06/01/2026
Useful info! And as always if you need help reading a soil sample just bring it in and we’ll be glad to read it for you and give you recommendations! Come see us!
Let's demystify the process of translating nitrogen ( N ), phosphorus (P), and potassium (K) soil test recommendations to how much of each product is actually applied.
Soil test recommendations list N, P, and K as the following on a per-acre basis:
-Nitrogen is simply listed as pounds of N
-P is listed as pounds of P2O5 (not as pounds of elemental P)
-K is listed as pounds of K2O (not as pounds of elemental K)
Conveniently, fertilizer bags list their chemical analysis in the same N-P205-K20 format. A bag of 13-13-13 contains 13% N by weight, 13% P2O5 by weight, and 13% K2O by weight.
We like to use high-analysis fertilizers to custom mix applications for each food plot so we're not over-applying some and under-applying others. This means we often use:
-Urea (46-0-0): contains 46% N by weight
-Triple super phosphate (0-46-0): contains 46% P205 by weight
-Potash (0-0-60) contains 60% K2O by weight.
So let's say our soil test calls for 80 # of N, 60 # of P2O5, and 40 # of K2O per acre.
On a 1-acre food plot, we would apply the following rates of each product:
-Urea (46-0-0): 80 # / 0.46 = 174 # of 46-0-0 must be applied
-Triple super phosphate (0-46-0): 60 # / 0.46 = 130 # of 0-46-0 must be applied
-Potash (0-0-60): 40 # / 0.6 = 67 # of 0-0-60 must be applied
If you had a 2.5-acre plot, simply multiple each above number by 2.5 to get:
435 # of 46-0-0
325 # of 0-46-0
168 # of 0-0-60
If you need to apply secondary nutrients such as Mg, Ca, or S, find a fertilizer that contains them and use the same process. Secondary nutrients are listed after N-P-K. For example, a typical ammonium sulfate analysis is 21-0-0-24S, meaning 21% by weight is N and 24% by weight is S.
Plug and chug if you are using fertilizer with a different chemical analysis. These calculations will still work.
