Total Extractable P in Flooded Soil as affected by Struvite and Other Fertilizer-P Sources

Abstract- A sustainable P source is imperative to ensure food production can supply a growing global population. Waste-water recovered struvite (MgNH4PO4 · 6H2O) has emerged as an attractive option due to the ability to recover P from waste streams. The objective of this study was to evaluate total extractable soil P from electrochemically precipitated struvite (ECST) compared to other fertilizer-P sources [chemically precipitated struvite (CPST), diammonium phosphate (DAP), and rock phosphate (RP)] in two soil textures (two different silt loams and a silty clay loam) over time in a flooded-soil environment. An equivalent fertilizer rate of 24.5 kg P ha-1 was used. The change in water-soluble (WS) and Mehlich-3 (M3) extractable nutrient concentrations (P, K, Ca, Mg, and Fe) from their initial concentration was determined five times over a 4-month period. After 0.5 months, WS-P increased the most from the initial from DAP (27.6 mg kg-1), which did not differ from CPST or ECST. After 0.5 months, M3-P increased the most from the initial in ECST (82 mg kg-1), which did not differ from DAP. After one month and thereafter under flooded-soil conditions, M3-P increased the most from the initial and were similar among ECST, CPST, and DAP. After three and four months, WS-P was greater than the initial only in DAP, but remained similar to CPST, ECST, and RP, which did not differ from the initial. Comparable WS- and M3-P concentrations between ECST, CPST, and DAP under flooded-soil conditions support struvite’s agronomic potential as a prospective sustainable, fertilizer-P source.