Conservation tillage (CT) row crop production is currently not widely adopted in California. Recently, however, interest in evaluating the potential of CT systems to reduce production costs and improve soil quality is growing in many areas in the state. In 1997 and 1998, we evaluated four cover crop mulches (rye/vetch, triticale/vetch, Sava medic, and Sephi medic) in a CT-transplanted tomato system relative to the conventional winter fallow (CF) practice. In both years, yields were comparable to the CF under the triticale/vetch and rye/vetch mulches. Earthworm populations after 2 years of CT production were increased 2- to 5-fold under mulches relative to the CF system. Soil carbon was increased by 16% and 6% after 2 years of CT production under the triticale/vetch and rye/vetch mulches, respectively. Weed suppression under the triticale/vetch and rye/vetch was comparable to the CF with herbicide system early in the season in both years but was maintained through harvest in only one season. Soil water storage (0-90 cm) was similar at the beginning of the tomato season in triticale/vetch, rye/vetch, and fallow plots but was higher under the mulches during much of the last 45 days of the 1998 season. Further refinement of CT practices in California's vegetable production regions is needed before wider adoption is likely.
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