Cotton continues to be a tricky plant to get a consistent understanding on its responses to phosphorus and potassium fertilisers. Methodologies used successfully in broadacre annual cereal and pulse crop research haven't necessarily translated to similar benefits in the cotton crop. Biomass and tissue concentration differences are being measured with phosphorus and potassium application in early growth stages, but not necessarily at maturity or in yield. Some observations on what is happening, why and where research is heading are offered and explored.