Final answer:
Nitrogen is the element most needed for turfgrass growth and metabolism because it is crucial for photosynthesis, protein synthesis, and DNA among other plant structures.
Step-by-step explanation:
The element needed in the greatest amount for turfgrass growth and metabolism is Nitrogen (N). Nitrogen is essential because it is a major component of chlorophyll, which plants use to carry out photosynthesis, and it is a key part of amino acids, the building blocks of proteins. It's also present in DNA and other important plant compounds. Proper application of nitrogen can lead to more vigorous growth of turfgrass by promoting leaf and stem development. Although atmospheric nitrogen is abundant, it is not in a form readily accessible by plants and needs to be fixed into a form like ammonia to be utilized, which is why nitrogen fertilization is often necessary in agriculture and landscaping.