Certified Storm Water Operator Practice Exam

How many pounds of phosphorous are contained in a 50-pound bag of 20-10-5 fertilizer?

1. Two

2. Five

3. Ten

4. Fifteen

The correct answer is: Five

To determine the amount of phosphorus in a 50-pound bag of fertilizer labeled as 20-10-5, you can analyze the numbers on the label. These numbers represent the percentage of nitrogen (20%), phosphorus (10%), and potassium (5%) in the fertilizer, based on the total weight of the product. In this case, the phosphorus component is indicated by the second number: 10%. To find out how many pounds of phosphorus are in the 50-pound bag, you would calculate 10% of 50 pounds: 10% of 50 = 0.10 × 50 = 5 pounds. Thus, the amount of phosphorus contained in the bag is indeed 5 pounds, making this the correct answer. Understanding how to read fertilizer ratios and convert them from percentages to actual weights is essential for effective nutrient management in any stormwater operation or agricultural application.