Effects Of Water And Nitrogen Fertilizer On Biomass And Quality Of Alfalfa(Medicago Sativa) In Hexi Corridor

Alfalfa（Medicago sativa）has high nutritional quality and biomass production and is widely used as fodder in animal production.There are many factors influencing the alfalfa production,in which fertilizer and irrigation are two important factors.The applications of both nitrogen and irrigation have been the critical factors for improving water use efficiency and increasing biomass in alfalfa.Thus the determination of a reasonableapplication of nitrogenandirrigation is important for the optimization ofbiomass allocation and improvement of water use efficiency in alfalfa fields in Hexi Corridor.A field study was conducted in 2014in Jiuquan City（in the Hexi Corridor of Gansu Province,China）to research the effects of different irrigation amounts(W₁:60%of the conventional irrigation amount;W₂:80%of the conventional irrigation amount;W₃:the conventional irrigation amount,1 920 m³·ha^-1)and nitrogen application rates(N₁:0 kg·ha^-1;N₂:40 kg·ha^-1;N₃:80 kg·ha^-1;N₄:120 kg·ha^-1)on biomass allocation and water use efficiency of 2-year alfalfa pasture.1.Water and nitrogen coupling maintained the stability of alfalfa biomass by adjusting the production componentsUnder the different amount of irrigation and fertilizer,W₂N₂treatments had the potential to optimize plant height.Also,when the treatments on W₂N₃,the branch number per plant attended high-level.On the other hand,the different amount of irrigation and fertilizer have effected on growth of root system,indicating that W₂N₂treatments had the potential to optimized rootstock thick,root volume in the 0-20 cm,20-40 cm and 0-60 cm soil layers.What’s more,W₂N₃treatments had the potential to optimized aboveground-belowground biomass ratio.2.The interaction of water and nitrogen could improve the quality of alfalfa by increasing the content of crude protein and neutral detergent fiberThere are many quality factors influencing the production of alfalfa（CP、ADF、NDF、ASH、RFV）.When the treatments on W₂N₃,the CP,NDFattended high-level.What’s more,when the treatments on W₂N₂,the RFV attended high-level.3.Interactionnitrogen application and irrigation canimprove water use efficiency of alfalfaThe results suggested that W₂N₃increased water use efficiency.On the other hand,W₂and W₃also increased water use efficiency.What’s more,water use efficiency peaked under the treatment of 80 kg·ha^-1nitrogen.4.The ratio of aboveground to belowground biomass and water use efficiency was alsooptimized under W₂N₂or W₂N₃treatmentIt was concluded that 80%of the conventional irrigation amount and 40 kg·ha^-1of nitrogen applicationor80%of the conventional irrigation amount and 80 kg·ha^-1of nitrogen applicationorwere the optimal treatment for alfalfa pasture in Hexi Corridor.