Effects of Plastic Mulch Residue on Soil Fungal Communities in Cotton

Plastic mulch plays a crucial role in agricultural production in arid and semi-arid regions, positively impacting crop yields, salt suppression, and seedling protection. However, as the usage of plastic mulch extends over time, residue accumulation becomes a significant issue in these regions. To clarify the effects of plastic mulch residue on soil fungi, this study focused on three typical cotton-growing areas in Xinjiang. Using high-throughput sequencing technology, the study analyzed the changes in the fungal community structure and diversity in rhizosphere and non-rhizosphere soils across 27 cotton fields under three different levels of plastic mulch residue: 0–75 kg/ha, 75–150 kg/ha, and 150–225 kg/ha. The results indicated that Ascomycota and Basidiomycota were the dominant fungal phyla across all treatments. Increasing levels of plastic mulch residue reduced the fungal richness in the soil, with a greater effects observed on rhizosphere fungi compared to bulk soil fungi. The α-diversity of cotton rhizosphere fungi showed an increasing trend, followed by a decrease with increasing plastic mulch residue, in Aksu and Bazhou, peaking at 75–150 kg/ha. Conversely, in Changji, the α-diversity decreased with increasing plastic mulch residue. The α-diversity of non-rhizosphere fungi associated with cotton decreased with increasing plastic mulch residue. Plastic mulch residue significantly altered the soil fungal α-diversity and had a greater effects on rhizosphere fungi. Different levels of plastic mulch residue had varying effects on the β-diversity of rhizosphere and non-rhizosphere fungi, significantly influencing rhizosphere fungi in Aksu and Bazhou and non-rhizosphere fungi in Changji and Bazhou. Overall, different levels of plastic mulch residue exerted varying degrees of influence on the community composition and diversity of soil fungi associated with cotton, potentially reducing the fungal richness and altering the community structure with increasing residue levels.