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本文介绍农业系统中利用~(15)N 标记物估计生物固氮的某些最近进展。田间条件下豆科作物的固氮量,可根据豆科作物和非豆科作物的 A_N 值进行估计。在土壤含氮量十分低的情况下,为确保植株正常生长,对非固氮作物可施入正常量的~(15)N 标记肥料,但是对于豆科作物,为了不干扰其固氮作用,可施少量的~(15)N 标记肥料。当两个作物施以等量的~(15)N 标记肥料时,豆科作物的固氮量由豆科作物的~(15)N 原子百分超除以非豆科作物的~(15)N 原子百分超求得。乙炔还原法已被用于估计各种系统的固氮量。但是这个方法是短期的动态测量,因此当用来估计整个生长季的固氮量时,则需要多次取样测定。由于变异系数大,并需用~(15)N 对照或凯氏定氮校准测定结果,定量估计固氮显得很复杂。土壤和植物中的~(15)N 天然丰度,作为估计豆科作物固氮量的指标,已取得了有希望的结果。
This article presents some recent advances in the estimation of biological nitrogen fixation using ~ (15) N markers in agricultural systems. Nitrogen fixation of leguminous crops under field conditions can be estimated based on A_N values of legumes and non-leguminous crops. In the case of very low nitrogen content in the soil, to ensure normal plant growth, non-nitrogen-fixing crops can be applied with a normal amount of ~ (15) N-labeled fertilizers, but for leguminous crops, in order not to interfere with their nitrogen fixation, A small amount of ~ (15) N labeled fertilizer. When two crops were treated with the same amount of ~ (15) N-labeled fertilizers, the amount of nitrogen fixation in leguminous crops was divided by ~ (15) N atomic percent of leguminous crops by ~ (15) N of non-leguminous crops Atomic percentage exceeded. Acetylene reduction has been used to estimate the amount of nitrogen fixation in various systems. However, this method is a short-term, dynamic measurement and therefore requires multiple sampling determinations when used to estimate the amount of nitrogen fixation throughout the growing season. Due to the large coefficient of variation and the calibration results with ~ (15) N control or Kjeldahl determination, the quantitative estimation of nitrogen fixation is complicated. The natural abundance of ~ (15) N in soils and plants has yielded promising results as an indicator of nitrogen fixation in leguminous crops.