Estimating Fertilizer Amounts

Fertilizer instructions often are given as pounds of “actual nitrogen,” or some other nutrient. This can be confusing if you have a garden of unknown size and a bag of fertilizer. How do you know how much to put on?

For starters, you can assume that a pint of most chemical fertilizers weighs about a pound, and measure the fertilizer with two-cup (one pint) measuring cup from the kitchen.

For help in estimating the area of your garden, see How to Measure Area .

The percentage of each primary nutrient in the fertilizer is written on the label.

To find how much chemical fertilizer you need to provide a given weight of actual nutrient, divide the number of pounds of nutrient you need by the percentage of that element in the fertilizer.

For example, if you want to add 2 pounds of actual phosphate to your vegetable garden and your bag of fertilizer contains 20 percent phosphate. Divide the 2 pounds (the amount you want) by 20 percent (the percentage in the fertilizer): 2 divided by 0.20 equals 10. You will need to apply 10 pounds of the fertilizer to get the desired amount of phosphate.