Sidedressing Corn Without N Will Level Playing Field

Corn with pre-plant N was greener early.

Published on: Jun 30, 2008

The farmer who operates the Corn Illustrated plots, Jim Facemire, Edinburgh, Ind., reported that you could make out the section where no pre-plant N was applied before planting. That was a conscious move so that the CI crew could compare per-plant applications vs. sidedressing at the normal sidedressing time early in the season.

We reported this observation in Corn Illustrated update last week. What’s different now is that the corn has been sidedressed which didn’t get any N pre-plant. We will watch and report how long it takes for colors to change, and how long before the sidedressing plot catches up with the first plot, if it does.

In theory, it should catch it and pass it at some point, at least in yield potential. That’s because urea was applied pre-plant on the first part of the plot. Even though it was just days before a heavy rain, Jim Camberato, Purdue University soil fertility specialist, says only the part of the urea already in the nitrate form, about one-fourth of the N in the material, should have been subject to significant loss. If his theory is right, the lower amount of N available should show up later in the season.

How much N is available is on the minds of farmers everywhere right now. Wherever there has been major flooding, but crop is still left, much of it is or was yellow. One observer noted that besides the drowned-out acres, the ag stats folks ought to b reporting the number of acres stunted or impacted by the heavy rains. It’s many of those fields that while still there, may not yield up to par.

The corn in our plot for this particular study was planted the last week of May. So it was sidedressed by still relatively small. Why did differences in color show up so rapidly?

Here are a few ideas, based upon comments by agronomists. First, corn in these plots follow seed corn. So there is likely little if any residual N left behind for new plants to use.

Second, no starter fertilizer was applied. The farmer’s system is not set up for starter fertilizer applications. His decision was made years ago. To see if it’s still valid, Farm Progress is participating in another study co-sponsored by Extension in Indiana that is testing starter vs. no starter fertilizer at various populations, on the same two hybrids used in the CI plots, These are small-scale, replicated, randomized plots.

Third, soils were warm since planting was late. The plants that emerged and found N there waiting for them no likely took off growing well. The true test will likely come later in the season, when roots determine if there is still enough N there or not to complete the primary task of the plant- filling ears.