Abstract:

To explore the influence of straw returning years to the field after deep turning back on soil bacterial community in continuous cropping corn fields in the West Liaohe Plain,and provide theoretical guidance for continuous straw returning to improve soil fertility.This study takes corn straw leaving the field as a control (CK),based on the high-throughput sequencing technology of bacterial 16S rDNA V3-V4 region,combined with bioinformatics,we analyzed the characteristics of organic matter,nitrogen nutrients content,soil bacterial community structure and diversity changes in 0-20 cm and 20-40 cm soil layers of corn fields with continuous straw returning for 2(SR2),5(SR5) and 10 a (SR10).The results showed that SR2 had no significant difference with CK in soil organic matter and nitrogen nutrients content,while SR5 and SR10 significantly increased soil organic matter and nitrogen nutrient content;under different straw returning years,soil bacterial diversity was different and each had its own unique OTU,among which SR10 OTU had the largest number;alpha diversity index showed that the relative abundance and diversity of soil bacterial community were not significantly different between SR2 and CK,SR5 and SR10 increased significantly,and SR10 and CK had the largest difference;a total of 51 bacterial groups were obtained at the phyla level,including Actinobacteriota,Proteobacteria,Acidobacteriota,Crenarchaeota and Chloroflexi,whose relative abundance was more than 5%.The relative abundance of Proteobacteria,Acidobacteriota and Chloroflexi increased with the increase of returning years.RDA clustering analysis showed that the soil bacterial community structure of 0-20 cm soil layer SR2 was similar to CK,SR5 was more similar to SR10,20-40 cm soil layer,different straw returning years,treatments were different from CK,SR2 and SR5 were similar,SR10 had significant differences in community structure compared to SR5 and SR2.The contents of soil {\mathrm{NO}}_3^{-}-N, {\mathrm{NH}}_4^{+}-N,OM,and TN all had effects on bacterial flora,and they were soil {\mathrm{NO}}_3^{-}-N> {\mathrm{NH}}_4^{+}-N>OM>TN.The contents of soil organic matter and nitrogen nutrient had no significant difference between continuous straw returning for 2 a and CK,while continuous straw returning for 5 and 10 a were significantly increased.In summary,the microbial diversity and richness of bacteria showed minimal changes in the soil layers of 0-20 cm and 20-40 cm after continuous straws returning for 2 a.After continuous straws returning for 5 and 10 a,both soil layers significantly increased;the bacterial community structure continuous straw returning for 2 a was similar to CK in the 0-20 cm soil layer,while the bacterial community structure continuous straw returning for 2,5,10 a were changed in the 20-40 cm soil layer.

Key words: West Liaohe Plain, Straw returning years, Soil bacteria, Bacterial community, Bacterial diversity