Nitrogen (N) is essential to plant growth. As a constituent of protein, it is instrumental in critical plant functions from germination to senescence. As a component of the chlorophyll molecule, nitrogen has a primary role in photosynthesis and therefore yield accumulation in crops. Unfortunately, this critical plant nutrient can be easily lost from the soil by leaching or denitrification when excessive rainfall occurs (Figure 1).
When early-season N losses occur, or wet conditions prevent applying N early, rescue applications can be an effective remedy for corn producers. Another benefit to late application is the reduced risk of N loss and increased likelihood of N availability when the corn crop needs it most. This Crop Insights will discuss evaluating N losses, best practices for rescue N applications and expected corn response. Prior articles in this N-management series have discussed N rates (Shanahan, 2011) and N timing (Butzen, 2011).
Another way to estimate whether a rescue N application is needed is to use the Nitrogen Loss Scoresheet developed at the University of Missouri (Scharf, 2008). After estimating the amount of nitrate lost by either method above, a better decision can be made as to whether a rescue N application is needed and how much additional N is required.
Binder, D.L., D.H. Sander, and D.T. Walters. 2000. Maize response to time of nitrogen application as affected by level of nitrogen deficiency. Agron J 92:1228-1236.
Bremner, J.M. and K. Shaw, 1958. Denitrification in soil. II. factors affecting denitrification. Journal of Agricultural Science (Cambridge) 51:40.
Butzen, S. 2011. Nitrogen Application Timing in Corn Production. Crop Insights vol. 21 no. 6. Pioneer Hi-Bred, Johnston, Iowa.
Camberato, J. and R.L. Nielsen. 2010. Soil sampling for assessing plant available N following excessive rain or flooding. Corny News Network, Purdue Extension.
Emmert, D. 2009. Using canopy reflectance to monitor corn response to nitrogen and the effects of delayed nitrogen application. Master's Thesis. Purdue University.
Ferguson, R.B. 2006. Nutrient management for agronomic crops in Nebraska. Extension publication EC 155. University of Nebraska- Lincoln.
Fernandez, F. 2009. Have I lost my nitrogen this spring? the Bulletin No. 7, May 8. University of Illinois -Urbana.
Lee, C., J. Herbek, G. Schwab, and L. Murdock. 2007. Evaluating flood damage in corn. University of Kentucky Cooperative Extension Service Publication AGR-193.
Miller, H.F., J. Kavanaugh, and G.W.Thomas. 1975. Time of N application and yields of corn in wet, alluvial soils. Agron J 67:401-404.
Nelson, K.A, P. Scharf, W.E. Stevens, B.A, Burdick. 2010. Rescue nitrogen applications for corn. Soil Sci Soc Am J 75:143-151
Nielsen, R.L, E. Miller, J. Camberato. 2011. Personal Communication.
Russelle, M.P., R.D. Hauck, and R.A. Olson. 1983. Nitrogen accumulation rates of irrigated maize. Agron J 75:593-598.
Sawyer, J. 2007. Measuring the nitrogen status - 2007. Iowa State University Integrated Crop Management Newsletter, May 14, 2007.
Scharf, P. 2008. Soil samples show N loss. Integrated Pest and Crop Management Newsletter. Vol 18. No. 11, June 27, 2008.
Scharf, P. 2008. Nitrogen loss scoresheet. Integrated Pest & Crop Management Newsletter, University of Missouri.
Schwab, G. and L. Murdock. 2010. Estimating N losses in wet soil. Grain Crops Update. May 6, 2010. University of Kentucky Ag Extension (UK-Ag).
Shanahan, J. 2010. Using Crop Sensors to Improve Corn Nitrogen Management. Crop Insights vol. 20 no. 6. Pioneer Hi-Bred, Johnston, Iowa.
Shanahan, J. 2011. Determining Optimum Nitrogen Rates for Corn. Crop Insights vol. 21 no. 2. Pioneer Hi-Bred, Johnston, Iowa.
Strachan, S. 2004. Corn Grain Yield in Relation to Stress During Ear Development. Crop Insights Newsletter, Vol. 14, No. 1, Pioneer Hi-Bred International, Johnston, Iowa.
Thomison, P. 2010. "Late" applications of nitrogen to corn. In C.O.R.N. Newsletter 2010-17, The Ohio State University Extension.
Torbert, H.A., R.G. Hoeft, R.M. Vanden Heuvel, R.L. Mulvaney, and S.E. Hollinger. 1993. Short-term excess water impact on corn yield and nitrogen recovery. Journal of Production Agriculture 6:337-344.
1 The author gratefully acknowledges John Shanahan and Wade Givens for providing the precipitation map (Figure 1).