Effects Of Corn Straw Returning On Maize Yield And Soil Microbial Community Composition

As an important tillage measure in farmland management straw returning has a great influence on the improvement of soil nutrient soil structure and the distribution of soil microbial community.To reveal the effects of maize straw mulching on soil physical chemistry and microbial community composition,a single factor randomized block design was used in this experiment,and 5 treatments were set up,no straw returning to the field(T0),straw returning to the field 3000 kg·hm-2(Ti),6000 kg·hm-2(T2),9000 kg·hm-2(T3)and 12000 kg·hm-2(T4).Were sequenced and analyzed by high throughput sequencing and phospholipid fatty acids(PLFAs).The relationship between the amount of straw returned and soil physical and chemical properties,soil aggregate composition and distribution of aggregate carbon and nitrogen,soil biological shape,microbial community structure and bacterial diversity was studied under the condition of straw returning for 5 years.The main results are as follows,(1)After the continuous returning of corn straw to the field,the soil total carbon(TC),available nitrogend(AN),available potassium(AK)content all had obvious change rules.Compared with T0,the soil total carbon of T3 and T4 treatments increased by 4.29%and 6.13%,the soil available nitrogen increased by 11.41%and 13.86%,and the soil available potassium increased by 11.63%and 14.89%,The soil microbial biomass C increased by 45.1%and 69.5%(P<0.05)in T3 and T4 treatments.However,there was no significant difference in C/N ratio in short term(5 years).However,maize yield did not increase or decrease with the increase of straw returning time,and there was no significant difference in crop yield between treatments in the same year(P<0.05).(2)The returning of corn straw to the field can significantly affect the stability of soil aggregates and the carbon and nitrogen distribution of water-stable aggregates.There was significant difference between the percentage content of soil water-stable aggregates with size of 1-2 mm and T0 under T4 treatment.The percentage content of soil water-stable aggregates with particle size of 0.5?1 mm was also significantly higher in T3 than in T0.The average weight diameter of soil(MWD)and water stability coefficient(K)showed an increasing trend with the increase of straw mulching amount.On the whole,affected by the continuous straw mulching,the nitrogen content of soil water-stable aggregates was the highest in T3 treatment,but there was no significant difference in the carbon content of soil water-stable aggregates with different particle sizes.Multivariate analysis shows that.The proportion of soil water stable aggregates with a diameter of 5 mm was significantly positively correlated with soil MWD and K values.The cumulative variance contribution rate of the first and second principal components was 73.71%26.29%,which could reveal the relationship between the percentage of water-stable aggregates with different particle sizes and soil MWD and K value.The contents of total nitrogen and total carbon in soil water-stable aggregates were positively correlated with the contents of soil total carbon.The value of MWD and K of soil water-stable aggregates were increased and the formation of soil large aggregates(>5 mm in diameter)was promoted by the continuous application of corn straw.The difference of nitrogen content in soil water-stable aggregates was more significant than that of carbon,and nitrogen was more easily enriched.(3)After 5 years of straw returning to the field,the composition and distribution of microbial community in the soil had significant changes.Straw returning to the field significantly inhibited the increase of microbial biomass of soil bacteria gram-positive bacteria(P<0.05).The ratio of fungus/bacteria(F/B)was promoted,and the trend of the ratio of gram-positive bacteria/gram-negative bacteria(G+/G-)was completely reversed.The total phospholipid fatty acids(TPLFA)decreased with the increase of straw returned.(4)Soil bacterial richness and diversity were not significantly affected by straw returning treatments,and the dominant phyla were Proteobacteria,Bacteroidetes and Acidobacteri.Multivariate analysis showed that soil total phosphorus,total carbon,available potassium,pH and microbial biomass carbon directly affected the chaol index.Bacteroidetes,Verrucomicrobia and Proteobacteria were positively correlated with soil environmental factors.