Which statement best describes the function of topsoil in landscaping?

Topsoil plays a crucial role in landscaping, primarily because it is the layer of soil that contains the highest concentration of organic matter, nutrients, and microorganisms. This rich, fertile layer is vital for supporting plant growth, as it directly influences a plant's ability to access essential nutrients and water.

When plants grow in topsoil, they benefit from the balanced conditions that this layer provides. It fosters healthy root development and helps establish a robust ecosystem of beneficial organisms that contribute to nutrient cycling. This nutrient cycling is the process by which elements like nitrogen, phosphorus, and potassium are made available to plants through organic matter decomposition, enhancing soil fertility and supporting ongoing plant health.

While topsoil can play a role in drainage, its primary function extends far beyond this; it is not merely about allowing excess water to flow away but rather ensuring that plants can absorb the necessary moisture and nutrients. In addition, topsoil is indeed essential for successful gardening, contrary to any suggestion that it is unnecessary. For these reasons, the statement highlighting its importance in nutrient cycling and plant growth accurately captures its fundamental role in landscaping.