Abstract:Cottonseed meal was taken as the improver of saline-alkali soil with different salinity degrees to study the effects of cottonseed on soil microbial diversity and soil structure. Total DNA of soil samples were extracted and analyzed by a new generation of illumina HiSeq high-throughput sequencing technology, and soil micromorphology was observed by SEM. The results showed that with the increase of salinity and alkalinity, NaCl increased the proportion of micro aggregates gradually and made soil surface looser and more porous, but NaCO3 had the contrary effects, both such soil structures are not conducive to microbial activity. Cottonseed addition could increase the number of microbial communities in saline-alkali soil compared with conventional fertilization, the highest Shannon's index and the lowest Simpson's index for saline-alkali soil were obtained under medium saline-alkali concentration, which indicated that microbial richness was the highest with cottonseed addition. The microbial community under Saline treatment includes 10 phylums, of which the dominant is Proteobacteria, followed by Actinomyces, Acid Bacillus, Bacillus monilia, Green Bending bacteria, Bacteroidetes, Nitrosospiro, Wartericobacter, Firmicutes. In general, cottonseed addition to saline-alkali soil can improve the soil structure and increase the number of microbial communities to a certain extent. Adding cottonseed under moderate saline-alkali condition results in the highest microbial abundance in the soil, but there is no obvious difference in the predominant microbial phylum in saline-alkali soil.