2007 Volume 76 Issue 2 Pages 288-294
The effects of four fertilizer elements (nitrogen, phosphoric acid, potassium and lime) and compost on rice plant during the 77 years from 1926 were studied. Lack of adding nitrogen, phosphoric acid, potassium and lime significantly decreased the yield, conversely adding compost increased the yield. The ratio of the yield in the plot lacking nitrogen or phosphoric acid to that with four elements fertilized was considered to decrease gradually. On the contrary, the ratio of the yield in the plot with compost to that with four elements fertilized gradually increased. Therefore, it is considered that compost effect is increased gradually. However, it was uncertain why the ratio of the yield in the plot lacking potassium and lime to that with the four elements gradually increased. We found definite fertility of the soil without application of fertilizer and the effect of four elements on the yield.
