Determination of available phosphorus in alkaline soil by molybdenum blue spectrophotometry

Abstract

A rapid and accurate method for the determination of available phosphorus in alkaline soil by molybdenum blue spectrophotometry was established. The alkaline soil samples were extracted by Olsen method. The effects of absorption wavelength, amount of chromogenic agent, amount of reducing agent and colour reaction time on the determination results were investigated. The results showed that the optimal conditions were as follows: the maximum absorption wavelength was 700 nm, the amount of chromogenic agent was 1 mL, the amount of reducing agent was 1 mL, and the colour reaction time was 15 min. The linear range of phosphorus concentration was 0.3 ?g/mL ? 1.8 ?g/mL, and the recoveries ranged from 88.67 % to 92.17 %. The method is simple, sensitive and accurate.