Assessing Deficit Irrigation and Supplemental Irrigation as Water Management Strategies for Improving Maize Production in Benin

Abstract

Deficit Irrigation (DI) consists to provide the crop with water below its daily need (ETc) according to the sensitivity of its growth stages. The objective of this study was : (i) to assess the factors explaining maize response to irrigation water stress; (ii) assess the potential of supplemental irrigation and deficit irrigation for improving rainfed maize production; and (iii) to evaluate crop water productivity under irrigation water deficit in sub-humid climate of Benin. To achieve its objectives, the present study first reviewed through quantitative meta-analysis the overall response of maize to DI to identify the growth stage that will allow limited yield loss, and to understand the factors that explain maize response to water stress. Two field experiments were conducted under supplemental irrigation in 2018 and 2019 using four rates of fertilizers; and one experiment under deficit irrigation in 2019 using four (04) levels of DI (0, 25, 50, and 75% ETc). Irrigation water stress were applied based on daily crop evaporation determined from CropWat FAO database. For all experiments, a Randomized Bloc Design with 3 replications was used. The review showed that yield loss increases with increasing levels of DI at all growth stages, but yield loss was minimized in vegetative stage. In addition, the results from the review suggest that maize response to water stress is dependent on many factors such as climatic zone, cropping densities, and fertility management practices. The experimental results indicated that leaf area index (LAI) and plant height decreases in stressed treatments during the period of stress application, but the decrease was observed on different periods, suggesting a given sequence, or a process through which DI affect crop production. Grain yield decreases as water stress increases by 25%, 47%, and 82% respectively in D25, D50, and D75 treatments. There was no significant difference of stover yield between D0 and D25 in one side, and between D50 and D75 on the other side. Water Use Efficiency (WUE) and Irrigation Water Use Efficiency (IWUE) decreased as DI increases, respectively by 19% and 0.26% in D25 treatments, implying there’s an optimum deficit irrigation level for which yield loss would be reduced. Since farmers in West Africa context are more concerned about a sustained yield over a long period of time, that optimum deficit level should be determined, for instance through simulation on the long term base on scenario analysis, to make appropriate recommendations.