Effects Of Different Irrigation Treatments On Alfalfa(Medicago Sativa L.)Seed Yield And Quality In Arid Area Of Northwest China

In recent years,with the profound changes in people's diets and the strong demand for a good ecological environment,the supply-side reform of agriculture has been accelerated significantly,and modem grass-husbandry has ushered in a rare opportunity for development.As the king of herbage,Alfalfa(Medicago sativa L.)is playing a more and more important role in modern grass-husbandry,and"planting alfalfa like grain" has gradually become the industry consensus.The planting area of alfalfa in China is expanding year by year,and the market demand of high-quality alfalfa seed is also increasing.However,the production of alfalfa seed in China is still facing many difficulties,and one of the main problems is the low yield.Therefore,it is of great significance to explore the seed production irrigation mode of high and stable yield.This experiment was earried out in Wuwei,Gansu Province from August 2017 to August 2018.In this experiment,there are three irrigation methods,named membrane subsurface drip irrigation(MSDI),membrane drip irrigation(MDI),and membrane furrow irrigation(MFI).Among them,the MSDI's drip irrigation belt was buried to a depth of 15cm,the MDI's drip irrigation belt was fixed under the membrane,and the MFI adopted the three-ridge and four-ditch mode.In addition,Three irrigation gradients were set for each irrigation method.They are full irrigation(W1),deficit irrigation(W2)and dry irrigation(W3).Through observing the growth index,reproductive index,seed yield and quality index of alfalfa under different irrigation treatments,the following conclusions are drawn:(1)Different irrigation treatments have significant effects on overground growth indexes of alfalfa(P<0.05).The compensatory growth effect of deficit irrigation was evident in the main growth indexes of alfalfa.Comparatively speaking,the irrigation amount has great influence on the main growth indexes such as plant height,stem diameter and branch number,while the irrigation method has smaller influence on them.Within the setting range of irrigation quota in this experiment,the main growth indexes of alfalfa,such as plant height,stem diameter and branch number,were the highest under the treatment of MSDI+full irrigation(T1).If the water-saving effect was considered,the treatment of MDI+deficit irrigation(T2)was the ideal choice.(2)Different irrigation treatments have significant effects on the components of alfalfa seeds(inflorescence/branch,floret/inflorescence,pod/floret,seed/pod)(P<0.05).In general,under the treatment of MSDI+ full irrigation(T1),the seed composition factors of alfalfa were the highest,and the seed yield and quality of T1 also had the best comprehensive performance.(3)Different irrigation treatments have significant effects on the seed yield and quality of alfalfa(P<0.05).Water(especially during reproductive growth stage)is one of the key factors for high and stable yield of alfalfa seed.The indicators of MSDI+full irrigation(T1)were better in the whole,while those of MFI+ dry irrigation(T9)were the worst.Meanwhile,deficit irrigation did not significantly reduce the seed yield and quality of alfalfa.If only pursue the yield and quality of seeds,MSDI+full irrigation(T1)is the best irrigation method,and its yield reaches 959.92kg/hm~2.If the water-saving effect is comprehensively considered,the treatment of MDI+deficit irrigation(T2)is the optimal choice,and its yield can reach 943.02kg/hm~2.