The second number on a fertilizer label typically refers to what?

The second number on a fertilizer label represents the percentage of phosphorus (P) in the formulation. Fertilizer labels follow a standard format known as the N-P-K ratio, which indicates the three primary nutrients contained in the fertilizer: nitrogen, phosphorus, and potassium. In this ratio, the first number reflects the nitrogen content, the second number represents phosphorus, and the third number indicates potassium.

Phosphorus is essential for plant growth as it plays a crucial role in energy transfer, photosynthesis, and the formation of DNA and RNA, which are vital for the tissue development of plants. Recognizing the significance of phosphorus helps in understanding how to properly apply fertilizer for optimal plant health.

Understanding the roles of the other components is important, but in this case, the point of focus is that the second number clearly indicates phosphorus content, confirming why it is the right answer.