Pattern of water availability and water requirement for grain sorghum production at Samaru, Nigeria
AbstractThe performance of rain-fed sorghum [Sorghum bicolor (Moench)] in a dry sub-humid region of northern Nigeria is analysed in terms of adaptability to climate with particular reference to crop water availability. The water requirement of a 'Short Kaura' sorghum crop is about 700 mm. This amount is derived from a continuous function of the Et/Eo ratio and the corresponding stages of crop development over the 180 days of the growing season. The average annual rainfall of 1100 mm is distributed over 140 to 160 days. The water storage capacity of the soil is adequate to provide the water requirements of sorghum after the end of the rains and to extend the growing season by about 60 days. The pattern of the crop water requirement is then well matched to the pattern of water availability for rain-fed Sorghum production. The indigenous long sea on sorghum varieties are photosensitive and their heading coincides with the end of the rains when grain formation is dependent on the reserves of stored soil moisture. These varieties have a low grain yield potential and the period of vegetative growth is too long for efficient grain production at high levels of fertility. High growth rates during the first nine weeks suggest that the crop could be used for forage production. Non-photosensitive exotic sorghums (i.e. American hybrids and combine varieties) have short seasons relative to Nigerian varieties and give high grain yields, but of a quality unacceptable for human consumption in Nigeria. Sown at the beginning of the rains, the crop matures at the peak of the rainy period rendering harvest difficult. Because of wet harvest conditions the grain quality is poor. Late sown crops are difficult to establish and the yields are lower than those from early sowings. Production of local sorghums under irrigation during the dry season is not possible at Samaru because of low temperatures.