CORN Newsletter: 2004-09, April 13, 2004

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C.O.R.N Newsletter 2004-09
April 13, 2004 - April 20, 2004

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Which Source of Nitrogen is the Best?
by Robert Mullen


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This is an often asked question, which unfortunately does not have a simple answer. Like most agronomic questions, there is no all encompassing solution that will work equally across all field conditions and environments. When making a decision on a nitrogen (N) source, economics, soil conditions, and climate must all be considered. Nitrogen applied as anhydrous ammonia, urea, urea-ammonium nitrate (UAN), etc., if applied at equivalent rates of N, all contribute the same amount of N to the soil. Plants do not prefer one formulation over the other.

Anhydrous Ammonia

Because anhydrous ammonia (82% N) has historically been the cheapest source of N, it has been the most popular. Due to the nature of anhydrous, it must be injected into the soil which increases its cost of application. Improper sealing behind injection equipment can result in considerable losses of N. Care should also be taken to inject anhydrous at least 6 to 8 inches into the soil. This is especially important if planting just after application of N. Anhydrous ammonia can cause seed injury.

Dry Formulations

With the cost of anhydrous production within the U.S. rising, the price differential between anhydrous ammonia and alternative formulations has decreased. Urea (46% N) is the most popular dry source of N. Its high N analysis and cheap cost make it an attractive alternative to anhydrous ammonia. Caution should be exercised when surface applying urea in no-till production systems. Considerable losses of N by volatilization can occur, especially if dry weather follows application. Application of urea would ideally be followed by a small rainfall event or incorporation.

Ammonium nitrate (34% N) is another dry formulation consisting of 50% ammonium and 50% nitrate. Its popularity has decreased in recent years. In fact, some retailers no longer sell it in bulk. Ammonium nitrate is an attractive alternative to anhydrous because it does not contain any urea, meaning it is not susceptible to volatilization losses allowing for surface application. However, it is easily dissolved with very little surface moisture making it susceptible to leaching and denitrification.

Liquid Formulations

Liquid formulations of N, primarily as urea-ammonium nitrate (UAN – 28 and 32% N), have gained popularity in recent years. Its ease of application and handling as well as comparative pricing with dry formulations has aided its adoption rate. Due to the nature of UAN, broadcast application in no-till systems can result in considerable interception of the material by residue. Dribble applications of UAN can decrease this affect, or UAN can be injected below the soil surface. UAN is especially attractive as a source of N for sidedressing.

When selecting your source of N, consider all factors. The goal is to select the cheapest source that fits within your farming operation.

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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