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  4. 2007
  5. June

Fertilizer - Buy the numbers...

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Lately, forage producers have seen the cost of fertilizer increase sharply. Questions I have received in the past few weeks have included, "How do I figure out who's got the best price on fertilizer?" and "What did I just buy?" Let's look at how to determine the "true" cost of nitrogen by fertilizer source. If you have questions about comparing the phosphorus and potash, contact your Noble Research Institute soil and crops specialist for assistance.

To compare apples to apples, we first need to calculate the cost of nitrogen in a fertilizer product. Each fertilizer has an analysis that tells you the percent nitrogen (N) - phosphorus (P2O5) - and potassium (K2O) by weight. Urea is 46-0-0, and ammonium nitrate is 34-0-0. Both of these products contain nothing but nitrogen, but the nitrogen is at different percentages. Urea contains 920 actual pounds of nitrogen per ton, and ammonium nitrate contains 680 actual pounds of nitrogen by ton (2,000 x 46% = 920 and 2,000 x 34% = 680). How much actual nitrogen is in a fertilizer with an analysis of 27-0-0? Take the pounds in a ton (2,000) and multiply by the percent of actual nitrogen in the analysis (27%). Each ton of actual material that you purchase of 27-0-0 has 540 actual pounds of nitrogen.

Depending on the fertilizer analysis, there are large differences in the amount of actual nitrogen being purchased, so we need to break this down to a cost per actual pound of nitrogen.

For example, if urea is $412 a ton, ammonium nitrate $370 a ton, and 27-0-0 is $330 a ton (I am sure the prices have increased by now), we take the cost per ton and divide it by the pounds of actual nitrogen in a ton to determine the cost per pound of actual nitrogen. For urea, divide $412 by 920 and we are paying 45 cents per pound of actual nitrogen. For ammonium nitrate, divide $370 by 680 and we are paying 54 cents per pound of actual nitrogen. For 27-0-0, divide $330 by 540 and you see we are paying 61 cents per pound of actual nitrogen. While the 27-0-0 is the least expensive per ton, the same money would purchase 35 percent more nitrogen as urea, or 13 percent more nitrogen as ammonium nitrate. Not that I am picking on the 27-0-0, but it doesn't sound like the "best buy" anymore, does it?

When purchasing fertilizer, figure your price by the pound of nutrient - not the ton of product!

Cost Per Ton of the Fertilizer = Cost per Actual Pound of Nitrogen
Percent Nitrogen per Ton of Fertilizer x 2,000

If you have questions about the amount or type of fertilizer to use, do not hesitate to contact your Noble Research Institute soil and crops specialist.