Evaluating Putting Green Moisture Near the Surface.

Managing sand-based putting greens requires adequate moisture levels throughout the rootzone while ensuring firmness and playability at the surface. In addition to weather conditions, irrigation scheduling, wetting agent applications, and cultural practices all affect the soil moisture of putting greens. Greater understanding of how these practices specifically affect moisture at the green surface is of value to golf course superintendents. Time Domain Reflectometry (TDR) is a commonly used technology for monitoring rootzone volumetric water content (VWC) at various depths. However, most portable TDR measurement tools are not capable of evaluating moisture levels within the uppermost surface (1.2 cm) of the green. The objective of this work was to estimate VWC within the surface 1.2 cm of the green. A soil moisture meter (TDR300, Spectrum Technologies, Inc.) was modified to reduce the penetrating depth of its rods to 1.2 cm and readings were recorded in microseconds. Samples measuring 10.5 cm in diameter by 18 cm in height were taken from an existing ‘G2’ creeping bentgrass (Agrostis stolinifera L.) research green. All samples were saturated, placed in a dryer, and then removed at different time intervals to produce a range of volumetric water contents. TDR readings were taken using the modified TDR300 meter, after which the surface 1.2 cm of the sample was immediately cut and weighed. The cut sections were further dried at 105^oC for 24 hours and then reweighed to calculate VWC. Regression analysis resulted in a highly significant (P < 0.001) linear prediction equation [VWC = 0.0032(microseconds) - 6.2261] with a coefficient of variation = 0.96. These results offer promising opportunities for turf researchers, golf course superintendents, and industry professionals to further extend the capabilities of existing technology and more closely monitor, evaluate, and forecast how various products, practices, and conditions affect moisture at the putting green surface.