What The Research Says About Post-tassel Nitrogen Applications

 

Optimal nutrient application timing can be hard to nail down. Should you apply everything at the beginning of the season? Sidedress? If so, when? Many people wonder about nitrogen applications late in the season, even after post-tassel, as a way to increase yield. The basic thinking is that the crop still needs to take up half of its total N at this point in the growing season. The truth is, in locations with a shorter growing season, like Minnesota, we have no evidence that post-tassel N applications have any advantage.

 

Research by the University of Minnesota evaluated nitrogen application timing and its effect on different soil types across Minnesota to evaluate differences in economic optimum N rate and see whether split applications were beneficial at certain times throughout the season. It showed that if conditions dry out in July or August, you can actually end up reducing corn yield because the yield potential of the crop is either compromised if there was no sufficient N for the crop earlier in the growing season or the sidedress N does not get to the root because of the lack of moisture.

 

The only situation where a post-tassel application before R1 may be beneficial to increase yield is if the crop is severely limited by lack of nitrogen. In those cases, however, carefully evaluate the potential return on investment, as the nitrogen application can’t make up for the yield potential already lost.