Agronomic management based on multi-split topdressing increases grain yield and nitrogen use efficiency in rainfed maize in Vertisols of India

Conventional fertilizer nitrogen (N) recommendations for rainfed maize resulted in low N use efficiency (NUE) due to several reasons. This warrants application of fertilizer synchronous with plant requirements that could aid in improved productivity and NUE. In this backdrop, to optimize N rates for maize, a field experiment was conducted during 2014 to 2016 in Vertisols. Twelve treatments in combinations viz., N omission, skipping basal dose, multi-split topdressing at varying time either as broadcast or band placement, soil test crop response (STCR) based N with target yield 6.0 t ha⁻¹ and biochar application were investigated in a randomized block design (RBD). Late application of N rates (120 kg ha⁻¹) in 2 equal splits at knee high (V8) and tasseling (VT) stages with skipping of basal N, significantly increased grain yield, agronomy efficiency (AE), partial factor productivity (PFP), physiological efficiency (PE) and recovery efficiency (RE) to the tune of 16.3%, 45.1%, 15.3%, 14.0% and 37.9% than conventional recommendations, respectively. The higher yields and NUE with late application of N were ascribed due to positive significant linear relationship between yield and N availability. Factor analysis too revealed the one to one positive function of biomass with N uptake at V8 and VT. Principal component (PC) regression exhibited that PC1 acted as a major predictor for yield and dominated by leaf area index (LAI) and N uptake. Thus, we conclude that the multi-split N, to achieve higher yield and greater NUE, is strongly linked with late splits of N at V8 and VT.