Report: Benefits of Cover Crops May Outweigh Water-Use in California

Cover crops offer numerous benefits, including improved water infiltration, increased water storage, enhanced carbon capture, and better soil health, while also reducing runoff and erosion. These crops, planted between annual crops like tomatoes or among rows of tree and vine crops, are increasingly used despite concerns about their water consumption, especially since they don’t generate direct income.
 
Karen Ross, secretary of the California Department of Food and Agriculture, notes that cover crops are popular in the Healthy Soils Program because they provide many advantages, such as preventing soil erosion, enhancing soil health, suppressing weeds, controlling pests and diseases, and increasing biodiversity. Additionally, they can lead to increased profitability by reducing the need for other inputs, and they offer water-related benefits like improved infiltration and reduced runoff.

These benefits are particularly important in the San Joaquin Valley, where groundwater issues are severe. A new report assesses the water impacts of cover crops within the framework of the Sustainable Groundwater Management Act (SGMA), which aims to protect long-term groundwater resources. Ross emphasizes that although cover crops require some water, often supplied by rainfall, their numerous co-benefits make them worthwhile.

The report, created by a coalition including the California Association of Resource Conservation Districts, CDFA, Natural Resources Conservation Service of California, and UC Agriculture and Natural Resources, provides a comprehensive analysis of cover cropping practices in California's Central Valley under SGMA.

Cover Crops and Water Management

According to Daniele Zaccaria, a co-author and associate professor at UC Davis, wintertime cover cropping, which is typically rain-fed, doesn't necessarily increase water losses compared to bare ground. In fact, cover cropping can enhance soil-water dynamics, boosting soil water infiltration and storage while reducing surface runoff. To maximize these benefits with minimal water use, Zaccaria suggests more research is needed to understand how cover crops perform under various weather conditions.

Report Findings and Recommendations

The report’s authors addressed several key questions regarding the impact of cover crops on water cycles, how SGMA management accounts for these crops, and how to ensure that this practice remains viable for growers. The report synthesizes insights from over 100 multidisciplinary experts, policy analysis, interviews with Groundwater Sustainability Agency (GSA) staff, and contributions from over 30 authors. It offers recommendations to close knowledge gaps, integrate cover crops into policy and incentive programs, and strengthen data infrastructure to support sustainable groundwater management.

A critical recommendation is for the state to provide additional guidance to local GSAs, helping them navigate the complexities of groundwater management and optimize the use of cover crops within SGMA frameworks. This approach is vital for promoting sustainable water management practices, which are crucial for the agricultural and environmental resilience of the region.

Glenda Humiston, UC vice president for agriculture and natural resources, highlighted the collaborative nature of the report, which brings together perspectives from state agencies and private sector partners to offer the best science and policy options. By considering a broad range of factors, the report provides recommendations that help manage natural resources more effectively and avoid unintended consequences.

Sarah Light, a UC Cooperative Extension agronomy farm advisor and co-author of the report, emphasized that cover crops are a valuable tool for ensuring the resilience of California farms to climate extremes. She noted that understanding the role of cover crops in water budgets is essential to avoid discouraging their use in certain areas. This report offers guidance to GSAs and policymakers responsible for implementing SGMA in their regions.

The full report, “Cover Cropping in the SGMA Era,” is available for free download at Sustainable Conservation.

Sources: Sustainable Conservation, Morning AgClips
Photo: UCANR