Legume-grass mixtures improve biological nitrogen fixation and nitrogen transfer by promoting nodulation and altering root conformation in different ecological regions of the Qinghai-Tibet Plateau.

3 Results 3.1 Effect of the cropping pattern on aboveground dry biomass and nitrogen accumulation in the different ecological zones The cropping pattern, ecological zone, and their interactions had extremely significant ( p < 0.01) or significant ( p < 0.05) effects on aboveground dry biomass ( Table 3 ).

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