How many pounds of 10-6-4 fertilizer are needed to apply two pounds of actual nitrogen?

• A. 1 pound
• B. 2 pounds
• C. 20 pounds
• D. 200 pounds

Answer: (C)

Percent nitrogen on a fertilizer label tells you how much of the product’s weight is nitrogen. A 10-6-4 fertilizer has 10% N, so 0.10 of every pound is nitrogen. To supply two pounds of actual nitrogen, you need enough fertilizer so that 0.10 of its weight equals 2 pounds. Solve 0.10 × (fertilizer weight) = 2 → fertilizer weight = 2 ÷ 0.10 = 20 pounds. So 20 pounds of this fertilizer are needed. The other numbers (6 and 4) refer to P2O5 and K2O and don’t affect the nitrogen calculation. If you used 1 pound, you’d get only 0.1 pound of N; with 2 pounds you’d get 0.2 pound; with 200 pounds you’d get 20 pounds of N—far more than required.