enables the planting of

several thousand trees per day is one of the disadvantages of machine planting. In most instances

the greater speed results in less attention being

given to the condition of the indi-\ádual tree than

with hand planting. And yet each tree has an important function in the windbreak.

Therefore, a special eiïort should be made to

carefully check the following items by frequent

sampling :

1. Proper planting depth.

2. Roots not doubled up.

?>. Eoots not stripped.

4. Soil well packed about roots.

5. Trash not mixed in with roots.

6. Top not mechanically damaged.

7. Tree vertical.

Each tree row should be "walked" to check these

items following planting. The "walker" should

finn the soil about each tree with his feet, if the

packing wheels are not operating properly. It

may be desirable to stop the planting, make adjustments, and then resume at a speed that will

give the best planting job.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 41

r-323445—46-47-49—51-52—54

Figure 36.—Steps in hand planting by the Prairie States Forestry Project method: A,

Remove debris and dry soil; B, position of shovel for first insertion; C, shovel handle

pushed forward to break out soil behind blade; D, after pulling loose soil from hole,

the shovel is inserted a second time to make a firm vertical wall; E, tree roots are

placed against vertical wall, and loose soil pushed against them; F, hole is half

filled with loose, moist soil and firmed against roots with the foot; G, hole is filled

with soil and firmed about the tree with the feet.

HAND PLANTING

Hand planting, in contrast to machine planting,

makes it possible to give maximum individual attention to each planted tree. Detailed directions

are as follows.

All trash should be scraped off the planting

spot. Dig the hole deep enough to accommodate

most of the roots, leaving one side of the hole

smooth and vertical. Holding tree with one hand

at proper depth against the vertical side of hole,

throw in moist, loose soil against the lower root
42 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

system and pack fimily with tlie fist or heel. Continue to add loose soil (no trash) and pack firnily

until the hole is filled. Step on loose soil with

heel to settle it, and add more soil to fill flush with

surrounding ground. Kick a mulch of trash or

loose soil around the tree.

An improved method of hand planting, devised

by the Prairie States Forestry Project, uses a longhandled, round-pointed shovel with a straight

shank (fig. 3ß). With this method a minimum of

soil is moved and speed of planting is increased.

How To Cultivate and Protect Windbreak Trees

Failure to cultivate and protect windbreaks has

resulted in thousands of mediocre to worthless tree

plantings in the Great Plains. The presence of

such examples tends to discourage rather than

promote the planting of trees for windbreaks.

Lack of grass and weed control can completely

nullify the initial success of a good tree-planting

job using high-quality stock. This point has been

repeatedly emphasized in practically every bulletin, circular, news article, and leaflet written about

planting trees on the Plains. Reasons for control

of herbaceous vegetation were stressed in the section on land preparation. Vegetation control

after tree planting is just as important and is

covered in detail in this section.

In Plains tree plantations, protection measures

are as important as cultivation. Lack of protection against rodents, livestock, fire, insects, and

diseases can nullify in short order all previous care

in selection of trees, planting, and cultivation.

WHY CONTROL OF VEGETATION IS

IMPORTANT

Methods of vegetation control may vary, but all

are aimed at reducing the amount of herbaceous

plants likely to compete with trees for moisture,

and to prevent the shading and smothering of

trees by tall, overtopping herbaceous growth.

The importance of controlling herbaceous vegetation generally increases from the humid East to

the dry West. Results of experiments in South

Dakota showed that clean-cultivated trees after

four seasons, averaged over 3 feet taller, 1 inch

larger in diameter, and had more lower branches

than trees cultivated only once during a season.

The faster tree growth thus favored by clean cultivation made it possible to stop cultivation 1 year

earlier, because the trees crowns closed and shaded

out herbaceous vegetation.

Although the need for complete cultivation to

conserve moisture may be less in years of surplus

moisture, the need will remain to control weeds

and grass likely to overtop the trees. It is true

that during exceptionally windy weather, a moderate amount of herbaceous vegetation between

the tree rows is desirable to reduce the bad effects

of hot, drying winds on young trees. The area

immediately surrounding each tree, however,

should always be kept free of grass and weed

growth.

If a tree planting becomes thickly infested with

tall weeds and grass during the season, complete

removal of this vegetation surrounding the trees

during hot, dry weather is not recommended. The

sudden change of environment is usually too great

a shock for young trees. Therefore, in such a

situation, only the part of weeds overtopping the

trees should be removed. This can be done either

by high mowing or cutting by hand. Normally,

the mechanical control of weeds and grass is best

done while in the very young seedling stage. This

is much easier than trying to control large, coarse

weed growth, and it also conserves soil moisture.

Methods of Control

There are three ways to control unwanted vegetation in tree plantings. Chemicals sprayed or

applied dry at the proper time either inhibit seed

germination or kill the small seedlings of weed

species without damaging the trees. Mechanical

methods of cultivation cut the roots or tops of

weeds and grass, and kill them or reduce their

growth by either burying or throwing them on

top of the soil. Mulching wnth dead or processed

materials smothers weeds and grasses, stopping

growth.

Chemicals.—Recent tests using various chemicals in tree plantings have given excellent control of weeds and grasses, without injury to the

trees (fig. 37). Some tree species, however, are

more sensitive than others to herbicides. Chemicals can damage trees and therefore should be

used strictly as recommended. Soil type also influences the chemical effect and the rates recommended. Some injury to trees by chemicals may

be acceptable if no other control of herbaceous

vegetation is possible.

What to apply.—The chemicals simazine and

diuron have been tested for several years and are

effective through spraying treatment. Wettable

powders are better than dry or granular chemicals.

Weed growth stops when roots of newly germ-
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 43

Figure 37.^Scots pine plantation in midsummer in eastern Nebraska after chemical treatment in early spring.

weeds and grasses.

Tree rows remain free of

inated seedlings absorb the chemical. Some control is also effected by preventing the germination of seeds. Once sprayed, the treated area

should not be disturbed, since success of treatment depends on keeping the chemical in the surface 2 inches of soil. Most of the tree roots are

below this depth.

HoiD much to apply.—Recommendations for use

of simazine and diuron vary according to soil texture. For medium to heavy-textured soils, use 5

pounds of 80 ¡Dercent Avettable simazine powder or

4 pounds of wettable diuron per acre of area to be

covered. Sandy soils require a toeaher dosage because chemicals permeate them more rapidly. For

lighter textured sandy soils, use 2i/4 pounds of 80

percent wettable simazine, or 2 pounds of 80 percent wettable diuron per acre.

^Yhen to apply.—Chemicals should be applied

in the spring hefore weed seeds germinate. Application before a rain appears to be most effective.

If a week or two of dry weather follows application, the treatment loses much of its effectiveness,

because weeds begin growth before the chemical

reaches their root zone. If the weather is windy,

spraying should be postponed.

Hoto to apply.—A high-pressure sprayer giving

a constant pressure of 30 to 50 pounds and with a

"Teejet" No. 8002-E nozzle ^ is suitable. A backpack or a 2-gallon hand-operated sprayer with a

¡pressure gage can be used for small plantings (fig.

38). However, a power sprayer operating from

a f)miip on the tractor power takeoff and a container of 50 gallons capacity is recommended for

plantings of an acre or more. Agitation of the

solution is necessai-y since wettable powders tend

to settle. A bypass discharge into the bottom

^ Trademark, Spraying Systems Co., Bellwood, 111. The

identiflcation and description of commercial products in

tliis publication are solely for information purposes. Endorsement of any commercial product is not intended and

must not be inferred.
44 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

r-503717

Figure 38.—Backpack sprayer equipment for applying chemical to control weeds.

of the cliemical tank will provide agitation. All

screens should be 50-mesh or coarser.

The nozzle height should be adjusted to spray

an 18- to 20-inch swatli on each side of the tree

^o^y. The sprayer may be calibrated by determining the amount of water sprayed per acre at a

given rate of travel at constant pressure.

Cultivation.—Cultivation of tree plantings by

common farm equipment is best accomplished by

never allowing herbaceous vegetation to grow

large. Several cultivations will be needed during

each of the first two growing seasons. Fewer cultivations will be required as control of germinating weeds and grasses is accomplished. Equipment should be used in such a way as to keep the

soil fairly level, yet leave the surface in cloddy

condition for maximum wind erosion control and

absorption of moisture.

Rows of trees should not be ridged up as in corn

cultivation, because some trees, especially conifers, are sensitive to depth of soil around the stem.

Ridging often covers lower branches and inci'eases

likelihood of mechanical damage to the tree stem.

It also increases moisture runoff away from trees.

During the first year or two, tree rows may be

straddled by cultivation equipment. When the

trees are so tall that equipment whips the tree

crowns, it is best to cultivate on each side of tree

rows, destroying weeds as close to trees as possible

without hitting them.

Cultivation should be just deep enough to kill

weeds and grass. Cultivation deeper than 5 or 6

inches will interfere with tree root development.

If the planting has been cultivated in early season and growth of herbaceous vegetation is well

under control, any new growth of weeds or grass

after mid-August should be left standing. Late

cultivation of the trees has a tendency to sustain

growth into the fall, making some species more

susceptible to winter injury. As previously mentioned, the presence of some herbaceous vegetation

will furnish protection to trees and soil during

winter.

With moderate (10- to 14-foot) tree-row spac-
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 45

ing, cultivation after 8 to 10 years will no longer be

feasible or necessary. The tree crowns will close

together between rows; shading and accumulation of leaf litter will reduce weed growth until

little herbaceous vegetation remains. Crown

closure between rows will take longer when wider

spacings of 16 feet or more between rows are used.

The wider the row spacing, the more years cultivation will be required. Clean cultivation of a

strip of land on all sides of each tree planting is

recommended for all times as a protection against

wildfire.

A single-row cultivator is recommended by the

South Dakota extension forester as the best allaround implement for maintaining tree plantings.

Finger-type weeders for "over-the-row" cultivation while trees are small, are favored in the

Dakotas. Two-row cultivators, spring-tooth harrows, duckfoot cultivators, sweeps, and disk harrows are recommended and usejful under various

conditions (fig. 39, A). Sweeps and disk harrows

are required to clear thick stands of large weeds

in tree plantings. A single-disk is not recommended, however, because it ridges the soil toward

the tree rows. Spring-tooth harrows are useful

only for small seedlings of weeds and grasses.

Cultivation between trees in the rows, where

ordinary farm implements cannot work, requires

special care. Cultivation is not necessary if the

vegetation is chemically treated or frequently

hoed or mowed. However, special cultivators can

be purchased or constructed for this purpose. A

grape-hoe implement that is pulled by or swings

in and out from the side of the tractor works well

for controlling vegetation between trees in the

rows (fig. 39, S). For the extra touch that gives

trees the best opportunity to grow and develop,

there is no substitute for hoeing around each tree

with a hand hoe.

Mowing.—In normal to wetter seasons and especially in the eastern Plains, mowing instead of

cultivation between the rows may have some advantages. Mowing tends to favor establishment

of grass while reducing weed populations. A

grass cover of summer annuals, controlled by

mowing between tree rows, will reduce damage

from water erosion on sloping land. This is a

good practice when combined with chemical control of vegetation in the tree rows.

Mowing can be a substitute for cultivation only

under especially favorable conditions. As the

trees reach 3 to 4 feet or more in height, the danger of overtopping by weeds is less. At this point

mowing between tree rows can take the place of

cultivation as long as sufficient moisture is available in the soil. However, if soils become extremely dry owing to presence of deep-rooted

perennial grasses, cultivation rather than mowing

should be practiced, even in older plantations.

Mulching.—Mulching is not generally recommended for control of coarse weeds in tree plantings. To be effective in controlling weeds, the

mulch must normally be 6 to 10 inches deep, and

thus a source of mulching materials from other

than the tree planting area is required. However, the mowing and mulching of coarse grasses

has often been used successfully to retard growth

of vegetation. Vegetation mowed and allowed to

remain in place can make an effective mulch.

There are some disadvantages to mulching for

vegetation control. In the northern Plains, thick

mulches encourage large populations of small rodents which girdle trees during winter. Heavy

mulches tie up soil nitrogen as they decompose.

The organisms that break down the cellulose of

mulch materials require large quantities of nitrogen and therefore leave less available for the trees.

WHY PROTECTION IS IMPORTANT

Trees established in the Plains by planting or

natural means are normally subjected to greater

stresses in moisture, temperature, and wind than

trees in naturally forested areas. These extremes

of environment often damage trees. Furthermore, damaging agencies such as livestock, rodents, fire, insects, disease, and chemical weed

sprays may put additional restrictions on tree

growth unless the trees are given protection

against these agencies.

Tree establishment in the Plains is much too

difficult and costly to allow animals or plant pests

to nullify early successes. As previously mentioned, tree planting is a long-term investment.

Positive protective action against damage can be

a major item in the protection of that investment.

METHODS OF PROTECTION

Methods of protection vary according to the

damaging agency. Protection from grazing,

browsing, or trampling by livestock is effected

simply by fencing the tree plantation to keep

livestock out of it. Protection from insects or

diseases, on the other hand, is often difficult and

costly, since chemicals, sprayers, saws, axes, and

other equipment may be required. Treatments

must frequently be repeated to be fully effective.

Protection from volatile chemicals used to control

weeds in agricultural crops is a problem that can

be solved only on a community basis. Application of herbicides by field sprayers or aircraft

should not be done during windy weather, when

the chemical is likely to drift across tree plantings.

Livestock Damage.—When tree plantations or

windbreaks are open to use by livestock or are

fenced for use by livestock, damage to soil, tree

growth, and windbreak effectiveness is the result

(fig. 40). Cattle and horses browse the foliage

from lower limbs, break off small trees, trample

young seedlings, and compact the soil.
46 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

SCS-1B49, 17S1

Figure 39.—Well-maintained farmstead windbreaks in central Nebraska: A, Cultivation by disk harrow.

B, Cultivation close to trees by grape and berry hoe plow.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 47

lissa/l

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Figure 40.—Windbreak plantings damaged by livestock browsing. The lower levsl foliage has been destroyed. The soil has been

compacted and is almost impermeable to water.

Soil porosity and water infiltration are reduced

and runoff increased. Wind velocity through the

wmdbreak is increased near the ground and efficiency of protection on the leeward side is reduced. Shrubby species less than 4 feet tall are

usually hedged back to the ground.

Damage by lives<^ock may be temporary. A

moderately browsed tree plantation can be expected to recover in 10 years if livestock are kept

out. However, if extremely heavy browsing has

killed all shrubs, the lower level of the windbreak

will usually remain inadequate in foliage density

for many years.

Rodent Damage.—Damage by rabbits, mice,

ground squirrels, and gophers is usually most

severe when trees are young. Occasiorially a new

planting is so hard hit by rodents that complete

replanting is necessary.

In some winters, mice will girdle the bases of

larger trees beneath the snow. Rabbits often

girdle or debark the limbs of some species up to

whatever height the snow surface reaches. Rabbits and ground squirrels frequently chew off the

tops of 1-year-old conifers.

Control of rodents should be started the winter

before tree planting and continue through the

first season, if the rodent population is known to

be high. Although shooting, trapping, and chemical repellents all help to reduce damage, the most

satisfactory control method is use of poison baits

containing strychnine or arsenic. Recommended

formulations of poison compounds and techniques

of baiting can be obtained from the county agents

and local Soil Conservation Service personnel.

Strychnine alkaloid mixed with a starchy paste

or with alfalfa meal has been particularly effective. Care should be taken to place these baits

where domestic animals cannot reach them. Dead

rodents should be gathered up and buried so that

dogs and other tame animals cannot reach them.

Insect Damage.—Insect populations can often

build up to damaging proportions before the landowner is aware of the problem. Frequent inspections and alertness in recognizing insect damage

in early stages are the main items in an effective

protection program.

Insects must first be identified, then a careful

check made to determine the extent of the infestation. Assistance should be sought from county

agentSj extension entomologists, and forest entomologists for identification and recommended

controls.

Insect damage to trees and shrubs may be

grouped into the following categories, depending

on plant parts usually affected and the feeding

habits of the insects: (1) Leaves eaten, mined, or

galled; (2) buds, shoots, twigs, or flowers damaged; (3) main stem or large branches girdled,

weeviled, or bored ; (4) sucking of sap from leaves,

twigs, branches, or bark.

The leaf eaters are the most common insects

attacking trees in the Plains region. Many of
^o U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

them are o-eneral feeders, likely to occur on any Sap-feeding insects such as scales, mealybugs,

tree and shnib species. For example, tlie spring aphids, and red spider mites are nearly always

and fall cankerwonns, hornwomis, tent cat«rpil- present in the Plains area. They feed on most of

lars webworms, bagworms, leaf beetles, and the trees and shrubs used in windbreaks. Nor-

<rrasshoppers may attack and damage many kinds mally the damage they cause is not serious, but

of trees and shrubs under epidemic conditions occasionally they get out of control with favorable

(fio-. 41). Normally most trees and shrubs can weatlier conditions for their increase and a lack

witiistand a single defoliation; they will soon of predators. Their effects are usually seen only

recover if weathei- conditions are favorable. for 1 or 2 years, after which natural enemies bring

Damage to buds, shoots, and twigs is usually about control. In addition to the four categories

more serious in its effect than defoliation, because listed above, there are root-feeding insects, chiefly

recovery is slower and trees are often defomied. the white grubs, which curtail root development

For example, the pine tip moth, a termmal shoot of established trees.

borer, causes extensive damage to ponderosa pines The following tabulation lists the common and

by killing new shoot growth and retarding height scientific names of the more important insects

and. crown development. causing damage to tree and shrub species used in

Insects attacking the main stems or large windbi-eaks in the central Great Plains. Thenumbranches of trees are even more damaging. Cot- bers 1, 2, 3, and 4 denote the category of insect

tonwood borers, roundheaded and ñatheaded damage as given above,

borers, and carpenter worms frequently kül outright some broadleaf tree species. Pines and red- Cottonu-ood, poplar, and willow

cedars are not often attacked by borers or bark i Cottonwood leaf beetle Chrysomela scripta

beetles except during extremely dry periods. l Spring eankerworm Paleacrita vern-ata

Other serious pests which girdle the main stems ] í'a.V, <-aiikerworm AUophila pometaria

j. iii-iiiii j 1 Willow leaf beetle Chrysomela tnterrupta

of smaller trees mclude the cutworms and army- ^ Cottonwood dagger moth... Acrcmicta lepusculina

worms. 1 Eastern tent caterpillar Malacosoma ameriGonum

Figure 41.—Defoliation of caragana shrubs by grasshoppers.

1-386778
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 49

Cottonwood, poplar, and willow—Continued

1 Fall webworm Eyphantria cunea

2 Twig girdler Oncideres oingulata

3 Flatheaded apple tree Ohrysohothris femorata

borer.

3 Cottonwood borer Plectrodera scalator

3 Poplar borer Saperda calcarata

4 Poplar stem gall aphid Pcmphujus popidicaulis

4 Poplar petiole gall aphid--- Pe/)¡p?iií;Mí popuUtiunnversus

4 Poplar vagabond aphid Mordwilkoja vagabunda

American elm

1 Elm sawfly Cimhex americana

1 Mourning-cloak butterfly— Ni/mphalis antiopa

1 Spring cankerworm Paleacrita veníala

1 Fall cankerworm Alsophila pometaria

1 Elm leaf beetle Oalerucella luteola

2 Twig pruner HypennaUus villosus

3 Smaller European elm bark Scolytus multistriatus

beetla

3 Ehn borer Saperda tridentata

3 Flatheaded apple tree C'hrysohothris femorata

borer.

4 Elm cockscomb gall Colopha ulmicola

4 Woolly ehn aphid Eriosoma americanum

4 Scurfy scale Chionaspis furfura

4 European elm scale Oossyparia spuria

4 ELm scurfy scale Clnonaspis »mericana

4 Oystershell scale Lepidosaphes ulmi

Siberian elm

1 Fall webworm Hypliantria cunea

Bur oak

1 Green-striped mapleworm-. Anisota rubicunda

2 Oak twig pruner HypermaUus viUosus

2 Twig girdler Oncideres cingulata

3 Flatheaded apple tree Chrysobothris femorata

borer.

4 Oystershell scale Lepidosaphes ulmi

Oreen, ash

1 Great ash sphinx Sph inx chersi.^

1 White-lined sphinx Celerio lineata

3 Ash and privet borer Tylanctus bimaciilatus

3 Eastern ash bark beetle Leperisinus aculeatus

3 Carpenterworm Prionoxystus robiniae

3 Ash borer Podosesia syringae fraxini

4 Oystershell scale Lepidosaphes ulmi

Hackberry

1 Blackberry nipple gaU Pachypsylla celtidis mamma

1 Mourning-cloak butterfly Nymphalis antiopa

2 Twig pruner HypermaUus villosus

3 Flatheaded apple tree Chrysobothris femorata

borer.

4 Oystershell scale Lepidosaphes ulmi

Honeylocust

1 Blister beetle Epicauta spp.

2 Twig girdler Oncideres cingulata

3 Honeylocust borer Agrilus di-ffioilis

Black walnut

1 Walnut caterpillar Datana integerrima

2 Twig pruner HypermaUus villosus

3 Matheaded apple tree Chrysobothris femorata

borer.

4 Scurfy scale Chionaspis furfura

Boxelder

1 Boxelder bug Leptocoris trivittatus

1 Fall webworm Hyphantria cunea

1 Cecropia moth Hyalophora cecropia

1 Green-striiied mapleworm-. Anisota rubicunda

2 Boxelder twig borer Proteoteras willingana

3 Flatheaded apple tree Chrysobothris femorata

borer

4 Boxelder aphid Periphyllus negundinis

4 Oystershell scale Lepidosaphes ulmi

Garagana

1 Grasshopper Melanoplus spp.

1 Caragana blister beetle Epicauta subglabra

1 Nuttall blister beetle Lytta nuttallii

1 Alfalfa caterpillar Colias eurythema

American plum

1 Variable oak leaf cater- Heterocampa manteo

pillar.

1 Eastern tent caterpillar Malaoosoma americanum

Ghokecherry

1 Prairie tent caterpillar Malacosoma lutescens

1 Leaf webber Archips spp.

1 Fall cankerworm Alsophila pometaria

1 Eastern tent caterpillar Malacosoma americanum

1 Fall webworm Hyphantria cunea

Lilao

3 Lilac borer Podosesia syringae

syringae

4 Oystershell scale ' Lepidosaphes ulmi

Eastern redcedar and Rocky Mountain juniper

1 Bagworm Thyridopteryx ephemeraeformis

3 Eastern juniper bark Phloeosinus dentatus

beetle.

4 Red spider mites Tetranychus spp.

Ponderosa pine

1 Red-headed pine sawfly— Neodiprio-n lecontei

2 Nantucket pine tip moth— Rhyacionia frustrana

bushnelli

2 Pine tip moth Phyacionia neomexicana

3 Red turijentine beetle Dendroctmius valens

3 Ponderosa tn'ig moth Dioryotria ponderosae

4 Pine needle scale Phenacaspis pinifoliae

Austrian pine

3 Ponderosa twig moth Diorycfria ponderosae

4 Pine needle scale Phenacaspis pinifoliae

Scots pine

2 Nantucket pine tip moth— Rhyacionia frustrana

bushnelli

3 Ponderosa twig moth Dio-ryctria ponderosae

4 Pine needle scale Phenacaspis pinifoliae

4 Pine tortoise scale Toumeyella numismaticum

Jack pine

2 Nantucket pine tip moth— Rhyacionia frustrana

bushnelli

3 Ponderosa twig moth Dioryctria ponderosae

4 Pine tortoise scale Toumeyella numismaticum

Shortleaf pine

2 Nantucket pine moth Rhyacionia frustrana

3 Bed turpentine beetle Dendroctonus valens
50 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Disease Damage.—Trees infected by diseasecausing organisms are more likely to be killed when

weakened by extreme drouth than if maintained

in vigorous condition by irrigation and cultivation.

However, disease-causing organisms can attack

and kill perfectly healthy trees. As with insect

damage, prevention is better than the cure; and

early detection is of paramount importance. Frequent examination of tree stands should be followed up, if diseases are suspected, by a request for

aid from the county agent. Extension plant pathologist, or from a plant pathologist at one of the

Forest Service Experiment Station offices at

Lincoln, Nebr., and Bottineau, N. Dak.

Diseases are generally of three types, affecting :

(1) Foliage, (2) stems and branches, or (3) roots.

Organisms causing foliage diseases may become

established on many of the tree and shrub species

used in windbreaks. These organisms may reduce

the area capable of photosynthesis by penetrating

and ultimately killing the leaf tissues. They can

also enter the leaf petioles and move into the vascular system, thus killing the entire leaf. Cedar

blight fungus enters through the leaves, then

works into the small twigs, girdling them.

Leaf rust fungi, which often depend on an alternate host to maintain their life cycle, are fairly

common on many tree species in the Plains region.

Cottonwood leaf rust, green ash rust, and cedarapple rust are examples of diseases caused by these

fungi. Cottonwood leaf rust can also persist in

the absence of an alternate host.

Other foliage diseases such as needle cast and

the needle and twig blights frequently build up to

epidemic conditions on ponderosa, Austrian, Scots,

and other pines during warm, humid weather.

Several consecutive years of heavy infection by

these diseases can seriously weaken tr^es.

Stem and branch diseases are generally more

severe than foliage diseases in their effect on tree

gro'wth. They frequently affect the vascular (conducting) system and consequently cut off the movement of water from roots to leaves. When tliis

happens the entire tree or large portions of it wilts

and dies. Dutch elm disease, phloem necrosis, and

Dothiorella wilt are examples of stem and branch

diseases on elms. Diplodia on Russian-olive

causes wilting and death of stems and branches.

Wood-rotting fungi frequently enter trees

through wounds on the main stem and through

dead branch stubs. Although these fungi usually

do not cause death, they do weaken trees and subject them to easy breakage during wind and snow

storms.

Bacterial infection on the elms and some other

species causes wetwood (known also as slime-flux),

which brings about gradual deterioration of stems

and branches and sometimes death. Cytospora

canker, generally assumed to attack only weakened

trees, may be very severe on cottonwoods and

willows.

Root diseases, including those caused by nematodes, are often more difficult to diagnose than

diseases of above-ground tree parts. Root disease

fungi such as Fomes annosus and Phytophthora

species may occur in plantations of windbreak

trees, although little is known of the present distribution of these diseases. The cotton root rot

fungus Phymatotrkjhum oiwaivorum is present in

certain soils in Oklahoma and Texas and will kill

many species of trees planted on those areas. A

few tree species are somewhat resistant to this

rot.

The following tabulation lists the common and

scientific names and the symptoms of the most

common diseases that occur on the tree and shrub

species used in windbreaks in the central Great

Plains.

TREE AND SHRUB DISEASES

Cottonwood^ poplar^ and, willow

Poplar and willow leaf rusts. Melampsora spp.

SYMPTOMS: Yellow or orange powdery pustules on undersurface of leaves in summer. In

late summer or fall, small slightly raised orangeyellow areas appear, later turning dark brown to

black. Early defoliation if severe infection.

Leaf spot. Septorin spp. SYMPTOMS:

Small, angular brown spots, often with a pale

outer halo. Also causes bark cankers by infection in lenticels.

Leaf spot. Marssonina spp. SYMPTOMS:

Leaf spot and shoot blight. Spots usually most

conspicuous on upper leaf surface ; small, circular,

reddish brown with dark margin at first. Spots

may coalesce until entire leaf is affected.

Willow scab. Fusicladium saliciperdum.

SYMPTOMS: Olive-brown, velvety pustules

along main veins of lower leaf surfaces on willows. Young growing twigs often killed back to

previous season's growth.

Cytospora canker. Cytospora chrysosperma.

SYMPTOMS : Cankers are slightly sunken, round

to irregular areas on smooth bark of branches and

stem. Cankers often enlarge until stems are

girdled. Diseased bark becomes browTi and

sunken. Yellow to red spore tendrils appear on

dead bark during moist weather. Small branches

and twigs often die back without forming cankers.

Poplar canker. Dothichka populea. SYMPTOMS : Canker on branches and young stems,

which soon girdles and kills them.

Siberian el/m

Slime flux (wetwood). Envinia nimipressuralis. SYMPTOMS: Excessive sap flow from

crotches or wounds; bark turns grayish; wood is

water soaked. Dark brown streaks of discoloration appear in annual rings. Leaves may curl,

wilt, and drop if toxic sap is carried into branches.

Elm root rot. Chalaropsis thielavioides.
TREE WESTDBREAKS FOR THE CENTRAL GREAT PLAINS 51

SYMPTOMS: Grayish-white moldlike growth

on injured areas of roots. Outer tissues become

dark brown to black, and break down to a slimy

mass.

American elm

Dutch elm disease. Ceratocystü idmi. SYMPTOMS : Leaves wilt, curl, turn yellow, and fall

prematurely. In some trees only a few branches

wilt; in others entire tree wilts and dies in a few

weeks. Sapwood of wilted branches brown

streaked, appearing in cross section as dots in the

aimual ring. Evidence of elm bark beetles in

crotches of tree.

Pliloem necrosis. Virus. SYMPTOMS : Leaves

curl, droop, turn yellow or brown, and fall prematurely in June or July. On trees killed quickly

in 2 to 3 weeks, leaves merely wilt, turn brown,

and remain on tree. Inner bark, especially at base

of tree, turns butterscotch color and often smells

like wintergreen.

Ehn wilt. DotMorella ulml. SYMPTOMS:

Leaves wilt and young twigs die back. Wilt

spreads gradually downward through tree, sometimes killing it.

Verticillium wilt. Verticillium alho-atrum,.

SYMPTOMS : Leaves wilt suddenly and fall prematurely. Branches die back and contain brownish streaks, or broken rings of discoloration in cross

section.

Leaf spot (anthracnose). Gloeosporium, ulmicolum. SYMPTOMS: Elongated, raised leaf

spots along leaf veins.

Elm black spot. Onomonia ulmea. SYMPTOMS : Lesions appear on leaves, which usually

fall prematurely. Most serious during very moist

seasons.

Slime flux (wetwood). Erioinianimipressuralis.

SYMPTOMS: See Siberian elm.

Sycamore

Anthracnose. Onomonia, véneta- SYMPTOMS : Leaves turn brown as they expand in

spring ; leaves fall prematurely.

Honeylocust

Thyronectria canker. Thyronectrm austroamericana.. SYMPTOMS: Slightly depressed

bark cankers ranging from pinhead size to 14 vich

diameter, eventually enlarging or coalescing to

girdle the branch. Gummy exúdate occurs on

many cankers.

Northern catalpa

Basal canker. Unknown disease. SYMPTOMS : Large basal canker.

Oreen ash

Leaf spot (anthracnose). Oloeosporvmn aridum. SYMPTOMS : Large irregular brown spots

usually along leaf edge; leaves fall prematurely.

Ash rust. Piœcinia perldenniospora. SYMPTOMS : Leaves deformed and twigs and petioles

swollen. Fruiting bodies (aecia) on leaves,

petioles, and twigs soon after swelling.

Hackherry

Witches'-broom. Sphaerotheca phytoptopMla.

SYMPTOMS : Broomlike growths on twigs and

branches. Buds swell and open wider than normal, with bud scales distorted or enlarged. Shoots

from affected buds dwarfed and clustered, and

leader or long shoot fails to develop.

Bur oak

Oakleaf blister. Taphr'ma caerulsscens.

SYMPTOMS : Circular, raised, wrinkled, yellowish-white areas' up to i/^ inch in diameter on upper

leaf surface.

Oak wilt. Ceratocystis fagacearwm. SYMPTOMS : Leaves wilt and turn bronze in upper

crown; spreading from upper crown downward

and inward. Leaves color at apex and lobes first,

spreading to midrib and base. 'Single branches

most usually affected, with additional branches

each subsequent year.

Leaf spot (anthracnose). GTiomonia- véneta.

SYMPTOMS : Brown dead areas appear that follow veins to leaf edges. Some affected leaves are

curled. Leaves fall prematurely.

Boxelder

"Blight." 2, 4-D herbicides. SYMPTOMS:

Leaves on new shoots chlorotic and deformed.

Verticillium wilt. Verticillium. sp. SYMPTOMS : Leaves of single branches or one side of

crown wilt suddenly. Dark streaks appear in one

or more annual rings.

Russian-olive

Canker. Diplodia sp. SYMPTOMS : Leaves

wilt and turn light tan; branches die, and gum

frequently exudes from branches and stem. Roots

are killed.

Russian midherry

Slime flux (wetwood). Erioini-a nimipressuralis. SYMPTOMS : See Siberian elm.

Bacterial spot. Pseiidomonas mori. SYMPTOMS: Black lesions on leaf petioles and small

twigs.

Chokecherry

Western-x. Virus. SYMPTOMS : Leaves dull

to brilliant red in late July, early August. Following years' leaves are smaller and occur in

rosettes, and plants frequently die in third or

fourth year after infection.

Leaf spot, shot hole. Coccomyces lutescens.

SYMPTOMS : Chlorotic lesions on leaves; become

necrotic and often fall out. Severe infections

produce general blighting and leaves fall

prematurely.
52 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 260

Black knot. Dibotryon morbosum. SYMPTOMS: Hard dark swellings on branches; affected branches usually killed.

HonsysucMe

Leaf blight. Herpohasidhtm deformam.

SYMPTOMS : Leaves brown and usually rolled

or twisted.

American plum

Necrotic ring spot. Virus. SYMPTOMS:

Leaves contain very fine and pale circles and lines,

or may have yellow blotches, circles, or spots and

be tattered. New leaves show most symptoms;

young shoots often die back.

Brown rot. ScJerothiia frucHocola. SYMPTOMS : Blighted shoots. Cankers on branches.

Mummified fruit clinging to branches.

Plum pockets. Taphrina communis. SYMPTOMS : Fruits peculiarly enlarged and hollow,

containing a thin shell with no seed. Shoot tips

and leaves enlarge and are often twisted or curled.

Bacterial canker. SYMPTOMS: Cankers on

stems, often exuding gum.

Caragana

Leaf spot. Phyllosticta gaUm-um or Septorm

spp. SYMPTOMS: Small spots appear on

leaves; leaves fall prematurely.

Skunkhush suQiiac

Leaf spot. Septoria spp. SYMPTOMS:

Small spots appear on leaves; leaves fall prematurely.

Lilac

Powdery mildew. Mlcrosphaera alni. SYMPTOMS : "White, powdery appearance on leaf surfaces. Leaves become crinkled and distorted.

Bacterial blight. Pseudomoruts syringae.

SYMPTOMS: Dark, black stripes appear on

young shoots in early spring; spots may occur on

leaves ; immature leaves turn black and die ; flower

buds turn black.

Nanking chern'y

Leaf spot. Coccomyces hiem-ali<s. SYMPTOMS : See Chokecherry.

Necrotic ring spot. Virus. SYMPTOMS:

See American plum.

Bacterial canker. SYMPTOMS : See American

plum.

Ponderosa pine

Hard pine needle blight. Dothistroma pini.

SYMPTOMS: Slightly swollen dark spots or

bands appear in late summer on 1-year-old needles.

Distal ends of needles turn brown and die. Fruiting bodies protrude from leaf surface by May and

needles fall prematurely.

Pine twig blight. Diplodia pinea. SYMPTOMS : Newly elongating shoots are infected before needles are half grown. Needles cease

growth, turn brown, and die. Fruiting pustules

appear at needle base and on sheaths.

Western gall rust. Peridermium harknessii.

SYMPTOMS: Globose to pear-shaped galls on

branches. Large confluent aecia form on the galls

and witches'-brooms frequently form just above

the galls.

Austrian pine

Hard pine needle blight. Dothistroma pini.

SYMPTOMS : See Ponderosa pine.

Pine twig blight. Diplodia pinea. SYMPTOMS : See Ponderosa pine.

Scots pine

Western gall rust. Peridermium harknessii.

SYMPTOMS : See Ponderosa pine.

Hard pine needle blight. Dothistroma pini.

SYMPTOMS : See Ponderosa pine.

Pine twig blight. Diplodia pinea. SYMPTOMS : See Ponderosa pine.

Jack pine

Needle rust. Coleosporium solidaginis. SYMPTOMS : Conspicuous white fruiting bodies (aecia)

appear on needles in spring and summer.

Eastern redcedar and Rocky Mountain Juniper

Cedar blight. Phomopsis juniperovora.

SYMPTOMS: Foliage on branch tips becomes

light, then brown, and finally gray. Lesions form

on invaded stem tissue; small stems are girdled.

Fruiting bodies (pycnidia) appear on leaves and

stems.

Cedar-apple rust. GymnosporangiuTn juniperivirginianae. SYMPTOMS : Brown globoid galls

appear on branches. During moist weather in

spring, jellylike orange spore masses develop from

galls.

Many trees and shruis

(In certain areas of Oklahoma and Texas)

Cotton root rot. Phymatotrichum omnivorum.

SYMPTOMS: Areas in which root rot affects

plants are typically circular in shape. Seedlings

die suddenly ; older trees show gradual reduction

in growth and vigor, with leaves off color. Eoots

badly rotted, with shrunken and shriveled epidermis.
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 53

How To Manage Windbreaks

Management of windbreaks is the final step in

the series of practices beginning with hxnd preparation for trees and culminating in a system of

windbarriers that provide longtime effective protection for farmlands.

Good management of windbreaks has two general objectives: (1) To maintain and improve the

vigor and growth of individual trees and shrubs

for best foliage density and longevity, and (2)

to maintain and improve the structure of the

windbreak in its entirety so that it functions as

an effective barrier in reducing wind velocity.

Management should begin as soon as trees have

become well established and before any crowding

takes place. The time cannot be stated as a specific number of years after planting, because this

will vary according to rate of growth and spacing

between trees and rows. Under average conditions, however, the need for starting management

practices will probably arise between the 5th and

10th years after planting.

After 5 to 10 years of growth the faster growing trees, such as cottonwood and Siberian elm,

will be 20 to 30 feet tall and crowding each other

if planted 8 to 10 feet apart. The faster growing

shrubs will be 8 to 10 feet tall and tending to lose

their lower foliage.

As trees grow, the relationships among them

change. The density and position of tree crowns

change in relation to height above ground and

neighboring trees. Some changes are also brought

about rather abruptly when extreme drouth, cold,

insects, diseases, or fire offset tree stands. These

changes affect the structure of windbreaks, and

consequently modify their influence in reducing

wind velocities.

Good management attempts to anticipate these

changes by installing treatments to maintain and

constantly improve tree growth and windbreak

structure. For example, with severe crowding

the stress of competition for moisture and light

can cause rapid loss of vigor or death of trees.

One aim of management is to forestall such losses

by treating windbreaks before they lose -vagor.

Some specific objectives of windbreak management are described in the following section. These

include the most common problems encountered

in older windbreaks. Keeping the objectives in

mind, the manager should first examine the windbreaks carefully to assess their present condition.

If the vigor and growth of trees and shrubs appears to be declining, a thinning or release treatment may be needed. If foliage density of the

lower level is sparse, a cut and coppice treatment

or perhaps an interplanting is indicated. If the

windbreak is wider than necessary, treatments to

remove ineffective rows and to increase lower level

foliage density should be considered.

The "Methods of Management" described later

(p. 54) can be used to improve the growing conditions and structure of most windbreaks. These

methods will often provide a means for correcting

mistakes in composition, arrangement, or width.

OBJECTIVES OF MANAGEMENT

Relieve Crowding

Since windbreak trees are normally planted

rather closely together (6 to 10 feet) to form a

barrier as soon as possible, it follows that they

will begin to crowd one another after 15 to 20

years of age. This crowding should be relieved

to keep the trees most healthy and vigorous.

Some sijecies such as eastern redcedar can tolerate shaded and crowded situations. Others such

as cottonwood and pines require more space and

sunlight. Some species on being shaded and

crowded grow vei-y slowly and finally die. Others

remain alive though supjiressed, until the stand is

opened up by diseases, insects, or drought, at which

time they resume growth.

Certain signs of deterioration are evident in

trees suffering from shading, crowding, moisture

stress, etc. Some of these signs are loss of color,

loss of foliage particularly from the oldest

branches, thinning of the upper crowns, presence

of diseases and insects, and greatly reduced annual diameter growth of the stem. The incidence

of diseases and insects generally increases as conditions such as crowding and lack of moisture become more severe.

In many 20-year-old windbreaks the interior

tree rows, especially hackberry, honeylocust, and

Siberian elm, show extreme effects of crowding.

The signs are narrow crowns of low \'igor and the

presence of diseases and much dead wood. Under

crowded conditions Siberian elm appears to be a

rather short-lived species, insofar as maintenance

of good vigor is concerned. Thinning of interior

broadleaf rows will stimulate growth and increase vigor of the remaining trees. It should

result in increased foliage density in the middle

and upper levels of windbreaks.

Release Conifers

The suppression of pine and redcedar rows by

fast-growing broadleaf species, such as Russianolive, green ash, and boxelder, is a common problem in many field windbreaks in the central Great

Plains.

Since conifers are one of the most important

components of windbreaks in providing longevity

and effectiveness the year round, they should be

given special consideration in management.
54 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Release to provide growing space and to eliminate overtopping by adjacent rows of trees will

stimulate growth and increase the vigor of conifers. Redcedars apparently respond more quickly

to release than the pines. Release should be done

before crowding becomes severe, so that lower

branches of conifers are retained. Once suppression has killed lower branches of pines, they will

no longer produc« lower foliage density. Redcedars, on the other hand, can remain suppressed

for quite a time and still respond in growth of

lower branches.

Add Conifers

In many windbreaks having ineffective or no

conifer components, one of the major objectives

of management should be to add redcedars and

pines. These trees will enhance the effectiveness

of windbarriers during winter and early spring,

and will add longe^aty to all broadleaf plantings.

Wliile most broadleaf trees and shrubs will probably be adequate for snow control, they make poor

barriers for reduction of wind movement during

winter and spring when they are not in leaf.

The addition of several rows of conifers will

also help to offset any desired reduction in windbreak width. Because the foliage of conifers is

dense, windbreaks containing them need not be

so wide to be fully effective.

Modify Low-Level Density

As short trees and shrubs grow they tend to lose

their lower branches, especially if crowded. Since

the function of shrubs is to form a dense barrier

close to the ground, it is important that such

plants not be allowed to grow tall and spindly.

They should be cut back to the ground every 4

or 5 years, so they will sprout anew and provide

dense foliage close to the ground.

In windbreaks lacking low-level foliage because

of ineffective shrub rows or damage by grazing animals, the density may be increased by several

methods. Several broadleaf tree or shrub rows can

be cut to the ground and allowed to sprout. As

an alternative, new rows of shrubs or eastern redcedar can be planted witliin or on the outside of

the present planting.

When it is necessary to reduce low-level foliage

density to increase snow spreading effects, some

tree and shrub rows should, be cut and stumps

treated to prevent sprouting. Pruning the lower

branches of trees will also reduce low-level density.

Reduce Width

The desire to reduce windbreak width often

comes from the observation that a strip of land

adjoining the windbreak is not producing crops

because of shading and competition from trees.

In many cases windbreaks containing 10 or more

rows of trees and shrubs may be reduced in wádth

by cutting out certain rows that contribute little

or notliing to density and effectiveness of the barrier. When this can be done without changing the

windbreak structure appreciably, it is good practice.

In windbreaks containing eff'ective rows of conifers, usually the side opposite from the conifers

can be sacrificed to reduce width. However, rows

of trees which alone provide the height needed for

an effective barrier should not be cut. Examples

of resulting windbreak profiles when rows are cut

to reduce width are shown in figure 42.

CROSS SECTION

.-^A

mwMàn

10- row Dense lower level

MÙ

6- row

ííkk.

Permeoble lower level

^V^/-^,^^'\/~>

5- row

4 - row

Dense lower level

Open lower level

2- row Very open lower level

Figure 42.—Examples of windbreak profiles resulting when diffwent

tree rows are removed fo reduce widfh.

METHODS OF MANAGEMENT

Thinning and Release Cutting

Thinning and release cutting designed to alleviate crowding and to improve individual tree

growth and vigor may take different forms. One
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 55

method is the removal of single trees from around

individual trees to be favored with more space.

Another method is the removal of an entire row

of trees which is crowding a more desirable row

of trees (fig. 43, A).

It is not possible to recommend either one of

these methods of thimiing over the other, since no

experimental work has been done using the fonner.

However, the latter method, which is termed row

thinning, may be the easiest and most economical

of the two, since tree felling can begin at one end,

and proceed along each row with little difficulty

in the felling work. In removing single trees tlie

space for felling is more limited, and the chance

for damaging or hanging up trees greater.

To relieve crowding in windbreaks having two

or more rows of Siberian elm at close spacing, such

as 6 to 8 feet between trees, in rows 10 to 20 feet

wide, alternate rows should be removed (fig. 44).

In contrast to the thinning of interior rows of

broadleaf species, the release cutting of outer rows

to free conifers from overtopping is fairly simple.

If survival of conifers has been good despite

crowding, the overtopping tree rows should be cut.

If few conifers remain, no treatment is called for.

A^lien rows of pine are released, the stumps of

cut trees should be allowed to sprout to provide a

renewal of low-level density. Sprouts should

then be cut back everj^ 4 or 5 years to prevent

repeated crowding. In releasing redcedar from

overtopping trees, the stiunps of cut trees may be

treated with chemical to prevent sprouting. In

this instance, the redcedar crowns will thicken up

to provide low-level density, and there will be no

need to retain the broadleaf sprouts.

In any thinning or release treatment, removal of

enough trees to reduce crowding may drastically

change the structure of the windbreak. This is

especially true in older plantings that have grown

for 20 years or more with no previous management. In a crowded windbreak the lower foliage

of inner tree rows will have diminished to nothing,

and when trees are removed the result will be an

extremely porous windbreak of greatly reduced

F-503718, 719

Figure 43._A, A release cutting within c. windbreak »o free eastern redcedar from crowding by green ash. B, Stump sprouts of green

ash several feet tall, only 3 months after cutting the trees.
56 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Figure 44.—A row of Siberian elm within a windbreak cut to

release other Siberian elm rows for Increased growth and

vigor.

effectiveness for slowing wind. This situation

calls for one of the following special measures.

One way is to improve the lower level density of

the windbreak before thinning it. Outside rows

of shrubs or trees should be cut back to the ground

in the spring of the year. Thinning within the

windbreak can then follow 6 to 12 months later, at

which time the sprouts of cut trees or shrubs will

be dense enough to provide an effective lower level.

Another way is to add shrub or tree rows to one or

both sides of the windbreak several years prior to

thinning. Thus by putting management practices

into effect one step at a time, rather than all at

once, the density and continuity of a windbreak

can be maintained. It can continue to function

effectively throughout the period of silvicultural

work.

Coppicing

The cutting of trees and shrubs and management of their coppzce sprouts appears to be a very

effective method for controlling growth of laro-e

shrubby trees that overtop conifers, and at the

same time improving the lower level density of

windbreaks.

Nearly all broadleaf tree and shrub species used

in windbreaks in the central Great Plains will produce vigorous sprout growth when cut back to the

ground. Species such as Siberian elm, honeylocust, hackberry, mulberry, and green ash of 20

years age will grow sprouts 4 to 6 feet tall in one

growing season after cutting (fig. 43, B).

The regrowth of cut shriibs is generally much

thicker near the ground level than the previous

uncut plants, because many more stems are produced from the stump and from roots near the

surface. American plum, lilac, chokecherry,

honeysuckle, caragana, and tamarisk may all be

improved in density as shrub rows by this practice.

Trees originally planted to function as shrubs,

but which have grown to tree size, such as Russianolive, boxelder, mulberry, and osage-orange, may

also be improved if they are cut back to the ground.

With these species, however, cutting back must be

repeated every 4 or 5 years to maintain low foliage

density.

Interplanting

Where maximum wind reduction is desired, several rows of conifers should be added to broadleaf

windbreaks to strengthen the barrier density.

Eastern redcedar can be planted almost anywhere

within or on either side of well-established windbreaks, because this species can tolerate less light

and more crowding than other conifers. Pines

should be planted in a position of full sunlight to

make best growth.

Many field Avindbreaks with conifers only on the

south side are too open on the north side. Snow

blows through the barrier and forms drifts across

road rights-of-way leeward of the conifers.

These windbreaks need to be strengthened for

better snowdrift control by planting additional

conifer rows on the north side. In some cases, the

conifers can simply be planted as additional rows

north of the existing windbreaks. In other cases,

it is better to remove several rows of broadleaf

species on the north side before planting conifers.

All rows of newly established trees should be

maintained by the recommended cultivation methods for several years. WHien new tree rows are

planted within windbreaks, enough space should

allowed for cultivation equipment. Wlien this

is not possible, chemicals should be used to control

herbaceous vegetation.

Use of Natural Reproduction

In most well-established windbreaks that have

been protected from livestock use and fire, there

is an abundance of natural seedlings of various

tree and shrub species. Elms, ash, hackberry, lilac,

chokecherry, plum, boxelder, mulberry, honeylocust, black locust, and eastern redcedar ranging

from 1 to 10 years old are usually present. Seedlings have become established beneath the older
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 57

trees throughout many windbreaks, and especially

in the openings created by deteriorating, shortlived trees. This natural establishment of tree

seedlings in the understory of windbreaks will

help to maintain dense foliage in the lower level.

The undergrowth will also catch and hold more

snow for replenishment of soil moisture.

No research has been done to determine how

this natural growth should be managed. However, several possibilities are suggested until such

time as experimental results are available.

In windbreaks consisting of vigorous, moderate

to fast-growing established trees, the understory

reproduction need not be treated at all. It will

usually slow down in growth and remain in the

understory, to be utilized later on. On the other

hand, if the older trees are beginning to deteriorate, it may be desirable to stmiulate growth of

the understory to take the place of the dying

trees. This can be done in two ways:

(1) Manage the understory trees in row-wise

fashion by cutting out all saplings except those in

a row between the existing rows.

(2) Manage the understory trees as forest reproduction by selecting and favoring the best trees

and cutting all the remaming understory.

Either of these alternatives or modifications of

them will be necessary in windbreaks to be developed from a naturally established understory.

Lacking any treatment, the natural reproduction

is likely to grow very slowly, lose its lower foliage,

and develop into spindly, sparse-crowned trees of

little value for windbreaks.

Pruning

Many windbreak owners have pruned the lower

branches of trees, especially conifers, with the idea

of improving their appearance. Pruning may improve the appearance of individual trees, but it

reduces the wind-breaking ert'ectiveness of plantings. In a windbreak, trinnning trees from below very often defeats the purpose for which the

windbreak was established.

Since the primary purpose of windbreaks is to

provide control of wind movement through density and height of foliage, the removal of limbs

and tree parts by pruning should not generally

be done. Pruning is recommended only to accomplish certain objectives, for example, as a special sanitary measure to reduce incidence of

diseases. Such a practice should be adopted only

on advice from tree disease specialists.

Another possible reason for pruning, however,

is to create an open lower level to obtain better

snow distribution. This practice is applicable only

where the main objective is to produce barriers

for snow distribution rather than maximum wind

control. However, even in the northern Plains

where better snow distribution on adjacent fields

is an important function of windbreaks, tree barriers are planted primarily for maximum reduction of soil blowing and protection of crops during

the growing season. Pruning therefore should be

done only in special cases where advised by windbreak technicians.

If pruning is needed, the branches should be

cut with a saw close to the trunk. Pruning is best

done in spring just before growth starts. This

will favor rapid callusing and wood growth over

the wound. Prune Siberian elm in summer, however, to reduce occurrence of wetwood. Protect

large wounds (more than 2 inches diameter) by

covering with an asphalt paint.
Appendix

EXAMPLES OF EFFECTS OF WINDBREAKS ON FIELD ENVIRONMENT

Air and Soil Temperatures

1. Daytime air temperatures 1 foot above

f^round with a strong south wind were up to 6° F.

Avarmer in the 0 to 4 H leeward zone and up to

5° F. cooler in the 4 to 25 H leeward zone compared to open field temperatures.

Nighttime air temperatures were up to 3° F.

warmer in the 0 to 25 H leeward zone than in the

open.

Type: Moderately dense, lO-row field windbreak 120 feet

wide and 25 feet tall with south sloping cross section.

Season and year: July and August, li).")H.

Place: Central Kansas, U.S.A.

Reference: Woodruff, Read, and Chepil, 19.59.'

2. Air temperatures near the ground averaged

2° to 3° F. cooler on oat fields between windbreaks than on oat fields in the open on hot days.

Air temperatures were up to 4° F. warmer in

protected oat fields than on oat fields in the open

on cool days and during the night.

Air temperatures on fallow fields between windbreaks were not significantly different than on

fallow fields on the open steppe.

Type: Series of parallel field windbreaks.

Season and year: 4-year study in summer, 1950's.

Place: Kamennaya Steppe, Russia.

Reference: Molchanov, 1956.

3. Daytime air temperatures averaged 5° to 6°

F. warmer 4 inches above ground, and 1° to 2°

warmer 4 feet above ground 0 to 10 H leeward

than on open fields.

Type: Series of narrow oak coppice windbreaks, 15 feet

to 45 feet wide at 160-foot intervals.

Year: 1940's.

Place: Holland.

Reference: Linde and Woudenberg, 1951.

4. Summer air temperatures averaged lower,

and winter temperatures averaged higher between

windbreaks than on open, unsheltered fields.

' See Literature Cited, p. 65. Additional references on

the variou.s subjects covered under examples of effects

can be found in a "Bibliography of Great Plains Forestry," published in May 1961 as Station Paper 58 by the

Rocky Mountain Forest and Range Experiment Station

of the Forest Service, U.S. Department of Agriculture.

Refiuests for this bibliography should be addressed to the

Director of that Station at Ft. Collins, Colo.

58

Type: Series of parallel windbreaks.

Season and Year: Summer, 1930's.

Place: Germany.

Reference: Nageli, 1941.

5. Air temperatures on cool, windy mornings

and afternoons were 3° to 7° F. warmer between

strips than on tlie open field.

Type: Series of 2- to .5-foot-wide strips of com, winter

rye, and sunflowers at 15- to 25-foot intervals.

Season and Year: Sunmier, 1950's.

Place: Russia.

Reference: Gotovcev, 1957.

6. Soil temperatures on cool, windy mornings

and afternoons were 3° to 5° F. warmer at 4-inch

depth, and 2° to 3° warmer at 8-inch depth between strips, than on the oi>en field.

Type: Series of 2- to .5-foot-wide strips of com, winter

rye, and sunflowers at l.> to 2.5-foot intervals.

Season and Year: Summer, 1950's.

Place: Russia.

Reference: Gotovcev, 1957.

7. Soil temperatures at 20-inch depth were 3°

F. cooler at 0.5 H leeward and about 1° wanner

at 2 H leeward than in open during spring and

summer. They were 3° to 5° cooler at the same

locations during fall and winter.

Type: Dense, cottonwood windbreak, 50 feet tall.

Year: Early 1900's.

Place: Nebraska, U.S.A.

Reference: Bates, 1911.

Atmospheric Humidity

8. Average monthly relative himiidity was 2 to

3 percent higher during the day on oat fields between windbreaks than on oat fields of the open

steppe.

Relative humidity was 4 to 5 percent higher on

protected fields of oats than on open steppe oats on

hot summer days.

Relative humidity was 2 to 3 percent higher on

protected fallow fields than on open steppe fields

of fallow fields.

Type: Series of parallel field windbreaks.

Season and Year: 4-year study in summer, 1950's.

Place: Kamennaya Steppe, Russia.

Reference: Molchanov, 1956.

9. Average relative humidities during growing

season :

April May June July

Protected fields 66.0 57.9 45.0 .50.4

Open steppe 63.0 54.7 42.3 47.6
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 59

Type: Series of field windbreaks.

Season and Year: Summer, 1946-^8.

Place: Astrakhan, Russia.

Reference: Kas'yanov, 1950.

10. Average relative humidity was 8 percent

higher in fields between windbreaks than on open

prairie.

Eelative himiidities averaged 11 percent higher

between windbrealvs than on open prairie in tlie

morning liours.

Type: Series of field wimlbreaks.

Season and Year: Summer, 1933.

Place: Russia.

Refei-ence: Sokolova, 1937.

11. Relative humidities ^vere over 80 percent

during lialf the growing season in the sheltered

area. In contrast, they exceeded 80 percent for

only one-third of the growing season in the open

area. Midday humidity averaged 2 to 4 percent

higher in shelter than in the open.

Type: T\\-o 7-foot-tall slat (snow fence) barriers oriented

east-west and .JO feet apart.

Season and year: May to August, 19.59.

Place: Central Nebraska, U.S.A.

Reference: Bagley and Gowen, 1962.

12. Average relative humidity 1.5 feet above

soil on days of greater than 50 percent liumidity

was 62 percent at 0 to 6 H leeward and 60 percent

at 12 to 30 H leeward, compared to 57 percent on

the open prairie.

Eelative humidity was 45 percent at 0 to 6 H

leeward and 40 percent at 12 to 30 H leeward,

compared to 38 percent on the open prairie, on

days of less than 50 percent humidity.

Type: Field windbreaks 30 feet wide and ^50 feet tall.

Season and year: Summer, 1934.

Place: Rostashi, Russia.

Reference: Bodrov, 1933.

13. Dewfall was 200 percent greater on fields

protected by windbi-eaks than on open fields.

Heaviest dew was in the 2 to 3 H leeAvard zone.

Season and year: Summer, 1940's.

Place: Germany.

Reference: Steubing, 1952.

Evaporation

14. Windbreaks reduced e\aporation and increased soil moisture in the 0 to 30 H sheltered

zone as compared to open, unsheltered areas.

Type: Series of 30- to 40-foot-tall field windbreaks at

1,300- to l,6(X)-font intervals.

Season and year: Summer, 1930.

Place: Russia.

Reference: Kalashnikov, 1953.

15. Nonproductive evaporation (from soil) was

27 percent less on sheltered fields than on the open

steppe.

Productive evaporation (transpiration) was 22

percent greater on sheltered fields than on the open

steppe.

Type: Series of 2-row, 30- to (iO-foot-tall poplar windbreaks at tiOO-foot intervals.

tieasoH and year: Summer, 19.33.

Place: Traiii^-Volga, Russia.

Reference: L'vovic-h, 19.^4.

16. Evaporation during hot days was less on

fields between windbreaks than on open fields.

Type: Series of parallel field windbreaks.

Season and Year: 4-year study in summer, 1930's.

Place: Kamennaya Steppe, Russia.

Reference: Molehanov, 1956.

17. Evaporation rates leeward of windbreak

compared to open field were :

40 percent at 5 H

60 percent at 10 H

80percentat20H

Same as open at 25 H

Type: Windbreak of Japanese Black Pine, 5 feet tall and

20 feet wide.

Year: 1940's.

Place: Jaixui.

Reference: lizuka and others, 1930.

18. Evaporation from water surface was 15 percent less at 4 H leeward and 9 percent less at 16 H

leeward than in open.

Type: Series of parallel 3-row, 20-foot-tall windbreaks at

640-foot intervals.

Season and Year: May-September, 1031-34.

Place: Saskatchewan, Canada.

Reference: Staple and Lehane, 1935.

19. Evaporation rate at 2 to 10 H leeward of

open-type windbreaks was 80 percent of open field

evaporation.

Evaporation rate in the same zone leeward of

dense-type windbreaks was only 40 to 65 percent

of open field.

Type: 50-foot-taH eottonwood windbreaks of different

densities.

Year: Early 1900's.

Place: Nebraska, U.S.A.

Reference: Bates, 1911.

20. Evaporation from the soil layer 0 to 8 feet

deep was reduced by 2 to 2.5 percent in the 0 to 5 H

leeward zone compared to open field with AA-ind

from the south.

Evaporation from the same soil layer was increased by 2 to 3 percent in the 0 to 2 H windward

zone under the same south wind.

Type: Various types of field windbreaks.

Season and Year: Summer, 1936-38.

Place: Kansas and North Dakota, U.S.A.

Reference: Bates, 1948.

Snow Distribution

21. Average depths during 3 yeai'S of heavy

snowfall were :

26 inches near barrier at 0 to 6 H

7 inches on stubble at 25 H

3 inches on summer fallow at 25 H

Average depths during 2 years of medium snowfall were :
60 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

15 inches near barrier at 0 to 3 H

4 inches on stubble at 25 H

3 inches on summer fallow at 2.5 H

Type: Series of parallel barriers consisting of l-row

caragana hedges 8 feet tall and 3-row field windbreaks

25 feet tall.

Season and Year: Winter 1950-52 (heavy) and winter

1953-54 (medium).

Place: Manitoba and Saskatchewan, Canada.

Reference: Staple and Lehane, 1955.

22. Snow depth was gTeater and freezing depth

was less in sheltered area as compared to open

fields. As a result, soil moisture was increased in

the 0 t-o 20 H leeward zone, with maximum soil

moisture adjacent to windbreak.

Type: 12- to 16-year-old field windbreaks, 16 to 20 feet tall.

Season and Year: Winter, 1949-.50.

Place: Russia.

Reference: Dauitov, 1953.

23. Distribution of snow was very uneven on

leeward field with large drifts in zone nearest

windbreak.

Snow was blown off the leeward field in the

240 to 600 feet zone, and in this zone freezing

was deeper and moisture supply lower than where

covered by snow.

Type: Multirow field windbreaks, 3 to 5 years old.

Place: Rostov, Russia.

Reference: Garjugin, 1955.

24. Water content of snow was 4.9 inches in

sheltered fields compared to only 2.2 inches on

open, unsheltered steppe.

Type: Series of 2-row poplar windbreaks, 50 to 60 feet

tall, and at 600-foot intervals.

Season and year: Winter, 1953.

Pla-oe: Trans-Volga, Russia.

Reference: L'vovich, 1954.

25. Coefficient of snow blowoff (blowoff as percent of total fall) was 6 percent on fields surrounded by tree windbreaks compared to 68 percent on open land.

Type: Pattern of field windbreaks.

Season and year: Winter, 1930's.

Place: Kamennaya Steppe, Russia.

Reference: Panfilov, 1937.

Soil Moisture and Runofif

26. Moisture content of top 3 feet of soil was

25 to 30 percent higher in the 10 to 12 H leeward

zone than on open, unsheltered fields.

Type: 5-row field windbreaks, 33 feet tall.

Season and Year: Early summer, 193n's.

Place: Vladimir, Russia.

Reference: Banasevieb and Zakharov, 1940.

27. Moisture content of soil was high on fields

in protection area of windbreaks compared to low

moisture and drouth experienced on unprotected

fields.

Type: Series of field windbreaks

Year: 1946--17.

Place: Kamennaya Steppe, Russia.

Reference: Bumatski and Suchalkina, 1949.

28. Moisture content of top 3 feet of soil was

20 percent less in the 0 to 2 H sheltered area in

vineyards than in the open. But it was 25 to 30

percent more in the 10 to 12 H zone than in the

open, and was the same at 20 H.

Place: Russia.

Reference: Masinskaja, 1950.

29. Four to eight inches more water was stored

in the soil profile beneath the trees in windbreaks

than in the soil of the fields betweerj windbreaks.

Type: Series of field wdndbreaks.

Place: Russia.

Reference: Karandina and others, 1956.

80. Soil moisture in the 0- to 6-inch surface

layer was 13 percent greater on sheltered fields

than on open, unsheltered fields. There was up to

23 percent more moisture in the profile of sheltered

fields as compared to open fields.

Type: Black locust windbreaks.

Place: Rumania.

Reference: Catrina and Marco, 1955.

31. Soil moisture was depleted to 4 feet deep by

tree roots in the 0 to 2 H strip leeward of windbreaks. Moisture was 12 to 15 percent greater in

the 0 to 2 H strip when isolated from tree roots by

trenching.

Season: End of summer.

Place: Rumania.

Reference: Georgescu and others, 1954.

32. Soil moisture 0 to 2 feet deep was less under

trees and at edges of windbreak than in the open

field.

Type: Austrian pine windbreak, 20 feet tall and 98 feet

wide, with no undergrowth.

Soil moisture 0 to 2 feet deep was greater in the

0 to 20 H sheltered zone than in open fields.

Type: Chestnut windbreak, 13 feet tall, with dense undergrowth.

Soil moisture 0 to 2 feet deep was greater in the

sheltered zone of 700 feet between a windbreak and

forest area than on open, unsheltered fields.

Type: Ash and alder windbreak 65 feet tall and 200 feet

wide, with dense undergrowth.

Year: 1940's.

Place: Obristvi, Vinor, and Pisty, Bohemia.

Reference: Maran and others, 1950-51.

33. Moisture in surface 4 feet of soil was 3t/^ percent greater in the 0 to 5 H sheltered zone than in

the 10 to 20 H zone.

Frost depth under 3 feet of snow was only 0 to

4 inches in the 0 to 5 H sheltered zone compared

to 24 inches on open, unsheltered fields.

Type: Field windbreak 24 feet tall.

Year: Dry year of 1936.

Place: Great Plains, U.S.A.

Reference: Stoeckeler and Dortignac, 1941.

34. Runoff on an area with 6 percent of land in

field windbreaks was reduced to 43 to 63 percent

compared to runoff on open steppe. With 18 per-
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 61

cent of land in field windbreaks runoff was

reduced to 25 percent.

Type: Field windbreaks at right angle to slope.

Year: 1930's.

Place: Kamennaya Steppe, Russia.

Reference: Basov, 1949.

Soil Properties

35. Soils of sheltered fields, compared to soils of

the open steppe had :

(a) higher humus content

(b) 2 to 21/^ times higher aggregate stability

(c) lower horizon of effervescence (carbonate

accumulation)

(d) less water-soluble salts

Type: 18-year-old windbreak.

Place: Saratov, Russia.

Reference: Saralidze, 1955.

36. A clayey chernozem soil of moderate depth

beneath the windbreak trees, compared to adj acent

sheltered fields, had :

(a) higher humus content

(b) more nitrogen and phosphorus

(c) higher aggregate stability

Cereal and grass field soils adjacent to windbreaks had a higher percentage of water-stable

aggregates than fields on the open steppe.

Type: 50- to 60-year-old windbreak.

Place: Russia.

Reference: Bjalyi, 1950.

37. Soil structure was better in the 0- to 328-foot

zone near windbreaks than on open, unsheltered

fields.

Type: 15-year-old windbreaks.

Place: Trans-Volga, Russia.

Reference: Maljanov and Saralidze, 1957.

38. Water-holding capacity of soil was 4 to 5

times greater in windbreaks than on adjacent

arable fields.

Type: Windbreak of old trees.

Place: Russia.

Reference: Molchanov, 1955.

39. A heavy loam chernozem under the trees in

a windbreak had 30 times more water-stable aggregates larger than 1 mm. in size, than similar

soil on open, plowed land. Soil porosity, infiltration, and resistance to erosion were all better in

the 0 to 7 H sheltered zone than in the open,

unsheltered zone.

Type: Oak-ash windbreak, 60 years old.

Place: Kuibyshev, Russia.

Reference: Mustafaev, 1957.

40. Porosity and infiltration capacity of a

sandy loam soil was greater in the 0- to 32-foot

sheltered zone than in the open, unsheltered field.

Soil in the sheltered area of 0 to 900 feet, compared to the open fields, had:

(a) thicker A and B horizons

(b) higher humus content

(c) deeper carbonate accumulation

(d) less sulfates

Type: 23-year-old shrub windbreak, 3 to 12 feet tall.

Place: Caspian lowland, Russia.

Reference: Birjukova, 1955.

41. With increasing distance from windbreaks,

soils in less sheltered areas had:

(a) less depth of humus

(b) less depth of effervescence (carbonate

accumulation)

(c) less humus, nitrogen, and acidity

(d) more nitrates anil exchangeable bases

(e) deteriorated structure

Place: Russia.

Reference: Baiko, 1955.

42. Soils beneath trees in windbreak compared

to soils on open, unsheltered fields, had :

(a) depth of A horizon increased by 5 to 8

inches.

(b) increased porosity and permeability in

A and B horizons

(c) increased leaching of calcium sulfate

(d) ground water raised by 16 to 27 inches

Type: 50-year-old irrigated windbreak of elm, maple, and

caragana.

Place: Stalingrad, Russia.

Reference: Birjukova, 1958.

43. On arable land with 10 percent slope the

soil in the 0- to 390-foot zone on downhill side of

windbreaks as compared to open, unsheltered

fields had:

(a) less topsoil erosion

(b) less calcium carbonate accumulation

(c) greater humus content

Type: Single-row black locust windbreak, 26 feet tall and

13 feet wide.

Place: Hungary.

Reference: Lady, 1956.

44. Shifting sandy soils are stabilized by patterns of windbreaks at 50- to 60-foot intervals.

Type: Windbarriers of Scots pine, Austrian pine, locust,

and poplar.

Place: Hungary.

Reference: Babos, 1919.

45. Soil blowing leeward of windbreaks was

decreased to 50 percent at 30 H, 18 percent at 20

H, and to only 0.14 percent at 10 H, compared to

open-field soil blowing.

Place: Japan.

Reference: lizuka, 1950.
62 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

EXAMPLES OF EFFECTS OF WINDBREAKS ON CROPS, LIVESTOCK,

AND FARMSTEADS

Field Crops

1. Average wheat yields during years of

heavy snow were :

(a) 27 bu./A. at 0 to 15 H leeward.

(b) 20 bu./A. at 15 to 25 H leeward.

Yields during 2 years of medium snow were :

(a) 21 bu./A. at 0 to 15 II leeward.

(b) 22 bu./A. at 15 to 25 H leeward.

Maximum wheat yields in years of heavy snow

were :

(a) 32 to 36 bu./A. at 0 to 6 H leeward.

(b) 19 to 21 bu./A. at 25 H.

Type: Series of l-row caragana field windbreaks 8 feet

tall,

rear.- 1950-54.

Place: Saskatchewan, Canada.

Reference: Staple and Lehane, 1955.

2. Wheat, rye, barley, and oat yields showed a

36-bushel total increase per one-half mile of windbreak in the 0 to 14 H leeward zone of high-yielding fields over the average of unprotected areas,

in North Dakota and South Dakota.

The same crops showed a Ti-bushel total increase per one-half mile of windbreaks in the 0 to

14 H leeward zone of low-yielding fields over the

average of unprotected areas.

Corn yields averaged 19 percent greater in the

2 to 10 H leeward zone east of windbreaks than

on unprotected fields in Nebraska.

Type: 40-year-old cottonwood and boxelder windbreaks

of medium density, and averaging 40 feet tall.

Year: 19.3-5-41.

Place: North Dakota. South Dakota, and Nebraska, U.S.A.

Reference: Stoeckeler, 1962.

3. Of 331 farmers interviewed, 83 percent estimated yield increases on protected compared to

unprotected fields. Their estimates, averaged,

were—

(a) com, oats, barley

(b) wheat and flax

(c) rye and soybeans

8V2 bu./A. increase

31/2 bu./A. increase

51/^ bu./A. increase

Type: 10-row field windbreaks, 30 to 50 feet tall.

Year: lf).52-.";4.

Place: South Dakota, U.S.A.

Reference: Ferber, Ford, and McCrory, 1955.

4. Corn yields between windbreaks compared

to yields on open, unsheltered fields showed a net

increase of 267 lb. per acre where windbreak interval was 1,100 feet; 222 lb. per acre at 1,950-foot

interval, and 125 lb. per acre at 3,250-foot interval. *

Type: Series of parallel field windbreaks at various

intervals.

Place: Ukraine, Russia.

Reference: Kuz'micev, 1958.

5. Crop yields in shelter of windbreaks compared to open, unsheltered fields showed these

increases:

(a) 20 percent, summer wheat.

(b) 56 percent, winter wheat.

(c) 26 percent, rye.

(d) 48 percent, barley.

Type: System of field windbreaks.

rlar: 1926-30.

Place: Kamennaya Steppe, Russia.

Reference: Gorshenin and others, 19.34.

6. Barley, oats, and winter wheat in shelter of

windbreaks compared to open, unsheltered fields

gave yield increases of:

(a) 100 to 400 percent in severe drouth years.

(b) 50 to 60 percent in moderate drouth

years.

(c) 10 to 15 percent in years of no drouth.

Type: System of field windbreaks of various types.

Year: 1930's.

Place: Kuibyshev, Russia.

Reference: Karuzin, 1936 and 1947.

7. Wheat yields were increased by 48 percent

on sheltered fields between windbreaks as compared to yields on open fields.

Type: Series of field windbreaks 15 feet tall and 12 feet

wide, spaced ;328 feet apart on contour.

Yields in 0 to 20 H leeward zone were increased

37 percent for rye, 25 percent for oats, and 39

percent for clover hay compared to open field

yields.

Type: Oak-birch windbreaks, 13 to 25 feet tall.

Year: 1937^1.

Place: Central Forest Steppe, Russia.

Reference: Shaposhuikov, 1946.

8. Oat yields were 25 to 28 percent greater on

sheltered than on open, unsheltered fields.

Type: 5-row field windbreak with open lower level.

Year: 1930's.

Place: Vladimir, Russia.

Reference: Kuckeryavykh, 1940.

9. Winter wheat, with equal amounts of moisture at start of growth, yielded twice as much in

18 H -leeward zone as on open fields.

Type: Ash4ocust windbreak, 18 feet tall and 50 feet wide.

Year: 1950.

Place: Russia.

Reference: Kalashuikov. 1955.

10. Crop yields on sheltered compared to open,

unsheltered fields were:

(a) wheat—27 bu./A. vs. 11 bu./A.

(b) oats—65 bu./A. vs. 19 bu./A.

(c) com—45 bu./A. vs. 17 bu./A.

(d) hay—5,240 Ib./A. vs. 1,057 Ib./A.

Type: Field windbreaks.

Year: 19.52-53.

Place: Dobrudja, Rumania.

Reference: Lupe, 19.54.

11. Wlieat yielded 20 to 50 percent (6 bu./A.)

more on sheltered than on open, unsheltered fields.

Maximum yields were at 82 feet leeward of wind-
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 63

break. Oats yielded 18 percent more on sheltered

fields.

Type: Field windbreaks at 800- to 1,000-foot intervals.

rear; 1952-53.

Place: Baragan, Rumania.

Reference: Lupe, Catrina, and Marou, 1956.

12. Wlieat yielded 18 percent more in the 2 to

10 H sheltered zone than on open, unsheltered

fields. Maximum yield increases were in the 6 to

10 H leeward zone.

Type: Field windbreaks of pines 20 feet tall, and poplar

and eucalyptus 33 feet tall.

rear; 1939^2.

Place: Italy and Sardinia.

Reference: Pavari and Gasparini. 1943.

13. Wheat and rye yields were greater on sheltered than on open, unsheltered fields.

Type: Earthwall hedges as windbreaks.

Place: Schleswig-Holstein, Germany.

Reference: Thran, 1952.

14. Winter wheat and rye had greater grain

and straw weight in the 2 and 3 H sheltered zone

than on open, unsheltered fields.

Weed population on fields adjacent to windbreaks was reduced because weed seeds were blown

into and trapped in the windbreak where they do

little harm.

Place: Germany.

Reference: Steubing, 19.52.

15. Oats yielded 9 percent more on the west

side at 0 to 30 H than on open, unsheltered field.

Oat-barley straw yielded 10 percent more on east

side at 0 to 15 H than on open, unsheltered field.

Type: Artificial barrier, 8 feet tall.

Year: 1950's.

Place: Germany.

Reference: Hanke and Kaiser, 1957.

16. Barley, oat, and spring wheat" yields were

greater in shelter of windbreak than on open,

unsheltered fields.

Type: 15-year-old windbreak, 12 feet tall.

Year: 1940's.

Place: Iceland.

Reference-: Kristjanson, 1955.

17. Cotton lint yield was 46 percent greater in

the 3 H sheltered zone than on open, unsheltered

fields. Average yield was 23 percent greater in

the 1 to 22 H zone. Cotton seed yield was 27

percent greater in the 1 to 18 H zone.

I'eor; 1938-40.

Place: Oklahoma, U.S.A.

Reference: Stoeckeler, 1962.

18. Cotton stands in 5 to 10 H leeward zone, as

compared to open field stands:

(a) germinated 2 to 3 days earlier.

(b) grew 2 to 8 inches taller.

(c) flowered 4 to 5 days earlier.

(d) fruited more heavily.

(e) yielded 1.6 to 3.1 percent more fiber.

Year: 19.">0's.

Place: Kiangsu, China.

Reference: Anonymous, 19G0.

19. Rice yields decreased 51 percent at i^ H

leeward, but were increased 3 percent at 1 H; 33

percent at 3 H ; 49 percent at 6 H ; 33 percent at

9 H; 28 percent at 12 H; and 8 percent at 15 H,

compared to open, unprotected fields.

Type: Willow-ash windbreak 13 feet tall.

year; 1950's.

Place: Japan.

Reference: Matsui and Yokoyama, 1955.

20. Tobacco yield (cured) was 10 percent

greater in shelter of windbreak than on open field.

Leaf quality ^yas larger and brighter, and nicotine

content was lower on sheltered field.

Place: Germany.

Reference: Kreutz, 1952.

Forage Crops

21. Alfalfa yielded 60 to 70 percent more in best

part of protected field as compared to overall field

average.

rear; 1935.

Place: North Dakota, U.S.A.

Reference: Bates, 1944.

22. Mixed alfalfa, timothy, and red clover hay

yielded 37 percent more in the 1 to 7 H leeward

zone than the normal field average.

Type: Conifer windbreak 17 feet tall.

re«r; 1940's.

Place: Wisconsin, U.S.A.

Reference: Trenk, 1948.

23. Crested wheatgrass yield at 0 to 2 H leeward

(south) was double the yield at 9 H leeward.

Five-year average yield was 1,209 lb. per acre in

0 to 2 H zone compared to 887 lb. at 9 H.

Type: Single-row windbreak, 18 feet tall.

Year: 1938.

Place: Wyoming, U.S.A.

Reference: Quayle, 1941.

24. Sweetclover and wheatgrass hay, 1 to 3 years

old, yielded 2 to 4 times more in shelter of windbreaks than on the open steppe.

Place: Voronezh, Russia.

Reference: Ignatlev, 1940.

25. Pasture grass in sheltered area in a year with

precipitation 46 percent above normal as compared

to open fields had :

( a ) 68 percent more dry weight.

( b ) 108 percent more vitaniin C.

( c ) 144 percent more protein.

( d) 85 percent more starch.

Grass yields.in sheltered areas in a dry year were

one-third of normal, compared to no yield on open,

unsheltered areas.

Type: 65-foot-wide windbreak.

Place: Hungary.

Reference: Benkovits, 1955.
64 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 2 50

26. Hay crops were heavier on slieltered than on

open, unsheltered fields.

Type: Poplar windbreaks.

Year: Years with late frost or spring drouth.

Place: Eberswalde, Germany.

Reference: Joachim, 1955.

27. Grass and clover hay yielded 22 percent more

on sheltered than on open unsheltered fields.

Type: Series of parallel conifer windbreaks.

Year: 1909-25.

Place: Jutland, Denmark.

Reference: Soegaard, 19.54.

Vegetables and Fruits

28. Tomatoes yielded 60 percent more at early

harvest, 16 percent more at total harvest, and green

snap beans 37 percent more on sheltered areas between barriers than on open, unsheltered plots.

Tomato yields averaged 30 tons per acre in shelter

and 26 tons per acre in open.

Type: Two 7-foot slat (snow fence) barriers oriented

east-west and 50 feet apart.

Season and Year: May to August, 19.59.

Place: Central Nebraska, U.S.A.

Reference: Bagley and Gowen, 1962.

29. Yields of 35 varieties of snap beans in sheltered area were :

(a) 5,080 Ib./A. at 2 H.

(b) 4,7581b./A.at4H.

(c) 4,526 Ib./A. at 6 H.

(d) 3,859 lb./A. at 8 H.

Type: Single-row poplar windbreak, 20 feet tall.

Year: 1936.

Place: Wyoming, U.S.A.

Reference: Babb and others, 1941.

30. Virginia crab apples yielded 99 lb. per tree,

ger year in shelter compared to 21 lb. in open,

[ibernal apples yielded 32 lb. in shelter and 3 lb.

in open.

Year: 1928-49.

Place: North Dakota, U.S.A.

Reference: Duncan, 1950.

31. Citrus groves yielded a net advantage of

$77 per acre per year with full shelter protection

as compared to partial shelter.

Type: Eucalyptus windbreaks, 60 feet tall.

Year: 1927-33.

Place: California, U.S.A.

Reference: Metcalf, 1936.

32. Potato yields were estimated 80 bushels per

acre greater on sheltered than on open, unsheltered

fields.

Type: lO-row, field windbreaks, 30 feet tall.

Year: 1952-54.

Place: South Dakota, U.S.A.

Reference: Ferber, Ford and MoCrory, 1955.

33. Yield increases on windbreak-sheltered

fields compared to open fields were:

(a) 138 percent for cucumbers.

(b) 240 percent for tomatoes.

(c) 228 percent for beets.

(d) 115 percent for carrots.

(e) 158 percent for potatoes.

Year: 1932.

Place: Saratov, Russia.

Reference: Suss, 1936.

34. Cucumbers, tomatoes, cabbages, sugar beets,

and early potatoes yielded significantly more in

sheltered than on open, unsheltered fields.

Type: Strips of rye, corn, and sunflower at 15- to 25-foot

intervals.

Year: 1950's.

Place: Russia.

Reference: Gotovcev, 1957.

35. Cucumbers yielded more and earlier on sheltered than on open unsheltered fields.

Type: Strips of winter rye.

Place: Leningrad, Russia.

Reference: Byckova, 1958.

36. Strawberry yields were greater on sheltered

than on unsheltered fields.

Type: Rows of sorghum or corn sown every 5 to 6 rows of

berries.

Year: 1950's.

Place: Ukraine, Russia.

Reference: Bereznoj, 1956.

37. Yields of potatoes increased 16 percent and

sugar beets 23 percent under windbreak shelter as

compared to open fields.

Year: 190ft-25.

Place: Jutland, Denmark.

Reference: Soegaard, 1954 .

38. Apple yields in bushels per acre in sheltered

area of windbreak were :

(a) 175 at 1.5 H.

(b) 90 at 3 H.

(c) 39 at 5 H.

(d) 30 at 6 H.

(e) 26 at 8 H.

Type: 4-row deciduous tree windbreak, 20 feet tall.

Year: 1919-22.

Place: Jutland, Denmark.

Reference: Soegaard, 1954.

39. Yield increases due to protection by windbreaks were 160 percent for Cox variety apples;

32 percent for Golden Delicious apples.

Year: Recent.

Place: Zeeland, Western Netherlands.

Reference: Inst. Voor Toegepast, 1956.

40. French beans yielded more and higher quality on sheltered than on open, unsheltered fields.

Type: Strips of corn and grain at 15- to 20-foot intervals,

rear.- 1950's.

Place: Netherlands.

Reference: Koomen, 1957.

41. Strawberries ripened earlier and yields increased in the 0 to 20 H sheltered zone compared

to open, unsheltered fields.

Type: Poplar windbrealc, 45 feet tali
TREE WINDBREAKS FOR THE CENTRAL GREAT PLAINS 65

Year: 1952-54.

Place: Netherlands.

Reference: Linde, 1955.

42. Yields of apples increased 75 percent and

pears 121 percent in the 6 to 12 H sheltered zone,

as compared to yields in the open.

Year: 5-year average in 1950's.

Place: Netherlands.

Reference: Rhee, 1957.

43. Potatoes yielded 21 to 24 percent more on

sheltered than on open, unsheltered fields.

Pla<:e: Germany.

Reference: Caborn, 1957.

44. Potato yields were greater on sheltered fields

than on open fields.

Type: Earth wall hedge windbreaks.

Place: Schleswig-Holstein, Germany.

Reference: Thran, 1952.

45. Sugar beets yielded 6 percent greater weight

and 8 percent higher sugar content in tjie 0 to 28 H

sheltered zone than in the 32 to 60 H zone.

Type: Poplar, ash, locust windbreak, 26 feet tall, 22 feet

wide.

Year: 1955.

Place: Germany.

Reference: Hanke and Kaiser, 1957.

46. Growth of peas and beans was greater in

shelter than on open fields, and better on sloping

than on level land.

Type: Tree windbreaks.

Year: 1950's.

Place: Japan.

Reference: Yamamoto, 1957.

Livestock

47. Cattle wintered in sheltered areas sulfered

fewer losses and rec^uired less feed for maintenance

than cattle wintered on open range. Tree windbreaks provided better protection tlian constructed

sheds.

Type: Tree and brush areas and sheds.

Year: 1920's.

Place: Montana, U.S.A.

Reference: Vinke and Dickson, 1933.

48. Ranches located in open, unprotected level

areas required an average of 50 percent more winter feed for stock than those located in areas having natural protection of topography, trees, or

brush.

Type: Tree and bru-sh areas of rough topography.

Place: North Dakota, U.S.A.

Reference: Johnson, 1947.

49. Value of tree protection estimated b_v 44 livestock feeders averaged $802 savings in feed and

$839 additional gain, or total of $1,313 average

annual saving (1929-35 prices) per farm with 100

cattle.

Type: Natural and planted tree stands.

Year: 1936.

Place: South Dakota, U.S.A.

Reference: Collins, 1952.

50. Siindliills I'anchers maintain that winter

losses from freezing, blizzard, snow, and inaccessil)le feed are greatly reduced if livestock have

access to protective ti-ee plantations.

Type: Conifer plantations.

Year: 1940's.

Place: Nebraska, U.S.A.

Reference: U.S. Forest Service.

51. High temperatures depress the yield of milk

cows that normally are high-level producers. Very

low temperature and high wind increases heat loss

from dairy cows. (Moderating etïects of trees and

\\indbreaks on temperature and wind are therefore

beneficial in obtaining highest milk production.)

Place: Netherlands.

Reference: Oosterlee, 1958.

52. Pigs require shelter from hot summer sun

and from cold winter wind. Windbreaks provide

cheap and profitable shelter, and prevent wind

erosion around paddocks.

Type: Deciduous windbreaks.

Place: Queensland, Australia.

Reference: Abell, 1947.

Farmsteads

53. Savings in fuel costs for house heating were :

(a) 25 percent (windbreak on north only).

(b) 33 percent (windbreak on north and

west ).

(c) 40 percent (windbreak on four sides).

Type: Tree windbreaks and artificial barriers.

Season and Year: Winter, 1936-37.

Place: South Dakota and Nebraska, U.S.A.

Reference: Bates, 1945 .

54. Calculated savings in use of natural gas at

Topeka, Kans., rates for homes with windl^reaks

was $10 per season compared to tliose with none.

Type: Windbreak at 2 H windward of house.

Year: 1950's.

Place: Kansas, IT.S.A.

Reference: Woodruff, 1954.

55. A\-erage annual wind damage (for 10-year

period) based upon 292 farms with various types

of windbreaks, ranged from $3.92 for those with

the best-rated plantings to $40.32 for those with

poorest plantings.

Type: E.xcellent to poor windbreaks.

Season and Year: Winter, 1940's.

Place: South Dakota, U.S.A.

Reference: Collins, 1952 .

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19.56. [A simultaneous study of root systems and water

regime in soils of shelterbelts ou southern chernozem.]

Trudy Inst. Lesa Akad. Nauk 29: 146-193. [Russ.]

[Soils & Fert. Abs. 20(1) : 57 (1957) No. 357.]

Karuzin, B. V.

1947. [Measures to obviate poor grain quality in the

southeast.] Sovet. Agron. 2 : 34-38. [Russ.]" [Field

Crop Abs. 1: 142 ( 194S) No. 743.]

and Shestoperov. G. P.

1936. [A study of the narrow shelterbelts in the Timashev District of the Kuibyshev region.] Polezashchitnye Polosy [ Shelterbelts : Experiments of AllUnion Res. Inst. for Improvement of Farmland by

Forestation.] 6: 117-169. [Russ.] Transi, by C. S.

Beliavsky, U.S. Dept. Agr. Library Transi. No. 7311,

3S pp., 1937.

Kas'yanov.

1950. [The quantitative and qualitative significance of

the role of shelterbelts.] Lesn. Khoz. 1: 3,8-45.

[Russ.] [Forestry Abs. 12: 54 (1950) No. 323.]

Koomen, J. P.

1957. [Experience with windbreaks in vegetable growing.] Meded. Proefst. Groent. Volle Grond, Alkmaar

6, 43 pp., illus. [Dutch. Eng. summary.] [Hort. Abs.

27:547 (1957) No. 3415.]

Kreutz, W.

1952. [The importance of wind protection for tobacco

growing.] Dtsch. Tabakb. 32(11): 93-95. [Ger.]

[Hort. Abs. 27 : 94 (1957) No. 603.]

Kristjansson, K. K.

1955. [Experiments with shelterbelts at Sams-stodur in

Fljotschlid.] Arsr. Skograektarf. Islands 1955: 38-

44. [Icel.] [Forestry Abs. 17: 65 (1956) No. 433.]

Kueheryavykh, E. G.

1940. [The effect of shelterbelts of different structure

on crop yields.] Sovetsk. Agron. 10: 18-22. [Russ.]

[Forestry Abs. 4 : 29 (1942).]

Kuz'micev, V. P.

1958. [The influence of shelterbelts, with different distances between belts, on maize yields.] Lesn. Hoz.

11(6) : 28-32. [Russ.] [Forestry Abs. 20(3) : 394

1959) No. 3193.]

Lady, G.

1956. [Investigations on the soil protecting effect of a

horizontal shelterbelt.] Erdesz. Kut. 3: 69-75.

[Hung.] [Soils & Fert. Abs. 20(5) : 301 (1957) No.

1920.]

Linde, R. J. van der.

1955. [Research on shelter for fruit-growing.] Jversl.

Proefstat. Fruit., Voile Grond, Wilhelminadorp, pp.

59-62. [Dutch.] [Hort. Abs. 26 :231 (1956) No. 1526.]

and Woudenberg, J. P. M.

1951. On the microclimatic properties of sheltered

areas : the oak-coppice sheltered area. Meded. Inst.

Toegep. biol. Onderz. Nat. 10: pp. 151. [Eng.]

[Forestry Abs. 13(2) : 173 (1951) No. 1221.]

Lupe, I.

1954. [The influence of forests and .shelterbelts on climate and agricultural crops.] Rev. Padurilor 69(4) :

170-175. [Rum.] [Forestry Abs. 16: 217 (1955) No.

17.58.]

Catrina, I., and Marcu, G.

1956. [The influence of shelterbelts on yields of wheat

and oats in Baragan and the Dobrudja in 1952 and

1953.] Bui. Sti. Acad. Repub. Rom. (Sect. Biol.)

8(1) : 199-208. [Rum.] [Forestry Abs. 18(2) : 212

(1957) No. 1626.]

L'\"ovich, M. I.

1954. [Regulating the water balance of irrigated fields

by shelterbelts as a means of decreasing irrigation

rates.] Izv. Akad. Nauk Ser. geogr. No. 2: 29-44.

[Russ.] [Soils & Fert. Abs. 19(3) : 278 (1956) No.

1333.]

Maljanuv, A. P., and Saralidze, T. V.

1957. [The influence of shelterbelts on the structure of

the dark-chestnut soil of the Trans-Volga region.]

Pocvoved. 3:33-39. i [Russ.] [Forestry Abs. 19(1) :

14 (19.58) No. 26]

Maran, B., Lhota, O., and Uhlir, P.

1950. [luflueuce of shelterbelts on soil moisture.]

Sborn. csl. Akad. zemed. 23: 23-46. [Czech.] [Forestry Abs. 13(5) : 503 (1952) No. 3849.]

Lhota, O., and Uhlir, P.

1951. [Effect of shelterbelts on soil moisture at Vinor.]

Sborn. csl. Akad. zemed. 24: 189-215. [Czech.]

[Forestry Abs. 13(5) : 503 (1952) No. 3851.]

Masiuskaja, L. P.

19.50. [Establishing shelterbelts in vineyards.] Vinodelie i Vinogradarstvo SSSR, Moskva 10(6) : 22-24.

[Russ.] [Forestry Abs. 15:181 (1954) No. 1377.]

Matsui, Z., and Yokoyama, C.

19.55. [On the efficiency of the wind-break hedge in

protecting the rice crop in Horomui District]

Hokkaido Forest Expt. Sta. Spec. Rpt. No. 3, pp. 168-

177. [Jap.] [Forestry Abs. 16 : 515 (1955) No. 4103.]

Metcalf, Woodbridge.

1930. The influence of windbreaks in protecting citrus

(jrchards. Jour. Forestry 34 : 571-580, illus.

Molchanov, A. L.

1955. [Water-holding capacity in plowed, fallowed, and

forested chernozem.] Trudy Kazakh, gidrometerol.

Inst. No. 5 : S-15. [Russ.] [Soils & Fert. Abs. 19(5) :

414 (1956) No. 1941.]

1956. [Air-temperature, air-humidity and soil-tenmperature regimes in the fields between shelter belts.]

Trudy Kazakh, gidrometeorol. Inst. 7: 57-65.

[Russ.] [Soils & Fert. Abs. 20(2) : 89 (1957) No.

4.S5.]

Mustafaev, Kh. M.

1957. [Changes in the properties of ordinary chernozems under shelterbelts of different ages [and] in the

space between l)elt.s.] Pocvoved. 6 : 102-107. [Russ.]

[Forestry Abs. 19(2) : 158 (19.58) No. 1286.]

Nageli, W.

1941. [On the significance of windbreaks to protection

of cultivated agricultural land.] Schw. Zeitschrift f.

Forstwesen 11: 265-280. [Ger.] [From Caborn,

19.57, Shelterbelts and Microclimate.]

Oosterlee, C. C.

1958. An investigation into the influence of climatic

factors on the heat balance and milk yield of the

cow, in relation to the question of building farms in

the Netherlands. Koninklijke Drukkerij C. C. Callenbach N.V.-Nijkerk, 216 pp. illus. [Dutch. Eng.

summary.]

Panñlov, J. E.

1937. [Shelterbelts on the watershed plateau of the

prairie zone of the Volga region.] Polezashchitnye

Polosy [Shelterbelts: Report of All-Union Sei. Res.

Inst. for Improvement of Farmland by Forestation.]

8: 3-64. [Russ.] Transi, by C. P. de Blumenthal,

U.S. Dept. Agr. Library Transi. No. 7315, 66 pp., )37.
68 U.S. DEPARTMENT OF AGRICULTURE HANDBOOK NO. 250

Pavari, A., and Gasparini, M.

19-43 [The protective effect of windbreaks on cereal

cultivation.] Mariano Ricci, Via S. Gallo .HO [Florence], pp. 34. [It.] [Forestry Abs. 9:177 (li>47)

No. 869.]

Quayle, W. L. . . ^

1941. Practical results from the state experiment farms.

A slielterbelt increases hay yields, (p. 9) Wyo. Agr.

Expt. Sta. Bui. 243, 43 pp., illus.

Rhee, .J. A. van.

1057. [Problems of orchard shelter in Zeeland.]

Meded. Dir, van de Tuinbouw. 20(7) : 416-420.

[Dutch. Eng. summary.] [Hort. Abs. 28(1) : 43

(19.58) No. 230.]

Saralidze. T. V.

19.55. [The effect of shelter belts on dark chestnut soils

of the Trans-A^olga region.] Nauch. Ezhegod. 1954,

Saratov. Univ. 332-333. [Russ.] [Soils & Pert. Abs.

20(2) : 93 (1957) No. 518.]

Shaposhnikov, A. P.

1946. [Growth and influence on crop yields of tree plantations for erosion control in the central forest steppe]

Nauchny Otchet VNIALMI za 1941-42, Sel/Khozgiz

(Moscow) pp. 82-90. [Rnss.] [Forestry Abs. 9:

174(1947) No. 858.]

Soegaard, B.

19.54. Outline of shelterbelts and shelterbelt tests in

Denmark. lUFRO 11th Cong. Proc. 19.53 (Rome)

Sec. 11, No. 3, pp. 246-269, illus. [Eng.] [Forestry

Abs. 15: 314 (19.54) No. 2523.]

Sokolova, N. S.

1937. [Influence of shelterbelts on the yield of agricultural plants : grains, products of truck farming and

oil-bearing plants.] Polezashtchitnye Polossy [Shelterbelts : Report of AU-Union Sei. Research In.st. for

Improvement of Farmland by Porestation.] 8: 120-

158. [Russ.] Tramsl. by C. P. de Bluiuenthal, U.S.

Dept. Agr. Library Transi. No. 7317, 68 pp., 1937.

Staple, W. .1., and Lehane, J. .1.

19.55. The Influence of field shelterbelts on wind velocity,

evaporation, soil moLsture and crop yield. Canad.

Jour. Agr. Sei. 35 : 440-453, illus.

Steubing, L.

1952. [Dew and the influence of windbreaks on it.]

BioL Zbl. 71 (.5/6) : 282-313. [Ger.] [Forestry Abs.

14: 53 (1953) No. 349.]

1952. [The influence of shelterbelts on microclimate.]

Dtsch. Landwirtsch. 3(10) : 523-526 [Ger.] [Forestry Abs. 14 : 170 (1953) No. 1219.]

Stoeckeler, .J. H.

1962. Shelterbelt influence on Great Plains field environment and crops. U.S. Dept. Agr. Prod. Res. Rpt.

No. 62, 26 pp., illus.

and Dortignac, E. J.

1941. Snowdrifts as a factor in growth and longevity

of shelterbelts in the Great Plains. Ecology 22: 117-

124, iUus.

Suss, N. I.

1936. [Achievements in the improvement of agricultural lands by forestation. ] Selskoe Khoziaistvo

SSSR. Ezhegodnik, 1935 (Moscow) pp. 172-183.

[Russ.] Tran.sl. by C. P. de Blumenthal, U.S. Forest

Serv. Div. Silvics No. 286, 23 pp., 1936.

Thran, P.

19.52. [Increased yields obtained by shelter from wind

affftrded by hedges on earth-walls in Schleswig-Holstein.] Berichte des deuts<-hen Wetterdienstes in der

U.S. Zone, Bad Kissingen No. .32: .57-59. [Ger.]

[Forestry Abs. 15(1) : 49 (19.54) No. 289.]

Trenk, Fred B.

1948. Influence of i>lanted tree belts in plainfield sand

on erosion control and moisture conservation. Iowa

State Col. Jour. Sei. 22(4) : 449-461, illus.

Vinke, Louis, and Dickson, W. F.

19.33. Maintenance of beef cows for calf production.

Mont. Agr. Expt. Sta. Bui. 275, 35 pp., illus.

Woodruff, N. P.

1954. Shelterbelt and surface barrier effects on wind

velocities, evajKjration, house heating, and snowdrifting. Kans. Agr. Expt. Sta. Tech. Bui. 77, 27'pp.,

illus.

Read, R. A., and Chepil, W. S.

1959. Influence of a field windbreak on summer wind

movement and air temperature. Kans. Agr. Expt.

Sta. Tech. Bui. 100, 24 pp., illus.

Yamamoto, R.

1057. [Micro-meterological conditions and growth of

crop plants on a slope ground as influenced by windbreaks.] Jap. Crop Sei. Soc. Proc. 26(1) : 27-29,

illus. [Jap.] [Field Crop Abs. 11(2) : 140 (1958)

No. 844.]

ADDITIONAL REFERENCES

Consult the following publications for other tree and

shrub recommendations for the Great Plains :

Tree and shrub species for the northern Great Plains.

U.S.D.A. Circular 912. 19-53.

( Out of print ; may be seen in libraries.)

Windbreaks and shelterbelts. Montana State College,

Extension Service Bulletin 318. 1962.

Shelterbelts for South Dakota. South Dakota State

College, Extension Service Circular 492. 1957.

Trees for wind protection in northwest Oklahoma.

Oklahoma Extension Service Circular E-721. 1961.

The farmstead windbreak. Colorado State Forest

Service. C.S.U. Ft. CoUins. 1962.

Trees for Colorado farms. Colorado Extension Service

Bulletin 39.5-A. 1951.

Windbreaks in conservation farming U.S.D.A. Misc.

Pub. 759. 1958.

Shelterbelts for the northern Great Plains.

U.S.D.A. Fanners' Bui. 2109. 1957.

The Great Plains shelterbelt In 1954. Nebr. Agi.

Expt. Sta. Bui. 441. 1958.

Shelterbelt influence on Great Plains field environment

and crops. U.S.D.A. Prod. Res. Rpt. 62. 1962.

U.S. GOVERNMENT PRINTING OFFICE : 1964 O—691-791