We compared the crop yields and economic performance of organic, lowinput, and conventional farming systems over an eight-year period based on research from the Sustainable Agriculture Farming Systems (SAFS) Project in California's Sacramento Valley. The SAFS Project consisted of four farming-system treatments that differed in material input use and crop rotation sequence. The treatments included four-year rotations under conventional (conv-4), low-input, and organic management, and a conventionally-managed, two-year rotation (conv-2). The four-year rotations included processing tomato, safflower, corn, and bean and a winter grain and/or legume doublecropped with bean. The conv-2 treatment was a tomato and wheat rotation. In the lowinput and organic systems, inorganic fertilizer and synthetic pesticide inputs were reduced or eliminated largely through crop rotation, legume cover crops, composted manure applications, and mechanical cultivation.All crops, except safflower, demonstrated significant yield differences across farming systems in at least some years of the experiment. Yields of tomato and corn, the most nitrogen (N)-demanding crops in the rotations, responded most years to the farming-system years treatments, while bean and the winter grain/legume displayed treatment differences less often and instead tended to vary more with yearly growing conditions. Nitrogen availability and/or weed competition appeared to account for lower crop yields in the organic and low-input systems in some years. The economics of all farming systems depended mainly on the costs and profits associated with tomato production. The most profitable system was the conv-2 system due to the greater frequency of tomato in that system. Among the four-year rotations, the organic system was the most profitable. However, this system's dependence on price premiums leads to some concern over its long-term economic viability. Among the low-input cropping systems, corn demonstrated clear agronomic and economic advantages over conventional production methods. Based upon these findings, we suggest that future research on organic and low-input farming systems focus on developing cost-effective fertility and weed management options based upon improved understanding of N dynamics and weed ecology.

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