Total potassium includes all forms of potassium in soil, such as mineral-bound, exchangeable, and water-soluble potassium. It plays a vital role in plant growth by regulating water balance, enzyme activation, and photosynthesis. While only a fraction of total potassium is readily available to plants, it serves as a reserve to replenish exchangeable potassium over time. Adequate potassium levels improve crop yield, quality, and resistance to stress. Source: Soil Science Society of America.