Analysis Or Fertilizer Grade

By The Old House Web

Analysis Or Fertilizer Grade

The analysis or grade refers to the minimum amounts of N, P2O5 and K20 in the fertilizer. A 10-10-10 fertilizer would contain 10 percent nitrogen (N), 10 percent P2O5 equivalent and 10 percent K2O equivalent. In 50 pounds of 10-10-10, there are 5 pounds of N, 5 pounds of P2O5 equivalent and 5 pounds of K2O equivalent.

In the future, fertilizers will most likely be expressed entirely in the elemental form--N-P-K--rather than the N- P2O5-K2O used today. Then today's conventional 10-10-10 fertilizer will be a 10-4-8 fertilizer. The percentage of P in P2O5 is 43.6, so multiplying the pounds of P2O5 by .436, gives the pounds of actual P in a fertilizer. The percentage of K in K2O is 83, so multiplying the pounds of K2O by .83 gives the actual K in a bag of fertilizer.

If any of these elements are not present in the formulation, a zero would appear in the analysis. For example, ammonium nitrate has no phosphorus or potassium, and its analysis is 33-0-0.

To compute the number of pounds of nitrogen in a 100 pounds bag of ammonium nitrate (NH4NO3) multiply 100 x .33, which equals 33 pounds of nitrogen. Dividing 33 by the unit cost yields cost per pound of nitrogen.

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