Mechanisms of 915 MHz Microwave Thermal Treatment on Physicochemical Properties and Microbial Communities in Sugarcane Continuous Cropping Soil

Long-term sugarcane monoculture triggers severe continuous cropping obstacles accompanied by notable soil microecological degradation, including nutrient immobilization, soil acidification, salinization and microbial community imbalance. Physical soil remediation via industrial microwave irradiation represents a promising approach to alleviate soil degradation. Nevertheless, the interactive variations in soil structure, fertility and microbial communities under gradient 915 MHz industrial microwave irradiation remain poorly understood. This study aimed to clarify the correlations among physicochemical properties, microbial structure and functional genes of sugarcane continuous cropping soil under microwave thermal regulation. A continuous 915 MHz microwave device with power gradients (0, 2, 4, 6, 8 kW) and a fixed irradiation duration of 10 min was adopted. Soil samples were incubated for 0, 15 and 30 weeks for comprehensive parameter determination. The results demonstrated that appropriate microwave power exerted positive regulatory effects on soil thermal intensity, aggregate disruption and microbial succession. Soil organic matter (SOM) and pH were key factors modulating the distribution of beneficial and pathogenic microorganisms. The 4 kW treatment disintegrated compact soil aggregates, activated mineral-bound nutrients, relieved soil acidification and salinization, and upregulated genes responsible for nutrient mineralization and antifungal metabolism to sustain high abundances of partial biocontrol fungi. In contrast, high-power treatments (6 kW and 8 kW) induced substantial early-stage SOM loss, reduced soil pH and aggravated salinization in the late incubation stage, thereby inhibiting symbiotic beneficial fungi. Collectively, 4 kW was the optimal microwave parameter in this study to coordinate soil structural, nutritional and microecological balance. This study provides a theoretical basis and technical guidance for the green remediation of soil plagued by sugarcane continuous cropping obstacles.