Water Productivity of a Maize Crop under Deficit Irrigation Scheduling Using Gravity Drip System

Abstract

This study was carried out to determine the impact of deficit irrigation scheduling strategies on water productivity of a maize crop using gravity drip system of irrigation. The experimental treatments were based on water application regulated at selected crop growth stages. The treatments comprising a control treatment which was given full irrigation (irrigated at 100 % water requirement) and a full deficit treatment which was irrigated at 50 % water requirement. The other treatments were irrigated at 50 and 75 % of water requirement at different growth stages of the maize crop. The irrigation interval was alternated between three and four days. The overall average dripper discharge was found to be 0.56 l/hr. The depths of water were applied ranged from 432 to 699 mm for both seasons. Grain yields, biomass yields, seasonal evapotranspiration and crop water productivity were determined. The grain and biomass yields for the two seasons ranged from 1.56 to 3.52 and 5.63 to 11.53 t/ha, respectively, while the seasonal evapotranspiration varied from 289 to 483 mm. The irrigation water productivity with respect to grain yield and biomass yield varied from 0.41 to 0.63 and 1.33 to 1.98 kg/m3 for both seasons. The vegetative stage seems to be very sensitive to yield reduction for both seasons. Therefore, it is more advantageous to apply stress at flowering and grainfilling stage in the study area because of the interception of rain which may overturn the effect of moisture stress during grain-filling stage.The highest crop yield, seasonal water use and water productivity were obtained in the treatment that was fully irrigated, which implies that the deficit irrigation did not improve the crop response or water use efficiency. The results suggest that under high water application efficiency deficit irrigation practice may not lead to higher crop water use efficiency or the maize crop