引言 以植物残余物或无机N肥施入土壤,可被植物吸收,或自土壤植物系统失去,或被土壤微生物固定逐渐转化成固定状态。由于试验的条件,这种转化程度的变异甚大。通常,施N肥的50％为植物吸收,25％因不同的机制而损失,其余25％留在土中程度不同的成为固定状态。 应用~(15)N同位素作无机肥施用,研究N对于植物的有效性,已有许多工作者作过。利用植物残余物作N肥的周转及有效性也已有报告。现在的研究 Introduction Plant residue or inorganic N fertilizer applied to the soil, can be absorbed by plants, or lost from the soil plant system, or by microbial immobilization of soil gradually transformed into a fixed state. Due to the experimental conditions, this degree of transformation varies greatly. Normally, 50% of N fertilizers are absorbed by plants, 25% are lost due to different mechanisms, and the remaining 25% remain in soil at different levels and become immobilized. Application of ~ (15) N isotopes as inorganic fertilizers to study the effectiveness of N for plants has been done by many workers. The use of plant residues as a turn-around and effectiveness of N fertilizer has also been reported. Now research