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CHAPTER 8. THE MANAGEMENT OF SOYBEANS
JACKSON L. CARlTFX A h 9 EDGAR E. HARTWIG
IS. Water Requirements and Utilization
.4. Water Needs in Relation to Pla
B. Irrigation and Soil Management .
X. Growth-Regulating Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XI. Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. When to Harvest . . . . . . .
B. Harvesting Methods . . . . .
XII. Seed Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XIII. Discussion . . . . . . . . . . . . . . . . . . . .
The soybean, Glycim mar ( L . ) Merrill, has become a major crop in
the United States, the acreage harvested for beans increasing from only
190,000 acres in 19%)to over 26 million acres in 1961. It now ranks fourth
ESTIMATED W O R L D T O T A L
FIG. 1. World soybean production, 1960. (Source of data: Foreign Agricultural
Service, U . S. Department of Agriculture.)
among the cash crops in this country and first among oilseed crops of
the Western Hemisphere. The United States now produces about 57
per cent of the total world crop of soybeans (Fig. 1 ) .
Many developments have contributed to the rapid increase in soybean
THE MANAGEMENT OF SOYBEANS
production, among them a steady expansion in the market for soybean
oil and meal in this country and a strong export demand for the crop.
Research on production problems and the development of superior
varieties by breeding have had a major role in increasing the efficiency
of production. Agricultural engineering research leading to the development of the combine harvester has been of considerable importance in
the complete mechanization of soybean production.
Soybean management is the application of the sciences of plant
breeding, plant pathology, plant physiology, soil management, engineering, and economics to the growing of soybeans. The most profitable soybean culture comes from the use of all these sciences. An old variety
such as MAMMOTH YELLOW,
under some conditions, could produce a
yield of 40 bushels. However, MAMMOTH YELLOW is susceptible to several
diseases which frequently limit seed yields and is subject to lodging and
shattering. The newer, improved LEE variety is resistant to several diseases
to which MAMMOTH YELLOW is susceptible, has greater lodging resistance
and improved seed holding. These factors reduce production hazards
and permit greater stabilization and efficiency of production.
Literature on soybean management is extensive. One of the first,
and little recognized, publications was that of Mooers (1908). He
presented information on varietal interaction to date of planting and row
width and gave directions for planting, cultivating, and harvesting the
crop, as well as data on chemical composition of the seed. The first
book on the subject was that of Piper and Morse (1923); twenty-six
years later appeared a general review of soybean breeding and management by Weiss (1949) followed by a review of production by Morse
( 1950) and of structure and genetics by Williams (1950). Recently,
reviews were made on physiology ( Howell, 1%0), nutrition ( Ohlrogge,
1960), and genetics and breeding (Johnson and Bernard, 1962). This
review brings together the recent research on culture and management.
The first commercial crushing of soybeans from domestically grown
seed was in North Carolina in the fall of 1915 (Dies, 1943). By 1920,
production was 3,000,000bushels and the leading states were North
Carolina, Virginia, Alabama, Missouri, and Kentucky-North Carolina
producing 55 per cent of the total. By 1931, the center of production had
shifted to the North Central States, where it is at present (Fig. 2 ) .
Soybean production has been spreading over additional areas of the
United States as better varieties and improved production methods have
been developed. Soybean acreage in the United States increased 124 per
cent during the period 1949-1960, while cotton acreage dropped 44 per
FIG.2. Soybeans harvested for beans, acreage 1959. (From Bureau of the Census, U. S. Department of Commerce.)
United States Soybean Acreage and Production Dataa by 5-Year Intervals, 1925-1960
Data from Economic Research Service, U. S. Department of Agriculture.
Grown with other crops.
Acreage grown alone, plus one-half the interplanted acres.
JACKSON L. CAR'ITER A h 3 EDGAR E. HARTWIG
cent, wheat acreage 31 per cent, oats 28 per cent, all hay 5 per cent, and
corn acreage 4 per cent ( Kromer, 1961 ) .
Up to 1941, over half of the soybean acreage was for hay, grazing,
or green manure. The trend toward production for processing has been
strong since then because of the demand for soybean oil and meal, so
that at present virtually all soybeans are grown for processing (Table I ) .
Long-run prospects indicate that as the demand for soybean meal
increases, production lvill continue to expand.
1. Processing to Obtain Oil a d Meal
Processing in this country was at &st by hydraulic press, later by
expeller or screw press, and now almost entirely by hydrocarbon solvent
extraction. A moist heat treatment is given to the solvent meal to destroy
certain protein digestion inhibitors and improve the absorption of some
of the amino acids, making the meal an escellent protein supplement in
feeds. Soybean meal now supplies nearly 56 per cent of the protein
concentrates in this country. For the 1959-1960 processing year, approximately 8,400,000 tons of meal were used in feed, 650,000 tons for
export, and 30,000 tons for food and industrial purposes. The yield of
meal is about 46.5 pounds per bushel of soybeans processed.
Soybean oil, cIassed as a semidrying oil, is used for food purposes and
also in several industrial products. Soybeans now supply about 35 per
cent of the total fats and oils produced in the United States. The yield of
oil per bushel has increased from 9.7 pounds in 1950 to 11 pounds
in 1960. This increase has been due in part to the change in
processing from the expeller method, which left 4 or 5 per cent of the
oil in the meal, to the solvent method, which leaves only about 1 per
cent in the meal, and also to the development of improved soybean
varieties with higher oil content. The principal use of soybean oil is in
food (margarine, 31 per cent; shortening, 34 per cent; other food uses,
24 per cent), constituting 89 per cent of the oil use. The remainder is
used in paints and varnishes, other drying oil products, and miscellaneous
nonfood products. Extensive research is being done to improve flavor
stability of soybean oil for food use and to increase the list of products
that can be made from the oil (Cowan and Witham, 1959).
2. Hay and Green Manure
The use of soybeans for hay and for grazing and plowing under
increased in importance from the start of production in this country to
about 1940, when nearly 7 million acres were grown for these purposes
THE MANAGEMENT OF SOYBEANS
(Table I ) . After that, the use of soybeans for hay and green manure
decreased rapidly and the acreage has dropped to less than a million.
II. Soil and Climatic Adaptation
A. AREASOF PRODUCTION
IN THE UNITED
The principal area of soybean production is in the North Central
region (Fig. 2 ) , where, in 1961, over 77 per cent of the United States
crop was produced. Here, as in the eastern portion of the great central
plain of Manchuria, a large area has been found to be particularly well
adapted to soybean production ( Weiss, 1949).
The two other major areas of soybean production in the United States
are the Mississippi delta and the Middle Atlantic coast. Production has
not extended very far west in the central Great Plains, except where the
crop can be irrigated. In this area, low rainfall and the high temperatures
frequently cause moisture shortages ( Swanson, 1951) . With supplemental
irrigation, especially during the pod-filling period, soybean culture can
be extended into this area successfully. The high plains of Texas and
west-central Nebraska represent such areas. Good yields have been
obtained under irrigation in southern California and in some areas of
eastern Oregon and Washington, but here soybeans are competing with
other crops having higher per acre value.
The soybean will succeed on nearly all soil types except extremely
deep sands. Soybeans are better adapted for production on clay than
either corn or cotton. The crop is also well suited for production on muck.
For best results, soils should be limed to pH 6.0 to 6.5 and soils of low
fertility should be supplied with those mineral elements in which they
1. Effect of Temperature on Plant Growth
The effects of temperature on soybean yields have not been studied
extensively. Runge and Ode11 (1960) found that yields were slightly
lower when temperatures were above average during July and August.
They found above-average maximum temperatures in June and September
resulted in small increases in yield. Prompt emergence in the field is
important for weed control. Plants grown in the greenhouse under
controlled conditions at 60°F. took 7 to 10 days to emerge, compared to
3 to 5 days for those in 70°, 80°, or 90" chambers. Early-planted soybeans
often require 10 to 14 days to emerge, but later plantings, when the soil
JACKSON L. CARTIER AND EDGAR E. HARTWIG
is warm, will emerge in 5 to 7 days (Smith et d.,1961; Nagata, 1960;
Hartwig, 1954 ). In addition to affecting rate of germination of soybeans,
temperature also affects rate of growth and the time required for the
plants to shade the ground between the rows, an important consideration
in weed control as well as yield. Smith et al. (1961) found that soybeans
planted on May 5 had shaded only 59 per cent of the ground in 2 months
but those planted on June 5 had shaded 86 per cent. Hartwig (1954)
found the rate of growth increased markedly as temperature at planting
M A Y 10
A P R I L 10
FIG. 3. Diagrammatic comparison of relative height and width at 6 weeks after
emergence for the average of four varieties of soybeans planted at Stoneville, Mississippi, April 10, May 10, and June 10, 1944-1951.
time increased. Figure 3 shows the relative growth 6 weeks after
emergence on the dates indicated.
Temperature affects blooming date, as pointed out by Garner and
Allard ( 1930). They stated that sustained summer temperatures below
75' to 77'F. will ordinarily delay blooming, a decrease of 1" causing a
delay of 2 or 3 days. Variation from year to year in date of flowering of a
given soybean variety planted on a particular date is due chiefly to
differences in temperature, whereas differences between varieties are due
chiefly to their response to length of day.
There is a minimum temperature for most growth processes, which
for all practical purposes appears to be about 50°F. Parker and Borthwick (1943) found that floral induction was greatly inhibited at 50°F.or