Question

What are the forms / pools of K in the soil? Which two pools constitute the available K to the plant in a growing season? Discuss briefly the relationship between these two pools.

Answer 1

1. There are Various types /forms / pools of K in the soil.

Soluble Potassium

Exchangeable potassium

Fixed potassium

Structural Potassium

2.* The soluble and exchangeable potassium pools are the most important sources of potassium available to plants

3. Soluble Potassium

The most available but smallest pool is soluble potassium, which is dissolved in the soil water and also called the soil solution. Plants take up most of their potassium directly from this pool, and so deplete it very rapidly.

Exchangeable potassium
* Soluble potassium is closely linked to the much larger pool of exchangeable potassium which is held on the negatively charged surfaces of soil particles and are also called cation exchange sites.

Exchangeable potassium is released into the soil solution as plants deplete the soluble potassium, allowing for a regular resupply. But the size of the exchangeable potassium pool will determine the effectiveness of resupply