Rhizosphere soil properties of waxy sorghum under different row ratio configurations in waxy sorghum-soybean intercropping systems

To overcome the continuous planting obstacle and promote the sustainable production of waxy sorghum, a two-years field experiment was performed to determine the responses of waxy sorghum rhizosphere soil properties to different row ratio configurations in waxy sorghum-soybean intercropping systems. The treatments included five row ratio configurations, which were two rows of waxy sorghum intercropped with one row of soybean (2W1S), two rows of waxy sorghum intercropped with two rows of soybean (2W2S), three rows of waxy sorghum intercropped with one row of soybean (3W1S), three rows of waxy sorghum intercropped with two rows of soybean (3W2S), and three rows of waxy sorghum intercropped with three rows of soybean (3W3S), and sole cropping waxy sorghum (SW) was used as control. The nutrients, enzyme activities, and microbes of waxy sorghum rhizosphere soil were investigated at the jointing, anthesis, and maturity stages. Results showed that rhizosphere soil properties of waxy sorghum were significantly affected by row ratio configurations of waxy sorghum intercropped soybean. Among all treatments, the performances of rhizosphere soil nutrients contents, enzymes activities, and microbes contents were 2W1S > 3W1S > 3W2S > 3W3S > 2W2S > SW. Compared to SW treatment, the 2W1S treatment increased the organic matter, total N, total P, total K, gram-negative bacteria phospholipid fatty acids (PLFAs), and gram-positive bacteria PLFAs contents and catalase, polyphenol oxidase, and urease activities by 20.86%-25.67%, 34.33%-70.05%, 23.98%-33.83%, 44.12%-81.86%, 74.87%-194.32%, 81.59-136.59%, 91.44%-114.07%, 85.35%-146.91%, and 36.32%-63.94%, respectively. Likewise, the available N, available P, available K, total PLFAs, fungus PLFAs, actinomycetes PLFAs, and bacteria PLFAs contents under the 2W1S treatment were 1.53-2.41, 1.32-1.89, 1.82-2.05, 1.96-2.91, 3.59-4.44, 9.11-12.56, and 1.81-2.71 times than those of SW treatment, respectively. Further, the determining factors of soil microbes were total K, catalase, and polyphenol oxidase for total microbes, bacteria, and gram-negative bacteria, total P and available K for fungus, available N, available K, and polyphenol oxidase for actinomycetes, and total K and polyphenol oxidase for gram-positive bacteria. In conclusion, the 2W1S treatment was the optimal row ratio configuration of waxy sorghum intercropped with soybean, which can improve the rhizosphere soil quality and promote the sustainable production of waxy sorghum.