What does "nutrient cycling" involve?

Nutrient cycling refers to the natural processes that enable the movement and exchange of nutrients among various components of the ecosystem, including soil, plants, animals, and the broader environment. This cycle is fundamental to maintaining soil fertility and supporting plant growth. Through processes such as decomposition, nutrient uptake by plants, and the subsequent waste or decay from animals, nutrients are continuously recycled.

In this process, elements like nitrogen, phosphorus, and potassium are utilized by plants for growth and development. When plants die or excrete waste, these nutrients return to the soil, where they can be taken up again by other plants. Additionally, microorganisms play a critical role in decomposing organic matter, further facilitating the cycling of nutrients. Thus, option B comprehensively captures the essence of nutrient cycling as an essential environmental process that sustains agricultural productivity, ecosystem health, and biodiversity.

Other choices describe specific nutrient interactions or implications rather than the broader concept of nutrient cycling itself. For example, the intake of nutrients directly from fertilizers is a form of nutrient supply but does not encompass the dynamic interactions involved in cycling. Similarly, storing nutrients in plants during winter or the accumulation of nutrients in groundwater sources represents narrower activities that don't cover the entirety of nutrient cycling.