Selecting Fertilizers Based on Soil Test Results
Nutrient Analysis on Fertilizer Labels
Fertilizer labels display three numbers to show the percentage by weight of nitrogen (N), phosphate (which contains phosphorus, P) and potash (which contains potassium, K), always in that order (N-P-K).
To Select a Fertilizer Product That Provides Nutrients Recommended in Soil Test Results
(1) Look at the pounds of N-P-K recommended in the soil test results. For example, the results might recommend 15 lbs N + 5 lbs P + 10 lbs K. The amounts recommended are usually for 1000 square feet of area.
(2) Find a fertilizer with the same ratio of those numbers. For example, 15-5-10 is the same ratio as 3-1-2 or 12-4-8 or 9-3-6. Do the best you can.
(3) If the test results recommend adding N, base the amount needed on N:
1- In the left column, find the percent of N in the fertilizer product.
2- In the top row, find the pounds of N recommended in the test results.
3- Find the intersection in the table, to find pounds of fertilizer to apply.
NOTE: If N is not recommended to be added, then base step (3) on any nutrient that the test results do recommend adding.
NOTE: Add amounts as needed. For example, if the soil test recommends 8 lb N, find the amount of fertilizer that provides 4 lb N, and multiply by 2.
Pounds of Fertilizer Product Needed to Supply a Specific Number of Pounds of a Particular Nutrient to a Specific Area
|% of Nutrient
|Pounds of Nutrient Desired|
From the GardenPro Answer Book; revised and updated by Lois Berg Stack, Ornamental Horticulture Specialist, University of Maine Cooperative Extension.