A study appearing in Nature Communications based on field and greenhouse experiments at the University of Kansas shows how a boost in agricultural yield comes from planting diverse crops rather than just one plant species: Soil pathogens harmful to plants have a harder time thriving.
"It's commonly observed that diverse plant communities can be more productive and stable over time," said corresponding author James Bever, senior scientist with the Kansas Biological Survey & Center for Ecological Research and Foundation Distinguished Professor of Ecology & Evolutionary Biology at KU. "Range lands with numerous species can show increased productivity. But the reason for this has been a bit of a mystery."
While crop rotation and other farming and gardening practices have reflected benefits of a mix of plants, the new research points to one important mechanism underpinning the observation: the numbers of microorganisms in the soil that eat plants.
"Diverse agricultural communities have the potential to keep pathogens at bay, resulting in greater yields," Bever said. "What we show is that a major driver is the specialization of pathogens, particularly those specific to different plant species. These pathogens suppress yields in low-diversity communities. A significant advantage of range-land diversity is that less biomass is consumed by pathogens, allowing more biomass for other uses, such as cattle. The same process is crucial for agricultural production."
The new data was developed at the University of Kansas using field experiments at the KU Field Station, along with greenhouse assays and feedback modeling using computers. This project was supported by large collaborative grants to KU from the National Science Foundation and the U.S. Department of Agriculture.
"We conducted an experiment manipulating the number of plants in a plot and varying precipitation levels—we had from one up to six species in a plot," Bever said.
"Then, we evaluated the composition of the soil-pathogen microbiome. What we found is that the variation in pathogen composition in monocultures significantly predicted the yield when combined. When there are distinct pathogen communities, mixing them leads to a greater release of pathogens from your neighbors. The worst scenario is when a neighboring crop has the same pathogens. In that case, you're experiencing double density—your crop pathogens and those from your neighbor crop."
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