Assessing spring maize responses to irrigation and nitrogen regimes in north-west India using CERES-Maize model

Inadequate availability of fresh water and rising cost of fertilizers warrant their judicious use in agriculture. In intensively-cropped Punjab state of north-west India, alarming decline in groundwater resources pose a challenge to spring maize that otherwise has high profitability. This study is an assessment of water use and productivity responses of spring maize to irrigation and nitrogen regimes in a subtropical environment using CERES-Maize model. Database was generated from a field study on maize planted in second half of February with combinations of two irrigation regimes viz., irrigation water to pan evaporation ratio of 1.0 (I1.0) and 0.5 (I0.5), and four N rates viz., 0, 50, 100 and 150 kg ha−1 on a sandy loam soil. Irrigation and N had significant effects on grain yield, water use and N uptake. Performance of the model was reasonable with normalized root mean square of deviations between simulated and measured values less than 20% for harvest-time biomass, grain yield and water use; and slightly greater variance (30%) for grain N uptake. Scenario analysis showed that ET-based water productivity (WPET) was greater in January 31 than February 14 planted maize crop. The WPET was greater with I0.5 than with I1.0 suggesting that increase in yield was less than proportional increase in ET. The WPET responses to N with increase in irrigation were greater at lower than at higher initial soil water.