The goal of Southern Minnesota Beet Sugar Cooperative is to optimize the factory’s capacity. To do this the grower’s goal is to raise enough high-quality sugar beets to meet the needs of the factory. This may occasionally mean that some sugar beet acres will not be harvested because of greater than anticipated root yield and a limited factory slice capacity. Little information exists on management practices for optimum field corn production following unharvested sugar beet. The objectives of this study were to determine if the unharvested beet roots need to be removed, if starter fertilizer would increase corn grain production, and if corn needs more nitrogen applied after unharvested beet roots compared to harvested beet roots. This trial was conducted as a randomized complete block with four replications and repeated over four years. Plots contained either harvested or unharvested beet roots from the previous growing season with all the fertilizer being applied to the corn in the spring based upon a two-foot soil sample.
All four years had very different environmental conditions. There was an interaction between treatment and year for corn grain yield. However, this interaction was in the magnitude of grain yield response. In all years, corn grown in plots where beet roots were not harvested had less grain yield than corn grown in plots where the beet roots were harvested. In all production years, the use of an extra 40 lbs of nitrogen per acre over the standard recommendation increased the corn grain yield in the plots where the beet roots were not harvested. The results from all years shows the importance of additional nitrogen for field corn production after unharvested beet roots because of the tie-up of nitrogen from the extra carbon left in the soil by the unharvested beet roots.