This document describes the determination of potassium in compound fertilizers using the potassium tetraphenylborate gravimetric method, inductively coupled plasma atomic emission spectrometry, or flow analyzer method, through either heating and boiling extraction or ultrasonic extraction. For the heating and boiling extraction, the potassium tetraphenylborate gravimetric method is the arbitration method. This document applies to the determination of potassium content in compound fertilizers. The determination of potassium content in other potassium-containing inorganic fertilizers may take this document as a reference.
