A 

Y*,-- 

e4zBzs.- United States 

Vepartment of 

Forest Service 

Northeastern Forest 

Experiment Station 

Research Paper 

N E- 500 

1982 
The Aul-haa 

Merrill C. Hoyle is principal plant 

physiologist at the Forestry 

Sciences Laboratory, Northeastern 

Fores"rxperiment Station, Durham, 

New Hampshire 03824. He received 

his B.S. and M.S. degrees from the 

University of Massachusetts, and 

his Ph.D. degree from the University 

of New Hampshire. He conducts research on enzymatic and hormonal 

mechanisms of growth regulation in 

trees, 

Manuscript received for 

pubiication 13 May 1981 

Abstract 

An automatic mat-watering system for growing hardw~ood seedlings in containers was designed 

and tested. The system has only 

one moving part, and no electrical 

requirements. There is no need to 

calculate different watering schedules for different growth phases, 

different hardwood species, or 

different evapotranspiration conditions. Results were excellent with 

mat wa"reng combined with simple, 

peat-vermiculite mixes, and pelfeted, slow-release fertilizers. The 

system is economical, simple, and 

physiologically ideal. Mat watering 

was effective in growth rooms, controlled environment chambers, and 

greenhouses. 
Introduction 

Production of container-grown 

tree seedlings for reforestation has 

become an increasingly important 

practice in modern forestry (Tinus e t 

al. 1974). Research has concentrated on the development of specialized containers. Potting mixes, 

photoperiod, light intensity, 

temperature regimes, carbon dioxide levels, and fertilizer formulations 

have been studied also. By comparison, less research has been done to 

improve the watering system. 

Hand watering or various 

electro-mechanical systems for 

automatic watering are used generally. The most elaborate automatic 

system is a moving boom that 

passes back and forth over the 

seedlings during irrigation (Tinus 

and McDonald 1979). Hand watering 

is a simpie system, but it is costly 

because of wages and is subject to 

errors in human judgment. 

Automated systems have purchasing, installation, and maintenance costs, which can be moderate to high, and are subject to mechanical and electrical breakdown. 

Overhead watering systems are generally adequate for conifer seedlings, but not for broadleafed hardwood seedlings. Leaves of hardwood seedlings cover the soil surface and prevent wetting from 

above. Hardwood seedlings wilt and 

die unless hand watering is used as 

a back-up system. 

In all of these watering systems, the potting soil goes through 

a wet-up and dry-down cycle. After 

wet-up by the watering system, drydown occurs due to evapotranspiration. The problem is to regulate the 

frequency and duration of watering 

to prevent wilting and subsequent 

growth retardation. Because 

evapotranspiration varies with species grown, day length, ambient air 

temperature, and relative humidity, 

watering programs usually require 

constant monitoring and frequent 

changes. 

Another problem with automatic watering systems is breakdown during nights, weekends, and 

holidays. Consequently, alarm systems must be installed to cover 

periods when personnel are absent, 

and thus, more costs are incurred. 

An ideal water system should 

be: 

1. Economical to purchase, install, 

operate, and maintain. 

2. Simple to install, operate, and 

maintain. 

3. Completely automatic. 

4. Reliable-that is, no breakdowns. 

5. Able to satisfy the plants 

moisture needs through all 

stages of growth. 

Details for constructing a 

simple, automatic, mat-watering system that meets all the above criteria 

are given here, The mat-watering 

system was used in growth rooms 

and controlled environment chambers as well as in greenhouses. 

Also, different potting mixtures and 

different types of commercial fertilizers were tested for their compatibility with mat watering. Birch 

was the principal species used in 

these experiments. Several other 

hardwood species were tested to 

verify the results obtained with 

birch. 

Methods and Materials 

Bench Setup for Mat Watering 

A typical setup for mat watering in a growth room is shown in 

Figure 1. A bench or table that is 

level from side to side along its entire length, with a solid top and flat 

surface, can be used, and the top 

should be swept clean of particulate 

matter. A wooden trough about 15 

cm wide and 12 cm deep was constructed across one end of each 

bench. The trough was lined with 

heavy-duty polyethylene to make it 

waterproof, and the bench was covered also. The end of the table with 

the trough was raised with shims to 

tilt downward 2 degrees. 

A simple float valve' was 

clamped into the trough and hooked 

to the water supply with a garden 

hose. This valve contains the only 

moving part in the whole system. 

After prolonged use, the unit may 

not shut off the water completely. 

This is easily remedied by replacing 

the plastic valve (several spares 

come with each new unit). Water 

level in the trough was adjusted to 

about 2.5 cm below the top edge by 

raising or lowering the float valve. 

Mats for capillary watering are 

generally made of synthetic fibers 

such as polyester. Large rolls of mat 

made especially for capillary watering can be purchased from most 

greenhouse suppliers.* A single 

thickness of this mat on greenhouse benches is recommended. If 

the bench area is not large, inexpensive polyester blankets from a local 

department store can be used. 

Coloring in the blanket is not a 

problem. Cut to size so the edges of 

the mat are about 2.5 cm away from 

edges of the bench top and place 

on the bench. Small pieces can be 

used by overlapping. About 10 cm 

of one end of the mat was draped 

into the water trough. The rest of 

the mat was thoroughly wetted and 

left to equilibrate. At equilibrium, 

the mat will be saturated, but water 

will not run off the bench. If water 

drips off the side, check to see if 

the bench top is level (side-to-side) 

and not warped along the long axis. 

The water trough was covered with 

black polyethylene to keep debris 

out and prevent the growth of algae. 

used Dare-0-Matic, Farm Tank Float 

Valves, Battle Creek, Michigan, purchased from a local farm supply store. 

The use of trade, firm, or corporation 

names in this publication is for the information and convenience of the reader. 

Such use does not constitute an official 

endorsement or approval by the U.S. Department of Agriculture or the Forest 

Service of any product or service to the 

exclusion of others that may be suitable. 

ZI used Troy Flo Thru Moisturing Mat 

and milled Wisconsin peat moss from 

Griffin Greenhouse Supplies, Inc., 1619 

Main Street, P.O. Box 36, Tewksbury, 

Massachusetts 01876. 
Figure 1.-Components of an automatic mat-wafering system in a growth room are: A-wet mat on plastic covered bench, B-water 

trough with float valve (troughs in background are covered to prevent algae growth), and 6-complete setup with potted seedlings 

and overhead lighting. 
The setup for automatic mat 

watering in controtled environment 

growth chambers (Fig. 2) and greenhouses (Fig. I I) was essentially the 

same. 

Container Setup 

Almost any rigid container is 

compatible with mat watering. 1 

have used plastic pots from 7.5 crn 

to 20 cm in diameter and different 

size Styroblocks. One or more holes 

are needed in the bottom for inserting wicks. Wicks can be cut from 

pieces of mat and inserted with 

tweezers (Fig. 3). Ten-cm plastic 

pots with three wicks in the bottom 

of each were used in all the experiments described in this paper. In 

unreported tests based on the results of these experiments, a variety 

of other containers were Crested with 

different hardwood species. 

Patting Mixes and Fertilizers 

Different potting mixes containing peat with perlite, and/or vermiculite were tested. The different 

combinations were mixed when dry 

then wetted with lap water. Fertiiizers were added next. Pols containing wicks were filled with the 

different combinations of mix and 

fertilizer and placed on a wemat. 

Equilibrium between water in the 

mat and water in the soil mix was 

obtained when all free water drained 

from the soil mix and only capillary 

water remained. This was usually 

accomplished within a half hour. 

Seedling Establishment 

Paper birch (Betula papyrife~a) 

was the primary test species used 

in these experiments. Some experiments also used yellow birch 

(Betula ailegkaniensis). Birch seeds 

were germinated in shallow trays of 

potting mix under lights and transplanted into pols or germinated in 

the pots. In the latter case, Oil Sorb 

(composed of kaolinite clay) was 

sprinkled over the birch seed and all 

pots were covered with plastic until 

the seed germinated. Two weeks 

after germination, seedlings were 

thinned "i the most vigorous seedling per pot. Two true leaves were 

Figure 2.-Mat bvalering setup in a controlled environment growth chamber 

Figure 3.-Plastic containers with wicks in place. Wicks are most easily 

inserted with tweezers. 
usually present. Seedlings were 

grown for 8 more weeks in all 

experiments. Height measurements 

were taken weekly. All other measurements were taken at the end of 

this 8-week-growth period. 

Photoperiod 

Twenty-hour photoperiods were 

used in these experiments with 

birch and in all subsequent tests 

with other species in the greenhouse. Hardwood species in New 

England are long-day plants requiring a minimum photoperiod of 14 to 

16 hours. For commercial production in greenhouses, long photoperiods are achieved most economically by interrupting the dark period 

for an hour. 

Germination of Other Species 

Tested 

European black alder (Alnus 

glutinosa) seed was collected locally and germinated directly in the 

containers. Black locust (Robinia 

pseudoacacia) seed was collected 

locally, taken from the pods, treated 

with concentrated sulfuric acid, and 

germinated in the containers. An 

inoculum made from crushed root 

nodules that were dug from under 

wild trees was given once after 

germination. Red maple (Acer 

rubrum) and silver maple (Acer 

saccharinum) were collected locally 

and germinated in the containers. 

Sugar maple (Acer saccharurn) and 

northern red oak (Quercus rubra) 

were collected locally, germinated 

in the cold at 3.5"C, and planted 

when radicals were 2.5 cm long. Pin 

cherry (Prunus pennsylvanica) and 

black cherry (Prunus serotina) were 

stratified with moist forest humus in 

the cold at 3.5"C and planted after 

germination at room temperature. 

Sweet gum (Liquidambar styraciflua) 

collected in Pennsylvania was germinated in the containers at 

ambient temperatures. 

Results 

Birch Experiments 

Experiment I. Comparisons of 

yellow birch growth were made between two potting mixes (peatvermiculite- PV and peat perlitePP), two types of fertilizer 

(Osmocote-solid and Rapid-Groliquid), and two methods of 

watering (automatic mat watering 

and hand watering in trays under 

each pot). Pelleted Osmocote (18-6- 

12) was mixed in at the rate of 6 

glpot. A solution of Rapid-Gro (25 

gllO I) was used to wet the mix initially, and 25 mllpot was added each 

week thereafter. 

For height growth, mat 

watering was better than hand 

watering, PV was better than PP, 

and Osmocote was better than 

Rapid-Gro with PV but not PP (Table 

1). The tallest seedlings averaged 40 

cm 8 weeks after appearance of the 

first true leaf. The best treatment 

combination-PV with a one-time 

application of pelleted, slow-release 

fertilizer and automatic mat watering-was also the most convenient 

and the most economical. 

Dry matter production (Fig. 4) of 

leaves, stems, and roots was best 

with the same combination of 

factors. However, with PV, RapidGro was equal to Osmocote in dry 

matter production with mat watering, but not with hand watering. The 

cause of this reduction in growth 

associated with hand watering was 

not determined. 

Further comparisons were 

made between yellow-birch growth 

in the mixes described above and 

the peatlite mixes developed at 

Cornell University (Boodley and 

Sheldrake 1967). The Cornell peatlite 

A is a 1 : 1 mixture of peat and 

vermiculite, and peatlite B is a 1 : 1 

mixture of peat and perlite. Both 

peatlite mixes are fortified with 

ground limestone, superphosphate 

(20%), 5-10-5 fertilizer, borax, c helated iron, and a surfactant. In general, peatlite B produced greater 

height and dry weight than peatlite 

A (Table 2), but both Cornell mixes 

were inferior to the growth obtained 

with the PV mix and Osmocote. 

Experiment 2. Because of the 

excellent results with mat watering 

in the first experiment, only mat 

watering was used in this and all 

subsequent experiments. Pelleted 

Osmocote was tested against solutions of Rapid-Gro and Universal. 

OSMOCOTE (18-6-1 2) was added at 

the rate of 6 glpot. Rapid-Gro (20-20- 

20) and Universal (23-19-17) solutions of 5 gllO I were added initially 

and 15 mllpot were added each 

week. Trace elements were also 

tested by additions to Osmocote 

and Rapid-Gro (Universal, 23-1 9-1 7, 

Table 1.-Effect of watering technique, type of potting mix, and 

type of fertilizer on height growth (cm) of yellow birch 

seedlings. 

Peat-vermiculite Peat-per1 ite Fertilizer 

treatment Mat Tray Mat Tray 

None 

Osmocote 

Rapid-Gro 
3 PEAT- PERLITE 

- Control Osmocote Rapid-Gro 

U, t I-------- - 

- - 

-1LSR LSR L S 

PEAT -VERMICULITE 

Control Osmocote Rapid Gro 

- LSRLS R LSR 

Figure 4.-Effect of watering technique, type of potting mix, and type of 

fertilizer on dry matter production of yellow birch seedlings. L-leaves, 

S-stems. R-roots. 

Table 2.-Effect of Cornell mixes with mat or tray watering on 

height (cm) and dry weight (g) of yellow birch 

seedlings. 

Peatlite A Peatlite 5 Growth 

measurement Mat Tray Mat Tray 

Stem height 16.5 17.7 24.3 26.5 

Leaf weight 0.8 0.8 1.1 1.1 

Stem weight 0.2 0.3 0.5 0.5 

Root weight 0.3 0.5 0.3 0.5 

was already fortified with trace efements). Solutions of Universal Soluble Trace Element Mix (1 gi1O I) 

containing Fe, Mn, Zn, Cu, B, and 

Mo were added initially and 15 

milpot were added each week. 

Paper birch was the test species. 

Total height, diameter at 1 cm, and 

dry weights were measured at 

termination. 

Osmocote produced the largest 

seedlings among the three fertilizers tested without additional nutrient supplements (Table 3). , 

Universal was more effective than 

Rapid-Gro when both were used at 

equal concentrations. Comparable 

treatments for yellow birch in 

Experiment 1 with Osmocote and 

Rapid-Gro (Fig. 4) showed greater 

dry weights of leaves and stems. 

Solution concentrations used in this 

study were made to give 100 ppm of 

N. The manufacturers have aecommended this level of N to give adequate growth and still not burn the 

foliage. The addition of trace elements to Osmocote and Rapid-Gro 

gave additional increases in all 

growth measurements. The best 

treatment was Osmocote with 

supplemental trace elements. These 

birch seedlings were about 40 cm 

tall with sturdy stems and good leaf 

and root development. 

Experiment 3. Experiments 1 

and 2 showed that a simple PV mix 

incorporating pelleted fertilizer was 

entirely compatible with automated 

mat watering for producing fast 

growing, healthy birch seedlings. 

The quantity of nutrients in the tap 

water used in experiments 1 and 2 

was not known. Therefore, we made 

additional experiments to compare 

tap water with deionized water. 

Also, long-term release Osmocote 

(18-6-12, 8 to 9 months) was cornpared with the short-term release 

Ostmocote (14-14-14, 3 to 4 months). 

Both types were at the rate of 6 

glpot. Height and dry weight of 

paper birch seedlings were 

measured at termination. 
Table 3.-Effect of solid and liquid fertilizers with microelements 

on height (cm), diameter (mm), and dry weight (g) 

of paper birch seedlings using automatic mat 

watering. 

Height Diameter Dry weight Fertilizer 

treatment Leaves Stem Roots 

Rapid-Gro 22.8 3.7 1.2 0.3 0.2 

Rapid-Gro + micro 31.1 4.2 1.5 0.5 0.5 

Osmocote 39.5 4.4 2.4 0.8 0.5 

Osmocote -c micro 41.3 5.4 3.0 1.1 0.7 

Universal 29.3 4.4 1.6 0.5 0.6 

Table 4.-Effecl of different fcrrmulations of Osmocote, using tap 

or deionized water for automatic mat watering, on 

height growth (em) and dry weight (g) sf pager birch 

seedlings. 

Dry weight 

Treatment Height 

Leaves Stem Roots 

Height of birch seedlings was 

slightly greater with tap water than 

with deionized water (Table 4). 

Otherwise, there were no differences in height growth or dry 

weight due to type of water or type 

of Osmocote used. 

Experiment 4, In this experiment, a commercial preparation of 

PV known as Jiffy-Mix was tested 

with three levels (0, 3, and 6 glpot) 

of Osmocote (14-14-14). Jiffy-Mix 

contains small amounts of added 

nutrients, so some growth would be 

expected without Osmocote. Mat 

watering with deionized water and 

paper birch seedlings completed 

the setup. 

The maximum rate of height 

growth was about 2 cmiday for ail 

seedlings with Osmocote, and less 

than 1 cmlday for seedlings without 

Osmocote (Fig. 5). Three g of 

Osmocote110-cm pot produced the 

tallest seedlings and greatest dry 

weight (Fig. 6) of leaves and stems. 

In addition, this treatment produced 

greater dry weights than had been 

achieved in all previous experiments 

(compare Fig. 6 with Tables 3 and 

4). The highest level of Osmocote 

produced the shortest seedlings 

that were lowest in root weight and 

intermediate in stem and leaf 

weight. 

Experiment 5. Compacted bales 

of Canadian peat moss were used in 

all previous experiments when preparing PV mixes. Considerable time 

and effort were required to break up 

and sieve the compact peat moss 

before it could be mixed with vermiculite. In this experiment, milled 

(ground), loose Wisconsin peat 

moss2 was used in the PV mix. The 

loose moss was used without 

further sieving. Osmocote was applied at 5 gll0-cm pot. Mats were 

watered with tap water. Heights, 

diameters, and dry weights of paper 

birch seedlings measured at 

termination were: 

Height - 54.4 cm 

Diameter - 6.2 mm 

Leaves - 4.8 g 

Stem - 2.1 g 

in general, the growth obtained 

with Wisconsin peat moss was 

greater than growth with Canadian 

peat moss (Table 3 and 4), but comparable to results obtained with 

Jiffy-Mix and 3 g Osmocote110-cm 

pot (Figs. 5 and 6). 

Experiment 6. Osmocote 

(14-14-14) was tested at seven different levels, both in growth room 

and greenhouse (additional lighting 

was used in the latter to give a 20- 

hour photoperiod). Ten-cm pots of 

PV mix with Wisconsin peat moss 

were made up with 0, 1, 2, 3, 4, 5, or 

6 g Osmocoteipot. Height growth in 

the different treatments were 

measured weekly, the diameters and 

dry weights were measured after the 

usual 8-week period. 

In general, sharp optima for 

height, diameter, and dry-weight 

growth were not indicated (Figs. 7 

to 10). Best growth in all tests occurred between 4 and 5 g Osmocoteil0-cm pot. One and two g 

Osmocote levels definitely were deficient for best growth. Five g of 

Osmocote ensures maximum 

growth and avoids waste. 

Cool night temperatures in the 

greenhouse probably caused the 

slower germination and longer time 

to reach maximum rate of height 

growth (usually 1.5 cmlday) in this 

group. Dry-weight increments for 
the growing period were less for 

greenhouse than for growth room 

seedlings for the same reasons. 

Con t ro l .---.-- 

2 3 4 5 6 7 8 

WEEKS 

Figure 5.-Effect of Osmocote levels on height growth of paper birch 

seedlings grown in Jiffy-Mix with automatic mat watering. 

Leaves Stems Roots 

Figure 6.-Effect of Osmocote ievels on dry matter production of paper 

birch seedlings grown in Jiffy-Mix with automatic mat watering. 

Greenhouse Tests with Mat 

Watering 

Greenhouse benches were setup (Fig. 11) for mat watering in the 

same manner used for growth-room 

benches. Double thickness Troy Flo 

Thru mats were used to ensure adequate water supplies for the high 

density plantings. Mats were 91 cm 

wide and 455 cm long. The maximum length of wet mat that could 

be used was not determined. 

Batches containing 7 1 of peat 

(loose Wisconsin), 7 1 of vermiculite, 

2 1 of tap water, and 100 g of Osmocote (14-14-14) were made homogeneous in a small, electrically driven 

cement mixer. Styroblocks with 80 

cavities per block were filled with 

the mixture after wicks were inserted (Fig. 12). Cavities were sown 

with seeds of paper birch, black 

locust, and European black alder, 

covered lightly with Oil Sorb, and 

germinated under clear polyethylene 

to keep the surface moisture high. 

Seedlings were thinned to the most 

vigorous seedling per cavity 2 

weeks after germination. Growth in 

the greenhouse was continued for 

an additional 8 weeks. Natural day 

length was extended by using coolwhite fluorescent tubes to give a 16- 

hour photoperiod. Universal 

(23-19-17) was applied by hand 

sprayer at a rate of 5 gllO I of water 

midway through the growth period 

to ensure against deficiencies. 

After 10 weeks in the greenhouse, Styroblocks were set outside, and the seedlings were 

watered with a garden sprinkler 

(time clock operated) for 2 weeks to 

permit hardening-off. 

Seedlings of all three species 

showed good height growth and excellent foliar development (Fig. 13). 

Branches were absent in all species 

due to crowding in the Styroblocks 

(Fig. 13 and 14). Root development 

was prolific and essentially vertical 

(Fig. 14). Seedlings were easily extracted from the Styroblocks. 
0 

0 1 2 3 4 5 6 

OSMOCOTE I g I / POT l 10 cmI 

Figure 8.-Effect of Osmocote level on dry weight of paper birch organs 

using Wisconsin peat and automatic mat watering (growth room). 

OSMOCOTE I g I/ POT 1 10 crn i 

Figure -/.-Effect of Osmocote level on height and diameter growth of 

paper birch using Wisconsin peat moss and automatic mat watering (growth room). 

On the day of outplanting, 

seedlings were refertilized by immersing the styroblocks in a solution of Universal (Fig. 15). Seedlings 

were planted in dibble holes with 

Osmocote. 

First-year survival on the prepared planting site in Maine with 

chemical brush control was 95% or 

better for all species. Paper birch 

made the greatest increase in 

height growth followed by black 

locust and black alder (Table 5). 

Several other deciduous broadleaved species were grown under 

the same conditions described 

above with excellent results. Among 

those tested were yellow birch, red 

maple, silver maple, sweetgum, 

black cherry, pin cherry, and northern red oak. This last species required occasional treatments with 

Universal to keep the seedlings 

flushing. 

Discussion 

In the work described here, 

automatic mat watering produced 

hardwood tree seedlings of comparable or better development than 

hand watering. The three main advantages of mat watering were: simplicity, low cost, and being physiologically ideal. 

The simplicity of automatic mat 

watering is evidenced by the absence of elaborate plumbing, electrical timers, weighing devices, solenoid valves, electric motors, and 

special nozzles. Instead, all of these 

are replaced by a wet mat, a piece 

of garden hose, and a simple float 

valve-the only moving part in the 

whole system. 

Low cost is a result of the 

elimination of expensive apparatus 

and reduced wages for installation 

and maintenance. I have not made 

any comparisons of water use between mat watering and other systems, but suspect the former is 

less. Of course, the best strategy to 

reduce water consumption is to 

avoid growing seedlings during the 

hot days of summer when evapotranspiration is high. 
Table 5.-First-year-height growth (em) of alder, locust, and birch 

seedlings grown in Styroblocks in the greenhouse 

with PV, Osmocote, and automatic mat watering. 

Height 

Percentage of 

Species Before End of increase 

planting growing season 

European black 

alder 36 

Black locust 50 

Paper birch 27 

I - Diameter 

Figure 9.-Effect of Osmocote level on height and diameter growth of 

paper birch using Wisconsin peat moss and automatic mat watering 

(greenhouse). 

For water to be continuously 

available to the growing seedlings, 

the potting mix needs to be heid at 

its maximum capillary capacity 

(MCC). MCC is the amount of water 

a mix can hold against the pull of 

gravity when adequate drainage is 

afforded. Put another way, MGG is 

the water retained in the micropores 

and small capillaries after water has 

drained out of the macropores 

under the pull of gravity. At this 

point, the mix is fully charged with 

plant-available water and the macropores contain the necessary air for 

aerobic respiration. This condition 

of the potting mix is considered to 

be physiologically ideal. Automatic 

mat watering continuously maintains this physiological ideal status 

in the potting mix. As a result, seedling growth is never retarded by too 

much or too little water, which frequently happens in the wet-up and 

dry-down cycle that occurs with all 

other systems of watering. 

The composition of a potting 

mix is especially critical for automatic mat watering. The mixture 

must provide the necessary range of 

pores for adequate water and aeration. Also, the mix should have 

some capacity to ionically bind the 

basic plant nutrients Ca, Mg, and K, 

and it should be free of disease organisms and weed seeds. As reported here, a 1:l mixture of peat 

moss and coarse-grade vermiculite 

is fully compatible with automatic 

mat watering. A commercially available peatlite, such as Jiffy-Mix, also 

gave excellent results with mat 

watering and pelleted fertilizer. 

In my experience, the use of 

pelleted, slow-release fertilizer was 

the simplest, most economical 

answer to plant nutrition with mat 

watering. Materials such as Osmocote are not toxic, are easy to 
OSMOCOTE I g I / POT 1 10 em I 

Figure 10.-Effect of Osmocote level on dry weight of paper birch seedlings using Wisconsin peat and automatic mat watering (greenhouse). 

handle, and require one application 

(at time of mix preparation). About 5 

g of Osmocotei10-cm pot should 

suffice. Some species such as 

northern red oak may require additional fertilizer treatment. This can 

be accomplished with a complete 

nutrient solution such as Universal. 

Obviously, interested growers 

should make some tests of their 

own. 

The local water supply worked 

well for us. The chemicals added by 

the municipal treatment plant were 

a nuisance rather than a problem. 

For example, in our growth room 

salt accumulated at the end of the 

mat and this could reduce seedling 

growth in containers in the immediate area. Salt accumulation was 

caused by a constant high temperature (27°C) and low humidity (<20% 

RH), which resulted in high rates of 

evaporation. Three reccammendations if this problem occurs are: 

First, hang a triangular piece of wet 

mat over the end of the bench to 

elute the salts periodically; second, 

cut off the end portion (about 45 

cm) and replace it with new mat; or 

third, do not place pots on the end 

portion. Remember, however, that 

salt accumulated only with pots in 

our growth room and not with pots 

or Styroblocks in our greenhouse or 

growth chamber, where evaporation 

from the mat was much lower. 

All types of rigid containers 

tested worked well with automatic 

mat watering as long as wicks were 

placed in the drain holes. Plastic 

pots of all diameters and all sizes of 

Styroblocks were used successfully 

in our greenhouse, growth room, 

and controlled environment growth 

chambers. 

Figure 11.-Greenhouse bench with plastic cover: wet mat, and water 

trough with float valve setup for automatic mat watering. 

10 
Figure 12.-Styroblock shows the wicks used with automatic mat 

watering. 

Figure 13.-Styroblocks with 10-week-old seedlings, from [eft, black 

locust, European black alder, and paper birch, produced in the greenhouse with PV mix, Osmocote, and automatic mat watering. 
Figure 14.-Top and root development, from left, paper birch, 

black locust, and European black alder seedlings grown in a greenhouse. (Conditions as in Fig. 13) 

Figure 15.-Plastic-lined soaking box contains a dilute solution of 

Universal for treating container-grown seedlings before outplanting. 

Literature Cited 

Acknowledgments 

I am indebted to Martha Ward 

and Patrice Rodgers for their able 

technical assistance and to Dr. Larry Safford for the growth data given 

in Table 5. 

Boodley, J. W.; Sheldrake, R. Cornell 

peatlite mixes for commercial 

plant growing. 1967; Cornell Ext. 

BulI.1104; 11 p. 

Tinus, R. W.; McDonald, S. E. How 

to grow tree seedlings in containers in greenhouses. 1979; USDA 

For. Serv. Gen. Tech. Rep. RM-60. 

Tinus: R. W.; Stein. W. I.; Balrner, 

W. E., eds. Proceedings of the 

North American containerized forest tree seedling symposium. 

1974; Great Plains Agric. Counc. 

Pub. No. 68.458 p. 

U.S. GOVERKMEhT PRINTISG OFFICE: 1982-505-012:7 
Hoyle, Merrill C. Economical and simple production of containerized 

hardwood seedlings. Broomall, PA.: Northeast. For. Exp. Stn.; 1982; 

USDA For. Serv. Res. Pap. NE-500.12 p. 

An automatic mat-watering system for growing hardwood seedlings in 

containers was designed and tested. The system has only one moving 

part, and no electrical requirements. There is no need to calculate different watering schedules for different growth phases, different hardwood species, or different evapotranspiration conditions. Resu Its 

were excellent with mat watering combined with simple, peat-vermiculite mixes, and pelleted, slow-release fertilizers. The system is 

economical, simple, and physiologically ideal. Mat watering was effective in growth rooms, controlled environment chambers, and greenQDC: 232.329.6 

Keywords: Automatic mat watering, pelleted fertilizers, containerized 
Headquarters of the Xortheastern Forest Experiment Station are in 

Bmmall, Pa. Field laboratories are maintained at: 

@ Amherst, Massachusetts, in cooperation with the University of 

Massachusetts. 

Berea, Kentucky, in cooperation with Berea College. 

@ Burlington, Vermont, in cooperation with the Unive~ity of 

Vermont. 

@ Delaware, Ohio. 

Durham, New Hampshire, in cooperation with the University of 

New Hampshire. 

@ Hrunden, Connecticut, in cooperation with Yale University. 

Morgantown, West Virginia, in cooperation with West Virginia 

University, Morgantown. 

Orono, Maine, in cooperation with the University of M 

Orono. 

ns, West Visghia. 

Princeton, West Virginia. * Syracuse, New York, in cooperation with the State University of 

New York College of Environmental Sciences and Forestry at 

Syracuse University, Syracuse. 

University Park, Pennsylvania, in cooperation with the 

Pennsylvania State University. 

Warren, Pennsylvania.