While corn prices have been robust this year, nitrogen prices have kept pace, prompting producers to do all they can to be more efficient in their fertilization strategies.

Side-dressing, adjustment of nitrogen levels according to a site’s yield potential, and soil water availability for nitrogen up-take all are considerations when deciding how to get the most bang from your buck when fertilizing corn.

And while two years of research isn’t enough to make a definitive judgment on the best strategy, it does provide a hint as to what might influence corn response to nitrogen applications.

Auburn University researchers and Extension specialists recently released the results of a two-year study on nitrogen application on corn at two locations in Alabama.

In 2009 and this past year, the study was carried out at the Tennessee Valley Research and Extension Center in Belle Mina in north Alabama and at the E.V. Smith Research Center in Shorter, located in the central part of the state.

The main goal of each study was to evaluate the impact of nitrogen fertilizer rates and timing on grain yield of two corn hybrids under irrigated conditions.

The experiment consisted of 16 different treatments where the nitrogen was applied in three different ways: 1) all nitrogen applied at pre‐plant; 2) half of the total nitrogen was applied pre‐plant and the other half in a side‐dress application at the V6 growth stage; and 3) one-third of the total nitrogen was applied pre‐plant and the remainder in a side‐dress application at the V6 growth stage.

The corn hybrids planted were Pioneer 31P42 and DeKalb 67‐87.

Experimental plots were four rows wide by 30 feet long. Treatments were replicated four times in a randomized complete block design. Yield data was recorded after harvesting the middle two rows of each plot.

Because there were no yield differences between hybrids in respect to the nitrogen treatments, average yield data for both hybrids were presented in the study.

Yield and the amount of rainfall during critical crop growth periods — tasseling and grain filling — differed between years. Overall, yield was higher in 2009 than in 2010. In 2009, corn responses to high nitrogen rates resulted in higher yield than in 2010.

When yield data was averaged over total nitrogen applied independent of the split, there were no yield increases above 150 pounds per acre at the central Alabama location.

For both years, the yield reached a plateau at relatively high levels of nitrogen. In some cases, yield decreased as rate increased.

A different situation was observed at the north Alabama location in 2009 and 2010 with yield increasing as nitrogen rate increased.