How Do Conservation and Ecological Practices Effect Soil Water? a Meta-Analysis.

Increased rainfall variability is well documented in the historic record and is predicted to intensify with future climate change. Managing both excess water in periods of heavy rain and lack of water in periods of inadequate precipitation will continue to be a challenge. Improving soil resiliency through increased water storage is a promising strategy to combat effects of both rainfall extremes.  The goal of this research is to quantify to what extent conservation and ecological practices can improve key indicators of soil hydrology. We are conducting a global meta-analysis focused on studies where conservation and ecological practices are compared to more conventional management. To date we have analyzed 83 studies with more than 350 paired comparisons to understand the effect of management on water infiltration rates, and the database will be expanded to include studies measuring soil porosity and the water retained at field capacity. Statistical analysis has been done both with both a bootstrap method and a mixed model that weights studies based on precision while accounting for between-study variation. We find that conservation and ecological practices, ranging from no-till, cover crops, crop rotation, perennial crops and agroforestry, on average significantly increased water infiltration rates relative to more conventional controls (mean of 68%, standard error 29%). There were significant differences between practices, where perennial and agroforestry system show the greatest potential for improving water infiltration rates (> 450% increase). Cover crops also lead to a significant increase in water infiltration rates (> 70%) while crop rotations and no-till systems did not consistently demonstrate increases. We also found that studies needed to include alternative management for more than three years to detect a significant increase. Overall this global meta-analysis improves understanding of how alternative management, notably the use of continuous cover in agricultural systems, improves water dynamics.