Drought-Resistant Soils: A Bounds Analysis.

This study aims to show the extent to which improving soil water-holding capacity (WHC) can buffer crops against drought stress. The quantitative effects of changes in WHC on drought yield losses have not been rigorously assessed across the range of observed WHC. As a result, it is difficult to assess the importance of soil improvement as a strategy for drought adaptation.

Both anecdotal reports and long-term research studies indicate that incorporating cover crops, crop rotation, perennials, reduced tillage, and organic amendments can reduce yield losses under drought. One likely mechanism is that these practices increase soil organic matter (SOM) and reduce bulk density (BD), thus increasing WHC.

I simulated the effects of increasing SOM and reducing BD in the Cycles cropping system model, which implements the pedotransfer functions from Saxton and Rawls (2006) to represent soil water retention based on soil texture, SOM, and BD. A representative soil from Lancaster County, PA was parameterized and then transitioned into three states—degraded, average, and improved—through long-term runs of crop management systems that ranged from a full-tillage maize monoculture with stover removal to a 6-year rotation with minimum tillage, cover crops, perennials, and manure additions. Resulting SOM and BD were compared to field-measured values from the National Cooperative Soil Survey Soil Characterization Database to ensure real-world relevance.

After establishing the degraded, average, and improved soils, maize yield response to drought was assessed using multi-year runs based on historical climate data, which was manipulated to represent increasing drought severity. Results will show the yield impacts of changes in WHC, indicating the scope for adapting cropping systems to drought through soil improvement.