Assessment of Crop Water Productivity of Maize in Sub-Trophical Conditions under Tube Wells Irrigation System

This research study was conducted to find the water productivity, relationship between water productivity and depth of water applied and yield of maize crop. The study was based on two years primary data collected in 2012 and 2013 and the questionnaire was used as a research tool for collection of data required for the study. The effective rain fall was estimated through CROPWAT (computer based programme) using the meteorological data obtained from WAPDA (Water and Power development authority), where the discharges of tubewells were determined by volumetric method. The number of irrigations, time taken by each turn and crop yield was recorded with the help of a questionnaire. Result showed that the average yield of maize was 4295 kg ha-1, while the average water productivity was 0.76 kg m-3. The crop water productivity of maize ranged from 0.05kgm-3 to 1.8kgm-3, whereas the yield ranged from 978.26kg/ha to 7500kg/ha.The water productivity of maize decreased from 1.8kgm-3to 0.89kgm-3 when the depth of applied water increased from 99mm to 543mm. The results further revealed that the inadequate knowledge of farmers regarding depth of water to be applied at proper time and the frequency of irrigation were the main reasons for the low water productivity. It can be recommended that irrigation management with minimum applied depth of water is an important step toward the maximum crop water productivity