Soybean Yield Estimation (T.Ha-1.Season-1) Based On SmithS (1994) Climatic Criteria

A bushy, summer season legume, soybean (Glycine maximum) has three-fold leaves and grows to between 0.6 and 1.2 m (SPPCOM, 2005). Soybeans, planted in November - December, ideally require a MAP > 700 mm, with > 450 mm falling over the growing season. While relatively resistant to very high and low temperatures, optimum growth takes place at temperatures between 20 degree Celsius and 30 degree Celsius, with growth rates decreasing when daily maxima are > 35 degree Celsius and below 18 degree Celsius (Smith, 1994). Using Smith`s (1998) climatic criteria, yields of soybean are estimated using the effective rainfall for October to March and heat units (base 10 degree Celsius) for the same period, with modifications to yield made for soil properties and levels of management. Rainfall values were derived from the 1 arc minute (1` x 1` latitude x longitude) median monthly rainfalls generated for South Africa by Lynch (2004).