Research On Water Use,Yield And Quality Of Alfalfa Under Sprinkler Irrigation In Northwest Arid Region Of China

In the current situation of water shortage and the increasing demand for the high-quality alfalfa forage in stock farming,a field experiment on alfalfa evapotranspiration,growth characteristics,yield,quality and profits under sprinkler irrgation,was conducted in the northwest arid region of China.Three irrigation level was applied:A1:100%evapotranspiration of alfalfa,the irrigation amount in A2 and A3 were 66%and 33%of Al,respectively.Besides,a rain-fed treatment,A4 was the control.The main conclusions of this experiment are as follows:(1)The annual proportion of evapotranspiration in first growth period was high when winter irrigation was applied.When precipitation was sufficient,the evapotranspiration reached another peak in the third growth period.In one growth period,the higher evapotranspiration was observed in the branching stage.In addition,the irrigation amount,growth days,solar radiation and vapor pressure deficit were the main factors affected the evapotranspiration.(2)The evapotranspiration rate was higher in the third growth period when precipitation was sufficient and in the dry treatment,the evapotranspiration rate was low and declined through the growing season.The increasing evapotranspiration rate was observed with the maturity of alfalfa except the fourth growth period.(3)The plant height and stem-leaf ratio increased while the fresh-dry ratio decreased with the maturity of alfalfa.The higher plant height,stem-leaf ratio and fresh-dry ratio were obtained in the higher irrigation treatment and decreased with the decreasing irrigation level.Evapotranspiration correlated well with all of the growth characteristics.Plant height and stem-leaf ratio correlated well with the effective accumulated temperature,solar radiation,vapor pressure deficit and growth days,the fresh-dry ratio only affected by the effective accumulated temperature.(4)The yield in the first growth period was a large proportion of the annual yield when winter irrigation was applied.The producers could irrigated less in this period to save water and maintain the great yield.Alfalfa yield fitted well with the irrigation amount and evapotranspiration,but the fitting results varied between growth periods and growing seasons.Irrigation amount,effective accumulated temperature,solar radiation and growth days were the major factors affected the alfalfa yield.In addition,the plant height fitted well with the yield and was a simple method to predict the alfalfa yield.(5)The water use efficiency and irrigation water use efficiency declined with the increasing irrigation level.The water use efficiency in all treatments decreased through the growing season while the irrigation water use efficiency decreased from the first to the third growth period and maintain constant in the fourth growth period.The water use efficiency and irrigation water use efficiency were the combination influence of factors such as irrigation,evapotranspiration,growth characteristics and meteorology.The multiple correlation of irrigation amount and solar radiation could be used to predict the water use efficiency and irrigation amount and growth days could be used to predict the irrigation water use efficiency.(6)The crude protein in alfalfa decreased while the neutral detergent fiber and acid detergent fiber increased with the maturity.Lower neutral detergent fiber,acid detergent fiber,higher protein and relative feed value were obtained in the dry treatment.The fitting results between quality and other factors showed that the plant height could be used to predict the quality of alfalfa when the field management was good.(7)The profits of alfalfa forage could be predicted by the plant height and the yield affected the profit the most.The producers should give consideration to both relative high yield and premium quality of alfalfa to save the water and maintain the good return.