Submitted to: Proceedings of the International Salinity Forum
Publication Type: Proceedings
Publication Acceptance Date: April 11, 2005
Publication Date: April 25, 2005
Citation: Corwin, D.L. 2005. Mapping, monitoring, and assessment of salinity using apparent soil electrical conductivity. In: Proceedings of the International Salinity Forum, Managing Saline Soils and Water: Science, Technology, and Soil Issues. April 25-27, 2005. Riverside, CA pp:125-128. Interpretive Summary: Even though salinity buildup on irrigated lands is responsible for a declining resource base for agriculture, the exact extent to which irrigated soils are salinized, the degree to which productivity is being reduced by salinity, the increasing or decreasing trend in soil salinity development, and the location of contributory sources of salt loading to ground and drainage waters are not known. An overview is presented of work conducted by Corwin and colleagues that provides the methodology and guidelines for monitoring, mapping, and assessing soil salinity and associated soil properties (e.g., water content, texture, bulk density) using geospatial apparent soil electrical conductivity (ECa) measurements. The methodology uses ECa measurement guidelines and survey protocols developed by Corwin and colleagues for taking mobilized electromagnetic ECa measurements to direct soil sampling. The methodology has proved successful for a variety of agricultural applications including modeling non-point source pollutants (e.g., salinity, trace elements, fertilizers) in the soil, delineating site-specific management units for precision agriculture, and assessing changes in soil quality.
Technical Abstract: Geo-referenced measurements of apparent soil electrical conductivity (ECa) provide a potential means of characterizing soil spatial variability. It is the objective to present the practical technology, methodology, and guidelines for measuring, monitoring, mapping, and assessing soil salinity (and associated soil properties) using geospatial ECa measurements. Case studies are presented for agricultural applications including (i) modeling of non-point source pollutants in the vadose zone, (ii) precision agriculture, and (iii) soil quality assessment. In particular, a spatio temporal study of changes in soil quality, particularly salinity, is presented for a drainage water reuse study site. The spatio temporal study used electromagnetic induction ECa data and a response surface sampling design to select sample sites that reflected the spatial variability of a saline sodic field in California's San Joaquin Valley. Soil samples were collected in August 1999 and April 2002. Data from 1999 indicated high levels of salinity, which increased with depth, high levels of SAR, which also increased with depth, and moderate to high levels of B and Mo. The application of drainage water for 32 months leached salinity from the top 0-0.6 m, B from the top 0.3 m, and sodium and Mo from the top 1.2 m. Preliminary spatio temporal assessments using the ECa-directed sampling methodology indicate at least short term feasibility of drainage water reuse from the perspective of soil quality when the goal is forage production for grazing livestock.