Soil Nitrogen And Its Nitrification-denitrification Microbial Diversity In Jujube-cotton Intercropping System

Due to the highly concentrated utilization of nutrient resources in intercropping agroforestry system,underground competition between crops is the key to high yield in intercropping system.It is an effective entry point to improve the intensive use of intercropped land resources by changing the intercropped cropping mode and making full use of the advantages of interspecific ecological niche alternating and complementary,so as to meet the nitrogen demand of crop growth.In 2019-2020 in this study set up the experimental area,tarim basin,xinjiang in the middle of the local conventional pattern of young jujube planting cotton,by changing the distance from the tree and cotton planting rows,nitrogen content in the space and time distribution difference characteristics,nitrogen cycle change of key enzyme activity and its related functional microbe drive mechanism,in order to use complex system of intercropping advantage improve interspecific nitrogen use efficiency,to achieve the ecological conservation in arid,provides the theory basis for mechanism of interspecific competition for resources.The main conclusions are as follows:1.Jujube intercropping cotton planting mode of soil total nitrogen,nitrate nitrogen,ammonium nitrogen than monoculture planting patterns on average 2.2%higher,respectively,0.67%,11.5%,jujube interplanting in different planting patterns of M2 in the soil total nitrogen,nitrate nitrogen and ammonium nitrogen content is the highest,intercropping differences mainly comes from red jujube with different patterns of soil nitrogen content and cotton with time and space distribution of soil nitrogen and the content difference of level,intercropping group competition for soil nitrogen complementary effect,in the spatial distribution of the cotton can bring competition from jujube 0-60 cm soil layer soil nitrogen,jujube can supplement soil nitrogen from cotton alley in 40-100 cm soil layer.With the increase of the number of cotton rows planted among jujube trees in different crop alleys,the competition for soil nitrogen became more intense.2.The intercropping mode of jujube and cotton can significantly increase the activity content of key enzymes during soil ammonification and nitrification,and reduce the activity content of key enzymes during denitrification.Intercropping different planting patterns vary on the dynamic change of soil enzyme activity time,in the symbiotic period of intercropping may-July,M2 can significantly increase soil alcalase protease,urease and dehydrogenase activity and soil hydroxylamine reductase activity cultivation reached maximum on the M1,M3 soil nitrate reductase activity showed the highest in June-July.The activities of alcalase protease,urease and dehydrogenase in soil under different planting modes were mainly from cotton alley,while the activities of hydroxylamine reductase and nitrate reductase in soil were mainly from jujube alley.3.There were significant differences(P<0.05)between jujube and cotton intercropping patterns in the microbial community composition during nitrification and denitrification process,and Proteobacteria,Thaumarchaeota,Actinobacteria and Nitrospirae were dominant in the microbial community composition during nitrification and denitrification process.The relative abundance of dominant bacteria was relatively high on the M3,and relatively low on the M2.There were significant or extremely significant correlations between soil enzyme activity and soil nitrate nitrogen for most of the dominant bacteria.4.In the jujube cotton intercropping system,soil nitrate nitrogen and soil total nitrogen had more significant effects on soil enzyme activities,and there was a positive correlation between different forms of nitrogen.There was a high correlation between total nitrogen and nitrate reductase activities in the process of denitrification,and between nitrate nitrogen and urease and alcalase protease in the process of ammoniation.5.The total yield of jujube cotton intercropping system was significantly higher than SC and SJ.With the increase of tree age,the total yield of intercropping system in 2020 was 6.4%higher than that of 2019.The highest yield(7694.38 kg/hm~2)was obtained when cotton was planted 1.45 m away from jujube trees in the middle of jujube garden.There were significant differences in the yield of each component under different cropping patterns(P<0.05).Cotton planted in jujube garden contributed 51.8%to the total yield of intercropping system.The competitive advantage of intercropping cotton against jujube with different cropping patterns gradually weakened with the increase of intercropping,and the nitrogen use efficiency increased gradually.Jujube interplanting in different planting patterns in the distance of 1.45 m four lines of cotton planting in the intercropping system output,the highest increase gradually increase with increasing years of planting,intercropping advantage cotton relative to the red jujube interspecific competition gradually blurred,nitrogen competition,the largest amount of soil nitrogen and ammoniation process key enzyme activities were significantly higher than other intercropping processing,in the process of nitrification-denitrification,dominant bacteria overall lower relative abundance,inhibition of nitrification and denitrification is significant,to improve soil nitrogen use efficiency effectively.