Wastewater‐recovered struvite effects on total extractable phosphorus compared with other phosphorus sources

Abstract

Abstract Intentional precipitation of the phosphorus (P)‐containing mineral struvite (MgNH4PO4 · 6H2O) is an attractive option in sustainable water management due to the ability to recover P from various waste sources. Limited research has assessed struvite's potential as a fertilizer P source in agronomic soils compared with other conventional fertilizer P sources under flooded soil conditions, common for lowland rice (Oryza sativa L.). The objective of this study was to evaluate total extractable soil P over time from a wastewater‐recovered struvite (ST) material in a plant‐less soil incubation with two silt‐loam (SiL) and a silty clay loam (SiCL) soil in a flooded soil environment compared to monoammonium phosphate (MAP) and triple superphosphate (TSP). Replicated soil cups were amended at a rate of 24.5 kg P ha–1 and were sampled after 0.5, 1, 2, 3, and 4 mo. Total water‐soluble (WS) soil P concentrations increased the most from the initial in the ST treatment (69.9 and 52.2 mg kg–1 after 0.5 and 1 mo, respectively) than in any other treatment in the first month. However, throughout the remaining 3 mo of incubation, total WS soil P concentrations generally decreased, but remained greater than the initial, and were similar among fertilizer treatments. Averaged over time, total Mehlich‐3 (M3) soil P concentrations in all three soils increased the most from the initial in the ST treatment (66.6, 71.3, and 74.5 mg kg–1, respectively), which did not differ from MAP and TSP. The comparable total WS‐P and M3‐P concentrations among fertilizers under flooded soil conditions further support struvite's agronomic potential as an alternative fertilizer P source.