What factor significantly restricts the movement of phosphorous in soil?

The factor that significantly restricts the movement of phosphorus in soil is related to the physical properties of the soil, particularly low permeability or dry conditions. When the soil is dry or has low permeability, water movement through the soil is restricted. Phosphorus, being a polar molecule, tends to bind tightly to soil particles, especially clay and organic matter. In these conditions, phosphorus cannot easily move through the soil profile, limiting its availability to plants.

Dry soil often inhibits the dissolution and transportation of nutrients, including phosphorus, since they rely on water to move through the soil. In contrast, high moisture content or excessive rainfall can lead to nutrient runoff, while high soil pH levels typically influence the solubility of phosphorus but do not serve as the primary factor for restricting its movement as significantly as low permeability situations. Therefore, low soil permeability and dry conditions are critical in defining phosphorus mobility in soil.