Effects Of Water And Fertilizer Coupling On Alfalfa Production Performance And Soil Quality Under Drip Irrigation

Aiming at the problems of uneven water and fertilizer ratio,waste of resources and serious soil pollution during the construction of alfalfa in Ningxia Yellow Irrigation District,In this study,alfalfa juneng 7 was used as the test material,and the split-zone test design was adopted.Set 4 water gradients as main factors and 5 fertilization gradients as secondary factors to study the effect of water and fertilizer coupling on alfalfa growth performance,nutritional quality and soil quality under drip irrigation conditions.The results show that:1.Irrigation and fertilization have a very significant effect on the plant height,density and hay yield of alfalfa(P<0.01),but have no significant effect on the average growth rate,nutrients such as CP,ADF,NDF and RFV;The cumulative plant height,hay yield,irrigation water use efficiency and fertilizer partial productivity can reach the maximum and the average hay yield reached 19.49 t·hm-2 for two years,with a cumulative plant height of 331.81 cm.When the irrigation water is 6000 m3·hm-2,and the fertilization amount is 135kg·hm-2(N:30 kg·hm-2,P2O5:45 kg·hm-2,K2O:60 kg·hm-2).Under the gradient of 6750m3·hm-2,the number of branches and plants per square meter is the largest,with 52 plants and 503.33 branches per square meter;when the fertilization amount is 435kg·hm-2(N:120 kg·hm-2,P2O5:135 kg·hm-2,K2O:180 kg·hm-2),more plants can be obtained;No fertilization can significantly improve the branching ability of alfalfa,Under different fertilization levels.2.The number of soil microorganisms and enzyme activity decrease with the increase of soil depth;proper irrigation and fertilization can significantly increase the number of soil fungi and actinomycetes and the activities of sucrase and urease;The number of soil bacteria increased with the increase of irrigation volume,and gradually decreased with the increase of fertilizer application.The soil in the test area is mainly powder and is not affected by the depth of the soil layer,but the soil nutrients gradually decrease with the increase of the depth of the soil layer.Irrigation and fertilization have a significant effect on soil particle size composition and soil nutrients(P<0.01),with an irrigation volume of 6000 m3·hm-2 and a fertilization volume of 435 kg·hm-2(N:120 kg·hm-2,P2O5:135 kg·hm-2,K2O:180 kg·hm-2),soil N,P,K content is relatively rich,the soil quality index is the largest and more fertile.3.There is a significant correlation between soil factors and plant performance.Factors that contribute significantly to the growth of alfalfa include invertase activity,catalase activity,soil meal percentage,urease activity,available nitrogen content,available potassium Content,hay yield,number of actinomycetes,urease activity,available phosphorus content,total phosphorus,total potassium content.The available potassium content,urease activity and catalase activity have a significant positive effect on alfalfa production performance and nutritional quality,and are the main soil factors driving plant growth variability.4.The regression optimization model shows that the most suitable irrigation and fertilization range for alfalfa planting under drip irrigation conditions in this area is:irrigation volume 6000～6500m3·hm-2,and fertilizer application volume 250-320kg·hm-2.