New research into nitrogen (N) use by corn plants may change the way growers think about N management practices.

 “Because of the importance of N uptake prior to flowering, when yield potential is first set, corn growers have traditionally targeted N availability to this period," says Jason DeBruin, DuPont Pioneer research scientist. “Late applications were often disregarded, as N for grain development was thought to originate from vegetative tissues rather than current uptake.”

However, Pioneer research conducted over the last five years has shown that N needed for grain development is derived from both remobilized N (from leaves and stalks) and continued N uptake from the soil. In fact, modern hybrids have very different patterns of N uptake compared to older hybrids – less of their total N supply is taken up early, and more is extracted during reproductive development.

“Studies from 20121 and 20132 showed that new hybrids took up 29% and 40% more N post-flowering, respectively, than older hybrids," explains DeBruin. 

In addition, Iowa State University studies indicated that at high yield levels (225 bu/acre), 70 lbs. of N/acre must still be taken up post-flowering to support grain development3. Without that additional soil-extracted N during grain fill, corn yields would be severely limited.

There are three steps growers can consider to help ensure adequate N availability:

·  Apply 70% of the total seasonal N requirement prior to planting to help provide sufficient N for vegetative growth.

·  Apply the last 30% of required N as late during the growing season as ground equipment allows, but generally by tasseling.

·  Add a nitrification inhibitor to the late application to help delay N release.

To learn more about nitrogen uptake in corn, see the Crop Insights on

1Ciampitti, I.A., and T.J. Vyn. 2012. Physiological perspectives of changes over time in maize yield dependency on nitrogen uptake and associated nitrogen efficiencies: a review. Field Crops Research 133:48-67.

2Haegele, J.W., K.A. Cook, D.M. Nichols, and F.E. Below. 2013. Changes in nitrogen use traits associated with genetic improvement for grain yield of maize hybrids released in different decades. Crop Sci. 53:1256-1268.

3Abendroth, L.J., R.W. Elmore, M.J. Boyer, and S.K. Marlay. 2011. Corn growth and development. PMR 1009. Iowa State University Extension and Outreach, Ames, Iowa.