Effects Of Irrigation Methods And Phosphorus Application On Alfalfa Production Performance And Soil Quality

Due to the shortage of water resources in the arid and semi-arid regions of Ningxia and the unreasonable application of phosphate fertilizers,a series of problems such as low alfalfa yield,poor quality and serious soil environmental pollution have been caused.This study used alfalfa gan nong No.6 as the experimental material,adopted a two-factor split area test design,with irrigation as the main area,phosphorus application level as the secondary area,5 irrigation methods and 4 phosphorus levels were set to study the effects of different irrigation methods and phosphorus on the production performance,nutritional quality and soil environment of alfalfa.The results of the study are as follows:1.Under the same irrigation amount,there were significant differences in the total water content of the soil treated by different irrigation methods and the water content of different soil layers.The soil water content of the flood irrigation treatment was the highest in the soil layer of 40-60 cm,the soil water content of the sprinkler irrigation treatment was the highest in the soil layer of 20-40 cm,the soil water content of the three different burial depths of drip irrigation treatment was the highest in the soil layer of 20-60 cm,and the soil water content of the three underground drip irrigation treatment was significantly higher than that of the flood irrigation and sprinkler irrigation treatments.There was no significant difference between the 0-20 cm and 20-40 cm soil layers,and the soil water content of 30 cm underground drip irrigation was significantly higher than that of underground drip irrigation 10 cm and underground drip irrigation 20 cm.2.Irrigation mode and phosphorus treatment had significant effects on the annual hay yield,plant height,number of branches,stem-to-leaf ratio,thick stem,CP of alfalfa,and the effects on ADF and NDF and RFV were small,and the annual hay yield,plant height,number of branches and thick stem of alfalfa decreased sequentially with the increase of the number of mows.The annual hay yield,plant height,number of branches,thick stem,CP,RFV,water use efficiency and phosphate fertility partial productivity of the three underground drip irrigation treatments were significantly lower than those of the three underground drip irrigation treatments;among them,the annual hay yield,plant height,CP,water use efficiency and phosphate fertilizer partial productivity of alfalfa treated with underground drip irrigation of 30 cm reached the maximum value,and the number of branches was the largest in the underground drip irrigation treatment of 20 cm.The annual hay yield,3 stubble cumulative plant height,thick stem,branch number and CP of alfalfa increased first and then decreased with the increase of phosphorus,maximum reached under phosphorus(P2O5)treatment of 120 kg·m-2.When the irrigation method was 30 cm underground drip irrigation and the phosphorus application amount was(P2O5)of 120 kg·hm-2,the annual hay yield of alfalfa was as high as 18.80 t·hm-2,the plant height was 87.21 cm,The number of branches is 97 branches/m,the crude protein content was 23.62DM%,and the relative feeding value was high(172.08 DM%).3.Different irrigation methods had significant effects on alfalfa soil urease activities,sucrase activities,alkaline phosphatase activities and soil nutrients,but no significant effects on soil catalase activities and pH values.The content of available phosphorus and available nitrogenin in alfalfa soil showed a decreasing trend with the increase of the number of mows,and the available potassium content showed a trend of increasing first and then decreasing.The activities of soil total nitrogen,available phosphorus,urease and alkaline phosphatase in the flood irrigation and sprinkler irrigation treatments were significantly lower than those of the three underground drip irrigation treatments and the soil pH was higher than that of the three underground drip irrigation treatments.Phosphorus treatment had significant effects on soil total phosphorus,total nitrogen,available phosphorus,alkaline phosphatase activity,urease activity and catalase activity,but had no significant effect on soil alkaline hydrolyzed nitrogen,total potassium,invertase activity and pH.Compared with no phosphorus application,phosphorus application significantly increased the total nitrogen,total phosphorus and available phosphorus content of the tillage layer and reduced the available potassium content,and the alkaline phosphatase activity,urease activity and catalase activity showed a tendency to increase first and then decrease with the increase of phosphorus,and soil enzyme activity was lowest under phosphorus(P2O5)treatment of 120 kg·hm-2.Through RDA analysis,the soil factors that contribute greatly to production performance and nutritional quality include alkaline phosphatase,total nitrogen and catalase,and have significant positive correlations between production performance and nutritional quality,and are considered to be the main soil factors driving the growth variation of alfalfa.4.According to the gray correlation analysis,the irrigation method and phosphorus level suitable for alfalfa planting in arid and semi-arid areas of Ningxia were underground drip irrigation of 30 cm and 120 kg·hm-2 of phosphorus fertilizer.