## 4 Discussion  
The sequencing results and the alpha and beta diversity indexes indicate that soil fungal community structures, abundance and diversity varied among the four different tillage treatments and in different seasons. The alpha diversity index responded positively to season. The fungal community was significantly different under different seasons, tillages and crop residue treatments. Residue return with no-tillage increased soil fungal richness, community diversity and network complexity, and seasonal differences were stronger than under agronomic treatments. Agriculture practices have different influences on soil fungi; for instance, conservation tillage had positive effects on arbuscular mycorrhizal fungi, while saprotrophic fungi and bacteria were not affected by soil tillage [19]. As we expected, NT showed higher richness and diversity of soil fungi as compared with CT. The effects of tillage on soil fungi were diverse, and lots of studies recorded positive contributions of NT to the soil fungus community, such as showing increased diversity and abundance [14,44] as well as biomass [3]. The fact that the soil biological component was improved in NT changed the soil properties and reduced disturbance. NT soils exhibited significantly higher dehydrogenase, beta-glucosidase, phosphatase, urease and BAA protease activities than conventional deep -tillage soils [45]. Tillage, even if shallow and performed infrequently, had a negative effect on organic C and N pools [46]. Moreover, NT reduced the disturbances imposed on soil fauna, signifying that it provided a more stable environment for soil fauna [47]. The abundance and diversity of soil arthropods were significantly higher in no-tillage than in conventional tillage plots [48]. [PERSON] et al. (2004) found the negative effect of tillage on culturable soil-specific actinomycete communities [49], while [PERSON] and [PERSON] (2018) and [PERSON] et al. (2019) found that tillage practices had no effect on soil fungus and soil AMF communities [16,50]. Soil tillage usually decreases the amount of organic C stored in soils, and the return of crop residue reduces the negative impact of soil tillage, thus being beneficial to soil microbial systems [19]. The NTR system had higher fungal richness than the NT, indicating that stubble retention increased the number of fungal species. This confirms our hypothesis that soil residue cover results in higher soil fungal diversity relative to CT. [PERSON] et al. (2013) also found that NT amended with bagasse mulch had the highest soil microbial biomass and diversity (especially litter fungi, by 2 to 2.5 times) in sugarcane plantations [3]. Straw contains a large content of C, N, P and other nutrients, as well as organic substances, such as cellulose, hemicellulose and lignin, protein and sugar, and can be utilized by soil fungi. The NTR approach has been previously shown to significantly increase soil organic matter, total N and P, and the activity of phosphatase and sucrose, as well as reducing water evaporation and improving the water content of soil [51]. In addition, the dominant fungi we identified, Ascomycota and Zygomycota, are associated with litter decomposition, which accelerate residue decomposition, resulting in higher soil nutrients for microorganisms and crops. [PERSON] et al. (2014) also found that microbial biomass was highest in the NT with bagasse mulch compared to the NT without bagasse mulch, as well