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Pressures ranging from government regulation of air, water and food to the often unsympathetic views of an urban populace have put increasing demands on farmers to adopt more sustainable practices. Yet there is no set formula for doing so; the best way to achieve sustainability varies according to region and climate, and in many cases is still under study. UC scientists and farmers are working in partnerships across the state to learn which farming systems are most successful and economically viable.

The Sustainable Agriculture Farming Systems Project is one of several newer, large-scale experiments that have contrasted idealized cropping practices with existing ones. The common objective of these experiments has been to develop and compare cropping systems substantially different from current practice, with each system following separate rules of management. Difficult conceptual and methodological issues arise when both development and research are objectives in a project, and when many factors change simultaneously.

Cover-crop nitrogen supply and weed management were the most important challenges facing low-input and organic farming systems when compared to conventional systems in the first 4 years of the Sustainable Agriculture Farming Systems project at UC Davis. Cover-crop timing and management using appropriate equipment were important for the success of transitional systems. The participation of local farmers ensured that optimal agricultural practices were used to manage all farming systems. Researchers regularly consulted grower-cooprators to determine “best farmer practices” of conventional, low-input and organic farming systems.

Growers converting from conventional to low-input and organic farming systems must rely on organic sources for adequate soil fertility. At the Sustainable Agriculture Farming Systems (SAFS) project at UC Davis, we measured soil fertility and biological parameters in four farming systems. By the end of the first 4 years, pH and percent nitrogen were consistently higher in organic and low-input than conventional plots for all crops. Levels of organic matter, phosphorus and potassium were significantly higher in the organic than conventional 2-year plots. Microbial biomass levels were consistently higher in organic and low-input systems, while plant parasitic nematode numbers were consistently lower. Nitrogen deficiency appeared to be a problem in organic tomatoes during the transition period. More research is needed into the dynamics of soil nutrient availability in low-input systems. For instance, we may need to develop new methods of assessing soil fertility in organically fertilized systems.

The conversion from conventional to low-input or organic crop production requires changes in pest control tactics. In a 5-year study, abundance of most pests did not change dramatically between conventional and low-input or organically managed systems, with a few notable exceptions. Organic and low-input plots suffered significantly greater damage from tomato fruitworm in 1989 and stink bugs in 1992. The major long-term effect has been on weeds. Weed control methods differ among the systems and have resulted in more barnyardgrass in low-input and organic systems and field bindweed and nightshade in conventional systems.

The economic component of the Sustainable Agriculture Farming Systems (SAFS) project at UC Davis compared the financial performance of low-input and organic farming systems to conventional systems. All of the systems have been profitable over the first 4 years of the project. However, nei- ther the organic nor lo w-input systems have been able to show equivalent profits to either of the conventional systems on a whole farm basis without organic price premiums.

The use of cover crops continues to increase as farmers seek to improve soil quality and reduce chemical inputs. Research and grower experience have shown that cover crops can provide multiple benefits related to soil protection, soil fertility, groundwater quality and pest management. Choosing the right cover crop is critical to successful cover cropping.