Effect of Sulfur Fertilization on Productivity and Grain Zinc Yield of Rice Grown under Low and Adequate Soil Zinc Applications

This study aimed to investigate the responses in rice (Oryza sativa cv. Osmancik 97) production and grain zinc (Zn) accumulation to combined Zn and sulfur (S) fertilization. The experiment was designed as a factorial experiment with two Zn and three S concentrations applied to the soil in a completely randomized design with four replications. The plants were grown under greenhouse conditions at low (0.25 mg/kg) and adequate (5 mg/kg) Zn rates combined with S (CaSO₄·2H₂O) application (low, 2.5 mg/kg; moderate, 10 mg/kg, and adequate, 50 mg/kg). The lowest rate of S at adequate soil Zn treatment increased grain yield by 68% compared with the same S rate at low Zn supply. Plants with the adequate S rate at low Zn and adequate Zn supply produced the highest grain yield, with increases of 247% and 143% compared with low S rate at low Zn and adequate Zn supply, respectively. The concentration of grain Zn and S responded differently to the applied S rates depending on the soil Zn condition. The highest grain Zn concentration, reaching 41.5 mg/kg, was observed when adequate Zn was supplied at the low S rate. Conversely, the adequate S rate at the low soil Zn conditions yielded the highest grain S concentration. The total grain Zn uptake per plant showed particular increases in grain Zn yield when adequate S rates were applied, showing increases of 208% and 111% compared with low S rate under low and adequate soil Zn conditions, respectively. The results indicated that the synergistic application of soil Zn and S improves grain production and grain Zn yield. These results highlight the importance of total grain Zn yield in addition to grain Zn concentration, especially under the growth conditions where grain yield shows particular increases as grain Zn is diluted due to increased grain yield by increasing S fertilization.