Microbial soil legacies of crops under different water and nitrogen levels determine succeeding crop performance

Soil legacies mediated by abiotic and biotic factors can greatly influence succeeding plants, a phenomenon called plant-soil feedback (PSF). To date, the patterns and mechanisms of PSF remain largely unexplored in agroecosystems, especially how soil microbial legacies of crop species and management practices interact is poorly understood. We subjected four common arable crop species (wheat, maize, soybean and rapeseed) to water (sufficient or drought) and nitrogen (high or low) treatments to condition living soil. We analyzed soil nutrient properties and microbiome composition, and then grew the four crops in conspecific and heterospecific soils to examine intra- and inter-specific PSFs. We found that crop species, nitrogen and water treatments created differential effects on soil bacteria and fungi diversity and community composition. Wheat grew better in conspecific-conditioned soil than in heterospecific-conditioned soil, whereas maize and soybean performed better in heterospecific-conditioned soils regardless of water and nitrogen treatments. The PSFs of rapeseed depended on the water and nitrogen treatments. The dissimilarity of both soil bacterial and fungal communities showed a consistently positive correlation with the feedback effect for wheat, while it negatively correlated for maize, rapeseed and soybean. Path analysis showed that soil abiotic, bacterial and fungal legacies all impacted the corresponding crop growth. We show that via selecting crop species and by changing management practices we can create positive legacies that can enhance the growth of the succeeding crop. Hence, this work proposed a new way to capitalize on soil legacies for enhancing agricultural productivity.