Ag Alert Jan. 12, 2022

A SPECIAL GROWERS’ REPORT OF AG ALERT ® C A L I F O R N I A Trees & Vines ® Experts weigh benefits, downsides of cover crops

ByDennis Pollock More farmers are embracing the idea of using cover crops, touting advantages that come with increasing or- ganicmatter, porosity of the soil andwater retention. But questions remain about how much water cover cropsmay require or whether theywill have any negative impacts on their cash crop. Some of those quest ions were answered in a December virtual discussion on cover cropping for drought resiliency. The program was presented by the Madera/Chowchilla Resource Conservation District, American Farmland Trust, University of California Cooperative Extension, the East Stanislaus Resource Conservation District and the East Merced Conservation District. Among thequestionswere: “What about pest problems fromgrowing cover crops?” Anna Gomes, a doctoral student at Stanford University, pointed out that the interaction between cover crops and pests is specific to the crop system and organism. For example, she said, rodents prefer legumes and clo- vers; brassica vegetables may suppress nematodes; and cover cropsmay reduce infestationof navel orangeworms in almonds. But in grapes, legumes support the lifecycle of the three-cornered leafhopper. As to whether farmers will see changes in the first year after planting cover crops, Gomes said it can take six to eight years to see significant differences. She ex- plained that cover cropping is a “long-term investment in your soil.” Another question addressed how tomonitor improve- ments insoilwater infiltrationandwater-holdingcapacity. Gomes suggested measuring the height of the cover crop and collecting, drying and weighing the biomass of the cover to conduct simple andongoing determinations of soil aggregation. She also recommendedmakingwater infiltration determinations. “Youwill learn an awful lot if you do these simplemea- surements,” Gomes said. Her presentationemphasized that cover crops improve soil health. She said they usewater to grow, but it ismini- mal. Tillagematters.Not all cover cropspecies arecreated equal. Pest problems are unique to the crop and pest sys- tem, she stressed. Additionally, cover crops don’t eliminate full-season weeds. Soil change takes time but can be monitored. And cover crops improve on-farmwater management, she noted. In a follow-up to the webinar, sponsors sent out links to resources throughwhich growers can explore ground- cover options. Farmers who want to know more may search on- line for “Cover Crop Chart : Common Cover Crops for California.” That will lead to an overview from the U.S. Department of Agriculture Natural Resources Conservation Service of commonly used cover crop species in the state.

File photo shows cover crop thriving in Butte County. A Stanford researcher calls cover crops “a long-term investment in your soil.”

See COVER, Page 8

January 12, 2022 Ag Alert 7

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