Evaluation of a Geonics EM38 and NTech GreenSeeker Sensor Array for Use in Precision Turfgrass Management.

The use of sensors holds great promise for implementation of improved precision turfgrass management. In this study, we evaluated two pieces of equipment (the EM38 soil electrical conductivity [EC] sensor and the GreenSeeker-red normalized difference vegetation index [NDVI] sensor array) for their ability to serve as decision-making tools for turf managers. We first evaluated the sensor’s accuracy by comparing its performance with that of hand-held sensors, whose utility had been previously determined. We found that the EM38 EC values were closely correlated with soil moisture, as determined with a Spectrum Technologies TDR300 soil moisture meter (r^²=0.85, p<0.0001). The GreenSeeker NDVI values were correlated with chlorophyll index values as determined by the Spectrum CM1000 (r^² 0.91, p<0.0001). When we conducted sensor scans in southern California on fairways at four golf courses (representing kikuyugrass [Pennisetum clandestinum Hochst. ex Chiov.], bermudagrass [Cynodon L.C. Rich.] and ryegrass overseeded [Lolium perenne L.] bermudagrass) as well as on the GN1 bermudagrass turf track at a thoroughbred racing facility, the sensor array was able to detect moisture deficits and corresponding turfgrass quality reduction rapidly, and over large areas. Although the sensors provided reasonable sensitivity, data management and interpretation were complex, and are the primary barriers to practical use of remote sensing arrays for precision turfgrass management. The sensor array and data acquisition equipment consisted of a Trimble AgGPS 132 sub meter GPS receiver, a TDS400 Trimble Recon handheld computer, HGIS-pro software from Starpal, and a BSS4 buffered smart switch (B & B Electronics) to which the GPS, EM38 and GreenSeeker serial output cables were attached. Power was provided by a 12 VDC deep-cycle RV battery. The sensors were mounted on a sled constructed of 2-inch PVC pipe that was towed behind a utility cart.