Computational method for appropriate nitrogen level by soil diagnostics in Andosols of Japan

摘要

In farm production, it is important to reduce the cost of production and increase yield. It is necessary that countries like Japan that depend on import for resources reduce the quantity of the chemical fertilizer consumed in the cost of production. In this study, it was aimed to develop the soil diagnosis formula that was able to decide the appropriate amount of chemical fertilizer nitrogen. The evaluation method of available nitrogen of the soil was examined in the beginning. As a result, the phosphate buffer extractable N (PB-N) that used an oven dry (160 °C, 2 hour) soil sample was adopted for available nitrogen. Next, the amount of the chemical fertilizer nitrogen absorbed by Chinese cabbage, corn, and carrot was measured using ~(15)N labelledammonium sulphate. The multiple linear regression analysis was calculated using as dependent variable the absorbed chemical fertilizer nitrogen and explanatory variable that was the total amount of nitrogen absorption of crops, inorganic nitrogen, and available nitrogen. This multiple regression equation was adopted as a soil diagnosis formula. As a result, the amount of chemical fertilizer nitrogen was able to be reduced, while maintaining yield.