Water stress and weed competition are critical stressors during corn (Zea mays L.) development. Genetic improvements in corn have resulted in hybrids with greater abiotic stress tolerance; however, drought remains problematic. Therefore, with the expected change in precipitation throughout the Great Lakes Region, field (2019-2020) and greenhouse studies (February-April 2020) were conducted in East Lansing, MI to: 1) evaluate weed competition and water stress impacts on drought tolerant (DT) corn hybrid performance and 2) assess water stress and weed competition impacts on weed community composition and corn hybrid performance. In the field study, weed densities were lower under reduced precipitation and the communities were more diverse. As weed density increased, there was no difference in the rate of yield loss between drought sensitive (DS) hybrid under ambient or reduced precipitation. In contrast, as weed density increased the rate of yield loss was 1.8 times greater for DT hybrid grown under ambient precipitation compared to DT hybrid grown under reduced precipitation. Furthermore, as weed density increased the rate of yield loss was 1.3 times greater for DS hybrid grown under ambient precipitation compared to DT hybrid grown under reduced precipitation. There was no difference in the rate of yield loss as weed competition increased between DT and DS hybrid grown under ambient precipitation and DT and DS hybrid grown under reduced precipitation. Results from the greenhouse study confirm field study results. Overall, results demonstrate that reduced precipitation and increasing weed pressure decreases corn yield and impacts weed species diversity and evenness. Ultimately, integrated weed management will need to adapt to these changes for continued success under future climate scenarios.
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