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本文报道利用~(15)N同位素稀释法研究供给少量化合态氮素对单、混作苜蓿同氮贡献之影响和牧草对土壤氮素的吸收利用和贡献。合理施入化合态氮肥能提高苜蓿固氮能力,延长固氮高峰的持续时间。特别是对初建或低供氮能力的草塌,施入化合态氮肥尤为必要。混播情况下,发生明显的固氮产物转移。豆科牧草的固氮产物似乎比土壤氮素更易为禾本蓿牧草吸收利用。种植苜蓿能明显提高土壤氮肥力。牛尾草可能具有固氮能力。少量化合态氮素的施入对种植苜蓿牛尾草的土壤氮素肥力的提高有明显的促进作用。
In this paper, the effect of supplying a small amount of compound nitrogen on the contributions of nitrogen and nitrogen to single and mixed alfalfa and the contribution of forage to soil nitrogen uptake and utilization were studied by ~ (15) N isotopic dilution. Rational application of compound nitrogen fertilizer can increase nitrogen fixation ability of alfalfa and prolong the duration of nitrogen fixation peak. Especially for the initial build or low nitrogen capacity of the grass collapsed, Shi compound nitrogen fertilizer is particularly necessary. In the case of mixed broadcasting, significant nitrogen fixation product transfer occurred. Nitrogen fixation products from leguminous pasture seem to be more readily absorbed by grasses than forage nitrogen. Alfalfa planting can significantly improve soil nitrogen fertility. Potamogeton may have a nitrogen-fixing ability. The application of a small amount of compound nitrogen could obviously promote the improvement of soil nitrogen fertility in the planting of Medicago sativa.