Exchangeable K

1
Potassium Cycle Main cycle
Plant Uptake
Fertilizer K
Crop Residues
Animal Manures
Diffusion
Mass flow
Readily available
Exchangeable K
Soil colloidal surface
1 2 of total K
Soil Organic Matter
Adsorption
Readily available
Rapid exchange
Desorption
Soil Solution K
1 2 of total K
Release
Fixation
Slow exchange
Slowly available
Non Exchangeable K
1 10 of total K
Illite, Vermiculite, Chlorite
Microbial Pool
Weathering
Very slow exchange
Relatively available
Primary Minerals
90 98 of total K
Micas (Biotite, Phlogopite, Muscovite)
Leaching
Potassic Feldspars (microcline, orthoclase)
in soils with low CEC
Erosion
Runoff
2
Fertilizer Effects
Fertilizer K
Plant Uptake
Crop Residues
Animal Manures
Diffusion
Mass flow
Readily available
Exchangeable K
Soil colloidal surface
Adsorption
1 2 of total K
Soil Organic Matter
Rapid exchange
Readily available
Soil Solution K
Desorption
1 2 of total K
Microbial Pool
Leaching
in soils with low CEC
Runoff