The soil legacy effects of long-term maize and soybean intercropping based on the analysis of mycorrhizal infection and phosphorus absorption

To investigate the long-term intercropping continuously alters soil properties and microbial communities, creating legacy effects in the soil that influence the growth and nutrient acquisition of subsequent crops. This study investigated the soil legacy effect resulting from continuous implementation of different planting patterns over the medium to long termwithin single intercropping systems. Relying on Based on a long-term positioning field experiment started from 2017, the study focuses on dryland red soils under varying planting patterns (monoculture of corn and corn–soybean intercropping) and phosphorus application levels Superphosphate (at 0, 60, and 90 kg·hm⁻²). Through pot experiments involving with field soil(monocropped maize soils at P0, P60, P90 and intercropped soils at P0, P60, P90 are labeled as F1, F2, F3 and F4, F5, F6, respectively; categorized by sterilization status as native soil and sterilized soil), the effects of two phosphorus supply levels (0 and 40 mg·kg⁻¹, referred to as P0 and P60, respectively) on corn biomass, phosphorus uptake, partial land equivalent ratio, mycorrhizal colonization, soil available phosphorus, and phosphatase activities were explored.. The results showed that, compared with sterilized treatment, inoculation with in-situ bacterial agents significantly increased the corn biomass, phosphorus uptake, mycorrhizal colonization, and available soil phosphorus by 203.05%, 128%, 124.30%, and 21.05 respectively, and increased the equivalent ratio of the off-site soil by 0.21. Inoculation with the native bacterial agent F5 significantly enhanced both acid and alkaline phosphatase activities compared to other microbial treatments,, and significant interaction effects. Under various in-situ bacterial inoculation, compared with monoculture, intercropped corn fields exhibited increases in biomass (14.17%), phosphorus uptake (104.49%), mycorrhizal colonization (17.55%), soil available phosphorus (11.52%), and activities of acid (5.80%) and alkaline phosphatase (38.14%). In conclusion, both phosphorus supply level and planting pattern jointly influenced the soil legacy effect, indicating that reasonable intercropping combined with moderate fertilization can effectively improve plant-soil interactions, promoting crop growth, nutrient uptake and phosphorus activation.