Certified Crop Advisor Practice Exam

To meet a fertilizer recommendation of 26 lbs of P, how many pounds of 10-20-10 should be applied per acre?

1. 200

2. 300

3. 400

4. 500

The correct answer is: 300

To determine how many pounds of fertilizer with a guaranteed analysis of 10-20-10 should be applied to meet a phosphorus (P) requirement of 26 lbs per acre, it is important to understand the composition of the fertilizer. The numbers on a fertilizer label indicate the percentage of nitrogen (N), phosphorus (P), and potassium (K), respectively. In a 10-20-10 fertilizer, the second number, 20, represents the percentage of phosphorus. This means that for every 100 pounds of this fertilizer, there are 20 pounds of phosphorus. Since the objective is to apply 26 pounds of phosphorus, you can set up a proportion based on the percentage of phosphorus in the fertilizer: 1. Calculate the amount of fertilizer required to provide 26 pounds of phosphorus: Let x = the amount of fertilizer to be applied (in pounds). The phosphorus content from the fertilizer can be calculated as: \( 0.20x = 26 \) 2. Solving for x gives: \( x = \frac{26}{0.20} \) 3. This simplifies to: \( x = 130 \text{ pounds of 10-20-10 fertilizer} \) Since we