ABSTRACT
The tropics are characterized by a rather regular climate with regard to solar radiation, air temperature, wind speed and evaporation. Annual air temperature fluctuations generally have only a marginal effect on plant growth since temperatures are normally conducive for plant growth throughout the year. Life cycles of pests and diseases are often synchronized with those of the host plants and are frequently determined by climatological and ecological conditions. When planning cropping systems, the intensity of rainfall during different seasons should, therefore, be taken into account to help choose suitable crops and planting dates. In areas with marked seasonal rainfall patterns, variability and reliability at the start and finish of the rainy period are particularly important since the first determines planting dates and the latter determines whether early or late maturing varieties should be used. The amount of reliable rainfall in the pre-rainy period is small in many areas. This period is, however, important, since early planting is normally advantageous.
