Outcome Conservation tillage and cover crop systems for organic processing tomato production (Year 2)

This project investigated management strategies that combine conservation tillage and cover cropping practices for organic tomato production that could potentially reduce costs and improve long term fertility of organic fields. A 2-year field trial was conducted in an organic processing tomato field near Meridian, CA. Treatments compared 2 cover crop systems (legume mixture, legume/grain mixture) and 4 tillage practices (no-till, reduced tillage, strip tillage, conventional tillage). Results of the field experiment showed that weed pressure in the minimum tillage treatments and competition from regrowth of the cover crop reduced marketable fruit yields during the first season. Mineral nitrogen levels in the soil were also suppressed during the first growing season, which may have limited yields. In contrast, reduced tillage treatments had no effect on fruit yield in the subsequent year, presumably because the cover crop had more biomass, no regrowth and was terminated under moist soil conditions. Consequently soil mineral nitrogen levels were higher in all treatments during the second season. The grain/legume cover crop mixture provided the most surface residue in the reduced tillage treatments. However, the residue level was not sufficient to suppress weed growth. The results indicated that using the cover crops as a temporary mulch to suppress early weed growth and then incorporating the mulch to boost soil nitrogen levels as well as cultivate weeds, may be an economical management option for growers. Using the cover crop as a temporary mulch would also improve the timeliness of transplanting the tomato crop since most of the tillage needed to incorporate the cover crop before transplanting would be eliminated.

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