Salinity Estimates in Irrigated Soils Using Electromagnetic Induction

Electromagnetic induction (EM) is a useful mean of assessing soil salinity in large areas, particularly after its calibration on different soils. Electromagnetic induction was used to monitor spatial and temporal changes of soil salinity within the saline irrigation district of Flumen, Spain. Soil salinity patterns in this region are entangled because of intensive land leveling and irrigation. This paper presents the EM calibrations for two different parcels. The apparent electrical conductivity (ECa), measured with EM, was compared with the electrical conductivity of soil extracts both at saturation (ECe) and at a 1:5 soil-to-water ratio on a weight basis (EC1:5). Different approaches were tested for analyzing the data. The suitability of EM in assessing soil salinity is evaluated for each entire parcel and for individual points. The calibration equation developed at one date is found to be suitable to predict the salinity for the entire parcel from EM measurements taken at another date. Furthermore, the better estimation of ECe from EM readings as compared to the estimation of EC1:5 from EM readings, lead to the recommendation of the use of the saturation extract for calibration. INTRODUCTION Salinity is a critical and persistent problem in many irrigated lands in arid and semi-arid regions of the world. Soil salinity varies both spatially and temporally. The assessment of soil salinity status requires a large number of samples from various locations in the field and at various times. Collecting soil samples from the field for laboratory analyses is the traditional method for