Using Electro-Magnetic Induction to Determine Soil Salinity and Sodicity in Turf Root Zones

The traditional method of determining electrical conductivity (ECe) and sodium adsorption ratio (SAR) from saturated paste is destructive and time consuming. The electromagnetic induction (EMI) method determines apparent electrical conductivity (ECa) and offers an alternative to traditional wet chemistry methods. This study evaluated the effects of 2 yr of subsurface-drip and sprinkler irrigation with saline water on soil salinity and sodicity using both EMI technique and wet chemistry methods. Site specific calibration equations used to estimate ECe and SAR from ECa values were derived using a multiple linear regression (MLR) model included in the ECe sampling assessment and prediction model developed by the U.S. Salinity Laboratory. The ECe and SAR values were strongly correlated with ECa, with R-2 ranging from 0.82 to 0.98. Both wet chemistry methods and EMI data indicated that salinity and sodicity values were greater in turf irrigated with saline water from a subsurface drip system compared to a sprinkler system. Salinity in the top 30 cm ranged from <1 dS m(-1) in plots irrigated with potable water from both irrigation systems to 6.5 dS m(-1) in plots irrigated with saline water from a subsurface drip system. Similarly, SAR ranged from <1 mmol(1/2) L-1/2 in root zones irrigated with potable water regardless of the irrigation system, to >7 mmol(1/2) L-1/2 when saline water was applied from the drip system. Study results indicated that the EMI technique provides accurate predictions of the spatial distribution of both salinity and sodicity in turf soils watered from differing irrigation systems and water qualities.