Defining Site Specific Management Units (SSMU) for Precision Turfgrass Management.

A basic tenant of Precision Agriculture (PA) is identification of site-specific management units (SSMU) which are areas with similar soil texture, organic matter content, and slope; and, thereby, exhibit similar management requirements. Development of Precision Turfgrass Management (PTM) to foster input efficiency, including irrigation water inputs, will require procedures to accurately delineate SSMUs just as within PA. Spatial mapping of soil and turfgrass conditions requires a mobile platform with global positioning system (GPS) capability.  We used the  Toro Mobile Mapping device which is designed for rapid measurement of surface zone (0 to 10 cm depth) volumetric water content (VWC), turfgrass stress (NDVI, normalized differential vegetative index), and penetrometer resistance. Our objectives were to develop detailed protocols related to SSMUs that encompassed: an appropriate mobile sensor platform; defining the mapping purposes or filed application (in this case, defining SSMUs); mapping procedures; soil sampling; laboratory analyses of soil samples; selection of appropriate descriptive and spatial statistical analyses; and presentation of results in a geographic information system (GIS) format. These protocols were to be science-based, but practical so that all the information could be integrated into a formal Decision Support System (DSS) to allow incorporation of PTM into management decisions in the practical world.  The primary emphasis of this paper will be on defining the most appropriate means to develop SSMUs on complex golf course fairways. The pros and cons of eight different SSMU classification options will be presented along with the implications relative to practical use of the SSMUs for irrigation scheduling decisions as to where and when to irrigate on a site-specific basis (i.e., based on SSMUs rather than whole field/fairway areas).