# Calculating Fertilizer Rates

## Steps to Calculating Fertilizer Application Rate

Example is for a 40 foot by 100 foot lawn area, using a 20-2-2- fertilizer.

## Fertilizer Application Rate Table

Because soil test recommendations may not exactly match any fertilizer select a fertilizer that gives comparative amounts of nitrogen, phosphate and potash. In fertilizer application, it is most important to match the nitrogen requirement. The amount of fertilizer to apply that will give the recommended amount of nitrogen can be obtained from Table 1.

 Table 1. Amount of fertilizer to apply based on actual nitrogen recommendations Fertilizer Grade 0.1 pound N per 100 square feet 0.2 pound N per 100 square feet 1 pound N per 1,000 square feet 45-0-0 (urea) 0.2 0.4 2.2 37-3-3 0.3 0.5 2.7 36-6-6 0.3 0.6 2.8 33-0-0 0.3 0.3 3.0 32-4-4. 32-3-10 0.3 0.6 3.1 30-4-4, 30-0-10 0.3 0.7 3.3 28-3-3, 28-4-6 0.4 0.7 3.6 27-7-7, 27-3-3 0.4 0.7 3.7 25-5-5, 25-3-12 0.4 0.8 4.0 24-8-16, 24-0-15 0.4 0.8 4.2 22-4-4, 22-6-3 0.5 0.9 4.5 21-0-0, 21-3-12 0.5 1.0 4.8 20-20-20, 20-4-8 0.5 1.0 5.0 19-19-19,19-11-12 0.5 1.0 5.3 18-6-12, 18-3-6 0.6 1.1 5.6 16-8-8, 16-4-8 0.6 1.3 6.3 15-15-15, 15-5-5 0.7 1.3 6.7 13-3-9, 13-25-12 0.8 1.5 7.7 12-12-12, 12-4-4 0.8 1.7 8.3 10-10-10, 10-20-10, 10-5-5, 10-10-20 1.0 2.0 10.0 6-12-12, 6-2-0 1.7 3.3 16.7 5-10-10, 5-10-5 2.0 4.0 20.0 Example: If the nitrogen recommendation is for 0.1 pound Nitrogen per 100 square feet, and the fertilizer grade selected has a ratio of 18-6-12 (column 1), apply 0.6 lbs. of this fertilizer per 100 sq. ft. Note: Two cups (one pint) of dry fertilizer weight about 1 pound.

CMG GardensNotes on fertilizers

CMG GardenNotes on soil amendments

CMG GardenNotes on soil management

• CMG GardenNotes are available online at www.cmg.colostate.edu