Organic Vegetable Production as Affected by Compost Rate and Timing.

Long term organic vegetable plots were established at Tennessee Technological University’s organic research farm in 2007. The initial objective of the project was to determine optimum compost rate and timing of application (spring versus fall).  Tomato, squash, bell pepper, sweet corn, cabbage and onion yield results for the first two years of the study will be presented.  Four rates of compost (0, 10.7, 32.2, 53.7 Mg/ha, equivalent to 0, 4.8, 14.4 and 24.0 tons/acre) have been applied annually for two years to 144 plots that are 1.2m x 7.6m in a random block design. Organic practices are used on the plots, with cover crops and mulches utilized for weed control and soil management.  First year results show significant difference between compost rates, with the two highest rates having greatest yield in the tomato and squash plots while only the 0 rate was significantly lower in the pepper plots. Soil pH increased with increasing compost rate with the high rate having a pH of 6.8 compared to 5.8 in the control.  Second year vegetable and cover crop yield and soil analytical results will be presented and compared with first year data.  Thirty-six of the plots have compost applied in spring, while the other 108 plots have fall applied compost.  Organic vegetable yield and biomass and cover crop biomass based on compost rate and timing will be presented. Soil testing data will be presented with emphasis on pH, soluble salts, carbon and nitrogen to determine affect of compost on these components.