Soil management legacy alters weed-crop competition through biotic and abiotic pathways

Aims Agricultural practices often have persistent effects on soil physicochemical properties and soil biota, which can feedback to influence plant performance. We investigated management-induced differences in soil fertility and soil microbiota for their legacy effects on plant nutrient acquisition and crop/weed competition. Methods Sorghum bicolor (L.) Moench (sorghum), Ambrosia artemisiifolia (L) (ragweed), and Amaranthus powellii S. Wats. (pigweed) were grown as monocultures and mixtures in the greenhouse in soils with distinct management histories. Cross inoculations of sterilized soils were used to quantify biotic vs. abiotic influence on plant growth, nutrient uptake and competitive outcomes. Results Differences in management history led to a two-fold difference in soil organic matter (OM), and a 37% increase in N acquisition in all species in the high OM soil. The increase in N availability preferentially benefitted pigweed growth at the expense of sorghum. However, microbiota from the high OM soil alleviated the negative effects of pigweed competition on sorghum. Soil management legacy also affected sorghum tiller production and mycorrhizal colonization. Conclusion Management-induced differences in soil biotic and abiotic factors altered plant performance in a species-specific manner. Management legacy effects on soil microbiota have the potential to increase crop competitiveness against some weed species.