2026 Associates of Agriculture Certification Complete Practice Test

In a fertilizer label like 5-10-15, numbers reflect the percentages by weight of the three primary nutrients essential for plant growth: nitrogen, phosphorus, and potassium. These numbers are always listed in the same order: nitrogen, phosphorus, and potassium.

The middle number, which is 10 in this case, indicates the percentage of phosphorus (P) in the fertilizer. Phosphorus is crucial for various plant functions, including energy transfer, photosynthesis, and the formation of DNA and genetic material. It plays a vital role in root development and flowering, making it particularly important for fruiting and blooming plants.

The first number represents nitrogen, which is essential for plant growth and leafy development, while the last number represents potassium, important for overall plant health, disease resistance, and stress handling. Iron, while important for chlorophyll production, is not one of the three primary nutrients represented in these numbers. This understanding helps in selecting the right fertilizer based on the specific nutrient needs of plants.