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CULTURE AND USE

OF GRAIN SORGHUM

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Agriculture Handbook No, 385

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Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE
PRECAUTIONS

Pesticides used improperly can be injurious to man, animals, and plants. Follow the directions and heed all precautions on the labels.

Store pesticides in original containers under lock and key

—out of the reach of children and animals—and away from

food and feed.

Apply pesticides so that they do not endanger humans,

livestock, crops, beneficial insects, fish, and wildlife. Do not

apply pesticides when there is danger of drift, when honey

bees or other pollinating insects are visiting plants, or in

ways that may contaminate water or leave illegal residues.

Avoid prolonged inhalation of pesticide sprays or dusts ;

wear protective clothing and equipment if specified on the

container.

If your hands become contaminated with a pesticide, do

not eat or drink until you have washed. In case a pesticide

is swallowed or gets in the eyes, follow the first aid treatment given on the label, and get prompt medical attention.

If a pesticide is spilled on your skin or clothing, remove

clothing immediately and wash skin thoroughly.

Do not clean spray equipment or dump excess spray material near ponds, streams, or wells. Because it is difficult to

remove all traces of herbicides from equipment, do not use

the same equipment for insecticides or fungicides that you

use for herbicides.

Dispose of empty pesticide containers promptly. Have

them buried at a sanitary land-fill dump, or crush and bury

them in a level, isolated place.

NOTE : Some States have restrictions on the use of certain pesticides. Check your State and local regulations. Also,

because registrations of pesticides are under constant review

by the U.S. Department of Agriculture, consult your county

agricultural agent or State Extension specialist to be sure

the intended use is still registered.

III
Contents

Fagtí

General adaptation 2

Varieties and hybrids 4

Seed selection and treatment 5

Seedbed preparation 7

Planting . 9

Methods 9

Dates 10

Rates 11

Weed control 14

Cultivation 14

Chemical methods 15

Fertilizers 18

Irrigation 20

Harvesting, drying, and storing 21

Utilization 23

Feed value 23

Industrial use 25

Diseases 25

Seed rots and seedling blights 26

Foliar or leaf diseases 26

Inflorescence or head diseases 27

Root and stalk rots 27

Insects 29

Grasshoppers 29

Corn earworm 29

Sorghum webworm 29

Corn leaf aphid 29

Sorghum midge 29

Chinch bug 29

Other insect pests 80

Washington, P.C. Issued November 1970

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

Washington, D.C. 20402 - Price 20 cents

IV
CULTURE AND USE

OF GRAIN SORGHUM

By W. M. Ross, geneticist, and 0. J. WEBSTER, agronomist.

Crops Research Division, Agricultural Research Service^

Grain sorghum is a member of

the grass family and is closely

related to forage sorghum (sorgo), broomcorn, sudangrass,

Johnsongrass, and sorghum almum. It includes basic groups recognized in the United States as

milo, kafir, durra, hegari, feterita,

shallu, and kaoliang; pure-line

varieties derived by hybridization

and selection; and Fi hybrids.

For many years most of the

grain sorghums in the United

States were either milo or kafir.

Consequently, ''milo'' is still popularly, though not accurately,

used for all grain sorghums, including Fi hybrids. **Milo maize,''

''kafir corn," and "maize" applied

to sorghum are misnomers.

A sorghum called chicken corn

was introduced on the southern

Atlantic coast in colonial times,

but the culture did not persist

and the variety escaped as a

weed. A non-noxious type called

Guinea corn Vv^as introduced

durirp' ^he same period and was

c^ „d until the 20th century

i eiore disappearing. The crop as

^ The authors have revised and expanded the information in AIB 218,

''Culture and Utilization of Grain Sorghum," for this handbook.

we know it became established in

the late 19th and early 20th century. Practically all grain sorghums of economic importance,

until recent years, were introduced between 1874 and 1908 and

have been the base for varietal

improvement.

Today grain sorghum is a major crop of the Great Plains and

the Southwest. It is grown both

as a dryland and as an irrigated

crop. Texas, Kansas, and Nebraska account for over 80 percent of

the Nation's production (table

1). Most of the remaining production is in Arizona, California,

Colorado, Missouri, New Mexico,

Oklahoma, and South Dakota.

The Corn Belt and the South

produce from 1 to 2 percent of

the total.

Production in the United

States by 5-year periods for

1919-68 is shown in table 2. Except for the drought of the

1930's, yield per acre and total

production have trended upward

with a spectacular rise during

1958-68. Record grain production

was achieved in 1967 at 756 million bushels. The highest yield

per acre was in 1966 at 56 bushels

or 3,100 pounds.
AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Sorghum grain production in major States^ 1968 ^

State Acres

Yield

per acre ^

Total

production ^

Texas ..

Kansas

Nebraska

Oklahoma

California

Arizona .

New Mexico

Missouri

Colorado

South DakotaTotal or average (10 States) 13,705

Totalor average (U.S.)-. 13,971

ousands Bushels 1,000 bushels

6,196 55.0 340,780

3,475 47.0 163,325

1,776 58.0 103,008

638 41.0 26,158

360 70.0 25,200

231 79.0 18,249

279 56.0 15,624

216 66.0 14,256

290 35.5 10,295

244 34.0 8,296

13,705 53.0 725,191

13,971 53.0 738,507

^ U.S. Dept. Agr. Crop Rptg. Bd. report; includes sweet sorghum for seed.

^ No. 2 grain sorghum usually computed at 56 pounds per bushel.

^ Does not always equal acres X yield because of figure rounding.

TABLE 2.—Sorghum grain production in United States, 1919-68

Years Acres

Yield

per acre

Total

production ^

Predominant

type grown

1919-23.

1924-28..

1929-33.

1934-38.

1939-43-.

1944-48..

1949-53..

1954-58..

Thousands Bushels 1,000 bushels

3,786 18.2 68,761 Tall variety.

4,004 17.3 69,390 Do.

4,047 13.8 55,985 Do.

3,880 12.6 48,849 Do.

6,006 15.7 94,367 Transition.

7,035 17.4 122,333 Combine variety.

7,426 20.2 150,270 Do.

14,005 26.2 366,322 Transition,

13,378 41.1 550,250 Hybrid.

13,311 50.7 674,386 Do.

^U.S. Dept. Agr. Agr. Statis.

includes sweet sorghum for seed.

2 Does not always equal acres x

and U.S. Dept. Agr. Crop Rptg. Bd, reports;

yield because of figure rounding.

GENERAL ADAPTATION

Grain sorghum is grown chiefly in the Great Plains, where

most of the rainfall occurs

during the growing season. The

crop is planted at the beginning

of the wet period and harvested

at the beginning of the dry period. Warm, dry autumns normally

reduce moisture in the grain so

that it retains a bright color.

Wet periods following maturation of grain cause its discoloration and encourage fungus

growth. High-moisture grain

also introduces a storage problem. Generally these hazards are

more common to the eastern edge

of the sorghum-growing area and

to the Corn Belt, where artificial

grain driers are used, but they
CULTURE AND USE OF GRAIN SORGHUM

can occur in the driest areas of

the Great Plains in some years.

The superiority of grain sorghum over other crops lies in its

ability to produce grain with a

relatively limited supply of

water. The crop is unique in that

it can remain dormant during

stress periods and renew growth

when conditions are more favorable. Grain sorghum is not immune to heat and drought, and

prolonged periods of such weather may prevent plant and grain

development to the extent that a

crop cannot mature before frost

or yield is reduced. On the other

handj grain sorghum responds as

well as or better than most crops

to conditions of favorable rainfall or irrigation. Yields of 8,000

pounds or more per acre frequently are obtained with adequate moisture and high fertility.

The crop also is more tolerant of

flooding than corn^ but it does

not grow best under prolonged

wet conditions.

Maturity is an important consideration. The first varieties

grown were late maturing and

best adapted to Texas and Oklahoma. Improved selections of

earlier maturity enlarged the

main sorghum-growing area to

Kansas and Nebraska, and finally

varieties were bred for the shortgrowing seasons of the western

high plains and the north-central

plains. However, cool soil temperatures of the northern latitudes and at higher altitudes following planting can delay

seedling growth, and cool nights

can delay later growth and grain

maturity of the best adapted

types. They are deterrents to

consistent maximum production.

On the other hand, grain sorghum generally withstands the

high temperatures of the Southwest provided soil moisture is

adequate, although it is desirable not to have the crop flower

and set seed during the hottest

part of the summer. Because of

the long growing season, varieties can be chosen and planting

dates altered so that blooming

follows the usual adverse period.

Grain sorghum grows success- \

fully on all soils though it does ^

best on medium-textured types.

It grows slightly better on sandy ^

or light-textured soils than it

does on clayey or heavy-textured

soils. The latter can produce high

yields if moisture is ample, but

the crop will exhibit drought

symptoms during dry periods.

Usually the heaviest soils are

better adapted to wheat in the

Great Plains. Tillering of grain

sorghum tends to decrease as the

percentage of silt and sand soil

fractions increase. The sorghum

plant also tolerates medium high

pH's as evidenced by the alkaline

condition of many soils in the

growing region.

In addition to weeds, insects,

and diseases, birds are a serious

pest of grain sorghum. Sparrows

and blackbirds are the most destructive species in the United

States, though others sometimes

attack the crop. Destruction is
AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

most prevalent in fields that border farmsteads^ wooded streams,

and windbreaks. Damage to the

head begins at the milk stage and

lessens as the grain ripens. A few

varieties like Darset and Combine Sagrain^ certain brownseeded hybrids like AKS 614, GA

609, GA 615, and RS 617, and

some commercial hybrids are distasteful to birds. These types are

more likely to be grown in the

problem areas of Arkansas, eastern Oklahoma, and the Southeast

than in the Great Plains or

Southwest.

VARIETIES AND HYBRIDS

Most of the first improved

varieties came from selections in

milo and kafir and a few from

other basic types. Pure-line varieties were developed later

through hybridization and selection. All were tall growing, some

had recurved heads, and none

were adapted to machine harvest.

Some of these varieties like Pink

kafir, Blackhull kafir, and Dwarf

Yellow milo firmly established

grain sorghum culture in the

United States, These sorghums

were more dependable than corn

in the areas where grown and

were nutritious for livestock

feed.

Combine-height grain sorghum

that could be harvested with a

wheat header was developed before World War I by a farmerplant breeder, H, Willis Smith, of

Garden City, Kans. But his efforts were premature, and the

types were not accepted by either

the farmers or the agriculturalists of the day. Beaver, a shortstatured variety with an upright

head suitable "^or combine harvest, was relr :;d by the Oklahoma Agricultural Experiment

Station in 1928. It was grown on a

limited acreage but was soon replaced by the superior Wheatland

variety, which gained wide popularity. The latter marks the

beginning of the combine-sorghum era and a significant step

in grain sorghum improvement.

Acceptance of combine grain

sorghum was not immediate but

was stimulated by the drought of

the 1930's and fostered by the

release in the early 1940's of

stiif-stalked types like Martin,

Westland, Plainsman, Caprock,

and Midland. A farm manpower

shortage during World War II

also prompted their adoption.

These five varieties, along with

subsequent developments—Combine 7078, Combine Kafir-60,

Dwarf Kafir 44-14, Early Hegari,

Norghum, Redbine-60, Redbine66, Redlan, and Reliance—constituted most of the acreage when

hybrids were introduced in the

mid-1950's.

Hybrid grain sorghum is based

on a male sterility-fertility restoration technique. A method for

making hybrids on a large scale,

as by detasseling in corn, is impossible in sorghum because male

and female flowers are located
CULTURE AND USE OF GRAIN SORGHUM 5

together on the plant. The first maturity classes in relation to

hybrid seed was a three-way standard varieties as follows:

genetic male-sterile cross, but it ,^ ^ .^ , ^ .

lyi fîtwritiJ oLcm^ ¡^STt&s

was soon discarded in favor of a earlier than Norghum 300

more manageable single-cross Norghum . 400

system based on cytoplasmic male Reliance 500

sterility. Hybrid seed was avail- Martin 600

able in quantity for farm planting ^^^'""fir^ ;; 7, HI

-.f^rfT 1 li I ^ XT Dwarf Kafir 44-14 800

m 1957, and the amount of the

crop planted to hybrids rose rap- Most of the hybrids in the major

idly to nearly 100 percent in the g^'^in sorghum area are in the 500

following decade. Along with to 700 range, with the 600 series

favorable growing seasons and most common,

improved cultural methods, parti- hybrids developed by public

cularly increased fertilizer usage agencies may have a State prefix^

, .... T. r. -j 1, 1 e.g., OK (Oklahoma) and NB and more irrigation, hybrids help ,^' i x • i. .• xi j. ^ ^ ,f , ,, . ,, (Nebraska), indicating that recaccount for the remarkable yield -, ,. ^ • 4. j. ^ ... Í. i ommendation and interest were and production increases of recent ^^j^^^ ^^ ^^^ g^^^^ ^^ ^^^ ^i^^ ^^

y^^^^* release. Or they may have an RS

Grain sorghum hybrids are (Regional Sorghum) prefix, indi^

commonly designated by number, mating wider interest and wider

State and Federal agencies have initial distribution. Though some

adopted a uniform system of commercial companies number

nomenclature for experiment hybrids according to maturity, a

station hybrids. The hybrids are few name them as was the custom

assigned numbers based on with varieties.

SEED SELECTION AND TREATMENT

Plant only high-quality seed.

The cost is minor considering the

low amount sown per acre. High

quality in grain sorghum refers to

trueness to type, high and strong

germination, and freedom from

weed seeds, inert matter, and

other crops. These last three can

often be removed through cleaning, since sorghum seed is relatively large compared to seed of

many farm crops like grasses and

legumes. High germination results from harvesting mature

seed without freeze or mechanical

damage and storing it under proper conditions of temperature and

humidity. Artificial drying of

seed is sometimes used advantageously, but the temperature

must be controlled to maintain

germination. Laboratory germination tests eliminate most

poor seed lots before fields are

planted.

Clean seed of high germination

that appears uniform can produce

oiftype plants in the field. They
6 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

arise from two causes—plant

mutations during the growing

season and outerosses occurring in

the production field the previous

season. These ofFtypes are genetic

and are in addition to those coming from mechanical seed mixtures or from volunteer seeding.

Mutation to a taller height

occurs naturally at a low regular

frequency in most combine grain

sorghum varieties and hybrids.

Mutants appear to be worse in

high than in low plant populations. Their presence is an accepted fact of grain sorghum culture. The mutants are similar to

the rest of the population but are

a head or more taller. The cause

is an unstable genetic height

factor.

Outerosses in sorghum take

place because the crop is not completely self-pollinated. In hybrids

they can be potentially high, since

a large proportion of the production field has male-sterile seed

rows. Under ideal conditions an

abundance of pollen from the

male rows will pollinate the sterile plants as the flowers become

receptive. Under less ideal conditions airborne foreign pollen

will pollinate the sterile plants.

The most serious pollen contaminants are forage sorghum,

sudangrass, sorghum-sudangrass

hybrids, wild cane (shattercane),

Johnsongrass, and sorghum almum. They produce outerosses in

grain sorghum that are tall and

break over at combining, or they

shatter their seed before maturity. They have created sorghum

weed problems through propagation of undesirable progeny. Outerosses from other grain sorghum in small amounts are

usually not of economic importance and are seldom noticed

when the same seed colors and

same height factors are involved.

Reputable commercial seedsmen and producers under State

certification programs follow

stringent standards to assure the

production of high-quality seed.

They plant on clean ground, isolate hybrid crossing fields from

other sorghum fields, regularly

rogue oiftypes from the field, and

exercise good practices of harvest,

processing, and storage of the

seed crop. In addition to laboratory tests, they commonly make

field tests of seed lots in the

Tropics during the winter to detect those that are substandard.

Seed of hybrid grain sorghum

must be purchased new each

year; otherwise genetic segregation into many types and also

yield reduction will occur. Most

farmers are acquainted with this

from knowledge of hybrid corn.

Many grain sorghum hybrids

are available to the farmer, and

most of them are marketed by

commercial seed companies. A

decision for planting a hybrid

should be based on its performance over several years, since

erratic weather patterns can

greatly alter year-to-year performance. Data are available from

tests conducted by companies and

agricultural experiment stations.
CULTURE AND USE OF GRAIN SORGHUM

County agents have published

results of the latter.

Prior to the general use of

hybrids, grain sorghum was

treated with a fungicide on the

farm at the time of planting, if

treated at all. Little or none was

treated with an insecticide. A

fungicide treatment is desirable

to ward off soilborne organisms

that cause seed decay or attack

the young seedlings. Stands are

improved and greater seedling

vigor may be reflected in higher

yields at harvest. Fungicides will

control kernel smuts of sorghum

but not head smut.

Most hybrid seed is treated

with a fungicide-insecticide combination before packaging or distribution to the dealer. The insecticide protects against insects

that attack the seed in the soil

such as wireworms and kafir

ants. Captan and thiram are the

most common fungicides and

malathion, methoxychlor, and other insecticides are used.

SEEDBED PREPARATION

A well-prepared seedbed is essential for full stands and for

weed control. Tilling fields

usually improves soil structure

and often aids in warming the

ground. In dry areas of the Great

Plains, proper seedbed preparation helps conserve soil moisture.

In the Corn Belt and the South,

the seedbed for grain sorghum is

prepared similarly to that for

corn and cotton. The soil is

turned with a moldboard plow

and later tilled by disking and

harrowing.

In the central and northern

Great Plains, grain sorghum is

planted on fallow or it follows

wheat or sorghum. Tillage practices are the same in either

rotation except fallow ground

has an intermediate period of

summer cultivation. The moldboard plow is almost always used

for seedbed preparation on irrigated land. Stubble fields commonly are undercut or one-way

diskplowed after small-grain harvest if grain sorghum is to be

planted the following year. The

stubble is left standing by blading and holds blowing snow^

which increases the stored winter

moisture. Blade-type tools are

operated at a depth of 5 to 7

inches for primary tillage, such

as after wheat harvest, and less

deep for secondary tillage. Oneway disk plows do not cut so

deep and function best in years

of abundant rainfall when plant

growth is heavy and recurring. In

dry years they tend to destroy

the vegetation and pulverize the

soil. Formerly much land was

chiseled in preparation for planting grain sorghum. Chisels break

up the soil to a depth of 8 to 12

inches or more, and are used

when wind erosion is troublesome

during the winter and early

spring. Also, the lister was more

popular in former times, though

a modification of it, the bedder,

is popular in irrigated areas.
8 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

In the southern Great Plains,

much grain sorghum is grown by

continuous cropping. Fallowing

is not practiced in most of this

region because moisture evaporation is high and many soils are

sandy and have a low water-retention capacity. In the Southwest, grain sorghum usually is

grown in rotation with cotton.

In the spring the soil may need

tilling once to several times before planting grain sorghum.

Frequent tillage is necessary

when the spring is wet and weed

growth is rapid. The destruction

of weeds is important to avoid

competition with the crop. Grain

sorghum seeds often germinate

rather slowly, and the seedlings

are too small to compete successfully with weeds until about 4

weeks after planting. Soil-moisture loss by surface drying may

be high during dry spring weather, but usually fewer weeds grow

then. In much of the Great

Plains, land is tilled in the spring

with a high probability of getting

rain near planting time. It is not

advisable to plant in a dry seedbed unless the land is irrigated.

When the best summer-fallow

tillage methods are used, soil

moisture is stored and soil erosion by wind is prevented (fig. 1).

Blades, sweeps, chisel-harrows,

one-way disk plows, chisels, listers, and rod weeders may be

used. It is desirable to leave some

cover, to roughen the soil surface, or both for the winter and

early spring. Weed control on

fallow is necessary so that moisture is not depleted.

Because of costs, destruction

of residues, and adverse effects

on soil structure through compaction, farmers prefer to till the

soil as little as possible. If weeds

can be controlled with chemicals,

it is possible in some instances to

plant directly into wheat stubble

without seedbed preparation and

BN-36545

FIGURE 1.—Undercutting wheat stubble for next year's sorghum crop. Plant cover

will lessen erosion and help conserve rain and snow. (Courtesy of Kansas

Agricultural Experiment Station.)
CULTURE AND USE OP GRAIN SORGHUM

obtain good stands if the soil is

mellow. Minimum tillage methods such as plow-planting, tillplanting, and listing are sometimes used when sorghum follows

other crops. However, these

methods create relatively rough

seedbeds and may produce poor

stands. As more herbicides are

used in farming systems, preplant tillage operations may become less necessary.

PLANTING

Methods

Grain sorghum seed is small.

Do not plant it too deep, since it

lacks soil-penetrating ability.

Cover it immediately and firm the

soil to promote moisture absorption, germination, and emergence.

A 1-inch planting depth is sufficient if the soil is moist and

friable. A 2-inch depth may be

necessary when the soil is dry.

Newly planted sorghum is vulnerable to a hard rain followed

by rapid drying that crusts the

soil. When the seedlings have

emerged, further crusting causes

little damage. Sorghum is

planted in beds under irrigated

culture, and good emergence is

usually assured.

Plant sorghum either in rows

wide enough for tractor cultivation or in narrower rows if cultivation is not intended. Rowcrop planters for corn, cotton,

field beans, and sugarbeets can

be used when equipped with the

proper seed plates. In the Great

Plains where wheat farming is

practiced, much grain sorghum is

planted with a grain drill that

has various feeder holes plugged.

Planters especially designed

for grain sorghum also are popular. Many of them are modified

listers with furrow openers in the

front and covering devices in the

rear (fig. 2). They do not plant

as deep as the old hard-ground

listers nor do they plant as shallow as a grain drill. Nearly all

have a small rubber wheel at the

rear of the furrow opener that

firmly presses the seed into the

moist soil and improves stands.

They also have planting units

that are easily moved on a tool

bar to vary the row spacing.

Since traditionally corn was

planted in 40- or 42-inch rows

(wide enough for a horse to

walk), similar planting patterns

evolved for sorghum. However,

there is a trend toward narrower

rows, even on dry land, though

extremely narrow rows cannot be

cultivated. If weeds are controlled and if the same plant

population is maintained, grain

sorghum in narrow rows (e.g.,

20 inches) will ordinarily outyield that in wide rows (e.g., 40

inches). More efficient use of soil

nutrients and water results from

a more nearly circular feeding

area around each plant. In addition, there is more efficient use of

light as the plants are not so

crowded in the row. A canopy is
10 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

BN-3664g

FIGURE 2.—Conventional planting with loose-ground lister especially designed ior

sorghum. (Courtesy of Deere & Co.)

soon formed that shades the soil

surface, prevents rapid evaporation, and further conserves soil

moisture. On sloping land there

might be slightly less soil erosion

with narrow rows, though they

are not a substitute for other

conservation practices.

Narrow row widths are used

with large plant populations in

irrigated and in high rainfall

areas. They sometimes interfere

with cultivation, but techniques

have been devised to allow both

cultivation and irrigation down

the row. An example is the planting of double rows 12 inches

apart with 28 inches to the next

row set. This gives the same

plant population as 20-inch rows.

Other combinations may be used.

Dates

Soil temperature largely determines when grain sorghum

should be planted, assuming

moisture conditions are adequate.

Being semitropical in origin, it

should not be planted in the

spring until the soil is 65° to 70°

F. at the planting depth and

there is little chance of subsequent lower temperatures. Since

spring days are increasingly

longer toward the north, much of

the Great Plains from northern

Texas to South Dakota, as well

as the sorghum-growing area of

the western Corn Belt, warms up

enough for planting at about the

same time. This is from mid-May

to early June. Hybrid seed has
CULTURE AND USE OF GRAIN SORGHUM 11

allowed more successful earlier

planting than formerly when

varieties were used.

Planting actually begins in

mid-February in the coastal bend

of Texas and progresses northward until in the high plains of

Texas and New Mexico and in the

central plains of Kansas and

Nebraska planting is mostly in

late May and early June. Late

plantings of early maturing

types can be made in mid-July if

necessary in the southern plains.

A fall crop sometimes is planted

in the Lower Rio Grande Valley,

but frost damage is a risk.

Relatively early planting is

desirable where chinch bugs are a

problem. Much planting is done

in late March in north-central and

eastern Texas, April and early

May in central and eastern Oklahoma, from early to mid-May in

eastern Kansas, and mid-May in

eastern Nebraska. In these areas

the risk of poor stands from

early planting is preferable over

the risk of insect damage.

In the irrigated areas of southern Arizona and southern California, where high temperatures

in midsummer affect growth and

pollination, most of the grain

sorghum is planted from May to

early July. A small amount is

planted early, usually in March

or April to allow double cropping.

In the South, planting dates

range from April to July. The

late plantings often follow smallgrain harvest and provide two

grain crops in one season, but

successful midsummer plantings

depend on soil moisture and rainfall. The sorghum midge is more

likely to damage late plantings in

the South as it does in eastern

Oklahoma and north-central and

eastern Texas.

In the central and northern

areas, a common practice is to

plant full-season hybrids during

the early part of the optimum

planting period and progress

with earlier maturing types in

later plantings. More normal

growth is promoted. Stand failures are common with grain sorghum, and replanting often is

necessary. If the first planting is

made too late in the season and

replanting is done, the crop may

not mature.

In areas with longer growing

seasons, there is interest in "calendarization," which spreads

crop growth over the longest

possible period and lowers risks.

Under this system the earliest

hybrids are planted first, the midseason hybrids next, and the fullseason hybrids last. If irrigation

water is limited, peak requirements are lessened through calendarization.

Rates

Since sorghum seed is small,

emergence is difficult under suboptimum conditions. Poor stands

are commonplace and may be due

to inferior seed, improper seedbed preparation, inadequate or

maladjusted planting equipment,

or crusted soil resulting from a

heavy rain after planting. Be-
12 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

cause of experience with poor

stands, farmers tend to overplant. The use of high-quaUty

seed and good cultural practices

can do much to alleviate the

problems associated with obtaining a desirable stand, except for

soil crusting. Rotary hoeing a

crusted field prior to emergence

may help obtain a satisfactory

stand, but hoeing at emergence

may break off too many seedlings.

Planting rates formerly were

ex^Dressed in pounds per acre. The

recommendations did not give accurate stand expectations because of variation in seed size

among varieties. Grain sorghums

range from well under 15,000 to

over 20,000 seeds per pound. The

seed of most hybrids is larger

than that of varieties grown 15

years ago except some of the

true milos and feteritas.

A practical recommendation

for rate of planting is the seed

required for a given plant population per acre. Once the desired

plant population and the row

width are determined, then the

planter can be calibrated to drop

the required number of seeds per

foot of row. Table 3 lists plant

populations per acre for the commonly used row widths at two

assumed emergence rates. Recommendations formerly were

based on an average of 50 percent of the plants producing

seedlings. With improved seed

technology, one can now expect

75-percent emergence under favorable planting conditions. Using this figure and 20-inch row

spacing, a planter calibrated to

drop about tv/o seeds per foot of

row would produce 39,000 plants

per acre. If a lower emergence is

expected because of low soil ternTABLE 3.-—Plmit populations at 2 emergence rates m 3 row tüidths

Space Plants per acre at indicated emergence and row widths (inches)

between 100 percent 75 percent seeds

dropped

(inches)

10 20 40 10 20 40

Thousands Thousands Thousands Thousafids Thousands Thousands

1 627 814 157 460

2.-___ 314 157 78 235

3 209 105 52 157

4 157 78 39 118

5 125 63 31 94

6 105 52 26 78

7 90 45 22 67

8 78 89 20 59

9..- 70 35 17 52

10 63 31 16 47

11 57 28 14 43

12- 52 26 13 39

235 118

118 59

78 39

59 29

47 24

39 20

34 17

29 15

26 13

24 12

21 11

20 9
CULTURE AND USE OF GRAIN SORGHUM 13

peratures or other unfavorable ommend planting rates based on

conditions, adjustment in the

iiumber of seeds dropped per foot

can be computed readily from the

table.

Some experiment stations recsquare inches per plant. This is

merely a means of expressing

plant per unit of area. Plants per

acre can be computed by the

following equation:

43,560 sq. ft. X

144 sq. in.

square inch per plant plants per acre

Under a given set of field conditions, use approximately the

same population regardless of

the planting method or row

width, A problem of overseeding

often arises in grain-drilled sorghum, where the low rates required for dryland sorghum are

difficult to attain with this machine. However, some of the

newer grain drills for both sorghum and wheat can be geared to

plant a small amount of seed.

Some grain sorghum hybrids

have been developed that have

grasslike characters and require

a higher planting rate like small

grains.

Most of the dryland grain sorghum in the Great Plains is

planted to produce stands of between 15,000 and 50,000 plants

per acre, with usually 20,000 to

35,000. The lower rates are used

in the western areas of low rainfall and the higher rates on the

fringes of the Corn Belt. In areas

of higher rainfall or where irrigation is practiced, stands may

rani,fî from 50.000 to 100,000 or

rnv,re plants.

Under full irrigation, high

planting rates are necessary to

maximize yields. Ordinarily populations should range between

100,000 and 120,000 per acre.

With such stands, narrow rows

are necessary to prevent crowding within the row. As a result,

much irrigated grain sorghum is

planted with a grain drill High

populations require more water

and soil nutrients, and the plants

compete for sunlight and possibly carbon dioxide.

After the sorghum crop has

emerged, field stands should be

counted to determine whether

replanting is necessary. A sorghum field often appears to have

a poorer emerging stand than it

actually has, especially when a

low planting rate was used. Failure to make counts can result in

unnecessary replanting.

Sorghum partially compensates

for wide distances between plants

in the row by tillering. This

results in more heads and helps

adjust for yield differences provided the initial stand is not too

thin. Tillering is most pronounced

on heavy or clayey soils during

favorable seasons and provides

some latitude in planting rates.

However, planting rates should be

geared to the soil capabilities,

soil-moisture supplies at planting,

and expected rainfall or planned

irrigations.
14 AGRICULTURE HANDBOOK 385, U.S. DEFT. OF AGRICULTURE

WEED CONTROL

Sorghum, a warm-season crop,

is planted and grown under conditions favoring weed germination

and growth. Sorghum seedhngs

are relatively small and weak,

grow slowly under cool or adverse

conditions, and do not compete

with weeds. Therefore, weedy

stands must be remedied either

by replanting the sorghum crop

or by controlling the infestation.

Cultivation

Preplant tillage operations destroy many weeds. They include

cultivation early in the fallow

period as well as seedbed tihage

near planting. Usually weed

growth determines when the

operations are performed. Tillage

is minimum during periods of

little or no weed growth.

Planting at the proper time in a

weed-free seedbed promotes rapid

emergence of the sorghum and

gives it an initial advantage over

early weed growth. However,

weeds appear sooner or later and

are particularly troublesome following a rain, which promotes

germination and growth. Several

mechanical control measures are

available.

If the sorghum crop has

emerged, is well rooted, and is

several inches high and if the

weeds are small and shallow

rooted, rotary hoeing may be successsful. It destroys weeds in the

row as well as between the rows,

but it can damage the sorghum

plants. If the soil has crusted before crop emergence, the rotary

hoe can benefit stand establishment. Sometimes a spiketooth harrow is used in lieu of a rotary hoe,

but it is likely to damage young

sorghum plants.

Rotary hoeing is the only

means of cultivating drilled sorghum where the rows are too

narrow to use other cultivators.

It is not adapted to furrowed

plantings, though special rotary

attachments are available for cultivating listed crops.

Row-crop cultivators are most

commonly used for sorghum

planted in conventional rows

(fig. 3). Cultivation may also be

preceded by rotary hoeing. Tractor cultivators originally were

designed for conventional 40- or

42-inch rows, but equipment is

now available for 30-inch rows,

following the trend to narrow-row

corn culture, and is readily

adapted to sorghum. If row widths

less than 30 inches are used, special equipment such as sugarbeet

cultivators may be necessary.

Rows narrower than those used

for sugarbeets do not allow deployment of most farm tractors

through the field.

Most sorghum is cultivated one

to three times depending on the

reoccurrence of weed problems.

Cultivate only as deep as necessary to destroy weeds. Avoid

excessive root pruning to prevent
CULTURE AND USE OF GRAIN SORGHUM 15

BN-36647

FIGURE 3.—First cultivation with row-crop cultivator throwing dirt away from

young plants; second cultivation will throw dirt in and mound soil around

crowns. (Courtesy of Deere & Co.)

permanent plant damage. Only

rarely is it necessary to cultivate

sorghum to improve soil tilth and

to aid water intake during the

growing season. Good sorghum

crops have been grown without

any mechanical cultivation after

planting and soil structure has

not been affected, even on rather

heavy silty clay loams.

Flame cultivation is sometimes

used for cotton and may be

adapted to sorghum. The sorghum plants should be at least 12

inches tall, and the flame should

be directed basally in the row.

Generally only the tops of weeds

are killed, but the bottom leaves

of sorghum are likely to be damaged. Experimentation in a few

rows is advisable before flaming

the entire field.

Chemical Methods

Chemical control of weeds is a

part of the growing technology of

sorghum culture. When used correctly chemicals are a boon to sorghum production, but when used

haphazardly they may be a disappointment. For sorghum that

is drilled or planted in rows too

narrow for mechanical cultivation, chemicals may be the only

possible means of weed control.

The successful use of herbicides

depends on accurate calibration of

the sprayer and on closely following the label instructions with

respect to rate and time of application for specific soil types, climatic conditions, types of weeds

to be killed, their stage of growth,

and the stage of growth of the

sorghum itself.
16 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICUL ^

Herbicides are applied before

the sorghum is planted (preplant), before it emerges (preemergenee), or after it comes up

(postemergence). Rain after application increases effectiveness

of preemergence treatments, but

a heavy rain may concentrate

the chemical in the seed row, increase crop injury, and decrease

weed control. Planting seed 1 inch

deep or more increases the safety

margin. If no rain occurs after

chemical application, a shallow

mechanical cultivation, if possible, may aid in incorporation.

Several chemical herbicides are

registered for weed control in sorghum. Discussions here are based

on the amount of actual chemical

or active ingredient. Two of the

most widely used herbicides are

the related triazine compounds,

atrazine and propazine. Atrazine

is used as either a preemergence

or a postemergence spray depending on the area and other conditions. The preemergence rate is 1

to 2 pounds per acre and ordinarily controls small grassy and

broadleaf annual weeds. However,

crop injury is a risk and limits the

use of atrazine as a preemergence

treatment. Problems are likely to

arise when atrazine is applied on

coarse-textured (sandy) soil or

other soils low in organic matter.

- Atrazine is often successfully

used as a postemergence application. For best results the sorghum

should be at least in the two- to

three-leaf stage and the weeds

less than an inch tall. The chemical is particularly effective

against broadleaf weeds , g

weed and kochi-i ^nd it > ;. .atrol weed graoS^.. if they are

extremely small. Higher rates of

atrazine are used for postemergence (2 to 3 pounds per acre)

than for preemergence treatments.

Propazine is less likely to injure sorghum than atrazine, but it

may not control weed grasses as

well. It is used as a preemergence

application at 1 to 2^2 pounds per

acre. As with atrazine, injury to

the crop is likely if propazine is

applied on sandy soils or other

soils low in organic matter. Both

atrazine and propazine can be

banded or sprayed broadcast.

Only the latter is practical if the

crop is in rows too narrow for

cultivation.

In research, highly refined

mineral oil has been evaluated as

an additive to replace part of the

atrazine in postemergence treatments. The addition of oil reduces

the amount of atrazine required

per acre, slightly increases the

effectiveness, and decreases the

cost of the treatment. The decrease in amount of atrazine required probably lessens the

residual toxicity with respect to

subsequent crops. Injury to the

treated sorghum crop, however,

has been common, and the relative advantages of the combination treatment are doubtful.

Norea and propachlor also are

registered for control of weeds in

sorghum. Norea is applied preemergence at about 2 pounds per

acre. Sometimes reduced rates of
CULTURE AND USE OF GRAIN SORGHUM 17

norea and atrazine or propazine Root development is sometimes

are mixed together for more com- inhibited in sorghum by 2,4-D,

plete weed control where both and a normal-appearing crop may

broadleaf weeds and weed grasses lodge later in the season. Other

are present. Propachlor is used as symptoms of damage are brittle

a preemergence treatment at 4 to stalks, stunting, leaf curling,

5 pounds per acre. height variability, head sterility,

Continued research will prob- and yield reduction,

ably result in the development During wet seasons when

and use of other herbicides, either ground application of chemicals is

alone or in combination. Obvi- not possible, considerable acreously they will have to be very se- ages of sorghum are aerially

lective in their action. Controlling sprayed for weed control. Care

Johnsongrass and wild cane (shat- must be exercised to avoid damtercane) in sorghum fields by age to other crops in nearby or adchemical means is a special chai- joining fields, windbreaks, garlenge, for these pests are them- dens, and shade trees in or near

selves sorghum. Cultural and farmsteads. Application is best

rotational approaches to their made on a calm day. Even with

control are the most practical. ground application, the same preFormerly 2,4-D was the only cautions are advisable. Some

herbicide available for weed con- chemicals are volatile, and fumes

trol in sorghum. Although other can drift for several miles from

herbicides are now available, the field being sprayed. Mist

2,4"D is widely used in wet sea- (fine droplets) from chemicals

sons when other chemical and me- that are not very volatile can also

chanical weed-control methods are drift for several miles if applied

impossible or fail It controls only when the wind velocity exceeds 2

broadleaf weeds at rates used in or 3 miles per hour,

grain sorghum. The ester formu- f ^. ^ „ , , COMMON AND CHEMICAL NAMES

laLions are normally used at one« ^p HERBICIDES

fourth to one-half pound per acre ^ ^r • T

, ., . _ , ,, . Common name Criemtcalname

and the amme formulations at Atrazine. _ 2-chloro-4-(ethylamino)-

one-third to two-thirds pound per 6-(isopropylamino)-sacre. Though 2,4-D may injure triazine

sorghum at any stage of growth, Norea .- -..-.3-(hexahydro-4, 7-

it is less likely to do so when the methanoindan-5-yl)-l,

plants are 4 to 10 inches tall. A i=dimethylurea

basally directed spray will keep Propachlor. .._2-cliloro-N-isopropyl-

, -1 j_ j* 11 -in acetanihde

more chemical out of the leaf ^

IT IT 1 j_ i.1 Propazine 2-chloro-4, 6-bis

whorls and reduce danger to the (isopropyiamino)-scrop when it is over 10 inches tall, triazine

but this may not be possible if the 2,4-D... 2,4-dichlorophenoxyweeds are tall. acetic acid
18 AGRICULTURE HANDBOOK 385, U.S. DEPT. OP AGRICULTURE

FERTILIZERS

Grain sorghum is a soil-depleting crop. It feeds heavily on

nutrients, and when it follows

wheat, cotton, or grain sorghum,

the soil often is left low in fertility. However, with adequate fertilization, water, and proper management, most soils can sustain

high crop production. Experiments in Texas have shown that

the grain in a 100-bushel-per-acre

sorghum crop removes about 100

pounds of nitrogen (N), 14

pounds of phosphorus (P), and 14

pounds of potassium (K). Soil

amendments can be based on

these data plus other conditions

peculiar to the fields.

Nitrogen is most often the limiting element in grain sorghum

production, and the need is

related to soil type, moisture considerations, and yield level. On

dryland farms in the western

Great Plains, where the soils are

inherently fertile and rainfall is

low, response to nitrogen is generally limited to the wetter years.

On the other hand, good response

can be expected almost every season in the irrigated and higher

rainfall areas.

Rates of nitrogen vary considerably, but 20 to 40 pounds per

acre are commonly applied to dryland fields and 40 to 60 pounds to

the better soils in areas with

higher yield potential. If the nitrogen is not used because of

drought, it is carried as a reserve

for the succeeding crop, since soil

leaching is minor under these conditions. The need for nitrogen is

greater on sandy soils low in organic matter than on heavy soils.

Farmers have been using increasingly greater amounts of nitrogen

on irrigated sorghum. Less than

100 pounds per acre have been

used, but from 100 to 150 pounds

are common. Though extremely

high rates of nitrogen (200 to

300 pounds per acre) have been

used in the Great Plains, the additional yield increases may be

small and uneconomical. In the

South, extremely high fertilizer

applications are necessary, since

many of the soils are depleted

from heavy cropping and by excessive leaching from high rainfall.

Nitrogen is used at various

times but most often as a preplant

application, at planting, and as a

side dressing at cultivation. Since

this last is not always possible

with narrow-row culture, many

farmers use about one-half at preplanting and one-half at planting.

In areas with low winter temperatures and light precipitation, the

application can be made anytime

in the late fall or thereafter.

Some farmers use a little nitrogen as a starter fertilizer, but

more than 8 or 10 pounds per acre

with the seed will be detrimental

to germination. It is better to

place the fertilizer in a band a little to the side of the newly

planted seed.

Some apply nitrogen in irrigation water to the growing crop.
CULTURE AND USE OF GRAIN SORGHUM 19

This technique requires careful

metering of the fertilizer and

proper distribution of water in the

fields. Corrosion of the irrigation

system is a risk.

Various nitrogenous carriers

are available, and each is equally

effective on an actual nitrogen

basis. Cost per pound of nitrogen

availability of the product and

ease of application are deciding

factors as to which carrier to use.

Anhydrous ammonia is probably

the most common preplant carrier, though liquid nitrogen (an

ammonium nitrate urea aqueous

solution) is widely used. Prepared

fertilizers of different N-P-K

ratios or ammonium nitrate alone

are commonly used at planting.

Phosphorus and potassium requirements for grain sorghum are

not so great as for nitrogen, and

the soil reserves are generally

more adequate. However, continued high crop production may

make phosphorus application

advisable, and under certain conditions potassium may be deficient.

Soil tests, knowledge of the

soil type and its characteristics,

and experience will determine

whether phosphorus or potassium

amendments are necessary. Specific recommendations can be

obtained from the county agent

or the State agricultural experiment station.

Calcium deficiencies may occur

in the Corn Belt and in the South,

but liming is ordinarily a routine

fertility practice in these areas.

In most of the sorghum-growing

areas the soils are calcareous, and

problems sometimes arise from

high pH conditions. Iron deficiencies often occur in young

plants and are more common on

the lighter or sandier soils. The

problem is largely lack of availability to the plant rather than a

shortage of the element in the

soil.

Yellowing due to iron deficiency is unlike yellowing from

lack of nitrogen. The former

shows up in young plants, whereas the latter does not appear until

later in the season. Plants showing iron deficiency are more

likely to be uniformly chlorotic,

whereas nitrogen-deficient plants

exhibit symptoms on the older

leaves. Sorghum often outgrows

the iron deficiency as the plants

develop a more extensive rootfeeding area. The most practical

and most economical remedy for

iron deficiency is to use foliar

sprays of organic iron forms,

called chelates. They are more

conveniently used in sprays than

such inorganic forms as iron sulfate, whereas soil applications of

iron compounds require prohibitive amounts.

Zinc deficiencies often occur

on irrigated land that required

extensive land leveling. Chelated

forms of zinc are available for

correcting the problem. Experience has shown that zinc deficiencies tend to be alleviated after

several years of cropping and returning plant residues to the

ground.

Other plant nutritional problems may occur in specific areas
20 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

and may need special diagnosis.

Local or State agricultural advisers should be consulted.

Though commercial fertilizers

are generally used for sorghum,

there may be special situations

where manure is available as

from cattle feedlots or poultrylaying houses. Plant v^astes from

canning or food-processing plants

and sewage sludge are other examples of organic fertilizers. If

these sources can be obtained and

applied economically, they may be

utilized. Always incorporate them

into the soil through tillage to

promote decay and to prevent nitrogen losses to the atmosphere.

IRRIGATION

More than 25 percent of the

grain sorghum acreage in the

United States is irrigated, including most of the California, Arizona, and New Mexico crop.

Though grain sorghum is drought

tolerant, it responds to favorable

moisture conditions. Yields of

6,000 to 8,000 or more pounds per

acre often result from irrigated

plantings when fertility and plant

populations are optimum.

Limited water supplies are

most efficiently used through preplanting irrigations in the offseason, when work can be spread

over a longer interval than is

possible during the growing season. The best soils are medium or

medium-fine textured and have

deep profiles for high water absorption. Soil wet to 6 feet

preplant will often produce a satisfactory crop with only one

additional irrigation, usually at

booting or heading time. Sorghum

roots draw moisture reserves

from great depths if required, as

demonstrated in Kansas experiments, where the crop utilized

2 See also U.S. Dept. Agr. Leaflet 511,

"Irrigating Grain Sorghums."

water from a 90-inch depth when

the field was wet to capacity to 7

feet at planting and no additional

w^ater (except 5 inches of rainfall) was applied during the growing season.

Under full irrigation most

growers water two to four times

and depend on rainfall during the

growing season to supply about

half the requirements. But timeliness of irrigation is important

as plants should never show

drought stress. If the soil moisture falls below 25 percent in the

upper 2 feet, yields likely will be

adversely affected. Although the

period of heaviest water use is at

booting and heading, irrigation

may be necessary 2 or 3 weeks

after planting if no rain falls and

the weather is hot.

When fertilizers are applied

and no rain occurs, it will be necessary to irrigate early so that the

nutrients will be available to the

young growing plants. Soils low in

fertility utilize water more efficiently when fertilizers are used.

It is also more economical to irrigate with high rates (e.g., 4

inches at a time) if the soil is not
CULTURE AND USE OF GRAIN SORGHUM 21

sandy than to irrigate oftener

with lower rates.

Do not apply water once the

grain is in the dough stage. Excessive soil moisture at this time

encourages tillering and head

branching and prevents the plants

from drying out for harvest.

However, lodging can be a problem if soil-moisture supplies are

completely depleted before the

crop is mature.

Irrigation of most grain sorghum is with graded furrows, but

level furrows, level borders,

graded borders, and sprinklers

are sometimes used. Sprinklers

are adapted to rolling land and to

sandy soil. Gated pipes are popular in some areas for furrow irrigation because they reduce ditching, lessen head-ditch erosion, and

control the water better.

HARVESTING, DRYING, AND STORING

Nearly all grain sorghum is

harvested standing with a combine (fig. 4). In the central and

northern Great Plains, the crop

usually is harvested after frost.

In the other major production

areas where the growing seasons

are longer, combining is done

when the grain is ripe.

Sorghum grain readily threshes

free from the head when the seed

moisture content is 20 to 25 percent. The seed is physiologically

mature at even a higher level.

Though ripening is largely a process of lowering moisture content,

grain must reach a safe, low level

for harvest unless artificial drying is used; otherwise it might

spoil in the bin. A maximum moisture content of 13 percent in the

Great Plains and Southwest and

1 or 2 percent less in the Corn

Belt and South is desirable.

Hybrids with head stems that

dry out after the grain matures

are popular since they can be harvested earlier in the fall. Harvesting hybrids with green heads

must wait generally until a light

frost has killed the top of the

plant. Usually the grain is sufficiently low in moisture a week

after such a frost.

Since hybrids differ in threshability, concaves can be set and

cylinder speeds adjusted so that

any hybrid can be satisfactorily

threshed. Threshing should be as

clean as possible since bits of

stems, leaves, and head branches

carry much moisture.

Ordinarily grain sorghum does

not grow excessively tall under

dryland conditions, but it can

attain great height under irrigation and in wet seasons. Generally

the heads are better exerted when

the plants are tall. In thick plantings grain sorghum also tends to

grow taller and have smaller

heads. If lodging is a problem,

most of the crop can be salvaged

by installing pickup attachments

on the combine.

Wet grain, either from the

combine or in the bin after storage, is best handled by air drying.
22 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

FIGURE 4.—Combining a dryland field after frost.

BN-36546

(Courtesy of Deere & Co.)

Unheated air can be used if the

grain is not too damp or if the

humidity is not too high. Damp

grain and high humidity require

higher air volumes, and drying

operations may have to be limited to the drier parts of the day.

Hot-air driers are more popular in

the sorghum-growing areas of

higher rainfall where harvest

problems are common. They allow

combining before the onset of

inclement weather and before

lodging becomes serious.

Temperatures must be judiciously considered with hot-air drying. Grain heated over 200" F.

may lose some of its feed value

through oxidation of carbohydrates. Grain that is to be industrially milled should not be heated

over 140° as the starch may be

modified. A crop harvested for

seed should not be heated over

110° or germination may be reduced.

Before storing sorghum grain

thoroughly clean the bins. Sweep

floors and walls and then spray

with an effective insecticide that

is safe to apply and safe for livestock if the grain is to be fed.

Remove potential insect-breeding

grounds in and around the bins,

such as feed and seed residues

and dirty grain sacks.

Insect infestations later may be

controlled through fumigation.

Take precautions against inhaling

poisonous fumes and safeguard

against fire as some fumigants

are highly volatile. Generally

grain sorghum requires higher

rates of fumigants than wheat because the kernels are packed together more closely. It is for this
CULTURE AND USE OF GRAIN SORGHUM 23

reason that heating in the bin is

more of a problem.

Clumping of the grain and a

musty smell indicate excessively

high moisture and spoilage. To

prevent these problems, either

use additional air drying or move

the grain from one bin to another.

Moving several times may be necessary since lowering grain temperature is the primary efl'ect

rather than lowering moisture.

Generally spoilage is less serious

during cold weather. Much grain

is stored at temperatures too high

for continued safe storage, but

problems seldom occur if it is used

for feed by spring.

UTILIZATION

Feed Value

Grain sorghum is similar chemically to corn, but generally it is a

little higher in protein. However,

protein can vary considerably

depending on the conditions under

which the crop was grown. High

yields tend to lower protein,

whereas nitrogen fertilization

tends to increase it. Immature

grain, in which carbohydrate

deposition is incomplete, has more

protein than mature grain. Like

corn, grain sorghum is particularly deficient in lysine, and also

when the total protein is increased, the most essential amino

acids make up a relatively lower

percentage of the total.

The fatty acids in sorghum

grain and corn are almost identical, though corn tends to have a

little higher total fat content.

Mineral composition of the two

crops differs only slightly.

A major difference is in vitamins. Ordinary grain sorghum,

even with colored seedcoats, is

like white corn in that it is practically devoid of carotenoid pigments and vitamin A precursors.

The best yellow endosperm varieties from Africa have about half

as much carotenoid and xanthophyll pigments as yellow corn,

and adapted American-derived

breeding stocks often have less.

Yellow pigments dissipate more

readily from sorghum grain in

the head than from corn in the

shuck because of exposure to the

elements. Breeders are attempting

to develop better grain sorghums

with higher vitamin A content,

but it is necessary to have the

character in both parents of a hybrid. Grain sorghum is higher in

niacin, a B vitamin, than corn,

though this vitamin ordinarily is

not lacking in livestock rations»

Feeding experiments have

shown that grain sorghum and

corn are, in general, about equal

in feed value. Best results have

come from feeding sorghum, to

laying hens and to broilers. Also,

grain sorghum has or nearly

equaled corn in rations for milk

cows and for fattening lambs. It

has tended to be slightly less valuable than corn for fattening both

beef and swine, though in some

experiments they have been found

to be the same. The slightly lower
24 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

value for sorghum in feeding beef

and swine may be due to differences in fat content, amino acid

balance, and other unrecognized

chemical or physical differences

between the two grains. Meat flavor, texture, and appearance of

animals fed sorghum grain are

equal to those fed corn.

Feed differences are usually

reflected, sometimes unjustly, in

a market-price differential between the crops. When grain sorghum is priced 95 percent or less

than corn per hundredweight, it is

probably the better buy. If feed

grains are home grown, the dollar

return per acre in most of the

sorghum-growing area will be

greater for sorghum than for

corn because of higher yields.

Sorghum grain is highly palatable to livestock, and intake

seldom limits livestock gains. Certain varieties and hybrids, however, are less palatable, and the

bitterness is often associated with

tannins and phenolic compounds.

Some of t^se sorghum types

were developed to deter birds

from feeding in the ñeld. External conditions, such as molds on

weathered grain, can also affect

palatability. Mycotoxins produced

by molds on grain in the head or

on grain in the bin may affect

animal health.

Most sorghum grain is processed (cracked, ground, or rolled)

before feeding, though it was

common formerly to feed whole

sorghum grain to swine and

sheep. Sheep still utilize unground

grain effectively, but whole heads

should be ground if fed to sheep.

In addition, much of the sorghum

grain fed to cattle is modified

further by special processing,

such as steam rolling or flaking.

Feed efficiency allegedly is increased. In large commercial feedlots the use of more refined

processing equipment apparently

is economical.

High-moisture sorghum grain

(e.g., about 25 percent) may be

ensiled and later fed to cattle. The

grain keeps well if it is not

exposed to the air. Both upright

and trench silos have been used

successfully. This method of utilization allows earlier harvest and

eliminates problems associated

with bin storage of sorghum

grain. Also, high-energy silage

can be made from grain sorghum

heads alone or from the entire

plant. A crop often can be salvaged this way when it will not

mature for grain.

Pasturing cattle or sheep on

combined sorghum stubble is a

common practice (fig. 5). Both

roughage and dropped heads are

utilized. Some sorghums, particularly those with juicy stems and

leaves, are preferred for postharvest grazing. These same types,

however, are slowest to dry out

for combining unless a frost

occurs. The stalks from a lowyielding grain crop tend to have

more sugars than from a highyielding crop.

Stubble with secondary growth

should be pastured carefully, if at

all, because of the danger of prussic acid (HCN) poisoning. The
CULTURE AND USE OF GRAIN SORGHUM 25

FIGURE 5.—Cattle grazing on grain sorghum stubble after harvest.

Kansas Agricultural Experiment Station.)

BN-S6544

(Courtesy of

problem tends to be more serious

in the central am aorthern parts

of the sorghum region.

Industrial Use

Most of the grain sorghum

grown in the United States is fed

to livestock, but about 10 million

bushels are milled annually for

starch or flour or for producing

industrial alcohol. Both wet and

dry milling are employed, utilizing both waxy (glutinous) and

ordinary grain. Starch flour is

used principally in building materials, primarily wallboard. Other

uses are tor sizings, adhesives,

oil-well drilling muds, and food

products. Sorghum starch is converted to dextrose and is used in

the fruit-canning, baking, and

confection industries. Important

milling byproducts are livestock

feed and oil.

During World War II grain sorghum was a prime source of

industrial alcohol, and waxy sorghum starch was substituted for

tapioca. Research is developing

new industrial uses for grain sorghum as well as new grain

sorghums for these uses.

DISEASES

Diseases attacking grain sorghum can be classified as seed

rots and seedling blights, foliar

or leaf diseases, inflorescence or
26 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

head diseases, and root and stalk

rots. They are caused by fungi,

bacteria, and viruses, or they may

be physiological in nature.

Many diseases of sorghum cannot be adequately or economically

controlled by chemical means. Resistance is known for several diseases. Using resistant varieties or

hybrids when available will help

to minimize crop damage.

Seed Rots and Seedling Blights

Seed rots and seedling blights

are most severe when the soil is

wet and cold following planting.

Under such conditions the seed

fails to germinate because it is

attacked by various seedborne and

soil-inhabiting fungi that soon rot

it. To control these rots most

effectively, plant sound seed free

of cracks, treat it with a fungicide

such as captan or thiram, and

plant after the soil approaches

70° F.

Foliar or Leaf Diseases

Leaf diseases are generally

destructive in areas with high

rainfall and high humidity. Bacterial stripe, bacterial streak, and

bacterial spot often are present

but usually do not cause serious

losses. During warm, moist seasons these diseases may spread

rapidly from the lower to the

upper leaves until they destroy

much of the leaf surface.

The fungus leaf diseases

include anthracnose, leaf blight,

zonate leaf spot, gray leaf spot,

rough spot, target spot, sooty

stripe, rust, and downy mildew.

Other than downy mildew, these

diseases seldom reach economic

importance except in the South.

Downy mildew only recently became important and has been reported in several major sorghumgrowing States. Early infected

plants may become stunted and

chlorotic, characterized by yellowwhite streaked whorl leaves. A

midseason, nonsystemic condition

can occur in which ''down"

appears on the lower leaves and

terminates in leaf blighting. A

late-season systemic symptom,

the disintegration of leaf tissue,

gives a ragged appearance. Resistant varieties are the best means

of control. Another downy mildew, called crazy top, is not so

serious and occurs in low, wet

areas. The plants are stunted and

chlorotic, with thickened, twisted

leaves. If heads are produced, they

are proliferated.

Maize dwarf mosaic (MDM) is

the most serious virus disease of

sorghum, and it too only recently

became prominent. It is a mutant

of the sugarcane mosaic virus and

is transmitted by aphids. Early

infection produces stunting and

mottling. Older plants often have

a red-leaf symptom characterized

by striping or streaking with deep

pigmentation of necrotic areas.

Badly infected plants may fail to

head or produce abnormal heads

with sterility. As with downy

mildew, plant resistance is the
CULTURE AND USE OF GRAIN SORGHUM 27

best control for MDM. Destruction of Johnsongrass and other

host plants also is helpful.

Inflorescence or Head Diseases

Smuts are the most common

diseases infecting the floral parts

of grain sorghum. Head smut is

the most serious and attacks the

heads, usually destroying them

and leaving an open mass of

spores. Occasionally the head of

an infected plant may be sterile,

and smut galls appear later on

tiller heads or head side branches.

Other heads may show a proliferation of floral parts. Since the

disease is soilborne where it infects the young plants, seed treatment is of little help. However,

good resistance exists in certain

varieties and hybrids.

Covered kernel smut and loose

kernel smut are not so serious as

formerly when grain sorghum

was planted without fungicide

treatment. The diseases are similar except the galls are mostly

covered in the former and largely

broken in the latter. The three

sorghum smuts are not poisonous

to livestock, and grain that has

been contaminated with spores

can be fed without harmful

effects.

A small-seed condition, whereby

the panicle may be partially

sterile or may have variable patterns of normal and undeveloped

seeds, has occurred in many highproduction fields in recent years.

The cause is not known except the

disorder seems to be associated

with cool, cloudy, moist weather

following flowering.

Root and Stalk Rots

The most important root and

stalk diseases of grain sorghum

are periconia root rot (milo disease), anthracnose, charcoal rot,

fusarium and rhizoctonia stalk

rot, and weak neck.

Periconia root rot attacks

milo, darso, and their derivatives

but not other groups of grain sorghum. If susceptible seedlings do

not die soon after emergence,

they often have the appearance of

drought damage. Resistant mutants were found in milo, and now

all commercial hybrids are resistant to the disease.

Anthracnose stalk rot, also

called red rot, is caused by the

same fungus that causes anthracnose leaf blight. Culms or stalks

become invaded; the tissue becomes diseased, rots, and finally

dries; lodging or reduced grain

and stalk quality often results.

Good cultural practices and crop

sanitation help confine the disease in the absence of plant

immunity.

Charcoal rot attacks the stalk

as the plant nears maturity. The

pith dries and disintegrates so

that the stalk is weakened and

finally breaks at the base. A few

varieties are partly resistant to

charcoal rot, and this offers the

principal source of control. This

disease is most serious when the
28 AGRICULTURE HANDBOOK 385, U.S. DEPT. OF AGRICULTURE

plants suffer from a shortage of

soil moisture.

Fusarium stalk rot produces

symptoms similar to those of charcoal rot, but the spores in the rotted stalks are white instead of

black. The fungus apparently

enters the plant through openings

made by insects and mechanical

injuries. Fusarium rot is commonly found as a secondary infection in diseased plants.

Rhizoctonia stalk rot differs

from charcoal rot in that the

vascular fibers appear as light

streaks in a reddish discolored

pith. The fruiting bodies are

brown instead of black and appear

on the outside of the stalk

instead of inside.

Weak neck is a nonparasitic

disease. Combine-grain varieties

with heavy heads but a weak

head stem that dries when the

grain ripens often develop a rot at

the base of the head stem within

the boot where moisture accumulates. Bacteria and fungi cause

the rotting. The stem is weakened

so that the heads break during

high winds.

CAUSAL ORGANISMS OF SORGHUM

DISEASES

Common nam^e Causal organism.

Anthracnose Colleto trichum

graminicola ( Ces).

G. W. Wils.

Bacterial spot Pseudomonas syringae

V. Hall

Bacterial streak. Xanthomonas holdcola (Elliott) Starr

& Burkh,

Bacterial stripe

Charcoal rot

Covered kernel

smut

Crazy top

Downy mildew

Pseudomonas andropogoni (E. F. Sm.)

Stapp

. Macrophomina^

phaseoli (Maubl.)

Ashby

Sphacelotheca sorghi

(Lk.) Clint.

. Sclerophthora macrospora (Sacc.) Thrim.,

Shaw, & Naras

. Sclerospora sorghi

Westen & Uppal

Fusarium

stalk rot Fusarium. moniliforme Sheldon

Gray leaf spot... Cercospora sorghi

Ell. & Ev.

Head smut Sphacelotheca reiliana (Kuehn) Clint.

Leaf blight . _ Helminthosporium

turcicum Pass.

Loose kernel

smut Sphacelotheca cruenta

(Kuehn) Potter

Maize dwarf

mosaic— aphid-transmitted

virus

Milo disease Pericomxi circinata

(Mangin) Sacc.

Rhizoctonia

stalk rotRough spot

Rust

Sooty stripe

Target spot .

Zonate leaf spot

- Rhizoctonia solani

Kuehn

. Ascochyta sorghina

Sacc.

- Puccinia purpurea

Cke.

Ramulispora sorghi

(ElL&Ev.) L. S.

Olive & Lefebvre

HelmÂnthosporiuin

sorghicola Lefebvre

& Sherwin

Gloeocercospora

so'ïghi n. Bain t Edg
CULTURE AND USE OF GRAIN SORGHUM 29

INSECTS^

Several insect species attack

grain sorghum. Some of the

most important economically in

the United States include the

following species:

Grasshoppers

Grasshoppers frequently do

considerable damage to grain sorghum. If very abundant, they

strip the leaves from the plant

and feed on the heads.

Fields can be protected from

grasshopper injury by destroying

young nymphs in adjacent field

margins, ditchbanks, or wastelands with an insecticide before

they move into grain sorghum.

Proper tillage in the fall and

spring, if in conformance with

good soil conservation practices,

¥/ill destroy many grasshopper

eggs and reduce subsequent

infestations in the vicinity.

Corn Earworm

The corn earworm is found

throughout the grain sorghum

area. The larvae feed in the leaf

whorl and on the developing head.

Varieties with open heads give

some protection from this insect.

Sorghum Webworm

The sorghum webw^orm is often

abundant in the eastern part of

the grain sorghum area. When

abundant this insect may destroy

the developing grain. Destruction

^ l^repared by Entomology Research

Division.

of plant residues and early planting are cultural aids.

Corn Leaf Aphid

The corn leaf aphid is sometimes common on grain sorghum

throughout the central and southern Great Plains. It is usually

found in the central whorl or on

the panicle after emergence.

Occasionally it is so abundant

that it prevents the formation of

grain. No cultural control of the

aphid is effective.

Sorghum Midge

The sorghum midge sometimes

prevents the profitable production of grain sorghum in the

more humid areas. The adults lay

their eggs in the flowers, and the

larvae suck the juices from the

developing seed.

Locate grain sorghum fields as

far as possible from outside

sources of infestation, such as

Johnsongrass or earlier planted

grain sorghum. To reduce possible

damage, planting should be timed

so that sorghum will bloom when

the adult insects are not abundant

in the fields.

Chinch Bug

The chinch bug in some years is

a serious pest of grain sorghum

in the eastern part of the sorghum-growing region. The firstgeneration eggs are laid in fields

of small grain, where the young

nymphs feed. As the grain ripens

the older nymphs and adults mi-
30 AGRICULTURE HANDBOOK 385, U.S. DEPT, OF AGRICULTURE

grate to nearby corn or grain sorghum. They suck juice from the

plants and thus weaken and sometimes kill them. Chinch bug injury

can be reduced by planting resistant varieties early and as far as

possible from infested small

grains.

Other Insect Pests

Several other insects sometimes injure grain sorghum.

Among them are the southwestern corn borer, lesser cornstalk

borer, European corn borer, flea

beetle, stinkbug, fall armyworm,

white grub, greenbug, and various species of ants.

The greenbug became a serious

pest in most of the sorghumgrowing area in 1968. Infestations first occur on the lower

leaves and then move upward on

the plant. Small plants are completely destroyed and large plants

lose their lower leaves. A population of 30,000 aphids per plant is

not unusual. This aphid feeds and

reproduces during hot weather at

temperatures as high as 110° F.

No cultural control is effective,

but several insecticides are satisfactory if applied in time.

COMMON AND SCIENTIFIC NAMES

OF IMPORTANT INSECTS THAT

ATTACK SORGHUM

Common nmne Scientific name

Chinch bug Blissus leucopterus

(Say)

Corn earworm -.- Heliothis zea (Boddie)

Corn leaf aphid . Rhopalosiphum

maidis (Fitch)

European

corn borer Ostrinia nubilalis

(Hübner)

Fall armyworm. iSpodoptera frugiperda (J. E. Smith)

Greenbug Schizaphis graminum

(Rondani)

Lesser cornstalk borer Elasmopalpus lignosellus (Zeller)

Sorghum midge-. Contarinia sorghicola

(Coquillett)

Sorghum

webworm Celama sorghiella

(Riley)

Southwestern

corn borer Diatraea grandiosella

Dyar

?U.S. GOVERNMENT PRINTING OFFICE: 1970 O 387-729