February 12,2007

With demand for corn increasing along with ethanol production, Nebraska corn growers anticipate a much more positive economic outlook for 2007 than in recent years. By early February, the price for a bushel of corn was $3.60 to $3.80 — quite a change from a year ago when prices were closer to $2.00. At the same time, nitrogen fertilizer prices have dropped in some areas and may be less than in 2006.

 

Visit the UNL Soil Fertility and Nutrient Management Web site to download the new UNL Corn Nitrogen Recommendation Calculator and instructions.

Last winter (2005-2006) producers faced the rather unattractive combination of relatively expensive nitrogen fertilizer prices and low corn prices. This combination, coupled with research evaluating optimal fertilization rates for irrigated corn, led the University of Nebraska to adjust its nitrogen fertilizer recommendations for corn and sorghum.

Our base recommendation uses a price ratio of 8:1 - where the value of a bushel of corn is eight times the value of a pound of nitrogen fertilizer. For example, a corn price of $2.50/bu and a nitrogen price of $0.31/lb has a ratio of about 8:1. Nitrogen price per pound can be calculated from the price per ton, using the known nitrogen content of the fertilizer. Urea has a nitrogen content of 45%. A ton of urea contains 900 lb nitrogen. At a price of $350 per ton for urea, the price per pound of nitrogen is $0.39.

With the corn:nitrogen price ratios that existed in the spring of 2006, commonly in the range of 6:1 to 8:1, the economic adjustment to nitrogen fertilizer recommendations reduced rates by 20 to 40 lb/acre. These lower rates slightly reduced yield potential, but more importantly, they maximized profit.

With corn prices currently in the range of $3.60-$3.80/bu, and nitrogen fertilizer ranging from $0.25 to $0.45 per pound, the corn:N price ratio today can range as high as 13:1 to 15:1. This is certainly good news for corn growers in Nebraska; however, it means the economic adjustment added a year ago may generate recommendations of excessive nitrogen rates. At high corn:N price ratios, there may be slight increases in profit with higher fertilizer rates, but the incremental yield increase is relatively small, and the risk of leaving substantial residual nitrate-N in the soil becomes much higher. Consequently, we have added maximum (10:1) and minimum (5:1) values to the corn:N price ratio used in economic adjustments to nitrogen rates for corn. We believe these limits will not significantly impact profit potential for Nebraska producers, but will allow good stewardship, in that residual nitrate-N, which can leach and contaminate groundwater quality, will be minimized.

Economic adjustments to nitrogen fertilizer rates for corn are best made in the context of accurately accounting for all nitrogen sources. In Nebraska, the UNL recommendation procedure for corn is based on accurate soil sampling - every three to five years for organic matter, annually for residual nitrate-N - and accurate yield goal estimation, using at least five years of yield history. It is also important to account for other nitrogen credits which may be available - legumes as a preceding crop, nitrate in irrigation water and nitrogen derived from manure.

The most current nitrogen rate calculator for corn is available as a downloadable Excel spreadsheet from the UNL Soil Fertility and Nutrient Management Web site. If you have used this spreadsheet in the past, we encourage you to obtain the most recent version - UNL N calculator 2007.xls.

Richard Ferguson, Ken Cassman, Achim Dobermann, Gary Hergert, Charles Shapiro, Dan Walters, and Charles Wortmann
Soil Fertility Faculty