| This study was carried out to investigate water and nitrogen utilization characteristics,diversity and composition of bacterial community in a wheat-maize rotation field during winter wheat growing season in semi-humid area.It will provide evidences for further optimizing farming methods in this area,promoting the construction of soil beneficial microflora,and improving the utilization of soil resources.The effects of rotary tillage(X100),soil turned over and rotary tillage(F100),deep and rotary tillage(S100),deep and rotary tillage with adding super absorbent polymers(SAPs)(B100),deep and rotary tillage with no fertilizer(S0)on soil physicochemical property,winter wheat growth and yield components,water and nitrogen use efficiency were investigated.Then,high-throughput sequencing platform was used to analyze the correlation between the bacteria community diversity and structure,soil properties and winter wheat root length density.The main conclusions are as follows:Deep tillage significantly reduced soil compactness of 10~45 cm layer,significantly raised field moisture capacity and saturated moisture content of 0~40 cm layer,higher than rotary tillage treatment by 33.4%and 30.9%respectively.The content of ammonium nitrogen in deep tillage and adding SAPs treatments at jointing stage and harvest stage was significantly increased by 65.4%~134.3%compared with soil turned over and rotary tillage.Deep tillage significantly reduced the content of nitrate nitrogen in the upper-middle soil and the deep soil at harvest stage.The emergence rate,effective panicle number,heading rate of winter wheat,leaf area index and dry matter weight were significantly increased by deep tillage and adding SAPs.Deep tillage also significantly increased root length density(80.2%~104.2%higher than that of soil turned over and rotary tillage)below 30 cm at jointing stage,promoted root development of above 70 cm at booting stage(1.90~2.39 times higher),and enhanced root distribution above 40 cm at flowering stage(39.2%~80.9%higher).Compared with other treatments,the yield of deep tillage treatment was increased by 11.2%~15.5%on average.Compared with deep tillage,soil turned over and rotary tillage,water use efficiency(WUE_Y)in deep tillage with adding SAPs treatment was increased by 7.1%,9.1%and 8.8%,respectively.WUE_Y of deep tillage was increased by 4.6%and 6.2%on average,respectively,compared with soil turned over and rotary tillage.Deep tillage increased the nitrogen uptake efficiency(NUPE)and current nitrogen utilization efficiency(NUTE),which were higher than rotary tillage by 30.4%and 20.3%on average,respectively.Soil bacterial richness and diversity in 10~20 cm layer of deep tillage treatment showed a significant decrease trend.Deep tillage significantly increased the relative abundances of Nitrospirales,Rhizobiales,Burkholderiales and some typical ammoniated bacteria(Pseudomonas and Serratia)in plough layer,and decreased the relative abundances of some denitrifying bacteria(Rhodospirillales and Bacillus)(by an average of 58.2%and 92.5%,respectively).Surface soil pH,ammonium nitrogen and nitrate nitrogen contents have the strongest effects on the bacterial structure.In addition,there were significant positive correlations between the root length density and the relative abundances of Rhizobiales,Burkholderiales,Pseudomonas,Serratia,and the ammonium nitrogen content.The root length density also showed a significant negative correlation with the relative abundances of Rhodospirillales and Nitrosomonadales,as well as nitrogenous nitrogen content.It is thus clear that,deep tillage combined with SAPs can reduce soil compactness and the thickness of plough pan,improve soil water holding capacity,increase soil ammonium nitrogen content and nitrate nitrogen consumption,promote winter wheat growth and root deep expansion,enhance water use efficiency,nitrogen uptake efficiency,current nitrogen utilization efficiency,and increase crop yield.In addition,although deep tillage is not conducive to improve soil bacterial community diversity,deep tillage could significantly increase the abundances of biological nitrogen-fixing bacteria,ammonifying bacteria and nitrobacteria,and reduce the nitrogen loss caused by denitrifying bacteria. |
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