Potential of Soil Health-Building Practices to Enhance Crop Yield Resilience to Drought.

Given climate change projections that predict warmer and drier summer conditions in the northern Corn Belt, the vulnerability of the common corn­-soybean rotation to unfavorable climatic conditions is of concern. Improved yields in dry conditions under soil health-building management, including practices such as rotation diversification, cover cropping, and zero or conservation tillage, have been observed at long­-term trials and in meta­-analyses. These benefits are often attributed to improved soil properties and thus water retention, yet the question remains: do other mechanisms underlie the enhanced resilience of such systems? We hypothesize that higher yield under drought in more diverse rotations is due to not only increased water and nutrient availability but also enhanced access and uptake of soil resources through deeper roots and root-mycorrhizae associations. In summer 2016, we imposed drought stress using rainout shelters in corn plots across a rotation diversity and tillage gradient at the Elora Research Station long-term rotation trial (corn-soybean-based systems, established 1980, University of Guelph, Ontario, Canada). We will present results on the interacting effects of soil water and nutrient dynamics and root growth and resource uptake on water and nutrient stress indicators, growth, and yield, using a novel application of isotopic methods to assess root water uptake depth across a diversity-tillage gradient. This research integrates crop stress physiology with management to help elucidate the functional significance of improved soil health for corn yield resilience to drought. We aim to contribute to efforts to reduce vulnerability to drought stress in rainfed Corn Belt cropping systems. To the best of our knowledge, this is the first drought-imposition study at a long-term Corn Belt crop rotation and tillage trial.