Leaching characteristics of electrochemically precipitated struvite compared to other common phosphorus fertilizers in differing soils

Phosphate-rich struvite (MgNH4PO4 center dot 6H2O) can be reclaimed from wastewater as a fertilizer material to help provide clean water and sustainable food production. The objective of this study was to evaluate the leaching characteristics of wastewater-recovered electrochemically precipitated struvite (ECST) compared to other common fertilizer-P sources in soils from Arkansas (AR loam and silt loam), Missouri (MO silt loam 1 and 2), and Nebraska (NE sandy loam and silt loam). A bench-scale, soil-column experiment was conducted using five fertilizer-P sources (i.e., ECST, chemically precipitated struvite [CPST], monoammonium phosphate [MAP], triple superphosphate [TSP], and an unamended control [UC]) and leached six times over 15 weeks after fertilizer application. Leachate-P concentration changes from the UC differed among soil-fertilizer combinations over time (p < 0.05) but only in the AR-loam, where TSP (2.0-6.6 mg L-1) consistently had a larger leachate-P change from the UC than ECST (-0.04 to 3.1 mg L-1) in weeks 1-3. Leachate-NO3-N concentration changes from the UC among soils occurred only in week 1, where three of the six soils had NO3-N concentration increases >10.7 mg L-1 from their respective UC. Though inconsistent across the various soils evaluated, P-leaching losses relative to respective UC treatments were often larger from MAP and TSP than ECST and CPST. Results showed that P, NH4-N, NO3-N, Ca, Mg, and Fe leaching potentials differed among soils depending on initial soil pH and texture and fertilizer-P source; thus, soil characteristics and fertilizer-P source should be considered to minimize potential nutrient leaching losses.