Using Turtuosity and Bulk Electrical Conductivity Measurments to Estimate Salinity in a Sandy Soil.

The use of low quality saline water for turfgrass irrigation as part of a potable water conservation strategy has resulted in the need to monitor moisture and salinity levels in the rootzone to ensure adequate turfgrass quality. Traditional methods for determining soil moisture and salinity are destructive and require considerable time and money for field sampling and laboratory analysis. The development of new technologies, such as time domain reflectometry (TDR), provides the possibility for a non-destructive, accurate, reliable, and rapid measurement of moisture and salinity in a turfgrass rootzone. However, the measurement of salinity in soils by means of TDR is indirect and limited to bulk soil electrical conductivity (σ_b). Therefore, a model is required to estimate soil solution electrical conductivity (σ_w) from σ_b. In order to calculate σ_w the tortuosity factor t of the soil is required. The tortuosity factor t = (θ p σ_w / σ_b)^1/2 is calculated from θ -volumetric moisture content and p - total porosity and describes in an integral way the geometry of the porous space. Research has been conducted at New Mexico State University to estimate salinity in a sandy soil from determining the tortuosity factor from the analysis of photomicrographs and from the measurement of the bulk electrical conductivity by means of TDR. Results indicated a strong correlation between conventionally measured soil salinity values and estimates obtained from the tortuosity factor TDR measurements.