Associates of Agriculture (AG) Certification 2025 – 400 Free Practice Questions to Pass the Exam

A fertilizer labeled 5-10-20 refers to its nutrient content in terms of the three primary nutrients: nitrogen (N), phosphorus (P), and potassium (K). Specifically, the numbers represent the percentage by weight of each nutrient in the fertilizer.

In this labeling:

- The first number (5) indicates the percentage of nitrogen,

- The second number (10) indicates the percentage of phosphorus (in the form of phosphate, or P2O5),

- The third number (20) indicates the percentage of potassium (in the form of potassium oxide, or K2O).

Therefore, for a fertilizer labeled 5-10-20, phosphorus is represented by the second number, which is 10%. This means that 10% of the fertilizer is phosphate, corresponding to the phosphorus content.

So, when considering the options, the percentage of phosphate in the fertilizer is indeed 10%.