Electrochemically precipitated struvite effects on extractable nutrients compared to other fertilizer-P sources

Abstract- Recovery of struvite, or magnesium ammonium phosphate (MgNH4PO4 · 6H2O), from wastewater streams may provide an alternative to traditional phosphorus (P) fertilizers. Little research has assessed the behavior of struvite relative to other commercially available, fertilizer-P sources in historically row-cropped soils in the United States. The objective of this study was to evaluate total extractable P and other nutrients from electrochemically (ECST) and chemically precipitated struvite (CPST) compared to triple superphosphate (TSP), diammonium phosphate (DAP), monoammonium phosphate (MAP), and rock phosphate (RP) in a moist-soil incubation without plants using varying soil textures (loam, silt loam, and silty clay loam). A uniform application rate of 24.5 kg total P ha-1 was used for each fertilizer-P source. Soil sampling occurred six times over a 9-month period (0.5, 1, 2, 4, 6, and 9 months) to examine the change in soil pH and water-soluble (WS) and Mehlich-3-extractable nutrient concentrations (P, Ca, Mg, and Fe) from their initial levels over time. After 0.5 months, WS-P concentrations increased the most in the ECST treatment (41.6 mg kg-1), which did not differ from that of DAP. Throughout the remaining 8.5 months of incubation, WS-P concentrations generally decreased in most treatments, but were still greater than the initial by 9 months and were often similar among ECST, CPST, MAP, DAP, and TSP treatments. Comparable WS-P concentrations among ECST and MAP, DAP, and TSP under soil conditions near field capacity (~ 0.2 g g-1) supports struvite’s potential as a sustainable fertilizer-P source, thus warranting further investigation of the plant response to struvite use as an alternative fertilizer-P source.