Phosphorus Sorbing Materials: Sorption Dynamics and Physicochemical Characteristics

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Abstract
The effectiveness of various management practices to reduce phosphorus (P) loss from soil to water can potentially be improved by using by‐product materials that have the capacity to sorb phosphorus. This study evaluated the P sorption and desorption potential, and the physicochemical characteristics of various phosphorus sorbing materials. Twelve materials were selected and P sorption potentials ranged between 66 and 990 mg kg−1 Iron, and calcium drinking water treatment residuals (DWTRs), a magnesium fertilizer by‐product, aluminum, and humate materials all removed substantial amounts of P from solution and desorbed little. Humate had the highest maximum P sorption capacity (Smax). Materials which had a low equilibrium P concentration (EPC0) and a high Smax included aluminum and humate by‐products. In a kinetic study, the Fe‐DWTR, Ca‐DWTR, aluminum, and magnesium by‐product materials all removed P (to relatively low levels) from solution within 4 h. Phosphorus fractionation suggests that most materials contained little or no P that was readily available to water. Sand materials contained the greatest P fraction associated with fulvic and humic acids. In general, materials (not Ca‐DWTR) and magnesium by‐product were composed of sand‐sized particles. There were no relationships between particle size distributions and P sorption in materials other than sands. The Ca‐ and Fe‐DWTR, and magnesium by‐product also contained plant nutrients and thus, may be desirable as soil amendments after being used to sorb P. Further, using Ca‐DWTRs and Fe‐DWTRs as soil amendments may also increase soil cation exchange and water holding capacity.
Funding Information
  • Florida Agricultural Experiment Station
  • Florida Dep. of Agriculture and Consumer Services