Soil Fertility and Nutrient management (1+1)

K-transformations & availability in soils

K- Availability in soil
Potassum is present in soil solution as K+ ion which is readily available to plants. But this form is in dynamic equilibrium with exchangeable K which intern with fixed K. Fixed K is in equilibrium with mineral K. The available K is the solution-K and Exchangeable K which can be easily absorbed by plants.

K Cycle

K- Transformations in soil:

When potassic fertilizers are added to the soil, K may either remain in soil solution or in exchangeable form on the clay surface or in non-exchangeable form held by illitic clay minerals as fixed K which is not available to plants directly. Plants get K mainly from solution-K and exchangeable-K form. As and when the exchangeable K fraction is depleted form the soil substantially or exhausted by crop uptake, the non exchangeable form of K replenishes the exchangeable K and supply of K to plants is maintained and equilibrium is attained. The reserve source of K is mineral lattice K which undergoes weathering and releases K to soil. In all these transformations some sort of equilibrium is maintained always in soil among different forms of K thereby plants get continuous supply of K.