Impact of Fall Cover Crops On Processing Tomato Yield and Quality, Pest Pressure, Nitrogen Availability, and Profit Margins.

To evaluate the effect of fall cover crops on subsequent processing tomato production, a field split-plot factorial design trial was conducted on a sandy loam, 3.5% OM soil.  The main- and split-plot factors were fall cover crop type and tomato ammonium nitrate fertilizer rate (10 or 150 kg N ha^-1 preplant broadcast incorporated).  Cover crops were planted each fall after three main crops (peas, sweet corn, spring wheat) in 2007-09 and 2008-10.  Treatments included a no cover crop control and cover crops of oat (Avena sativa L.), cereal rye (Secale cereale L.), oilseed radish (OSR) (Raphanus sativus L. var. oleiferus Metzg Stokes), and mix of OSR and rye (OSR+Rye) drilled at 80, 67, 16, and 9+34 kg ha^-1, respectively. The following spring in 2010 and 2011, the trial was disked twice, tomatoes transplanted two weeks later and typical grower practices for pest control were followed.  During both growing seasons, cover crop type or N rate did not influence the level of damage caused by two insect pests or the incidence and severity of one fungal and three bacterial diseases. At harvest, processing tomato fruit quality (rots, insect or disease damage, Agtron colour, pH or soluble solids) was not affected by cover crop treatments. The lack of a cover crop by N rate interaction in soil and plant nitrogen analyses at harvest suggests that growers may not need to modify N fertilizer rates to tomatoes based on cover crop type.  In both years, marketable yield in the no cover crop treatment was lower or not statistically different than all planted cover crops. Profit margins over both years were 1320 $ ha^-1 higher with OSR compared to the no-cover. Thus, results from a systems-based approach suggest that the cover crops tested had no observed negative impact on processing tomato production and may increase profit margins.