Study on the Critical Value of Zinc and Effects of Zinc Fertilizer on Rice in Calcareous Soil

Under test condition of the nitrogen, phosphorus, potassium in the optimum amount of fertilization and the soil available zinc content of 1.0~1.5 mg/kg, the ear number, grains per panicle, 1000-grain weight, plant high, ear length and yield increased with the increase of zinc fertilizer. The results showed that the yield of rice was highest when the amount of zinc sulfate was 22.5 kg/hm2, it increased by 12.7% compared to the control. The trends of different soil were similar. The yield in fluvio-aquic soil increased more than that of paddy soil, the ear number in fluvio-aquic soil was higher, but the grains per panicle in paddy soil was higher than that of fluvio-aquic soil. Regressive analysis showed that the optimum amount of zinc sulfate was 21.5~23.0 kg/hm2, the yield reached 9300~9800 kg/hm2. The critical value of soil available zinc deficiency for rice was 1.48 mg/kg.