Fertilizer Calculator

Quantity of Nutrient Required per Acre (pounds)
Percentage of Nutrient in Fertilizer (%)
Width of Planting Bed (Feet)
Length of Planting Bed (Feet)
Pounds of Fertilizer to Apply per Acre
Pounds of Fertilizer to Apply per 1,000 Square Feet
Ounces of Fertilizer to Apply per Square Foot
Pounds of Fertilizer to Apply per Bed


* Formula: (Recommended rate per acre X 100) / % nutrient per lb = lbs of fertilizer per acre

There are several ways to use this calculator. Some examples are given below.

Lime

This is an example of how to use it for determining the amount of lime to apply to a bed based on soil test recommendations. There is an explanation of soil test reports at this link; Soil Test Notes
This is a copy of the soil test report for a new bed we will be raising tomatoes on;
soiltestLime
Our soil test came back with a soil ph of 5.9 in an area for a new tomato bed. The recommendation was for 2.5 tons of lime per acre to bring the ph into range for vegetable crops. There are 2,000 lbs in a ton, so the recommendation is for 5,000 lbs of lime per acre. The type of lime recommended was unspecified AG Lime and is considered to be a 100% concentration. The size of the bed is 30'x 80'. Click "Show Result" and the output is given in pounds per acre, Pounds per 1,000 square feet, Ounces per square foot, and Pounds for the bed size we have entered. In this case we need to add about 275 pounds of lime to the 30'x 80' bed.
fertcalcLime

Fertilizers, Nitrogen

soiltestN
The recommended Nitrogen ammendment for the bed is 80 lbs of N per acre. We will be using Harmony with an assay of 5-4-3, or 5% N, 4% P, 3% K. Lets start by figuring how many pounds of Harmony would be required to get the equivalent of 80 pounds per acre on our 30' x 80' bed.
fertcalcN
It will take 88 lbs of Harmony to meet the N requirement. Notice that it would take 1600 lbs of Harmony at a 5% N concentration to get 80 lbs of N per acre.

Fertilizers, Phosphorous, P

soiltestP
The recommended Phosphorous ammendment for the bed is 100 lbs of P per acre. Again using Harmony with an assay of 5-4-3, or 4% P. Figuring how many pounds of Harmony would be required to get the equivalent of 100 pounds of P per acre on our 30' x 80' bed. Notice I changed each of the first two inputs to 100 lbs and 4% respectively.
fertcalcP1
It would take 138 lbs of Harmony to meet the P requirement. But if we do that we'll overload on N. Enter 64 lbs per acre in the top box and you'll see that it works out to 88 lbs of Harmony, which is what we needed to use to meet the N requirement. We'll need to find a way to get the remaining 36 lbs/acre of P without adding N.
fertcalcP

Fertilizers, Potassium

The recommended Potassium ammendment for the bed is 50 lbs of K per acre. Harmony has 3% K. Again changing both of the first two inputs to 50 lbs and 3% respectively and we need 91 lbs of Harmony to get the K ration recommended. At 88 lbs of Harmony in the bed we would have the equivalent of 48 lbs per acre vs the 50 lbs/acre recommended, well within the 10% variability considered acceptable.
fertcalcK

88 lbs of Harmony 5-4-3 will meet the soil test requirements if we can find a source of P to finish out the phosphorus requirement. Soft Rock Phosphate has an assay of 0-3-0. Plug in 36 lbs/acre in the "Quantity of Nutrient Required per Acre" box, and 3% in the second box. Click "Show Result", we'll need 66 lbs of 0-3-0 Soft Rock Phosphate and 88 lbs of 5-4-3 Harmony to meet the fertilizer requirement.