No 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.

A sustainable P source is imperative to ensure that food production can supply a growing global population. Wastewater-recovered struvite (MgNH 4 PO 4 • 6H 2 O) has emerged as an attractive option because of the ability to recover P from waste streams.This study aimed to evaluate total extractable soil P from electrochemically precipitated struvite (ECST) compared with other fertilizer-P sources [chemically precipitated struvite (CPST), diammonium phosphate (DAP), and rock phosphate] 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 concentrations was determined five times over a 4-mo period. After 0.5 mo, WS-P increased the most from the initial value with DAP (27.6 mg kg -1 ), which did not differ from CPST or ECST. After 0.5 mo, M3-P increased the most in ECST (82 mg kg -1 ), which did not differ from DAP. After 1 mo and thereafter under flooded conditions, M3-P increased the most from the initial value and was similar among ECST, CPST, and DAP. After 3 and 4 mo, WS-P was greater than the initial value in DAP only, but remained similar to CPST, ECST, and rock phosphate, which did not differ from the initial value. Comparable WS-and M3-P concentrations among ECST, CPST, and DAP under flooded conditions support struvite's agronomic potential as a prospective sustainable fertilizer-P source.

Recovery of struvite, or magnesium ammonium phosphate (MgNH4PO4 · 6H2O), from wastewater streams may provide an alternative to traditional 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 with 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‐mo period (0.5, 1, 2, 4, 6, and 9 mo) 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 mo, 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 mo of incubation, WS‐P concentrations generally decreased in most treatments but were still greater than the initial level by 9 mo 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) support 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.

No abstract