Chemically Precipitated Struvite Dissolution Dynamics over Time in Various Soil Textures

Abstract

Phosphorus (P) is a fundamental nutrient in agricultural production and is one of three major components in common fertilizers. The majority of fertilizer -P sources are derived from phosphorus rock (PR), which has finite abundance ; thus a sustainable source of P is imperative for future agricultural productivity. A potential sustainable P source may be the recovery of the mineral struvite (MgNH 4 PO 4 ·6H 2 O) from wastewater treatment plant effluent , but struvite behavior in soils of varying texture is not well characterized. The objective of this study was to assess the dissolution dynamics of a commercially available, wastewater-recovered struvite product over time in a plant-less, moist-soil incubation experiment with multiple soil textures. Chemically precipitated struvite (Crystal Green; CG) from municipal wastewater in pelletized and finely ground forms were added to soil cups at a rate of 24.5 kg•P•ha −1 containing soils of varying texture (i.e. loam, silty clay loam, and two different silt loams) from agricultural field sites in Arkansas. Soil cups were destructively sampled five times over a 6-month period to examine the change in water-soluble (WS) and weak-acid-extractable (WAE) P, K, Ca, Mg, and Fe concentrations from their initial concentration. After 0.5 months, both WS-P and WAE-P concentrations increased (P < 0.05) more from initial concentrations of the finely ground CG in all soils, which averaged 76.2 and 158 mg•kg −1 , respectively, than in the pelletized CG treatment, which averaged 14.0 and 12.2 mg•kg −1 , respectively, across all soils. Over the course of the 6-month incubation, WS-and WAE-P concentrations generally increased over time in the pelletized and decreased over time in the finely ground treatment, confirming the slow-release property of pelletized CG that has been previously reported. The results of this study provide valuable insight regarding struvite-P behavior in various soils and provide further supporting evidence for the utilization of struvite as a potential alternative, sustainable