UMN Turf Research
Determining Plant Available Water Irrigation Thresholds
By: Ryan Schwab, Josh Friell, Gabe Olson-Jensen, & Eric Watkins University of Minnesota
Precision irrigation in the golf course industry is commonly adopted as new technologies, philosophies, and research make water conservation measures more accessible. One of these practices, threshold-based irrigation, can conserve water while maintaining acceptable playing surfaces. This approach involves setting a soil moisture threshold, and once the soil dries to that value, irrigation will be triggered. Informally, many on the golf course already execute this practice by monitoring soil moisture quantified by volumetric water content (VWC) with a portable soil moisture sensor and watering areas that 48
have dried down to a certain VWC value or below. The introduction of in-ground soil moisture sensors has allowed real-time point measurements of soil moisture to be observed remotely. These can be favorably placed in areas that need constant monitoring and be a valuable tool for threshold-based irrigation by dialing in the “when” and “where” irrigation decisions. Availability of water to the turfgrass plant is largely dependent on soil type, as one rootzone may hold onto water tighter than another. Therefore, instead of using VWC as a metric for soil moisture, it may be more beneficial to use plant available