Integrating nitrogen fertilization with crop residues to improve nitrogen management in intensively managed cropping systems

Sustainable nitrogen (N) management represents the nitrogen-use efficiency (NUE) of crops associated with agricultural productivity. The NUE and sustainable N management index (SNMI) of different crops were evaluated with two levels of crop residues (no residue, NR vs. 30 cm residue, CR) and four levels of N fertilizers (control, CL; farmers' practice, FP; national recommended dose, RD; and 125% of RD, 1.25 RD) on intensively managed potato, maize and rice-based cropping systems during 2020-2022. Increasing N fertilization increased winter and monsoon rice yields, while the effects were similar for pre-monsoon rice. Despite site and season specific, NUE showed mixed effects of CR and N rate interaction, being higher in CR-1.25 RD for rice and potato but lower for maize. Likewise, SNMI was lower in 1.25 RD coupled with CR for rice and potato but opposite for maize. Despite NUE corresponds well with the SNMI, the latter fits better with the crop yield, nutrient uptake, N requirement and N use model, suggesting that SNMI predicts optimum N management. Using the SNMI, a scatter diagram-based model optimized N fertilization for crops were: 169, 152, 187, 92, and 112 kg N ha-1 for potato, maize, winter rice, pre-monsoon rice and monsoon rice respectively.