Objective Effects of tilling and straw-returning on the physicochemical properties and microbial communities of soil on a cotton-potato rotating cultivation field were studied.

Methods On a field of cotton cultivation rotating with potato farming, soil was treated with no-tillage (NT), no-tillage with straw-returning (NTS), application of rotary tillage (T), and rotary tillage with straw-returning (TS) to determine the effects on the physicochemical properties, enzyme activities, and rhizosphere microbial community of the soil. RDA analysis was performed to examine factors in the treatments that altered the soil properties.

Results Comparing to NT, by returning the spent straws to the field, NTS significantly increased the contents of soil hydrolyzable nitrogen to 244.66 mg·kg⁻¹ and available potassium to 411.00 mg·kg⁻¹. Similarly, TS significantly increased available phosphorus to 388.73 mg·kg⁻¹ and total phosphorus to 1.82 g·kg⁻¹. Additionally, the treatment significantly reduced the bulk density, enhanced the porosity, and increased the water-holding capacity of the soil at cotton boll stage. But straw-returning did not significantly affect the enzyme activity in soil. However, T significantly heightened the catalase activity at cotton seedling stage and the sucrose enzyme activity at boll stage. Microbiologically, NTS significantly raised the fungal Shannon diversity, while TS significantly increased the taxa of fungi like Aspergillus that related to organic matter degradation. The microbial community became significantly abundant with Proteobacteria and Bacteroidetes, as affected by the changes in organic matter and phosphorus content in soil when straws were returned in NTS and TS. The redundancy and network analyses indicated that the microbial structure was also jointly affected by pH and that a higher functional synergy was exerted in the bacteria than the fungi community.

Conclusion The rotary tillage with returned straws of TS significantly improved the soil physical structure, increased the readily available nutrients, and maintained a diverse microbial community. On the other hand, straw-returning without tillage (i.e., NTS) consumed less energy and saved on labor for tilling the field benefiting the ecosystem. Hence, tillage and straw-returning on a cotton-potato rotation farming land would require evaluation of local soil conditions and economic goals prior to implementation.