What property of soil affects potassium's availability, mobility, and leaching?

The availability, mobility, and leaching of potassium in soil are significantly influenced by soil texture and organic matter. Soil texture refers to the size of soil particles, which determines how well the soil can retain water and nutrients. Soils with a higher clay content have a greater capacity to hold potassium, as the clay particles can bind the potassium ions, making them less prone to leaching. On the other hand, sandy soils are more prone to leaching because of their larger particle sizes and greater drainage capabilities, which allows potassium to wash away more easily.

Organic matter is another crucial factor, as it helps to enhance the cation exchange capacity (CEC) of the soil. This means that organic matter can improve the soil's ability to retain and provide essential nutrients, including potassium, to plants. When organic matter decomposes, it also releases potassium in a form that plants can absorb, thereby increasing its availability.

In contrast, while soil color and erosion rate, soil depth and drainage, and soil microbial activity can all play roles in nutrient cycling and soil health, they do not directly address the specific mechanisms by which potassium is retained in the soil and made available to plants. Hence, the correct answer emphasizes the critical interaction between soil texture and organic matter concerning potassium