The Midwest U.S. is predicted to experience longer dry periods as precipitation variability and temperatures increase. Growing season drought can be devastating to crop yields, but soil microbial communities have the potential to buffer yield loss through increasing plant drought tolerance and soil water retention. Adding microbes to agricultural fields have been shown to increase plant growth, but far fewer studies have examined the impact of microbial inocula on plant and soil microbial drought tolerance. We conducted a rainout shelter experiment to explore two main questions. 1. How does growing season drought affect soil microbial communities and plant growth in corn and soybean fields? 2. How do two microbial inocula affect drought tolerance of plants and soil microbial communities? At Kellogg Biological Station, we applied a bacterial inoculum and root inoculum from prairie soil to a corn and soybean field. Following microbial addition, we set up rainout shelters on half of our plots to block 100% of rain for 7 weeks in the summer of 2019. We measured soil microbial community composition using next-gen sequencing, soil microbial biomass, plant physiology using PhotosynQ, and seed mass.
Results/Conclusions
There was no effect of microbial inocula on soil microbial community composition one week after application of inocula. After 7 weeks of rainout shelter treatment, microbial community composition differed between crop and rainfall treatments (significant crop and rainfall treatment interaction). Bacterial diversity was higher in ambient rainfall plots than shelter plots for both crops, but the difference in bacterial diversity was greater in the soybean field than the corn field. Similarly, microbial biomass was higher in ambient rainfall plots for the soybean field, but not the corn field (significant crop and rainfall treatment interaction). For plant measurements, relative chlorophyll was higher in soybean than corn plants, while the light energy captured by photosystem II was higher in shelter plots than ambient rainfall plots. Seed mass was lower in shelter plots than ambient plots for soybean but not corn. In this study we show that the effect of drought on microbial communities can be mediated by crop species and crop responses to drought. Through exploring how interactions between soil microbial communities and crops influence drought tolerance, this study has important implications for maintaining crop yield under climate change.