The key role of local and global farmer networks in the development of conservation agriculture in California.

This article chronicles the history of California's Conservation Agriculture Systems Innovation (CASI) Center and how it has increased agricultural sustainability in the San Joaquin Valley, a major production area for the United States, by using agroecological practices to reduce soil erosion and conserve soil moisture, champion systems thinking, and create networks of farmers, advisors, and researchers. Early conservation agriculture systems in the United States and other continents have informed CASI since its inception in 1998, with an emphasis on reducing soil disturbance for better soil structure and biological activity, retaining biomass on the soil to support soil life, and diversifying crops to enhance biodiversity. CASI includes >2200 farmers, private sector, university, public agency, and environmental group partners. With timelines of its core research and extension education programs, practice adoption trends, and resource quality impacts, CASI's specific accomplishments are described and compared with the dominant tillage-intensive conventional systems of the past 90 years for crops such as corn, small grains, tomatoes, cotton, dry beans, and melons. An associated 25-year research station trial has shown that no-tillage and cover crop practices maintain productivity, increase soil quality (e.g., soil carbon and nitrogen, aggregation, and infiltration), greatly reduce dust that is detrimental to human health, and decrease annual production costs by $50-$75 per acre. CASI tracked a 40-fold increase in the use of strip-tillage in dairy silage production during the early 2000s and average annual increases in cover crop seed sales of about 25% in recent years. Outreach, extension, and farmer and industry education programs of CASI include documentary films on YouTube, blogs, workshops, and on-farm demonstrations. Interactions with other groups and networks are described along with their support for CASI's momentum-building strategies for impacts. Conservation agriculture is increasing in Central California and continued policy support will enable farmers and institutions to work together to accelerate even greater adoption in the future.