flowering stage to just before pod maturity. On the other hand, soybeans need less
water than maize.
Altitude: soya cultivation is restricted to altitudes which have about 100 days of
growing period with average temperatures above about 20°C. Some varieties, such
as Chippewa, are adapted to the lowland tropics.
Pests: insects can devastate fields of soya. The most serious are the Semi-looper
caterpillars, Bean Fly, Cutworms, Aphids and Snout Beetles.
Diseases: altogether at least 50 diseases attack soybeans; all three types of disease
occur:
- Bacterial—Stem Blight, Leaf Pustule, Bacterial Blight
- Fungal—Downy Mildew, Wild Fire, Frog-eye Spot
can be controlled to some extent by using a combination of resistant or tolerant
varieties with seed dressings and crop rotations. Aphid numbers may have to be kept
under control with insecticides to reduce Mosaic and other viral diseases, but spread
of the other diseases should be possible without recourse to pesticides.
Nutrient deficiencies: the symptoms of major, minor and trace element deficiencies
are described below; though these symptoms are often partly masked by diseases.
The most common are:
- Phosphorus—plants are stunted and have blue-green leaves.
- Potassium—leaf edges become yellow.
- Iron—yellowing between the leaf veins.
- Manganese—also yellowing between the leaf veins.
- Molybdenum—plants are stunted; more common in acid soils.
- Zinc—leaves & stems smaller than normal, yellow between leaf veins, especially
lower leaves.
Trace element toxicities:
plant, are crinkled with downward turned margins.
- Boron—crinkled leaves, which may fall off, and which die from the leaf margins
inwards.
For more information on Nutrient Deficiency, Trace Element Toxicity, etc., see
YIELD
The global average yields of soybeans have been steadily increasing for more than
20 years, from around 1400 kg/ha in the mid-1970s, to more than 1700 kg/ha in the
mid-1980s to around 2 MT/ha in the late 1990s (2.23 MT/ha in 2004, according to
produce more than 5 MT/ha.
Ideally soya seed should be stored at 10% moisture, and at no more than 12%
moisture if it is to be kept for any length of time.
All seed stocks should be handled and stored with great care in order to avoid
falls in germination rates that can be dramatic.
–Viral—Soybean Mosaic, Yellow Bean Mosaic. Most of these diseases of soybean
- Manganese—especially in acid soils; leaves, especially those at the top of the
1Cd, “Trace Elements” pages 23–29.
FAO). In good growing conditions, modern soybean varieties can consistently