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IV. Planting Methods and Equipment

IV. Planting Methods and Equipment

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THE MANAGEMENT OF SOYBEANS



379



seed (Cook et al., 1958). Illinois studies showed little difference in seed

yields when “conventional,” “plow-plant,” “plow-harow-plant,” and “tractor-track” systems were compared (Bowers et al., 1959).

On a Sharkey clay in Mississippi, fall plowing with a moldboard plow

increased soybean seed yields 5 per cent over yields in areas having no

fall treatment but disked in early spring to destroy winter weeds. After

the spring disking of plowed and not-plowed areas, both treatments were

worked with a spring-tooth harrow at 14- to 18-day intervals prior to

planting ( E. E. Hartwig, unpublished).

3. Deep Tillage



Soils having a silty-textured subsoil have a tendency to form compacted layers which restrict movement of water and also restrict root

development. Shattering this layer results in improved yields, especially

in dry years. In the fall of 1953, a Dundee silt loam in Mississippi was

chiseled 16 inches deep. Soybeans planted on May 10, 1954, showed

severe drought symptoms by late June on untreated areas, while soybeans on the treated areas were growing vigorously. In this very dry

year, seed yields on the deep tilled area were 35 bushels per acre as

contrasted to 8 bushels on the untreated area (E. E. Hartwig, unpublished). On soils with hardpans, deep tillage has increased the water

intake, increased root development, reduced drought damage, and improved the stand of cotton. Deep tillage gave no benefits on Sharkey

clay (Grissom et al., 1955).

Hobbs et al. (196l), in Kansas, found that deep tillage at 6 to 24

inches, with chisel-type implements on soils with definite restricting

layers, rarely increased yields sufficiently to pay the cost of the operation.



B. Row WIDTHAND PLANTING

RATE

1. Row Width

The row width which will result in maximum yield is dependent

upon length of growing season, growth type of varieties, and fertility

level of the soil. In general, with shorter growing seasons, row widths

narrower than the conventional 36- to 40-inch will result in highest yields.

However, when seed yields of 35 to 40 bushels are produced in 36- to

40-inch rows, increased yields from narrower rows are less frequent. If

post-emergence cultivation is necessary for weed control, then it appears

that row widths cannot be reduced below 28 to 30 inches. If preemergence chemicals satisfactorily control weed growth, the increased

yield from narrow rows must cover the cost of extra planting seed and

also increased quantities of chemicals. Rows too narrow to permit



380



JACKSON L. CARlTER Ahm EDGAR E. HARTWIG



cultivation would require a broadcast application of chemicals whereas

only a 12-inch band is treated in 36- to 40-inch rows. Consequently, the

cost of chemicals would be at least tripled.

Yields in Minnesota and Illinois in 18- to %-inch rows have been 15per

cent greater than in 36- to 40-inch rows (Lehman and Lambert, 1960;

Pendleton et al., 1960). In Manitoba, increases with narrow row spacing

were so small that it seemed important to adopt the row width in which

best weed control could be achieved with the equipment available (B. R.

Stefansson, personal communication).

In southeastern Kansas, 21-inch rows have produced higher yields

than 42-inch rows. A 75-pound seeding rate has been superior in

21-inch rows while 45 pounds per acre has been the optimum rate in

42-inch rows ( V. H. Peterson, personal communication).

In Virginia, North Carolina, Mississippi, and west Florida, narrow

row widths did not increase seed yield (Hartwig, 1957; R. L. Smith,

1959). Plantings in Arkansas at lower yield levels have, under some

conditions, shown a yield response from rows narrower than 36 to 40

inches (P. E. Smith, 1959). Results from the eastern shore area of

Delaware and Maryland have been variable.

2. Planting Rate

Results for planting rates within the row are, in general, similar for all

production areas. Planting rates of 6 to 12 viable seeds per foot usually

give most satisfactory results. Recommendations in most States will be

nearer the 12 seeds per foot rate. This heavier rate is recommended

largely from the standpoint of early season weed competition and also

for its influence on height of lower seed pod development. Since varieties

differ in seed size, growers should base planting rates on seeds per foot

rather than pounds per acre.

Results from planting OGDEN at rates of 30 to 150 pounds per acre

in west Florida for the years 1950 to 1955 showed little difference in

yields at rates of 30 to 120 pounds, but yields were reduced at rates of 135

and 150 pounds ( R . L. Smith, 1959). Plant spacings of 2 to 3 inches in

the row produced slightly higher yields in Indiana than l-inch or 4-inch

spacings. Plants spaced 1 inch in the row showed a greater amount of

lodging and matured slightly later than did thinner plantings (Probst,

1945). Spacings of 6 and 12 plants per foot produced higher yields in

North Carolina than did the thinner rates. There was greater lodging

at the 12-plant spacing than with 6 plants per foot. Yield differences

were small and not significant in Mississippi from plantings at 6, 9, 12,

18, and 21 seeds per foot. The 6-seed-per-foot rate required a longer

time to give complete ground shading in the row. The 9 and 12 seeds-per-



THE MANAGEMENT OF SOYBEANS



381



foot rate gave excellent early growth with a not too severe amount of

lodging (Hartwig, 1957).

Along with rates within the row, moderate skips in one row of an

otherwise complete stand have little influence upon the total yield.

Caviness (1961) found that a 2-foot gap in a 16-foot row resulted in a

very small and statistically nonsigngcant yield reduction. A 4-foot gap

resulted in a barely significant reduction, and with a 6-foot gap 95 per

cent of the check yield was produced. Similar results have been secured in

Ohio (L. C. Saboe, personal communication) and in Illinois (R. L.

Bernard and J. L. Cartter, unpublished).



C. DOUBLE

CROPPING

1. After Fall-Sown Grain Crops

The growing seasons for fall-sown grain crops and soybeans are such

that in many areas both can be grown during the same year with nearly

full production of each. One of the requirements is that each be

harvested as soon as it is mature and the other planted immediately.

Weather conditions may upset this schedule. Studies at Stoneville,

Mississippi, indicate that, for mid-June plantings, yields after oats are

approximately 10 per cent lower than for similar plantings where no spring

crop was grown. At Stoneville, October 15 is the best planting date for

oats, and they mature between May 25 and June 15.

One of the problems in double cropping is timely planting of soybeans

after small grain harvest without excessive loss of soil moisture. Plantings

on clay in the delta area of Mississippi have been most successful when

grain straw is burned and soybeans planted immediately without any

seedbed preparation, using planters equipped with a double disk opener.

Equally satisfactory stands have been obtained by planting in shredded

straw but the residue gives problems in cultivation. Burning straw also

kills seedling weeds.

Several workers (Brim et al., 1955; McAlister, 1958; Fullilove and

Reid, 1959) in the coastal plain area have obtained good results in

planting soybeans after small grain by using a lister type planter with

no previous seedbed preparation. In cultivation, the soil thrown out from

the lister furrow is worked back into the row. This method works best

in relatively sandy soils with moderately high rainfall.

In some areas use of oats for silage has proved desirable. This practice

would permit earlier planting of soybeans and would reduce the straw

problem.

2. After Peas

In northern areas where peas are grown for canning or freezing,

the crop is harvested in late June or early July, and soybeans have been



382



JACKSON L. CARTER Ah’D EDGAR E. HARTWIG



planted after peas. Many of the problems are similar to those for planting

after small grain, except that all top growth of the peas is removed in

harvesting. Results obtained in Minnesota and Wisconsin indicate that

soybean yields of 10 to 15 bushels can be produced after a crop of peas

is harvested (J. W. Lambert, J. H. Torrie, personal communication).

D. SPECIALMETHODSOF PLANTING

Many soybean growers have been of the opinion that larger yields

could be produced from a given land area if two crops differing in requirements were planted in alternate rows. A survey of farm practices

with soybeans (Smith and Hope, 1920) showed that farmers believed

that by planting soybeans and corn in alternate rows, each would produce

75 per cent of a full crop, thus giving a 50 per cent greater yield than if

the two crops were grown separately. This theory has been tested in

North Carolina, Ohio, Illinois, and Iowa with alternate rows, paired rows,

and other interplanting patterns. At times interplanting has given small

increases in total production, but it appears that increased management

problems overbalance the production gains.

In many of the older production areas, soybeans have been interplanted in the row with corn. In some cases the corn has been harvested

and the residue plus soybeans grazed with livestock. In other cases the

soybeans were grown only to add nitrogen for the following crop. As

fertilization rates for corn in the southeast have increased and plant

populations have also been increased, soybeans have failed to survive

in the interplantings. Data from North Carolina show no difference in

corn yield between corn planted alone and with soybeans interplanted.

There was no seed production on the soybeans.

The possibilities for planting two soybean varieties of different maturities or growth types in alternate or paired alternate rows has been explored. In Mississippi, interplanting the varieties JACKSON and LEE,

which differ by 12 to 15 inches in height and 12 days in maturity, produced yields equal to the mean for the two varieties grown alone (E. E.

Hartwig, unpublished ) . J. W. Pendleton (personal communication )

found no yield increases in Illinois from interplanting an early variety

in the middle of the rows of a late maturing variety at the time of the

last cultivation.

Limited studies have been initiated to determine whether northsouth row direction might permit more light to be received by the soybean plant, resulting in higher yields. Results at Winnipeg, Manitoba, and

at Urbana, Illinois, have shown no effect of row direction on yield (B.

R. Stefansson, J. W. Pendleton, personal communication).



THE MANAGEMENT OF SOYBEANS



E. TYPESOF



383



EQUIPMENT



Soybeans may be planted with planters designed for row crops or

with a grain drill with all feed cups covered except those needed for

row planting. A row planter with good press wheels provides more

uniform depth and better covering of the seed. In some heavy clays,

the surface layer dries rapidly in the process of seedbed preparation.

In such soils, a double disk opener has been found very beneficial in

getting the seed placed below the loose dry surface into moist soil under

conditions favorable for prompt germination (Fig. 7). If narrow rows

are used, provision must be made for cultivating equipment to accommodate the narrower row spacing.



Double disc opener



Sword opener



FIG.7. Cross section of seed furrows. Effect of djfferent types of furrow openers

on seed placement. The double disk permits placement of seed in moist soil with a

minimum of soil disturbance. (From Mississippi State College Agricultural Experiment Station Information Sheet 576, March, 1958.)



The rotary hoe is very effective in early season weed control in soybeans (Lovely et al.,1958). For later cultivation, conventional row crop

equipment is used.

V. Rotation Practices and Erosion Control



A. EFFECTON SOYBEANYIELDS

The soybean can be used advantageously in many crop rotations, and

no standard rotation can be given that will apply to every farm. Depending upon the use of the crop, soybeans have been classed as soil

improving or soil depleting. Sears (1939) found that where the crop was

plowed under, it returned about 90 pounds of nitrogen per acre, and

where it was harvested for beans and the straw returned to the soil,

there was a gain of about 16 pounds of nitrogen per acre. When the



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JACKSON L. C A R T E R AND EDGAR E. HARTWIG



soybeans were combined and the straw burned, there was a loss of

about 3 pounds of nitrogen per acre. Also, under comparable conditions,

Sears estimated that corn, oats, and wheat would remove 40, 26, and

36 pounds of nitrogen, respectively, but his estimates were made for a

rather low (40 bushel) yield of corn. Typical rotations for the midwest

farming areas usually suggest soybeans following corn in the cropping

sequence, as corn can utilize to advantage the nitrogen furnished by

turning under a deep rooted, small-seeded legume sod, whereas, wellnodulated soybeans do not benefit from the high level of nitrogen.

At Stoneville, Mississippi, with good weed control, soybean yields in

a continuous cropping system have been similar to yields produced in

a 2- or 3-year rotation with cotton.

The advantage of soybeans in the rotation cannot be explained altogether on the basis of the returns from the crop, according to Pond

(1950). Some of the other advantages given were ( 1 ) the labor requirements are low; ( 2 ) soybeans do not compete too seriously for labor at

peak periods; (3) soybeans can be planted later than other crops with

reasonable assurance that they will m a t u r e t h i s is especially important

in a wet spring; ( 4 ) as a cultivated crop they aid in weed control; ( 5 )

they stand drought better than some other crops; ( 6 ) soybeans do better

than many other crops on spring plowing; and ( 7 ) soybeans improve

the physical condition of the soil.

A crop rotation in which soybeans do not appear oftener than once

in three or four years aids in controlling certain diseases such as brown

stem rot. Where the soybean cyst nematode is a serious problem, nearnormal soybean yields may be obtained in a 2-year rotation if a nonsusceptible crop is grown during the year out of soybeans (J. M. Epps,

personal communication).



B. EFFECTON



THE



FOLLOWING

CROP



Soybeans improve soil tilth by shading and protecting the soil from

rain. The roots and the bacterial action they foster tend to loosen the

soil mass and make it more easily penetrated by nioisture and by roots

of the succeeding crop. Soybeans leave heavy compact soils in much

better physical condition than do corn and small grains (Calland, 1949).

Soybeans as a crop seem to be less depressing on soil productivity than

corn when judged by crop yield (Strickling, 1950).

Results from studies conducted in Minnesota show that corn yields

following soybeans are greater than those following oats. This yield

increase was attributed largely to greater residual nitrogen in the soil

after a crop of soybeans (Schmid et al., 1959).



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