Improving use efficiency of applied phosphorus fertilizer by zinc fertilization in Basmati rice-wheat cropping system

Rice-wheat rotation is the most important cropping system of the Indo-Gangetic plains. On-farm experiment was conducted to reveal the effect of Zn fertilization on yield, uptake of nutrient, utilization efficiency (UE) and grain output per unit of fertilizer use through agronomic efficiency (AE) of P and Zn in rice-wheat rotation. The experiment was conducted with rice (cv. Pusa Basmati 1) and wheat (cv. UP–2425) by imposing twelve treatments involving four different doses of P (0, 20, 40 and 60 kg P₂O₅ ha⁻¹) and three different doses of Zn (0, 2.5 and 5.0 kg Zn ha⁻¹) with three replications. The yield of basmati rice was not significantly influenced by P×Zn interactions however, for wheat, a conjoint dose of 60 kg P₂O₅ and 5 kg Zn ha⁻¹ gave the highest grain yield (5.43 t ha⁻¹). Phosphorus utilization efficiency (PUE) of wheat was higher compared to basmati rice however, the reverse was true for zinc utilization efficiency (ZUE). Utilization efficiencies of the two nutrients diminished as their rate of fertilization increased, in both the crops. The AE of applied nutrients, in basmati rice varied from 31.4 to 49.7 kg grain kg⁻¹ P and from 43.2 to 121 kg grain kg⁻¹ Zn. In wheat, AE for P varied from 26.9 to 65.5 kg grain kg⁻¹ and for Zn from 56.4 to 83 kg grain kg⁻¹. In conclusion, the utilization and agronomic efficiency of P in basmati rice can be increased by using 40 kg P₂O₅ and 2.5 kg Zn ha⁻¹.