氮肥施用对作物吸收土壤氮的影响——兼论作物氮肥利用率

EFFECT OF N FERTILIZER ON UPTAKE OF SOIL N BY CROPS WITH SPECIAL DISCUSSION ON FERTILIZER NITROGEN RECOVERY RATE

在15N标记肥料微区试验中采取了抑制土壤中氮生物固持作用的措施——用长期不施肥试验地、小麦拔节前施15N标记KNO3,成功显示了影响施氮作物吸收土壤氮的另一个过程:肥料氮对土壤氮库的稀释作用(或作物吸收养分过程中肥料氮和土壤氮的库替换作用)的存在;试验中施氮作物较不施氮作物少吸收土壤氮,呈现负的ANI(加入氮交互作用)。生物固持作用和肥料氮对土壤氮库的稀释作用是两个作用相反且交织在一起的过程,其相互抵消、平衡后的最终结果可以是正ANI,也可以是负ANI,决定于两者影响力的强弱。由于受上述过程的影响,用田间试验估测作物氮肥利用率,无论15N标记法或传统的差值法,均不可能获得可信的结果。作为替代方法,比值法可避免上述过程的影响,经本试验检验,结果良好。

In a microplot^15N-labelled fertilizer N experiment, where measures were taken to inhibit bio-immobilization of nitrogen, application of ^15Nlabelled KNO3 to wheat prior to its shooting stage,and the microplot experiment being carried out in Treatment CK （a treatment of another field experiment that has never been fertilized） successfully exposed another process that affected uptake of soil N by crops, i.e. dilution of soil N pool or substitution of N in the pool by fer- tilizer N. The crops applied with N fertilizer absorbed less soil N than those applied with nothing, showing negative ANI. Biological N immobilization and dilution of （fertilizer N on） soil N pool are two opposite and intermingled actions. Counteraction and balance of the two actions might lead to positive ANI or negative ANI depending on which one is stronger. As is affected by the above-discussed process, it is almost impossible to assess N fertilizer recovery rate with reliable result by means of field experiment using either^15N-labelling method or traditional difference method. As an alternative, the proportion method could help skid over the obstacle and has been verified in this experiment with better results.