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

Oats 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 have 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 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. Compared to the OO treatment, the BO treatment had the greatest impact on soil properties and bacterial α-diversity, while fungal α-diversity was highest in the MO and CO treatments. Crop rotation also shifted the soil microbial community structure, the dominant bacterial phyla were Actinobacteriota, Proteobacteria, Chloroflexi, and Acidobacteria, while the dominant fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota. Principal coordinate analysis (PCoA) showed significant differences in both bacterial and fungal communities between the five treatments. 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 influenced the oat yield. Our findings suggest that buckwheat-oat rotation may be the most suitable crop rotation pattern for enhancing soil quality and oat yield in southwest China, maize-oat is not recommended due to its damage to soil nutrients and microbial communities.