Performance testing of natural turfgrass sports fields requires sampling to obtain information on surface properties (e.g., soil moisture, soil compaction, surface hardness, and turfgrass vigor) (Carrow et al., 2010; McAuliffe, 2008). Several researchers have conducted performance testing to evaluate or develop standards for these properties to improve player safety and field playability (Bartlett et al., 2009; Canaway et al., 1990; Holmes and Bell, 1986; Jennings-Temple et al., 2006; McClements and Baker, 1994). Perhaps the most widely adopted testing procedure in the United States is the American Society for Testing and Materials F1936–10, a specification to measure impact attenuation in the field for a variety of sports with a lightweight handheld apparatus (ASTM, 2010). International sport governing bodies, such as the Fédération Internationale de Football Association, also provide a handbook of test methods to assess the performance of surface properties on soccer fields (FIFA, 2012). Previous research and current testing protocols use handheld data acquisition devices to sample at 5–12 locations and use descriptive statistics to analyze the data.
A more detailed approach of performance testing can be accomplished with spatial analysis and the creation of surface maps to detect variability of a given property across a field. Spatial analysis has been used extensively in agronomics to implement precision agriculture (Emery and González, 2007; James and Godwin, 2003; Taylor et al., 2003). Precision turfgrass management (PTM) is a new, but similar concept that focuses on enhancing input efficiency and management decisions through the application of inputs, such as water, fertilizer, and cultivation, only where, when, and in the amount needed by the plant (Bell and Xiong, 2008; Carrow et al., 2007, 2010; Krum et al., 2010; Stowell and Gelernter, 2008). PTM was developed and based on the premise of site-specific management, which requires detailed site information through intensive sampling (Carrow et al., 2010); therefore, previous sampling methods are likely insufficient.
Minimal research has been conducted on the spatial analysis of sports field surface properties. Three studies have been published using handheld sampling devices in which a GPS was used to obtain geo-referenced field data. Miller (2004) measured surface hardness of two soccer fields with a Clegg Impact Soil Tester (CIST) (Lafayette Instrument Co., Lafayette, IN) at a 10 × 10 m sampling grid (80 samples). Freeland et al. (2008) sampled surface hardness with a CIST on an American football field with a 9.1 × 9.1 m sampling grid (77 samples). Caple et al. (2012) collected data for several surface properties on three soccer fields at the beginning, middle, and end of the season using a sampling grid of unspecified dimensions (135 or 150 samples depending on the field). Maps were created from the data to evaluate the spatial and/or temporal variability of the measured surface properties.
Mobile data acquisition devices equipped with GPS are pertinent for rapid sampling of spatial data in agriculture (Adamchuk et al., 2004; Corwin and Lesch, 2005; Rhoades et al., 1999); however, few mobile devices are currently available for use in turfgrass. Developed in 2005, the Toro Precision Sense 6000 (PS6000) was the first and only mobile multisensor sampling device engineered for turfgrass sites (The Toro Company, Bloomington, MN). The PS6000 was engineered for simultaneous rapid sampling of soil moisture (VWC; %), soil compaction (penetration resistance; MPa), and plant performance (NDVI; unit less with best = 1.0) of complex turfgrass sites. This device has an onboard GPS unit that identifies the latitudinal and longitudinal location of each sample. Carrow et al. (2010), Flitcroft et al. (2010), and Krum et al. (2010) have used the PS6000 for timely data collection and spatial mapping of golf course fairways to develop site-specific management units and protocols to improve irrigation practices and implement site-specific cultivation; however, no research has been published evaluating its use on natural turfgrass sports fields.
Mobile devices are ideal for intense data sampling for spatial analysis, but handheld devices are more practical due to their greater availability and lesser cost. Increased adoption of spatial analysis of sports field properties along with enhancements in technology will create opportunities for the use of all devices. Therefore, it may be important to compare the two sampling methodologies to determine if they generate similar data. The objective of this study was to compare handheld and mobile data acquisitions of soil moisture (VWC), soil compaction (penetration resistance), and turfgrass vigor (NDVI) on several natural turfgrass sports fields using two sampling grid sizes.
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