How to Calculate Fertilizer Rate Per Acre

Putting the right amount of fertilizer in the ground is good stewardship of money and the environment. Using too much will cost you more than you need to spend, and may wash away to pollute areas that don't need any fertilizer. Fertilizers are made up of a variety of substances, and calculating just how much of that is the actual fertilizer versus other material is important. For example, if you want to use 5 lbs. of nitrogen on an acre field and you are using ammonium sulfate at 21 percent nitrogen you would use this calculation.

Instructions

1. • 1

     Divide the total number of pounds of nitrogen you need by the percentage of nitrogen in your fertilizer. In this example, this is 5 divided by .21.

   • 2

     Calculate the answer at 23.8 lbs. of ammonium sulfate to reach 5 lbs. of nitrogen.

   • 3

     Change the total number of pounds of fertilizer and the percentage found in the product according to your needs.