Theory 108/Soil Science
Phosphorus Is a Sorption Ratio
The claim
Plant-available phosphorus is set by the ratio of sorption to desorption capacity rather than by total soil phosphorus.
01The mechanism
Phosphorus binds to iron and aluminium oxides; availability depends on how tightly it is held, not how much is present.
02Predictions
- P1Availability should track the ratio.
- P2Total phosphorus should mispredict.
03Refutation
Availability tracking total phosphorus would remove the sorption term.