Predicting Nitrate Leaching in Cotton under Semi-arid Conditions: Comparison of Models

A field experiment was conducted in micro-plots on cotton at Hisar (Haryana), representing the subtropical climate zone of India to predict nitrate leaching using LEACHM and Field Capacity Layer (PAL) models. Predicted NO₃–N values in the different depths at various stages of cotton growth by LEACHM were closer to the observed values as compared to those obtained by the PAL model as evident from R² values of 0.941 for LEACHM and 0.384 for PAL. LEACHM predicted the losses of N {NH₄-N (volatilization) and NO₃ (leaching)} during cotton growth period at 34.7 kg ha⁻¹ (7.5 and 27.2 kg ha⁻¹) in unfertilized plots; whereas under N fertilized conditions, the value was 66.4 (38.5 and 27.9 kg ha⁻¹). Simulations indicated that NO₃ leaching did not change much even with an input of 86 kg ha⁻¹ fertilizer N. LEACHM successfully predicted the nitrate distribution in profile compared to PAL model and around 28 kg ha⁻¹ of NO₃ was predicted to be lost to underground waters under these conditions. Similar N uptake for unfertilized as well as fertilized plots, hinted that there is need to further refine the model parameters especially for cotton as this crop has hardly been subjected to prediction research.