December 28, 2021
KMJ580's Don York, who produces the daily “Ag Report” on the Fresno-based radio station, interviewed Alyssa DeVincentis and Jeff Mitchell about work they and a larger team of researchers at UC Davis conducted on water-related impacts of winter cover crops throughout the Central Valley. The interview aired at 5:05 AM on York's Tuesday, December 28th, broadcast and can be heard by clicking on the link here below.
The work that DeVincentis and Mitchell summarized with York involved ten almond orchard and tomato field sites in which side-by-side comparisons of soil water content during the winter cover cropping period from November through March were conducted from 2017 through 2019. The study sites spanned San Joaquin Valley sites in Arvin, Shafter, Five Points, and Merced, as well as Sacramento Valley locations in Davis, Durham, Orland, and Chico. Basic conclusions stemming from the work include the finding that cover crops grown in the winter growing window do not lose more soil water than fallow bare ground despite considerable dogma about the likelihood that they deplete soil water reserves during the winter growing period.
This finding adds important information that may help local Groundwater Sustainability Agencies (GSAs) create groundwater management plans that are required for compliance with SGMA, the Sustainable Groundwater Management Act. If remote-sensed imagery is used to determine a farm's overall water use, winter cover crop vegetation may appear on satellite images as a net water loss, while in actuality, because cover crops perform other functions such as improving soil water infiltration from rain, increasing soil aggregation and water holding capacity, and reducing the energy available at the soil surface by providing shade by the cover crop canopy, the net effect tends to be no additional water loss relative to a bare soil surface during the winter period.
The team that worked together on this research included then UC Davis PhD student, DeVincentis, her major professor, Samuel Sandoval-Solis, Daniele Zaccaria, Anna Gomes, then an undergraduate student at Davis and now a PhD student at Stanford University, and CASI's Mitchell.
The project is summarized in a manuscript that will be published in an upcoming issue of UC's quarterly peer-reviewed journal, California Agriculture, in 2022. A pdf copy of the research article is also available below.
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