Submitted to: Geoderma
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/13/2005
Publication Date: 4/1/2006
Citation: Corwin, D.L., Lesch, S.M., Oster, J.D., Kaffka, S.R. 2006. Monitoring management-induced spatio-temporal changes in soil quality through soil sampling directed by apparent electrical conductivity. Geoderma. 131:369-387. Interpretive Summary: The reuse of drainage water is one means proposed to reduce drainage water volumes in the southern San Joaquin Valley of California. However, the long-term sustainability of drainage water reuse is a major concern and has not been established. One aspect of the sustainability of drainage water reuse involves an evaluation of the spatial and temporal changes in soil quality that occur due to irrigation with drainage water. This study is a preliminary assessment (1999-2002) of a long-term drainage water reuse on a forage crop to evaluate the detrimental effects occurring over time to soil physical and chemical properties on an 80-acre field located in central California's San Joaquin Valley. Soil samples from 1999 showed the site to be high in salinity, sodium, boron, and molybdenum, all of which can be detrimental to either crop yield or to livestock. Preliminary analyses from 1999-2002 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.
Technical Abstract: Characterizing spatial and temporal variability of soil properties at field and landscape scales is tremendously important for a variety of agronomic and environmental concerns including solute transport modeling of non-point source pollutants in the vadose zone, precision agriculture, and soil quality assessment. The objective is to demonstrate the utility of ECa-directed soil sampling in quantifying spatio-temporal changes in soil chemical properties resulting from drainage water reuse. A soil quality assessment was conducted on a 32.4-ha saline-sodic field in California's San Joaquin Valley in August 1999 and April 2002 to evaluate the spatio-temporal changes that had occurred as a result of irrigation with drainage water over that time period. Using geospatial electromagnetic induction (EMI) measurements of ECa and a spatial response surface sampling design, 40 sites were selected that reflected the spatial variability of the ECa measurements. Duplicate samples were taken at eight sites to study local-scale variability. At each site soil-core samples were taken at 0.3-m intervals to a depth of 1.2 m and analyzed for 28 physico-chemical properties. Maps created with a GIS show spatio-temporal changes of dynamic soil properties. Data from 1999 indicated the presence of high levels of salinity, which increased with depth, high levels of sodium adsorption ratio (SAR), which also increased with depth, and moderate to high levels of B and Mo. The application of drainage water for 32 months resulted in leaching of the surface 0.6 m of soil. The leaching fraction over the time period from 1999-2002 was estimated to be 0.10. Preliminary spatio-temporal analyses from 1999-2002 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.