Long-term Application Effect of Silicate Fertilizer on Soil Silicate Storage and Rice Yield

Monitoring of soil fertility and crop productivity in long-term application of silicate fertilizers is necessary to use fertilizers efficiently. This study was conducted to investigate effects of continuous application of silicate fertilizer for rice cultivation from 1969 to 2014. The treatments were no silicate fertilizer treatments (N, NC, NPK, and NPKC) and silicate fertilizer treatments (N+S, NC+S, NPK+S, and NPKC+S). The 46-yr input of $2\;ton\;ha^{-1}yr^{-1}$ of silicate fertilizer increased pH 0.6 ~ 1.1 and exchangeable Ca $2.0{\sim}2.4cmol_c\;kg^{-1}$ in silicate fertilizer treatments (N+S, NC+S, NPK+S, and NPKC+S) compared with no silicate fertilizer treatments (N, NC, NPK, and NPKC) because silicate fertilizer included Ca component. Also, available silicate concentrations of silicate fertilizer treatments (N+S, NC+S, NPK+S, and NPKC+S) increased $169mg\;kg^{-1}$ compared to no silicate fertilizer treatments. In Period II ('90~'14), the mean annual Si field balance varied from 62 to $175kg\;ha^{-1}yr^{-1}$ in silicate fertilizer treatments, indicating continuous accumulation of soil Si. Silicon uptake and grain yield of rice had greater differences between N treatment and N+S treatment than other treatments. This showed that the application of silicate fertilizer had greater effect in nutrient-poor soils than in proper nutrient soils. Thus the application of silicate fertilizer led to improvement the fertility of soil and increasement of rice production for the lack of soil nutrients.