Enhanced Efficiency Nitrogen Fertilizer: Coated Urea

B. T. Geary, S. R. Fahning, B. G. Hopkins
Brigham Young University
INTRODUCTION
  • Nitrogen (N):
    • An essential plant nutrient (most commonly deficient)
    • Makes up about half of global fertilizer sales
    • Use efficiency is low, much is lost to atmosphere or leached 
  • Environmental concerns: greenhouse gases, reactive gaseous N, water quality
  • Enhanced Efficiency Fertilizers (EEF) should:
    • Increase N uptake by plants
    • Reduce environmental impacts of N fertilizers
    • Maintain or improve crop yield/quality
    • Be affordable (generally have higher cost, but needs to be offset by reduced rates and/or increased crop value)
Photo by International Plant Nutrition Institute
 
PRINCIPLES OF N EEF USE
  • EEFs have been effective to improve crop yield and/or quality, but not under all circumstances
  • EEFs vary in mode-of-action and, thus, vary in effectiveness in various sitations 
  • Greatest benefit is where N loss risk is high
  • Another potential benefit where fertilizer seedling damage can reduce yields
  • Match EEF release with crop N uptake patterns
  • Likelihood of response increases with species with relatively small, inefficient root systems (such as potato & turfgrass)
  • Potential yield loss if delayed N availability into late season, especially for some sensitive crops (such as sugar beet & winter wheat)
  • EEFs that depend on temperature driven microbial activity and chemical reactions may release slowly in the cool spring
  • EEFs that are inhibitors are only effective on certain portions of the N cycle.
    • Urease inhibitors only impact urea (eg. UAN is only 50% urea and, as such, half of the product is unprotected by the inhibitor) 
    • Nitrification inhibitors only impact ammonium (eg. 25% of UAN is in the nitrate form and this portion is unprotected by the inhibitor)
SUMMARY

Overall EEFs are valuable and have their place in crop production. With this being said, it is crucial to understand and balance the costs to find if it will be worth the extra cost through increased crop yield and quality. Through the use of EEFs, crop yields can increase with the correct usage and placement, but the situation varies and there is not a general practice that will work everywhere. Lastly one of the large reasons for these products is that they can potentially protect the environment from the losses and leaching of fertilizers. We should be wise with resources we have and use them efficiently to sustain future use. 

 
References
  • Brown, B. 2009. Slow-release nitrogen in Pacific Northwest wheat production systems. Crops and Soils. 42:27-28.
  • Ebelhar, S.A., C.D. Hart and J.D. Hernandez. 2005. Nitrogen source and rate effects on corn in southern Illinois. http://www.cropsci.illinois.edu/research/rdc/dixonsprings/pdfs/ESN%20Effects%20on%20Corn%20in%20Illinois%2005.pdf.
  • Grant, C.A. and R. Dowbenko. 2008. Enhanced Efficiency Fertilizers. Reduced Tillage Linkages. http://www.reducedtillage.ca/docs/Enhanced_Efficency_Fertilizers.pdf. 22 pp.
  • Hopkins, B.G. 2020. Developments in the use of fertilizers. In Rengel, Z. (ed.) Achieving Sustainable Crop Nutrition. Ch. 19: 555-588. Cambridge, UK: Burleigh Dodds Science Publishing. (ISBN: 978 1 78676 312 9; www.bdspublishing.com).
  • Hopkins, B.G., C.J. Rosen, A.K. Shiffler, and T.W. Taysom. 2008. Enhanced efficiency fertilizers for improved nutrient management: potato (Solanum tuberosum). Crop Manag. http://www.plantmanagementnetwork.org/cm/element/cmsum2.asp?id=6920 https://doi:10.1094/CM-2008-0317-01-RV.
  • LeMonte, J.L., T.W. Taysom, B.G. Hopkins, V.D. Jolley and B.L. Webb. 2009. Residual soil nitrate and potato yield with polymer coated urea. In: Proceedings, Western Nutrient Management Conference. Vol 8. March 4-5. Salt Lake City, Utah. p. 77-78.
  • Tiessen, K.H.D., D.N. Flaten, C.A. Grant, R.E. Karamanos and M.H. Entz. 2005. Efficiency of fall-banded urea for spring wheat production in Manitoba: Influence of application date, landscape position and fertilizer additives. Canadian Journal of Soil Science. 85:649-666.
CATEGORIES OF N EEFs
ESTIMATES FOR LONGEVITY