Development of a Mobile 4-Wenner Array Based Salinity Monitoring Device for Turfgrass Situations.

Demand for water conservation on turfgrass sites is stimulating the use of alternative irrigation water sources, many of which may be saline in nature. Increasing soil salinity can result in several adverse plant and soil stresses such as: salt-induced drought, nutrient imbalances, toxic ion effects, and creation of sodic soils with associated poor soil physical conditions Soil salinity exhibits considerable spatial and temporal variability across the landscape since salts can accumulate at different levels depending on irrigation/rainfall applications, surface and subsurface water movement, and evapotranspiration [ET] patterns. Obtaining site-specific information on salinity status over large, complex turfgrass landscapes requires a means for salinity mapping.  We will discuss a mobile salinity monitoring device capable of determining GPS referenced bulk soil electrical conductivity (ECa) at three depths (0-10, 10-20, and 20-30 cm) and turfgrass stress (NDVI, normalized differential vegetative index). Bulk soil electrical conductivity was determined using a 4-electrode array [called 4-Wenner array] which consists of 4 equally spaced electrodes, a current generator, and a conductivity meter to determine electrical resistivity (ER) which is then converted to ECa.  Calibration to a hand-held 4-wenner array device and to gravimetric sampling for conversion of ECa to the saturated paste extract (ECe) standard will be discussed from three soil conditions – sand, sand-capped kaolinitic sandy clay loam, and a sandy clay loam.   We will apply salinity mapping to identifying salinity-based site specific management units (SSMUs) (these differ from SSMUs on non-saline sites, which are soil texture and organic matter based); and for site-specific irrigation for salinity leaching.