Effects of phosphorus and zinc application on yield and zinc nutrition of rice (Oryza sativa L.)

The intensive use of phosphorus (P) fertilizers in rice cultivation often induces zinc (Zn) deficiency in soils leading to nutrient imbalance, reduced Zn bioavailability in grains, and potential nutritional concerns for human health. A field experiment was conducted in an Inceptisol to study the effect of added P and Zn application on dry matter yield, P and Zn availability in soil, their uptake in plant and Zn recovery efficiency of kharif rice (Oryza sativa L.). The treatments included four doses of each P (0, 40, 60 and 80 kg ha− 1) and Zn (0, 5 kg ha− 1, 5 kg ha− 1 + one foliar spray and 5 kg ha− 1 + two foliar sprays). The application of P as well as Zn significantly increased the dry matter yield of rice. Phosphorus application up to 80 kg ha− 1 caused significant increase in soil P availability, P:Zn ratio and P uptake by the crop with a simultaneous decrease in availability of applied soil Zn, concentration and uptake of Zn by rice and Zn use efficiency. However, Zn application causes significant increase in Zn availability in soil, Zn content and uptake by crop. Phytic acid/Zn molar ratio in grain decreased to the tune of 24.04 and 34.34% upon Zn application through soil + one foliar and soil + two foliar, respectively, over the control. Zinc application further caused an increase in Zn-use efficiency by 1.5 and 2 folds upon soil + one foliar and soil + two foliar applications, respectively than only soil application. Zinc application through soil + foliar over basal application could be a useful strategy for Zn enrichment in grain and reduction of phytate/Zn molar ratios, thus enhancing their bioavailability when higher P doses were applied. The present investigation provides a good knowledge about the effect of phosphorus and zinc on soil P and Zn availability, dry matter yield of rice, their uptake and P/Zn ratio in plant. The paper also evaluated the influence of P and Zn application on phytic acid/Zn molar ratio in grain and use efficiency of Zn in rice.