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

Dry beans, an annual crop high in protein content and with considerable dietary benefits, are native to Central and South America. Dry beans require a MAP of 600 - 650 mm, of which optimally 400 - 500 mm should fall into their summer growing season (Smith, 1998). Excessive rain, however, causes flower drop and promotes diseases. Mean daily relative humidity should be between 50 and 60 percent (Smith, 1994). The ideal temperature range for dry beans is 18 – 24 degree Celsius. On average in the RSA, 50 000 ha are planted to dry bean varieties each year (NDA, 2006), of which 65 - 75 percent are red speckled beans, 10 - 20 percent small white beans and 5 – 10 percent kidney beans (Liebenberg, 2002).

Using Smith (1998) climatic criteria, yields of dry beans 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).