What describes the movement of ions from high to low concentration in soil?

Diffusion defines the natural movement of ions and molecules from an area of higher concentration to an area of lower concentration. This process occurs without the need for energy input and is driven solely by the concentration gradient. In the context of soil, when nutrients or ions are present in higher concentrations in a particular area than in surrounding areas, they will spontaneously move toward those areas of lower concentration until equilibrium is reached. This principle is fundamental to various processes in plant nutrition, as it allows roots to uptake essential ions from the soil more efficiently.

Mass flow, on the other hand, refers to the movement of water and dissolved nutrients in response to pressure gradients, while root interception involves the physical contact of roots with nutrients as they grow through the soil. Active transport requires the expenditure of energy to move ions against their concentration gradient, which is not the case in diffusion. Therefore, diffusion is the most suitable term for describing the passive movement of ions from high to low concentration in soil.