Enhanced Soil Moisture Assessment Using Narrowband Reflectance Vegetation Indices in Creeping Bentgrass

Turfgrasses are measured aesthetically and by their ability to withstand stressors. Historically, researchers quantified acceptability by visual quality, but inconsistencies necessitate the use of vegetation indices (VIs) as an objective measurement. Indiscernible relationships have been established between turfgrass canopy normalized difference vegetation index (NDVI) and important variables such as soil moisture and leaf chlorophyll content. Alternative and variable–specific indices have been established in cropping systems. The water band index (WBI) is used for predicting water availability in cropping systems but has not been explored within turfgrass systems. The objective of this study was to compare the relationships of established VIs with chlorophyll content of ‘L-93’ creeping bentgrass (Agrostis stolonifera L.) and water content of a sand-based root zone maintained under greenhouse conditions. All VIs were moderately to strongly correlated to total chlorophyll content (r = 0.49–0.85). Turf color was more closely related to chlorophyll indices than to wet-lab quantification. Only WBI (r ³ 0.80) and the green/red ratio index (GRI; r ³ 0.50) were consistently related to soil water content. The NDVI was weakly related to soil water content in one trial (r = 0.49). Nonlinear regression showed that WBI can be useful for estimating a decline in soil water content as water first becomes limiting for creeping bentgrass and may offer a viable means to assess water availability independently of non-moisture-related stresses and more accurately compared with previous indices. Future research will evaluate WBI on broader geospatial scales to assess practical application for turfgrass irrigation management.