Zinc Fertilization Enhances Growth, Yield, and Zinc Use Efficiency of Rice (Oryza sativa L. cv. Chai Nat 1) in Contrasting Soil Textures

Efficient nutrient management is vital to sustaining rice production in the sandy soils of Northeast Thailand, where zinc (Zn) deficiency and low organic matter often constrain yield. This study evaluated the effects of Zn fertilization on the growth, yield, and Zn use efficiency (ZUE) of rice (Oryza sativa L. cv. Chai Nat 1) grown under greenhouse conditions in contrasting soil textures (loamy sand and clay). Four Zn rates were applied: 0, 5, 10, and 15 kg ZnSO₄·7H₂O ha⁻¹ (0, 0.013, 0.026, and 0.039 g ZnSO₄·7H₂O pot⁻¹). Clay soil, with higher organic matter, nitrogen, and available Zn, supported greater vegetative growth, biomass, and yield than loamy sand. Zinc fertilization significantly increased plant height, tiller number, chlorophyll content, biomass, panicle number, grain number, and filled grain weight. Yield improvement in loamy sand was associated mainly with reproductive efficiency, whereas in clay it was driven by vegetative vigor, biomass accumulation, and Zn uptake. Thousand-grain weight was not affected by Zn. ZUE peaked at 5 kg ha⁻¹ in loamy sand and 10 kg ha⁻¹ in clay, with clay showing a greater overall increase in ZUE across Zn rates and loamy sand exhibiting diminishing returns at higher application rates, reflecting differences in Zn availability and retention capacity. Correlation, PCA, and SEM analyses confirmed soil-specific yield mechanisms. Overall, Zn fertilization improved rice productivity and tissue Zn concentration, with optimal rates differing by soil texture. These findings highlight the importance of site-specific Zn management in enhancing yield, nutrient efficiency, and biofortification in rice-based systems of Northeast Thailand.