fertilizer bag

Every fertilizer bag that you buy has a label called ” Guaranteed Analysis ” that gives you a list of nutrients in the fertilizer packed that bag. Reading and analysing the calculation of the nutrients is needed for the proper application of fertilizer that contains three nutrients -Nitrogen, Phosphorous, and Potassium. Before you use the fertilizer calculator, please watch the excellent youtube video on the topic of how to read a fertilizer bag label.

Video on How to Read Fertilizer Label?

Fertilizer Bags Nutrient Calculator

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What does N-P-K on the fertilizer bag stand for?

The N-P-K numbers listed on a fertilizer label on the front of the fertilizer bags, such as 16-2-3 represent the three primary nutrients (nitrogen, phosphorus, and potassium) as a percent of the fertilizer’s weight. The nutrients are present as nitrogen (N), phosphate (P2O5), and potash (K2O). In the example 16-2-3 fertilizer, the label tells you that:

  • 16% of the bag’s weight is composed of nitrogen
  • 2% of the weight is composed of phosphate
  • 3% of the weight is composed of potash

The remainder of the weight is comprised of other elements or filler.

Next, look for a small list, often on the back of the bag, titled guaranteed analysis. It will look something like this:

Formula for finding nutrients equivalent in the bag of fertilizer?

To determine the actual amount of each nutrient equivalent in the bag of fertilizer, multiply the weight of the bag by the percentage of that nutrient equivalent in decimal form. So to determine the actual nitrogen content in a 100-pound bag of 16-2-3 starter fertilizer:

100 (pounds) x 0.16 (percentage of nitrogen) = 16 pounds of actual fertilizer material.

100 (pounds) x 0.2 (percentage of Phosphorus) = 2 pounds of actual fertilizer material.

100 (pounds) x 0.16 (percentage of Potassium) = 16 pounds of actual fertilizer material.

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