Phosphorus (P) mobility and bioavailability in soil depend on the pools in which it resides. The identification of such pools is essential for the full understanding of P behavior in soil. We evaluated the molybdenum-blue ascorbic-acid method in an automated continuous flow injection analyzer (MB-FIA) to analyze P in two selective soil extractions for soil iron oxide (i.e., the acid ammonium oxalate, AAO, and citrate-dithionite, CD, procedures). Uninterrupted development of the color reaction was obtained at citrate and oxalate concentrations less than 50 mM and 35 mM, corresponding to molybdate/citrate and molybdate/oxalate molar ratios of 2.4 and 3.4, respectively. High precision (% RSD, 1.7 ± 1.3% for CD and 2.9 ± 3.7% for AAO), accuracy, and recoveries (105.7 ± 1.0% for CD and 99.8 ± 3.8% for AAO) were obtained. This study demonstrates the utility of the MB-FIA system for the determination of AAO- and CD-extractable inorganic P.
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science
- Soil Science