The purpose of this project was to evaluate the advantage of late split nitrogen (N) application in corn. Ongoing efforts to reduce N losses from farmland and the high cost of N fertilizer have increased the interest in the use of side-dress and split applications of nitrogen in corn production. Theoretically, applying some or all of the nitrogen requirements at side-dress timing when corn is in rapid N uptake stage can reduce possible N losses that would occur from pre-plant applications and result in more efficient use of nitrogen. Current side-dress timing based on the pre-side-dress nitrate test (PSNT) has proven to be only moderately successful in predicting nitrogen requirement. Research has indicated that nitrogen use efficiency may be improved by splitting nitrogen application between pre-plant/planting timing and a delayed side-dress application at the 12-14 leaf stage of corn. Some fertilizer dealers are now equipping high clearance sprayers with drop pipes and YDrop technology to side-dress corn without injection. Little field data exists that supports this approach. There is a risk to late side-dress application if weather conditions are wet. One approach to mitigate some of this risk is to apply most of the nitrogen required to meet the ‘average’ needs of corn yield expectation at pre-plant, and apply side-dress application as a top-up at a later crop stage so that seasonal growing conditions can be accounted for in the final determination of N requirements. The rate of top-up could be adjusted for weather conditions, yield potential or some other assessment such as optical reflectance (e.g. NDVI, Green seeker). This project was used to further explore these theories.

Read the entire report here: Improving Corn Nitrogen Management by Delayed Side-dress Application