Analyzing wheat productivity responses to climatic, irrigation and fertilizer-nitrogen regimes in a semi-arid sub-tropical environment using the CERES-Wheat model

In order to enhance crop productivity in water-limited environments, there is a need to evaluate and apply water-saving management practices. This study examined the applicability of the CERES-Wheat model under variable climatic, irrigation, and fertilizer-nitrogen (N) regimes. The objective was to analyze wheat yield responses to water- and N-application for optimizing crop productivity under water limitations in a semi-arid sub-tropical irrigated environment. Evaluation analysis showed that performance of the model was reasonable as indicated by close correspondence of simulated crop phenology, biomass accumulation, grain yield, and soil water and N use with measured data. The normalized root mean square of deviations ranged between 10 and 20% for most of the parameters. Cumulative probability distribution of simulated grain yield and ET showed that for a given irrigation regime, fertilizer N had greater effect on yield than on ET and caused greater water productivity. Scenario analysis also demonstrated that grain yield and water productivity response to irrigation were influenced by extractable water capacity of soils. Soil effects on grain yield were more pronounced under I0 regime, and the effect decreased with increase in irrigation. Post-sown irrigation was more effective under conditions of low initial soil water. Initial soil mineral-N status influenced the amount of fertilizer N for a given initial soil water and post-sown irrigation scenario.