Phosphate

For an ion (e.g. phosphate) to be leached out of a soil, the ion needs to be in soil solution. Very few phosphate ions will be in solution of any soil due to the process of phosphate fixation. Phosphate fixation transforms phosphate ions from soluble, mobile ionic form into an insoluble form of either iron-phosphate and aluminum-phosphate (in acidic soils) or calcium-phosphate (in alkaline soils).