A comparative study on annual crop yields, soil physicochemical properties, and system energy flow characteristics of different intercropping patterns in double-cropping rice fields

Rice, as a core crop crucial for both global and national food security in China, faces significant challenges due to the detrimental effects of continuous monoculture when subjected to long-term continuous cultivation. This phenomenon not only poses potential threats to soil ecological health but also endangers the sustainability of grain production. The paddy-upland multiple cropping system serves as an effective strategy to mitigate the challenges associated with continuous rice monoculture. However, the mechanisms through which this system influences soil physicochemical properties and energy flow dynamics within farmland ecosystems remain unclear. Our study established five treatments: Chinese milk vetch-early rice-late rice (CK), Chinese milk vetch-early rice-maize‖soybean (MRCB), rape-early rice-maize‖soybean (RRCB), rape-early rice-late rice (RRR), and potato-early rice-late rice (PRR). By measuring soil physicochemical properties, annual crop yields, and energy flow characteristics, the key physicochemical factors affecting crop productivity and energy flow patterns under different multiple cropping systems were analyzed. Our results showed that, compared to the CK treatment, the PRR treatment resulted in a significant increase in soil available potassium content, ranging from approximately 156.71% to 300.00%. In addition, the MRCB and RRCB treatments also showed higher available potassium content than the CK treatment in the winter cropping season and late rice season. Notably, the RRCB treatment yielded the highest rice actual yield among all five treatments, reaching (20868.52±633.57) kg·hm⁻². Correlation analysis further indicated a highly significant positive relationship between the rice yield of the RRCB treatment and the soil available potassium content. In terms of energy flow characteristics, the total primary productivity of the RRCB treatment increased by 568.58% compared to the CK treatment. In terms of the energy flow circulation index, the values for MRCB, RRCB, and PRR treatments were found to be 0.247, 0.228, and 0.388 respectively, all of which surpass the CK treatment. Furthermore, the RRCB treatment exhibited the highest light energy utilization efficiency, which was 2.42 times that of the CK treatment. Therefore, it can be concluded that the rape-early rice-maize‖soybean (RRCB) treatment has the potential to elevate the content of available potassium, thereby increasing the annual crop yield.