Rotational strip intercropping of maize and peanut enhances productivity by improving crop photosynthetic production and optimizing soil nutrients and bacterial communities

Context or problem: Rotational strip intercropping is a compound planting system using annual intercropping and interannual rotation of intercropped strips. Our previous work showed that the rotational strip intercropping of maize (Zea mays L.) and peanut (Arachis hypogaea L.) (RMP) improved crop productivity in comparison with the continuous monoculture of maize (CM) or peanut (CP). However, the effects of RMP on crop physiology and soil properties related to the productivity remain unclear. Methods: Crop productivity and physiology, soil nutrients, and bacterial communities under RMP were evaluated over six years and compared with CP and CM. Results: RMP significantly increased the crop productivity, with an average land equivalent ratio (LER) of 1.19. RMP increased maize yield by 16.01-21.68% compared with CM, with a partial land equivalent ratio (PLER) of 0.58-0.61. The maize physiological properties were markedly improved as indicated by the increased dry matter (DW) accumulation of the stem, soil and plant analyzer development (SPAD) value, and net photosynthetic rate (Pn) under RMP. The contents of soil organic carbon, available nitrogen, total phosphorus (TP), available phosphorus (AP), available potassium and total nitrogen were increased after peanut rotation. Microbial community structures were significantly affected by the soil layer and planting modes, and both microbial richness and diversity were significantly reduced in CP compared with RMP. Sphingomonas and Gemmatimonas were the dominant genera in the 0-20 cm soil layer and their abundance was positively correlated with the contents of TP and AP. Burkholderia-Caballeronia-Paraburkholderia, a genus that can break down autotoxins resulting from continuous cropping of peanuts and prevent infection, was the dominant and indicator genus in the 20-40 cm soil layer where direct belowground interaction of maize and peanuts occurs under RMP. Conclusions: In conclusion, increased productivity in RMP was largely the result of higher photosynthetic production of maize, caused by aboveground interspecific competitive advantage, and the optimization of soil nutrient composition and bacterial communities for peanut, caused by belowground interspecific interactions. Implications or significance: This study suggested that plant-soil-microbe interactions are key to the high productivity observed in RMP and should be considered in designing cropping systems for sustainable agriculture.