Modified ECa – ECe protocols for mapping soil salinity under micro-irrigation

Authors: Corwin, Dennis; SCUDIERO, ELIA - UNIVERSITY OF CALIFORNIA; ZACCARIA, DANIELE - UNIVERSITY OF CALIFORNIA, DAVIS

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2022
Publication Date: 4/27/2022
Citation: Corwin, D.L., Scudiero, E., Zaccaria, D. 2022. Modified ECa – ECe protocols for mapping soil salinity under micro-irrigation. Agricultural Water Management. 269. Article 107640. https://doi.org/10.1016/j.agwat.2022.107640.
DOI: https://doi.org/10.1016/j.agwat.2022.107640

Interpretive Summary: a) Problem Statement Altered weather patterns from climate change will bring an increase in the frequency and intensity of drought in water-scarce agricultural areas that rely on irrigation, causing a shift from sprinkler and flood irrigation to micro irrigation as seen in California’s San Joaquin Valley following the 2011-2016 drought. Current protocols for mapping field-scale salinity are inadequate for mapping the complex local-scale 3-dimensional nature of salinity resulting from micro-irrigation systems (i.e., drip, buried drip, micro sprinklers, etc.). b) Accomplishment Modified protocols were developed for mapping the complex soil salinity patterns that exist for drip irrigation systems on pistachio orchards in California’s San Joaquin Valley. c) Contribution The ability to map soil salinity on drip irrigated fields provides site-specific information identifying where to leach salts to minimize the crop yield decrement due to soil salinity. This information is essential for precision agriculture applications by NRCS staff, agricultural consultants, natural resource specialists, growers, and soil scientists in the university, government, and private sectors. The information is particularly applicable to water-scarce, arid and semi-arid agricultural areas that use drip irrigation to manage soil salinity.

Technical Abstract: Altered weather patterns from climate change will bring an increase in the frequency and intensity of drought in water-scarce agricultural areas that rely on irrigation. To handle the increased stress on finite water resources that droughts impose on irrigated agriculture, a shift from sprinkler and flood irrigation to micro irrigation will likely occur similar to California’s San Joaquin Valley’s shift following the 2011-2016 drought. Micro-irrigation results in complex 3-dimensional salinity patterns. Current field-scale apparent soil electrical conductivity (ECa) directed soil sampling protocols and guidelines are inadequate for mapping the complex local-scale 3-dimensional nature of salinity resulting from micro-irrigation systems (i.e., drip, buried drip, micro sprinklers, etc.). A field study was conducted to develop additional ECa-directed soil sampling guidelines to map local- and field-scale variability in salinity under drip-irrigation systems within an orchard (i.e., pistachio orchard) using hard (i.e., salinity or ECe, electrical conductivity of the saturation extract) and soft data (i.e., geospatial ECa measurements), which required an accurate ECa – ECe calibration. The revised ECa-directed soil sampling guidelines for drip irrigation on a mature pistachio orchard indicate that a single soil core should be taken 0.9-1.2 m perpendicular to the drip line within the tree root system, rather than at the drip line, to improve the ECa – ECe calibration. Calibration of ECa to ECe, improved from R2=0.25 to R2=0.73 for site Flores D01, and from R2=0.17 to R2=0.72 for site Flores D05. The improved guidelines broaden the scope of application of ECa-directed soil sampling to map field-scale salinity on orchards under drip irrigation. The information presented is of value and benefit to producers, agriculture consultants, cooperative extension specialists, Natural Resources Conservation Service field staff, and soil and water researchers.