What does a 10-10-10 NPK fertilizer indicate?

• A. It has more nitrogen than phosphorus
• B. It contains no phosphorus
• C. It contains equal percentages of nitrogen and potassium by weight
• D. It contains equal percentages of nitrogen, phosphorus, and potassium by weight

Answer: (D)

NPK numbers show how much of each nutrient is present by weight. The first value is nitrogen (N), the second is phosphorus as P2O5 equivalent (P), and the third is potassium as K2O equivalent (K). In a 10-10-10 fertilizer, each nutrient is 10% by weight, so nitrogen, phosphorus, and potassium are present in equal amounts by weight. This makes it a balanced, all-purpose fertilizer for general plant needs. Phosphorus is listed as P2O5 and potassium as K2O, but the key idea is that all three nutrients are equal in amount.