AG-ALARM: Cover crops offer water retention benefits ~ MAVEN’S NOTEBOOK

By Christine Souza, Ag Alert

As farmers across the state prepare for expected cuts to groundwater supplies under the Sustainable Groundwater Management Act (SGMA), they are trying to make the most of 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 on her farm near Snelling to improve soil health and attract beneficial insects, and she can now conserve water.

“Every percent increase in soil organic matter can store 75,000 to 90,000 liters of water per hectare,” Montes said of the water-holding capacity of soils planted with cover crops. “By covering the soil, we get much better water penetration.”

Cover crops, which are non-yielding crops grown to cover the soil and enrich soil diversity, have great potential for water conservation through improved water holding capacity and infiltration, according to a report entitled “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 growing cover crops and offers recommendations to close knowledge gaps and reduce policy barriers that prevent wider adoption of cover crops.

The report’s authors note that management actions by local groundwater protection agencies (GSAs) could have unintended consequences, such as preventing the planting of cover crops, an agricultural practice known for its soil health and other benefits.

The report notes that up to 40 percent of California’s total water use is for agricultural purposes and that only five percent of the state’s cropland uses practices such as cover crops. Large-scale cover cropping would have a positive impact and save more water.

Citing research conducted in California and the Mediterranean, the report says that planting cover crops increased water infiltration into the soil and reduced runoff by 40 percent or more, respectively.

Although the report noted that water use by cover crops is variable and can depend on many factors, it said that evapotranspiration from cover crops can be negligible compared to bare soil in perennial and annual systems.

Montes said her farm has always grown some cover crops, but last year she planted the soil-improving plants between all the rows of crop trees so no soil was left bare.

When the soil is planted with a cover crop, it lowers soil temperatures by 20 to 40 degrees, Montes said. Citing other benefits, she said the orchards have increased soil diversity and improved plant nutrition.

“It doesn’t matter if you grow organically, regeneratively, conventionally or whatever, the principles of healthy soil are universal,” she said.

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

“Properly managing a cover crop by avoiding excessive amounts of water really helps keep more water within the boundaries of the GSA,” said Silas Rossow, president and co-owner of California Ag Solutions. He said the only way to improve water use efficiency is to have healthy soil.

Leaving the soil fallow and not planting a cover crop is a missed opportunity to maximize water use on the farm, according to Rossow. The agricultural company began experimenting with different ratios of cover crop-seed mixes in commercial almond orchards in the fall of 2015.

“In 2015, the SGMA had just been passed, but it wasn’t on our radar yet,” Rossow said. “We soon realized that cover crops are extremely useful and can be used in resource-poor areas.”

Montes uses groundwater to irrigate her tree crops and gets some surface water from the Merced Irrigation District. She said farmers are concerned about the impact of the SGMA on property values ​​and the economy.

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

Over the past 15 years, the farm has grown cover crops, including grasses, grains and legumes, to increase crop nutrients, activate the soil, aid pest control and reduce input use.

“The cover crop suppresses our weeds and builds up the organic matter that holds water,” Polich said, adding that the farm’s cover crops are grown in dryland and do not rely on water from irrigation areas or groundwater. “In the SGMA era, we no longer use water through the cover crop. We are basically using rainwater that would otherwise evaporate.”

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

To support sustainable groundwater management, the report’s authors recommended integrating cover crops into policies and incentive programs and strengthening data infrastructure. They said proposals should be developed to create conditions that help farmers adopt cover crops within the SGMA.

When asked whether more farmers will plant more cover crops, Rossow replied: “It is the peer-to-peer networks that will make the decisive contribution to the adoption of cover crops.”

Glenda Humiston, University of California vice president for agriculture and natural resources, said the UC is working with state agencies and private sector partners to incorporate diverse perspectives and leverage the best science and actionable policy options.

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

The report on Cover Cropping in the Era of SGMA, compiled by Sustainable Conservation, is the result of a process developed by the California Association of Resource Conservation Districts, the California Department of Food and Agriculture, the 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 Ag Alert’s deputy editor. She can be contacted at [email protected].)