Enhancing Growth and Zinc Bioavailability in Rice (Oryza sativa L.) Cultivars through Agronomic Biofortification Strategies

Abstract

A field experiment was conducted using four rice varieties viz., Uma, Pournami, Gouri and DRR Dhan 45 under varying levels of ZnSO4 foliar application (control, 0.1 per cent, 0.5 per cent and 1.0 per cent) in a randomized complete block design. ZnSO4 @ 1.0 per cent recorded taller plants at panicle initiation (80.5 cm) and harvest stages (113 cm) and was comparable with ZnSO4 @ 0.5 per cent. Higher tillers per hill and dry matter production were also recorded at panicle initiation and harvest stages with ZnSO4 @ 1.0 per cent which was statistically similar to ZnSO4 @ 0.5 per cent. Zinc application at 0.5 per cent and 1.0 per cent enhanced Zn concentration in rough rice, brown rice, white rice, and rice bran. The highest Zn accumulation in white rice (21.2 mg kg⁻¹) was achieved with 1.0 per cent ZnSO₄ foliar spray, which was comparable to 0.5 per cent ZnSO₄ spray. Application of 1 per cent ZnSO₄ during maximum tillering and milk stage led to substantial reductions in the phytate: Zn molar ratio in rough rice (28.3), brown rice (32.7), white rice (6.31), and rice bran (25.9). Dhan 45 treated with 1.0 per cent ZnSO₄ achieved the lowest ratios in rough rice (18.9) and brown rice (21.8). Although the 1.0 per cent treatment yielded greater reductions in the phytate: Zn molar ratio, the 0.5 per cent ZnSO₄ treatment produced notable decrease in rough rice (30.2), brown rice (34.8), white rice (6.72), and rice bran (27.6) making it a viable option for lower Zn input. Overall, foliar application of Zn improved Zn bioavailability in both whole grains and milled rice, aligning phytate: Zn molar ratios closer to optimal levels for human nutrition.