Seed rate: 40–90 kg/ha. Seed size varies from 5000 to 40,000 per kilogram, the
average for modern varieties being about 10,000 20,000.
Seed spacing: a rule of thumb is to have between 25 and 40 plants per metre along
the row, with 60–100 cm between rows, to arrive at an optimum plant population of
about 400,000 per hectare.
Depth: 2–4.5 cm.
Intercropping: generally not recommended for soybean except when grown for hay
or forage, when it can be mixed with maize, sorghum or Sudan grass.
Inoculation: the seed should be inoculated with the appropriate strain of Rhizobia
when planted in soils which have either not grown soyabeans for two or three years
or which have never grown soya. In most cases, and if carried out properly, this
procedure will increase both the yield of seed and the amount of Nitrogen fixed in
the soil (1Fe).
GROWTH CONDITIONS
Day length: understanding the ways in which soybeans respond to the changing
introduce new varieties into an area. Most varieties of soybeans are very sensitive to
sensitive”. They tend to flower earlier as the day length becomes shorter. As a result
any one particular variety is well adapted to grow properly only in a narrow latitude
Northern hemisphere, if a soybean variety adapted to one latitude band is grown
north of this band it will flower, and therefore mature, later than normal, perhaps too
late before the winter. If that same variety is taken South of this latitude band, it will
flower and mature earlier than normal, producing small, underdeveloped plants—or
it may not flower at all.
Most soybean varieties are short-day plants they normally start to flower soon
Growth period: for mature beans, anywhere from 80 to 175 days, depending on the
variety, location and planting date.
Temperature: soil temperature at planting should be at least 10°C; 15°C is even
°
young and mature plants of most varieties can withstand a little touch of frost, but
not too much.
Growth habit: most varieties of soybean are determinate, meaning that the plant
only increases in height very little after it has started to flower, and also the
flowering period is relatively short so that the grains tend to mature at more or less
the same time. Other varieties, including many of the older, traditional ones, are
indeterminate, meaning that their height, or length, increases from two to four times
after it has started to flower. These types continue to flower over a much longer
period, so that the pods and seed also mature over a much longer period, as
Rainfall: to produce really good crops of soya, a regular supply of rain, or irrigation,
is needed. Water stress is particularly damaging during the period from the
length of day—the latitude, in other words — is very useful when deciding to
band, approximately 160–250 km from North to South. As an example: in the
photoperiod—the relative lengths of day and night and are said to be “photoperiod —
page 42.
after the day length begins to shorten ie 21st June in the northern hemisphere
and 21st December in the southern hemisphere. This topic is also discussed in 1Ej,
better. The ideal temperature range for growth for most varieties is 24 32 C. Both
discussed in 2Ei, page 42.