Prior Winter Wheat Straw Management Effects On Processing Tomato Yield Are Not Due to Altered Nitrogen Dynamics.

The anticipated removal of crop residues to meet the demand for bioenergy sector may have an impact on subsequent crop productivity and quality.  A field experiment was designed to evaluate the response of processing tomato yield and quality to typical winter wheat management practices of: 1) leaving the straw in the field –control treatment, 2) physically removing straw after wheat harvest, or 3) leaving the straw in the field with a fall application of calcium ammonium nitrate at 34 kg N ha^-1 to encourage straw decomposition.  The experiment was a split-plot factorial design with wheat straw management as the main-plot factor and nitrogen fertilizer (0 or 145 kg N ha^-1 preplant broadcast incorporated) to the tomato crop as the sub-plot factor.  Over three site-years, marketable and total yield was significantly higher in the control than the straw-removed treatment (total yield 81.6 vs. 71.9 T ha^-1 y^-1).  The straw+fall N treatment (total yield 77.8 T ha^-1 y^-1) was not different from the other two straw treatments.  Differences in processing tomato yield appear to be related to observed differences in the quantity of straw residue on the soil surface in the following spring.  There was more straw visible in the control treatment compared to the straw-removed treatment, while the straw+fall N treatment was inconsistent between years.  Nitrogen treatment had a significant effect on total processing yield, soil mineral N, and plant N but there was no N x straw management interaction. In addition, there were no differences among straw treatments in soil mineral N (preplant, in-season, or at harvest) nor tomato shoot and fruit N (%N content and total kg N ha^-1).  Differences in yield between straw management treatments were not due to observed differences in N dynamics.  Thus, removal of crop biomass can negatively impact productivity of the subsequent crop.