Submitted to: IMTA Workshop on Remote Sensing Technologies Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2005
Publication Date: April 1, 2005
Citation: Corwin, D.L. 2005. Salinity assessment at field and landscape scales using ECa sensing data. Proceedings IMTA Workshop Analysis of Technologies for Identification of Soil Salinity Through Remote Sensing, November 17-19, 2004, Jiutepec, Morelos, Mexico. pp: 11-20. Interpretive Summary: It is generally accepted that salinity buildup on irrigated lands is responsible for declining agriculture in many areas of the world, with an estimated 7% of the world's land area regarded as salt affected. However, the exact extent of the problem, 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. This global knowledge gap is due to the lack of a cost-effective, reliable means of mapping and assessing salinity at landscape scales. The most viable means of assessing landscape-scale salinity at the present is with mobile apparent soil electrical conductivity equipment (ECa). 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 ECa measurements. The methodology has been proven to be successful for a variety of agricultural applications including modeling salt loading to tile drains, delineating site-specific management units on irrigated fields, and assessing changes in soil quality at a drainage water reuse site. Results for the later case are presented.
Technical Abstract: Salinity affects 7% of the world's land area, causing reduced crop yield that is estimated in the billions of dollars. Assessing soil salinity at field and landscape scales by mapping its distribution is crucial to salinity management to mitigate detrimental impact on crop yields. Geo-referenced measurements of apparent soil electrical conductivity (ECa) provide a potential means of mapping and characterizing soil salinity. 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. A drainage water reuse study is presented where spatio-temporal changes in soil quality of a saline-sodic soil were evaluated. 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 field located on the west side of California's San Joaquin Valley. Soil samples were collected in August 1999 and April 2002. The properties of salinity, sodium adsorption ratio (SAR), B, and Mo were determined to be the most important in determining soil quality at the arid-zone site. 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.