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V. Effect of Climate and Location
MARTIN G. WEISS
largely attributable to climatic differenres. Extensive data on seed composition for 10 variet.ies of soybeans grown in five cornbelt states for
the years 1936-1939 and 1936-1940 were reported by Cartter (1941) and
Cartter and Hopper (1942), respectively. The components of variance
have been calculated from the analyses of variance reported in the latter
reference according to the method described by Crump (1946), and are
reported in Table 11. Relative to the interaction of location with years,
or the second order interaction, variance components attributable to years
or locations, with few exceptions, were not of sufficient magnitude to be
Components of Variance for Seed Size and Compositional Characters Attributable to
Varieties, Locations, and Years as Calculated from Analyses of Variance a
D.F. Seed Protein Oil
Iodine Ash Phos- Potas- Cal- Crude
No. % phonis sium cium fiber
4 4 . 1
Vars. x yrs.
Vars. X locs.
Vars. x loc. X
'Cartter and Hopper (1942).
statistically significant. Even though the locations were dispersed in
five states, effects attributable to soil and climatic factors were insignificant relative to the interaction of these factors. It is of further
interest to note that, in general, varieties exhibited a tendency toward
greater differential performance with years (climate) than with locations
(soil). In soybean variety and date of planting trials conducted in
Illinois, Indiana, and Iowa during the years 1940-1942, reported by
Weiss, et al. (1949), locations and years had approximately equal influence on yield and on the three seed compositional characters, protein
and oil content, and iodine number of oil. The influence of location on
lodging and maturity date, however, was greater than that of season.
Various components of climate a t widely separated locations were
correlated with seed compositional attributes by Viljoen (1937) in an
effort to determine the causative factors. Precipitation and mean maximum temperatures did not appear to be correlated with protein or oil
percentages. Mean minimum temperatures were strongly correlated with
high oil content (r = 0.88) and were moderately correlated with low
protein content (r = -0.48), both values exceeding the 1 per cent level
of probability. Regression coefficients revealed that with every degree
Fahrenheit increase in mean minimum temperature, oil content of the
beans increased approximately 0.44 per cent and protein content decreased 0.39 per cent. Mean temperatures, which were derived from the
daily minimum and maximum temperatures, were also correlated with
seed composition but to a lesser degree. Throughout the various locations, negative correlation between oil and protein contents were noted.
I n studies including five varieties planted a t five dates for 3 years a t
three locations reported by Weiss e t al. (1949) lateness of maturity as
conditioned by lateness of planting was found to be correlated with
degree of unsaturation of oil. Lateness of maturity as conditioned by
varietal differences was not found correlated with drying quality. In an
attempt to determine the cause for this association, mean temperatures
during the bean developmental period were correlated with iodine numbers. Among varieties and among dates of planting low temperatures
were found to be associated with high iodine numbers. Within varieties
the degree of association between low temperatures, as conditioned by
later planting, and high iodine numbers increased progressively with the
genetic lateness of the variety. These findings are in agreement with
previous observations by Cartter and Hopper (1942) who noted a tendency for oils with high iodine numbers to be produced at locations with
relatively low temperatures.
9. Simulated Hail Damage
Hail damage is particularly severe on h l l season crops, such as soybeans, and its occurrence in the western part of the corn belt is of sufEcient frequency to warrant attention. Following hail storms, certain
decisions must be made by the grower relative to abandonment of the
field or by insurance companies relative to adjustment of damage. These
decisions must be based on estimates of the degree of recovery and percentage reduction in yield which can be expected.
Variability in yield reductions resulting from hail damage largely
is caused by (1) degree of damage, (2) type of damage, and (3) stage of
growth when damage occurs. Limited studies on defoliation and removal
of parts of stems as reported by Dungan (1939, 1942) and Fuelleman
(1944) indicated that reduction in yields was roughly proportional to
degree of damage, and that reduction in yields varied greatly when
MARTIN G. WEISS
damage occurred a t different stages of growth. Provided the degree of
damage permitted retention of some primordia, reduction in yields increased progressively with age of plant until the pod development stage
when the beans were approximately one-half maximum size. At this
stage very severe reductions in yield occurred. Damage a t later stages
tended to be less severe in yield reduction. Effect of repeated defoliation
on total forage and seed production was reported by Gibson e t al. (1943).
Any degree of defoliation decreased seed yields to some extent. Seed
production, in general, was inhibited in proportion to the frequency and
severity of defoliation.
The results of extensive studies relative to the effects of simulated
hail damage covering a 4-year period were recently reported by Kalton
et al. (1949). The damage was inflicted by removing parts of the plant,
and breaking and bruising the plants by beating with light objects.
Three degrees of severity were studied. The effects on the plants as
measured by several agronomic and seed compositional characters, in
general, were in proportion to the degree of severity of the damage inflicted. The least reduction in yields occurred when the damaged plants
were 6 to 12 inches tall and the highest reduction occurred a t the time
seed development had been initiated in the lower pods. Reduction in
yield was further increased by weed growth in hail damaged plots, particularly when such damage was severe and occurred during early stages.
Heavy damage inflicted prior to and during the blossoming period delayed
maturity as much as 8 days. Damage inflicted later than the “green
bean” stage hastened maturity. Reduction in plant height was greatest
when the damage occurred during the blossoming period. Seed quality
was reduced only a t moderate and heavy degrees of damage, and only
when damage was inflicted while pods were maturing. Up to 2.4 per cent
reduction in the oil content of the beans resulted from damage to plots
prior to ripening of pods, whereas the protein content was unaffected.
The drying quality of the oil as measured by the iodine number was
increased by all degrees of damage during pod formation and early seed
Certain components of hail damage were studied individually to determine their effects on soybean production. Reduction of stand, which
occurs when some plants fail to recover from hail damage, was found to
reduce yield in progressively greater amounts when inflicted a t successively later stages of plant growth. Little effect on date of maturity or
plant height was apparent. Defoliation was found to reduce yield only
slightly when inflicted prior to blossoming. The highest reduction in
yield from 100 per cent defoliation during this period was 22 per cent.
However, up to 83 per cent reduction in yield occurred with removal of
all leaves during the critical stage when seed was developing in the lower
pods. Defoliation prior to blossoming delayed maturity, whereas, after
the green bean stage, removal of leaves hastened ripening. Reduction of
plant height was most severe if defoliation occurred during the blossoming period. Seed quality and size were reduced by defoliation during the
seed developmental stage. As to seed composition, the protein content
was unaffected by defoliation, the oil content was reduced particularly
when leaves were removed during the seed developmental periods, and the
iodine number of the oil was increased by defoliation during late stages.
VI. EFFECTOF CULTURAL
The soybean was initially considered an alternative crop for small
grains especially throughout the corn belt, and, consequently, was substituted for small grain in the existing rotations. The unsuitability of
soybeans as a companion crop for small-seeded legumes and the development of high-yielding, disease-resistant small grain varieties are factors
which have changed this system, When grown for bean production, the
soybean crop i s a t present largely considered an intertilled crop and,
therefore, competes with these crops in the rotation.
Throughout the corn belt, Englehorn (1944) st.ates inclusion of soybeans has frequently lengthened the rotation. Whereas corn-corn-small
grain-hay mixture was a common corn belt short-term rotation, it now
frequently becomes corn-soybeans-corn-small grain-hay mixture. Beeson
(1944) lists t,he following rotations for Indiana:
For most soils
-corn (1 or 2 years) -soybeans-small grain-hay
For grain farms
-corn (1 or 2 years)-soybeans-small grain with
sweetclover or clover seed crop.
For very fertile soils -corn-soybeans.
For southern Indiana-corn-soybeans-winter wheat or barley-lespedeza.
He notes that soybeans following corn in the rotation facilit,ates corn
borer control in that corn stalks are plowed under in preparing the land
I n a l-year survey of 4200 soybean growers in the principal producing
areas of Illinois, Indiana, and Ohio, Calland (1946) found corn preceded
soybeans in the rotation in 80, 77 and 55 per cent of the fields in the
t,hree states, respectively. Soybeans preceded soybeans in 13, 10 and 25
per cent of fields, respectively. I n Indiana and Ohio, oats and winter
wheat followed soybeans most frequently, each succeeding soybeans on
MARTIN G. WEISS
approximately one-third of the farms surveyed. I n Illinois corn and oats
followed soybeans on 67 and 25 per cent of farms, respectively.
On soils of low productivity, soybeans have by necessity replaced
another tilled crop without lengthening the rotation. Such a rotation
recommended for sandy soils in Wisconsin by Albert et al. (1947) is soybeans-oat8-legume, hay and seed-legume, seed, or hay and seed. Instead
of oats, ensiled corn and a winter grain may be substituted. When
grown for hay Trotter (1936) states that soybeans are a t times grown
in one-year rotations with winter barley in Missouri. Few data are
available at present which would indicate the relative merits of various
rotations including soybeans. The effect of soybeans on crop yields in
rotations is discussed in Section IX-2.
9. Fertilizers and
a. Response. Soybeans frequently have been classified as a (‘poor
land” crop. This concept probably originated from 2 sources: Frequently
soybeans yield relatively more than grain crops on soils of low productivity, and the response of soybeans to direct. application of commercial fertilizers is usually disappointing. However, marked yield variations are stimulated by differences in natural productivity of soil or
general fertility levels as conditioned by different soil management
(Cartter and Hopper, 1942; Lang and Miller, 1942; Norman, 1946; Vittum and Mulvey, 1944 and others). Some evidence is available, as
reported by Pierre (1944) and Norman (1946), that increases in soybean
yields as stimulated by high fertility levels are similar on a percentage
basis to yield increases exhibited by corn.
Although the response to direct application of fertilizers relative to
other crops has been low, under certain conditions material increases in
yield have been obtained. Correction of soil acidity with lime has, in
general, resulted in higher yields (Cartter, 1941; Collins et al., 1947;
Colwell, 1944; Nelson and Hart.wig, 1948; Pierre, 1944; Prince et al.,
1941 ; Vittum and Mulvey, 1944 and others). When soybeans were grown
on soils varying in pH from 4.6 to 7.7, Thatcher et al. (1937) found maximum yields resulted at p H 6.8. It is the contention of some workers that
the stimulation due to liming is attributable to fertilization with the calcium ion rather t.han to neutralization of the soil. Designation of soybeans as an acid-tolerant crop, according to Albrecht (1944) ,is equivalent
tjo intimating that the crop is tolerant to starvation. I n addition to increasing yield, application of lime was reported by Cartter (1941) to increase protein and decrease oil content of the beans.
On potash-deficient soils direct application of potash has resulted in
increased yields. Striking yield responses to pot,ash application were re-