Inorganic monophosphate determination in overland flow from irrigated grazing systems

This paper presents a novel technique for measuring soluble inorganic monop hosphate in water based on high performance liquid chromatography and flow injection detection (IC-FI). The IC-FI technology was applied to irrigation water from the Macalister Research Farm in South Eastern Australia. Overla nd flow was measured exiting two irrigation bays. Inorganic monophosphate c onstituted over 97% of the DRP component and between 86-93% of the total ph osphorus. Similar results were obtained from a channel that drained the exc ess irrigation water from the farm. This work supports the findings of othe rs that show DRP contributes a large portion of the P in runoff from grazin g systems. Additionally, it confirms this fraction is dominated by immediat ely bioavailable inorganic monophosphate, something that previously could o nly be inferred due to the limitations of the chemistry applied.