小麦吸氮规律与土壤中矿质氮的变化

在盆栽条件下,小麦吸氮有两个高峰:一是播后1月(分蘖期),二是来年2月(返青期)。小麦生长后期,植株吸收的氮素不但无增,反而明显减少。种与不种作物,土壤矿质氮都处在不断变化之中。整个趋势是,随着温度升高,NH_4~+-N不断减少,在种植作物情况下,减少更剧烈;NO_3~--N大致趋于稳定。后期,种与不种作物土壤中的NH_4~+-N和NO_3~--N含量基本一致,表明种作物的土壤,矿质氮在作物生长后期得到了恢复。不管种植作物与否或休闲期长短,土壤中的矿质氮最后都维持着大致一样的较低水平,有趋低现象。

Nitrogen Uptake Pattern of Wheat and the Changes of Mineral N in Soils

The pot experiment results obtained show that there were two peaks of nitrogen uptake by wheat: the first(tillering stage) and the fourth month (riviving period) fallowing sowing. At the latest stage, the total uptake nitrogen by wheat shoots was not increased, but decreased significantly. The mineral nitrogen in soil was greatly changed no matter whether wheat was planted or not. On the whole, the tendency is as follows.-with temperature raising, NH^-N gradually decreased, while NOJ-N remained stable, and the degree of decrease was higher in the soil with plants. However, at last, the NH^-N and NO^-N had nearly the same amounts in soils with or without plants, indicating that the mineral nitrogen was recovered in the soils with plants at last growing stage. No matter whether there was plant or not, and no matter how long were the fallowing periods, nearly the same level of mineral nitrogen in soil remained at last, indicating that the soil mineral N had a tendency to be low.