CROP COEFFICIENTS OF SOME MAJOR CROPS OF THE NIGERIAN SEMIARID TROPICS

Crop coefficient (Kc) curves for grain sorghum, cotton, maize, groundnut and millet were developed for the Nigerian semi-arid tropics (8° to 13°N; 5° to 15° E) based on grass reference et0 determined with the FAO-24 (Penman) procedure and lysimeter measured crop water use data at Samaru, Nigeria (11°11′N; 7°38′E). The recommended equation for estimating solar radiation from relative sunshine hours was determined to be Rs = [0.28 + 0.46( n N)Ra] using measured solar radiation data. A value of 1.6 was obtained for the ratio of day to night time wind speeds for the growing season (May to October) using an automatic weather station. A procedure was also developed to estimate daily minimum and maximum relative humidity from daily minimum and maximum temperatures and the usual relative humidity records. The Kc curves developed can be recommended for use in farm water management decisions throughout the semi-arid tropics of West Africa south of the Sahara. © 1990.