ESTIMATION OF CROP WATER REQUIREMENT FOR ONION IN MAIDUGURI, A SEMI-ARID ENVIRONMENT

The estimation of peak crop water requirement for matching farm sizes with available water is necessary for efficient water management. There are various methods of predicting crop water requirements ranging from those requiring several measured weather data (Penman, Jensen & Haise, and by Radiation); to those requiring single measured weather data (Blaney-Criddle) and the direct evaporation from class “A” pan. Out of these methods the most suitable method for estimating the crop water requirements for onion in Maiduguri a semi arid environment was determined to be the modified Blaney-Criddle method. The method was used to estimate the peak irrigation requirement for onion and was found to be in April amounting to 67 m3/day/ha which is equivalent to 1.28 l/s/ha at 60% efficiency. This value is within the acceptable limits of 1.0-1.5 l/s/ha recommended for canal design in arid and semi-arid regions.