Evaluating Corn Based Prediction Tools to Identify Adequacy of Soil Residual Nitrate for Wheat Establishment in the Mid-Atlantic.

Optimizing fertilizer nitrogen (FN) rates for corn (Zea mays, L.) are a priority for producers. However, due to environmental factors that vary annually, optimum FN rates are difficult to predict accurately early in the growing season allowing for potential residual nitrate (NO₃^-) remaining after corn harvest. Winter wheat (Triticum aestivum, L.) planted after corn is ideally suited to utilize residual NO₃^-. However, many farmers in the Mid-Atlantic will use 20-40 kg ha^-1 of FN at wheat planting without consideration to soil  NO₃^- level.  We hypothesize that there are sites following corn where residual NO₃^- is adequate for wheat establishment without using fall FN. Soil residual NO₃^-can be determined by analysis. However, waiting for lab results can be a limitation during the short period between corn harvest and wheat planting. Plants demonstrate visual and physiological signals that are reflective of their growing conditions including an indication of nitrogen availability. Corn-based tools which monitor plant greenness i.e., late season green leaf counts, chlorophyll meter readings, optical sensor readings and the corn stalk nitrate test (CSNT) can indicate adequacy of corn N fertilization and are being evaluated in this study. In addition, the quick-test known as the Pre-sidedress Nitrate Test (PSNT) that is used in the spring to determine side-dress FN requirement for corn is being tested.  This study was established to determine if the aforementioned indicators can identify sites that have adequate soil residual NO₃^- to establish wheat. This poster will summarize the results obtained through the summer of 2008 for this multi-year, multi-location study.