Experimental Study On Effect Of Different Irrigation Methods On Growth, Yield And Quality Of Alfalfa In Shiyanghe Basin

Shiyanghe Basin is a typical arid region in northwest China, where there is water scarcity and contradiction of agricultural water supply and demand. Studing effects of different irrigation methods on growth, water use efficiency and yield can provide a scientific guidance for water-saving planting of alfalfa and promoting alfalfa industrial development. In recent years, with the rapid development of animal husbandry, there begans to plant large-scale cultivation of high yield and high quality of alfalfa in northwest arid region, and the water consumption of alfalfa is higher than other crops, but less rainfall in this region, as irrigation depends mainly on the extraction of groundwater. Therefore, this thesis focused on the observation of growth, photosynthetic characteristic, yield and quality of alfalfa under different irrigation methods. The soil water content, alfalfa growth, quality, water use efficiency, photosynthetic characteristic and yield were observed under different irrigation methods in Shiyanghe Basin of Wuwei City, Gansu Province in the growing senson of 2014-2015. The main results are as below:(1) During the trials of two years, soil water content of subsurface drip irrigation treatment is the highest, and soil water content of furrow irrigation treatment is slightly higher than that of sprinkler irrigation treatment, and soil water content of no irrigation treatment is the lowest. Soil water content of all treatments during the trial appears consistently dynamic trend, with the emergence of irrigation or rainfall, and soil water content shows small peak of different degrees regularly. In the 2014 trial, soil water content of the third cutting all treatments is not only higher ihan that of the second cutting, but having a large fluctuation. In the 2015 trial, soil water content of no irrigation treatment decreases gradually, while soil water content of (he other three irrigation treatments decreases in the fist cutting, and soil water content keep relatively stable and fluctuate within a certain range during the second, third, fouth cuttings.(2) In addition to leaf ratio, other growth indexes of subsurface drip irrigation treatment are significantly higher than the other three treatments, and there is not significantly different between border irrigation treatment and sprinkler irrigation treatment Border irrigation treatment is slightly better than sprinkler irrigation treatment, and no irrigation treatment is the worst With the growth progress, indexes of all treatments of alfalfa show a decline trend, and no irrigation treatment can effectively reduce leaf ratio, then raise the proportion of leaf in alfalfa plants, which is beneficial to improve the quality of alfalfa. Compared to the other three treatments, subsurface drip irrigation treatment improves the photosynthesis of alfalfa, and under subsurface drip irrigation, "lunch" phenomenon is not obvious. Photosynthetic characteristics between all treatments show firstly increased and then decreased trend, and photosynthetic characteristics of the third cutting in 2014 and the second cutting in 2015 are the highest.(3) Different irrigation methods have a significant impact on alfalfa yield and water use efficiency. Among the three irrigation treatments, yield, water use efficiency and irrigation water use efficiency of subsurface drip irrigation treatment are significantly higher than border irrigation treatment and sprinkler irrigation treatment. In 2014, compared with other treatments, water use efficiency of no irrigation treatment is higher, but its hay yield is significantly lower than other three treatments, and water use efficiency of no irrigation treatment is significantly lower than other treatments in 2015. Yield of all treatments among cuttings is a decline trend. Alfalfa yield of subsurface drip irrigation treatment compared with border irrigation treatment, sprinkler irrigation treatment and no irrigation treatment is on average increased by 15%,20%, and 100%, respectively. Under the same irrigation conditions, subsurface drip irrigation treatment increases yield significantly.(4) Different irrigation methods have different effect on alfalfa quality. No irrigation treatment significantly increases the crude protein content of alfalfa, and decreases alfalfa fiber content, especially in the fouth cutting, but the quality of other three irrigation treatments is getting little difference with the growth of alfalfa. Crude protein yield of subsurface drip irrigation treatment is significantly higher than other treatments, no irrigation treatment has the lowest and the gap is increasing with the development of alfalfa growth period. Compared with boder irrigation treatment and sprinkler irrigation treatment, crude protein yield of subsueface drip irrigation treatment in 2014 increased by 16.32%,16.4%, in 2015 by 37.01%,52.33%, respectively, and subsurface drip irrigation treatment increases crude protein yield significantly. The relative feed value of no irrigation treatment is significantly higher than the other three irrigation treatments, and that of the other three irrigation treatments have reached to the excellent level of alfalfa standard classification of the United States. The results show that alfalfa quality of different irrigation treatments has good performance.