Effect On Nitrogen Reduction Of Soil Bacterial Community And Greenhouse Gas Emissions In Maize-soybean Relay Strip Intercropping System

Nitrogen fertilizer is an essential nutrient for crop growth.Excessive nitrogen application can increase crop yield,however,it increased agricultural production cost and affected soil environment and atmospheric environment.Reducing the nitrogen fertilization not only retrench the production cost,also can effectively alleviate the pressure of the environment.The reasonable planting patterns can improve land use efficiency and increase grain output per unit area,maize-soybean intercropping can effectively improve soil and crop nutrient uptake and utilization and improved soil nitrogen cycle.The experiment was based on the different planting patterns and the long-term nitrogen fertilizer.The method of two-factor crack zone test was designed.The main factor was the planting patterns which included monoculture maize?MM?,monoculture soybean?SS?and maize-soybean intercropping?IMS?.The second factor was nitrogen applicantion which included no N application?NN?,reduced N application?RN?and conventional N application?CN?.Our aim was to study whether the application of nitrogen fertilizer in maize-soybean intercropping system can guarantee the yield of crops and the variation characteristics of nitrogen uptake of crop.The characteristics of soil nutrient content,soil enzyme activity and soil bacterial community structure and diversity and greenhouse gas emission of maize-soybean intercropping system in different N application.The main results were as follows:1.Effects of different planting patterns and nitrogen application on nitrogen uptake of crop,soil total N content and crop yield.The maize yield was 4.65%higher than monoculture maize?MM?.Conventional nitrogen application was the highest in the yield of intercropping maize?IM?.The yield of IS was 15.92%higher than that of SS.The yield of IS were 24.97%and 46.23%higher under RN than under NN and CN,respectively.Compared with MM,The N uptake of stem in IM was increased by an average of 22.59%in two years.The nitrogen uptake of grain increased by 1.78%.Under different N application rates,the nitrogen uptake of grain in MM was higher under CN than under NN and RN.The nitrogen uptake of crop in IM was higher under CN than under NN and RN.Compared with monoculture soybean?SS?,The nitrogen uptake of stem in IS was decreased 22.59%.The nitrogen uptake of grain increased by 0.95%.2.Effects of different planting patterns and nitrogen application on soil physical and chemical properties.The soil total nitrogen content of IM was 22.59%higher than that of MM.The soil total nitrogen content of MM was the highest in RN.The soil total nitrogen content of MM were22.56%and 7.49%higher under RN than under NN and CN,respectively.The soil total nitrogen content of IS was 7.56%higher than that of SS.Under different nitrogen levels,the soil total nitrogen content of soybean was the highest in RN.The soil organic matter content of IM was higher than that of MM.The soil total nitrogen content of MM were highest under RN compared with that under NN and CN.The soil organic matter and available phosphorus content of IS was higher than that of SS.the soil organic matter content of soybean was the highest in RN.The soil pH of MM was higher than that of IM.The soil pH of MM was the highest in NN.The soil pH of SS was higher than that of IS.The soil pH of IS was the highest in CN.The activity of soil protease,urease and nitrate reductase of IM were 6.87%,27.86%and14%higher than that of MM,respectively.The soil protease activity of IM in maize full maturity were highest under RN compared with that under NN and CN,and the activity of urease and nitrate reductase of maize were highest under RN compared with that under NN and CN.The activity of soil protease and nitrate reductase of IS was higher than that of SS.The activity of protease and urease of soybean were highest under RN compared with that under NN and CN.The activity of protease were 11.24%and 14.28%higher than those of NN and CN,and the activity of urease were 8.44%and 4.37%higher than those of NN and CN.The soil nitrate reductase activity of RN were 18.87%and 21.15%higher than that of NN and CN.The phyla of Proteobacteria,Acidobacteria,Chloroflexi,Bacteroidetes,Actinobacteria and Gemmatimonadetes dominated in all maize soil fertilized treatments.The Shannon index of IM of 2017 were highest under CN.The phyla of Proteobacteria of MM and IM was higher than that of CK.The phyla of Proteobacteria of MM were highest under NN compared with that under RN and CN,and the phyla of Proteobacteria of RN and CN of intercropping maize was higher than NN.The Chloroflexi phyla of NN of intercropping maize was higher than RN and CN.Acidobacteria phyla of MM and IM was higher than that of CK.The phyla of Proteobacteria,Acidobacteria,Chloroflexi,Bacteroidetes,Actinobacteriaand Gemmatimonadetes dominated in all soybean soil fertilized treatments.The Shannon index of SS were highest under NN compared with that under RN and CN,however,the NN was the highest in 2017.The Proteobacteria of SS in CN was highest,and the Proteobacteria of IS in CN was highest.The phyla of Proteobacteria of SS and IS was higher than that of CK.The Actinobacteria was IS>SS>CK in 2017.3.Effects of different planting patterns and nitrogen application on greenhouse gas emissionsThe planting patterns and nitrogen fertilization affected the greenhouse gas emission of maize.The CO₂ emission flux of IM and MM was reflected as the absorption sink.The CO₂emission flux of IM was higher than that of MM under no nitrogen application.In 1 day,2 days,10 days and 20 days,the CO₂ emission flux of RN and CN were IM>MM.The CH₄ emission flux of MM and IM were a consistent pattern.The CH₄ emission flux of IM was higher than that of MM on the 10th and 20th day,and the others were MM>IM.The N₂O emission flux of in corn is MM>IM.At different nitrogen application levels,the CO₂ emission flux of MM was NN>RN>CN,and the CO₂ emission flux of IM was CN>RN>NN before the third day,and then the CO₂ emission flux of IM was RN>CN>NN.The CH₄ emission flux of MM and IM were CN>RN>NN,and N₂O emission fluxe of MM and IM were shown as CN>RN>NN.The CO₂ emission flux was IS>SS,and the CH₄ emission flux was SS>IS in RN.The N₂O emission flux was SS>IS in RN and CN.Under different nitrogen levels,the CO₂ emission flux of SS and IS were expressed as NN>CN>RN.The CH₄ emission flux of SS was CN>RN>NN and of IS was NN>CN>RN.The N₂O emission flux of SS was CN>RN>NN.