Novel Approaches to Detect Creeping Bentgrass Drought Stress Using Field Radiometry.

Water conservation efforts are a primary emphasis of turfgrass evaluation programs, because of the decreasing availability of irrigation water for recreational uses, as more irrigation is needed for traditional agriculture to feed a growing global population. Current methods to monitor soil moisture stress include the use of time-domain reflectometry and vegetation indices derived from spectral reflectance. Technologies that assist in the early detection of drought stress prior to symptom expression can be useful for more appropriate irrigation timing. Improvements in narrow-band reflectance measurements have proven beneficial in agricultural settings, but the use of field radiometry to detect moisture stress on creeping bentgrass is largely unexplored. Previous research has demonstrated that narrow-band spectral reflectance can be transformed to show herbicide-induced stress to annual bluegrass several days prior to visible symptom development, but this approach has not been explored for early detection of drought stress to creeping bentgrass. Dry-down studies were conducted on ‘007’ and ‘Memorial’ creeping bentgrass in Blacksburg, Virginia, with field radiometry and time-domain data collected daily. Data were transformed using previously described algorithms related to herbicide-induced stress, soil moisture stress, and turfgrass density. Unique spectral regions within near infrared and visible red edge light proved most useful for estimating water needs associated with drought symptom development, but did not provide substantial early detection before water availability became limited. Ongoing research is designed to more effectively detect drought stress prior to visible symptom expression.