田间小区试验研究了不同种植模式下苜蓿的共生固氮贡献,并利用~(15)N同位素示踪技术评估了苜蓿的％Ndfa和Ndfa,以及与之混作生长的牛尾草植株中来自苜蓿固氮产物的转移量。研究表明,豆科与禾本科牧草混作对发挥草地的优势有一定影响,混作条播在干草产量、全氮产量、％Ndfa和Ndfa等方面均优于间作与混作撒播模式,且高于单作苜蓿与牛尾草的平均值。用~(15)N同位素稀释法与~(15)N天然丰度法评估苜蓿的％Ndfa与Ndfa值时,无明显差异(P<0.05),前者还能准确测出混种牛尾革植株中的固氮产物转移量,后者则大大低估,甚至不能测出固氮产物转移。 Field experiments were conducted to study the symbiotic nitrogen fixation contribution of alfalfa under different planting patterns. The% Ndfa and Ndfa of Medicago sativa were evaluated by ~ (15) N isotope tracing technique, and the yield of alfalfa from the alfalfa nitrogen fixation products Transfer amount. The results showed that the combination of leguminous plants and gramineous pasture had a certain influence on grassland utilization. The mixed cropping was better than intercropping and mixed seeding in hay yield, total nitrogen yield,% Ndfa and Ndfa, With the average of the talon. There was no significant difference (P <0.05) in the% Ndfa and Ndfa values ​​of ~ (15) N isotope dilution and ~ (15) N natural abundance methods, Of the nitrogen transfer product, the latter is greatly underestimated, and even can not measure the transfer of nitrogen fixation products.