Theory 02/Thresholds & Tipping/Soil phosphorus
Phosphorus Tips on pH
The claim
Plant-available phosphorus rises abruptly above a soil pH threshold because iron and aluminium binding collapses, so liming can release phosphorus without adding any.
01Mechanism
Below the threshold, phosphorus is bound to oxides; as pH rises past it, the surface charge reverses and bound phosphorus desorbs.
02Prediction
Availability should jump at a pH threshold under constant total phosphorus.
03Refutation
Availability changing smoothly with pH would remove the tipping.