Cover crops offer water-holding benefits

By Christine Souza 

As farmers statewide prepare for anticipated cutbacks to groundwater under the Sustainable Groundwater Management Act, or SGMA, they are trying to stretch every drop of water to stay in business.

Merced County farmer Benina Montes, owner of Burroughs Family Farms, planted cover crops between rows of almond, walnut and olive trees at her farm near Snelling to improve soil health and attract beneficial insects. She is now seeing water savings.

“For every 1% increase in soil organic matter, you can hold another 20,000 to 25,000 gallons of water per acre,” Montes said of the water-holding capacity of soil planted with a cover crop. “By having the ground covered, we’re getting much better water penetration.”

Cover crops, any non-income generating crop planted to cover the soil and enrich soil diversity, hold great potential for water conservation such as improved water-holding capacity and infiltration, according to a report, “Cover Cropping in the SGMA Era,” published in May by a group of more than 30 authors.

The document highlights the water-saving benefits of planting cover crops and offers recommendations to bridge knowledge gaps and reduce policy barriers that disincentivize wider cover crop adoption.

Report authors suggested that management actions by local groundwater sustainability agencies, or GSAs, may have unintended consequences, such as discouraging planting of cover crops, a farming practice known for boosting soil health and other benefits.

Noting that farms account for up to 40% of California’s water use annually and that only 5% of the state’s arable land uses practices such as cover cropping, the report said planting cover crops at scale would be impactful and save more water.

Citing research results conducted in California and the Mediterranean, the report said cover cropping has led to increased infiltration of water into the soil and reduction of runoff, each by 40% or more.

Though the report found that water use of cover crops is variable and can depend on many factors, it said cover crop evapotranspiration can be negligible compared to bare ground in perennial and annual systems.

Montes said she has always had some cover crops growing at her farm, but last year she planted the soil-boosting plants between all rows of commercial trees, leaving no bare ground.

Keeping the ground planted to a cover crop, Montes said, lowers the soil temperature by between 20 to 40 degrees. Citing other advantages, she said the orchards have increased soil diversity and improved crop nutrition.

“It doesn’t matter whether you’re organic, regenerative, conventional, whatever— the principles of healthy soil are universal,” she said.

Montes partnered with Madera-based California Ag Solutions, a company that helps farmers with production practices such as cover cropping.

“Managing a cover crop correctly by not using excessive water really helps keep more water inside the boundaries of the GSA,” said Silas Rossow, president and co-owner of California Ag Solutions. He suggested the only way to improve water-use efficiency is with healthy soil.

Leaving ground bare and not planting a cover crop, Rossow said, is a lost opportunity to maximize on-farm water use. The farming services business began experimenting with different ratios of cover crop seed mixes in commercial almond orchards in fall 2015.

“In 2015, SGMA had just been passed, but it wasn’t on our radar,” Rossow said. “We soon realized that cover crops are extremely beneficial and can be plugged into resource-stricken areas.”

To irrigate her tree crops, Montes relies on groundwater and receives some surface water from Merced Irrigation District. She said farmers are worried about the impacts of SGMA on land values and the economy.

In Kern County, Josh Polich of Anthony Vineyards, a grower, packer and shipper of organic and conventional table grapes based in Bakersfield, said the farm’s approach to cover crops is “planting with a purpose.”

For the past 15 years, the farm has planted cover crops, including grasses, grains and legumes to increase crop nutrients, activate the soil, support pest management and reduce inputs.

“The cover crop suppresses our weeds and builds the organic matter, which is what holds the water,” Polich said, adding the farm’s cover crops are dryland farmed and do not rely on irrigation district water or groundwater. “In the SGMA era, we’re not using any more water by having a cover crop. We’re basically taking rainwater that would be evaporated.”

Polich said GSAs should consider cover crops and “understand the science, because those with cover crops are putting more water into that (groundwater) basin.”

To support sustainable groundwater management, the report authors recommended integrating cover crops into policies and incentive programs and bolstering data infrastructure. They said proposals should be developed to establish conditions to help growers adopt cover cropping within SGMA.

Discussing whether more farmers will plant more cover crops, Rossow said, “It’s peer-to-peer networking that is really going to move the needle with cover crop adoption.”

Glenda Humiston, vice president of the University of California Agriculture and Natural Resources, said the UC collaborated with state agencies and private-sector partners to include different perspectives and the use of best science and viable policy options.

“By taking a comprehensive view, we can advance recommendations for cover crop policies that help us meet multiple goals, manage our natural resources more effectively and avoid unintended consequences,” Humiston said.

The report on cover cropping in the era of SGMA, assembled by Sustainable Conservation, emerged from a process developed by the California Association of Resource Conservation Districts, California Department of Food and Agriculture, Natural Resources Conservation Service of California and UC ANR.

To view the report, visit https://suscon.org/wp-content/uploads/2024/05/SC-Cover-Crop-SGMA-Report.pdf.

(Christine Souza is an assistant editor of Ag Alert. She may be contacted at csouza@cfbf.com.)