Effect of Field Management Practices on Disease Development, Soil Chemistry and Yield in Organic Tomatoes

The effects of different strategies for transition to organic tomato production on timber rot (Sclerotinia sclerotiorum), early blight (Alternaria solani)and Septoria leaf spot (Septoria lycopersici)incidence and severity, soil chemistry and yield were studied. The four cropping strategies considered were 1)low input cover crop/fallow, 2)low input perennial mixed hay, 3)moderate input field vegetables, and 4)high input extended season vegetables under high tunnels. Each was considered with and without compost applications. Each cropping strategy was carried out for 3 years, and then all plots were cropped to fresh market tomato, cultivars Florida 47 and Mountain Spring in the fourth year. Annual applications of composted dairy manure during the 3-year transition and prior to tomato planting resulted in significantly less timber rot and early blight in high tunnels, and Septoria leaf spot in open field plots under the mixed hay transition strategy, than in the non-amended plots. Tomatoes in the mixed ay transition strategy tended to have less Septoria leaf spot than those in the open fallow and vegetable transitions. Septoria leaf spot was significantly higher in Mountain Spring than in Florida 47 in open-field plots. Transition strategy generally did not affect soil fertility, but, in all cases, compost amendment significantly increased soil C, N and other nutrients. Compost amendment in the each cropping strategy significantly increased total and marketable yield for green to pink and light red to red maturity stages of both cultivars. The high-tunnel vegetable cropping strategy significantly increased to total and marketable yield for both cultivars. There were no significant differences among cultivars in the total and marketable yield.