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田间试验采用裂区设计，在不同种植模式下采用１５Ｎ示踪研究了苜蓿与牛尾草混播及单播草地的产草量、产氮量和固氮量的变化。结果表明混作条播优于混作撒播和间作条播，前者更有利于发挥豆禾牧草混作草地的优势，三种处理年均牧草干重分别为１５３５．９、１２８０．８和１２４９．３ｇ／ｍ２；相应全氮产量为５０．８３、３６．６５和３６．８６ｇ（Ｎ）／ｍ２，年均固氮量分别为４２．３７、２８．２１和２８．４２ｇ（Ｎ）／ｍ２，年均固氮百分率分别为８３．４％、７７．０％和７７．１％。并对１５Ｎ同位素稀释法、１５Ｎ天然丰度法及全氮差值法测定的固氮百分率和固氮量进行了比较。
In the field experiment, split-plot design was used. The 15N tracing was used to study the changes of grass yield, nitrogen production and nitrogen fixation of mixed sowing and unicast grassland of alfalfa and oxtail grass under different planting patterns. The results showed that mixed sowing was superior to mixed sowing and intercropping sowing, the former was more conducive to play the advantages of mixed grass and soybean grass pasture, dry weight of the three treatments were 1535.9,1280.8 and 1249.3g / m2; Correspondingly The total nitrogen production was 50.83, 36.65 and 36.86g (N) / m2, and the annual average nitrogen fixation was 42.37,28.21 and 28.42g (N) / m2 respectively. The annual average nitrogen fixation percentages were 83.4%, 77.0% and 77.1%. The nitrogen fixation percentage and nitrogen fixation rate were compared by 15N isotope dilution method, 15N natural abundance method and total nitrogen difference method.