Positive Feedback Mechanisms of Deficit Irrigation Promote Soil Moisture Retention, Water Conservation, and Event Runoff Mitigation.

Municipal water restrictions in combination with deficit irrigation practices and sustained drought can affect turfgrass plant survival, and often will result in aesthetically unacceptable lawn quality.  Using a dry-season / wet-season adaptive irrigation approach, it has been demonstrated that complete recovery of lawn density can occur despite late summer bare soil cover reaching 70%.  Land cover and soil moisture conditions are well known to affect surface runoff.  Thus, a field study was conducted at the Texas A&M Turfgrass Field Laboratory in College Station, TX, to investigate the impact of deficit irrigation practices on St. Augustinegrass (Stenotaphrum secundatum (Walter) Kuntze) lawn cover, soil moisture dynamics, and event runoff volumes.  Preliminary results suggest soil moisture is the dominant driver for event runoff volume.  Mid-summer reductions in surface runoff associated with drier soil conditions represent a substantial positive feedback for further water conservation.  These benefits can be sustained for several rain events after curtailment of irrigation.