What is a recommended approach for applying fertilizer to established turf?

Using phosphorus only under specific conditions is recommended because it acknowledges the potential environmental impacts associated with phosphorus runoff. In Maryland, phosphorus can contribute to water quality issues, such as algal blooms in local waterways. Therefore, soil testing has become a pivotal aspect of nutrient management. This practice helps to determine if phosphorus is truly needed for the turf.

When soil tests reveal that phosphorus levels are already sufficient or excessive, applying phosphorus can be unnecessary and even harmful to the ecosystem. In this context, the recommendation to apply phosphorus only when specific conditions are met aligns with responsible fertilization practices that protect both the turf's health and the surrounding environment.

The other choices propose practices that could lead to nutrient overuse or environmental harm. Frequent fertilization or increasing nitrogen levels without consideration of turf needs can lead to excessive nutrient buildup, while applying phosphorus indiscriminately poses risks to water quality. Hence, focusing on phosphorus application in a cautious and informed manner significantly enhances sustainable turf management.