Soil Microbial Activity Response To Nitrogen Fertilizer Under Rice-Bean Cropping Rotation

In order to study the effect of nitrogen on soil microorganisms in maize-soybean crop rotation,this experiment selected Seiyu 335 and Jiyu 86 as the test materials and set four nitrogen levels to study soil microorganisms in maize-soybean crop rotation,maize-soybean crop rotation and soybean crop rotation.The relationship between soil microorganisms and nitrogen in maize-soybean crop rotation was clarified by analyzing the effects of soil physicochemical properties,soil enzyme activity,soil respiration rate,soil microbial community structure and diversity,and soil microbial functional structure.Compared to continuous crop,there were no significant changes in p H,water content,and nitrate nitrogen in corn-soybean rotation,while ammonium nitrogen content increased significantly.The activities of both carbon cycle enzymes and nitrogen cycle enzymes in the field basal soil showed that corn-soybean rotation > soybean continuous crop > corn continuous crop,and the enzyme activities in each cropping pattern increased with increasing nitrogen concentration when nitrogen was added,indicating that crop rotation and nitrogen addition could increase enzyme activities and thus promote soil carbon and nitrogen cycles.The basal respiration rate of soil under rotation was greater than that of continuous crop,and the addition of nitrogen induced an increase in soil respiration rate under rotation,which was significantly higher than that of continuous crop under the same nitrogen treatment.The soil respiration entropy(q CO2)of the rotation treatment was smaller than that of the continuous crop,indicating that the respiratory metabolism of soil microorganisms in the rotation was more used for microbial proliferation,which facilitated the improvement of the overall microbial activity under the rotation.Proteobacteria,Acidobacteria,and Bacteroidetes were the dominant phyla in the three cropping patterns.There was no significant difference in soil microbial diversity and abundance between corn-soybean rotation(CS)and corn continuous crop(Cm)and soybean continuous crop(Sm)when no nitrogen addition treatment was applied.Microbial diversity and richness showed significant changes after nitrogen addition,and microbial diversity and richness in soils of soybean continuous crop and corn-soybean rotation gradually decreased with increasing nitrogen concentration.The changes in soil microbial functions in the three cropping patterns varied with nitrogen concentration,and when the added nitrogen concentration was 0,the relative abundance of functional microbial groups involved in soil chemoenergetic heterotrophy,oxidative heterotrophy,and nitrate reduction under the rotation was greater than that of the two continuous cropping treatments,and the relative abundance of nitrification and aerobic ammonia oxidation functions in the rotation pattern increased with increasing nitrogen concentrationIn conclusion,crop rotation can improve the negative effects of continuous crop on soil,and crop rotation and nitrogen addition can regulate soil fertility mainly by changing microbial community structure,diversity,microbial functional structure and activity.