Effects of Crop Rotation With Oat on Soil Microbial Communities, Chemical Properties, and Oat Yield in Southwest China

Oats ( Avena sativa L ) had become an important crop in southwest China due to their high nutritional value and excellent adaptability to the challenging climate. Continuous oat cropping can lead to reduced oat yield and soil degradation; meanwhile, crop rotation has been proven to be an effective way to alleviate the obstacles of continuous cropping. However, the effects of different crop‐oat rotation patterns on oat yield, soil chemical properties, and microbial communities in southwest China remain unclear. To address this, we used high‐throughput sequencing and quantitative PCR of the 16S and ITS rRNA genes to investigate microbial communities in a multi‐pattern crop‐oat rotation experiment that ran from June 2020 to June 2023. The experiment included five treatments, each with five replications: OO (oat‐oat), MO (maize‐oat), PO (potato‐oat), BO (buckwheat‐oat), and CO (cabbage‐oat). Results showed that crop‐oat rotation significantly affected oat yield, soil chemical properties, and microbial communities. The highest oat yield was obtained from the MO and BO treatments, reaching 15.81 and 15.56 t/ha. Compared to the OO treatment, the BO treatment not only significantly increased oat yield but also markedly improved soil physicochemical properties and exhibited the highest bacterial diversity (Shannon at 6.315). In contrast, while the MO treatment achieved relatively high yield and optimal fungal diversity (Chao1 at 954.838), there were no significant differences in SOC and TN content compared to the OO treatment. Moreover, the soil microbial community structure in each crop‐oat rotation treatment showed significant differences from the OO treatment. Across all treatments, the dominant bacterial phyla were Actinobacteriota (28.62%–40.18%), Proteobacteria (17.20%–21.24%), and Chloroflexi (13.83%–26.91%), while the dominant fungal phyla were Ascomycota (50.49%–74.39%), Basidiomycota (14.29%–37.92%), and Mortierellomycota (7.46%–12.87%). Principal coordinate analysis (PCoA) showed significant differences in both bacterial and fungal communities between the five treatments; the first two axes collectively explained 58.99% and 50.08% of the total variance, respectively. Redundancy analysis (RDA) indicated that soil total nitrogen (TN) and pH were the most important factors shaping the bacterial and fungal communities in oat soil, respectively. The Structural Equation Modeling analysis (SEM) revealed that crop‐oat rotation affected the fungal community through its impact on soil organic carbon (SOC), thereby influencing the oat yield ( R 2 = 0.88). Our findings suggest that buckwheat‐oat rotation is the most suitable crop rotation pattern for enhancing soil quality and oat yield in southwest China.