The yield increase and land improvement effects of different sorghum/wild soybean intercropping patterns on reclaimed coastal salt pans

Purpose This study aimed to study the yield increase and land improvement effects of different sorghum/wild soybean intercropping patterns on reclaimed coastal salt pans and provide the theoretical basis for optimizing the intercropping pattern of reclaimed coastal salt pans and combining land utilization with land improvement. Specifically, the sorghum rhizosphere soil bacterial community structures under different cropping patterns were characterized. Methods Plot-based experiments were conducted on coastal salt pans reclaimed in 2015. Five treatments were set, i.e., monocropped sorghum (S), monocropped wild soybean (WS), row-cropped sorghum each row with one row of wild soybean (S1WS1), row-cropped sorghum each row with two rows of wild soybean (S1WS2), and mixed intercropping of sorghum and wild soybean (SWS), to study the biomass, yield of the sorghum and wild soybean, and rhizosphere soil of the sorghum. High-throughput sequencing methods were used to analyze the changes in rhizosphere soil bacterial community under the different cropping patterns, and redundancy analysis was conducted to reveal the relationship between the bacterial community structure and soil environmental factors. Results Compared with S, the yield increase rates under S1WS1, S1WS2, and SWS patterns were 10.16%, 13.15%, and 40.68%, respectively. The land equivalent ratios (LER) above 1 reflected the superiority of intercropping. Under the S1WS1, S1WS2, and SWS patterns, soil organic matter content increased, soil nitrogen and phosphorus contents increased, soil enzyme activity improved, and soil pH and salinity decreased. The Ace, Chao, and Shannon indices peaked under the SWS pattern, reaching 1.12, 1.12, and 1.04 times as high as those under monocropping. Actinobacteria , Proteobacteria , and Chloroflexi were the dominant bacterial phyla with an abundance above 10%. Soil nitrate nitrogen, alkaline phosphatase, and nitrogen to phosphorus ratio were the main environmental factors affecting bacterial community structure. Conclusion The crop yield increase rate, LER, soil organic matter, and nitrogen and phosphorus contents all increased under the S1WS1, S1WS2, and SWS patterns, and the above indexes peaked which appeared in the SWS pattern. The SWS pattern showed the best yield and land improvement advantages. Therefore, the SWS pattern was most conducive to achieve intercropping superiority and the best land improvement effect.