Abstract
Crop diversity may mediate the intensity of weed-crop competition by altering soil nutrient availability and plant-soil microbe interactions. A greenhouse experiment was conducted to analyze weed-crop competition in soils with varying crop diversity legacies. Soil greenhouse treatments included field soils (i.e., soil nutrient and microbial legacies), a sterile greenhouse potting mix inoculated with microorganisms of the field soils (i.e., microbial legacies), and a sterile greenhouse potting mix. Soils for the greenhouse experiment were sampled and assessed after two-years of conditioning with annual and perennial cropping systems under four levels of intercrop diversity. The greenhouse experiment involved growing one sorghum sudangrass (Sorghum bicolor (L.) Moench × S. sudanese Piper) crop plant and zero to six common lambsquarters (Chenopodium album L.) weed plants in soil from each diversity and cropping system treatment. The weed density treatments created a weed-crop competition gradient, which was used to quantify legacy effects of crop diversity. Weed-crop competition increased with crop diversity in both the field soil and inoculated soil treatments in the annual system. In the perennial system, differences in weed-crop competition intensity were driven by crop yield potential. In the perennial field soil treatment, crop yield potential was greatest in the highest diversity treatment, whereas in the perennial inoculated soil treatment, crop yield potential was greatest in the lowest diversity treatment. Results show potential for negative effects from previous crop diversity on weed-crop competition, and the divergent impact of microbial and nutrient legacies on crop yield potential. Future research should aim to evaluate the consistency of legacy effects and identify principles that can guide soil and crop management, especially in conservation agriculture where soil tillage and its microbial legacy reducing effects are minimized.
Highlights
Agricultural systems can be enhanced by understanding the drivers of weed-crop competition.Weed-crop competition is a major constraint to yield [1]
Research on the mechanisms that drive belowground competition and how management practices contribute to these effects is important for developing ecological weed management strategies that reduce the need for tillage and herbicides
After two years of conditioning by the continuous growth of crops differing in intercrop diversity, soil properties only differed at the cropping systems level (Table 2)
Summary
Agricultural systems can be enhanced by understanding the drivers of weed-crop competition.Weed-crop competition is a major constraint to yield [1]. Agronomy 2020, 10, 1373 our understanding of how specific farm management practices affect weed-crop competition remains limited. Research on the mechanisms that drive belowground competition and how management practices contribute to these effects is important for developing ecological weed management strategies that reduce the need for tillage and herbicides. Many farmers use herbicide-based weed control for conservation agriculture [4,5]. Such overreliance on herbicides is problematic because of the development of herbicide-resistant weeds, non-target impacts on biodiversity, and human health concerns associated with exposure to herbicides [6]. Ecological weed management will facilitate the sustainable intensification of conservation agriculture by reducing farmer reliance on herbicides
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