Date of Graduation

5-2020

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Kristofor R. Brye

Committee Member

Trenton L. Roberts

Second Committee Member

Lauren F. Greenlee

Third Committee Member

Edward E. Gbur

Keywords

phosphorus fertilizer, soil phosphorus behavior, Struvite, struvite soil response, sustainable phosphorus fertilizer

Abstract

Phosphorus (P) is a fundamental element that is involved in many essential biological processes in all forms of life and is a major component in commercial fertilizers. Traditional P fertilizers are derived from rock phosphate (RP), which is limited in supply and expected to be depleted over the next 250 years. Phosphorus recovery technology has been an area of recent interest due to the potential food security risk of traditional RP-derived fertilizer-P sources. Magnesium ammonium phosphate (MgNH4PO4 · 6H2O), which is the mineral struvite, is a wastewater-recovered mineral that has gained attention as a potential sustainable fertilizer-P source. The primary objective of this study was to assess the behavior of a simulated, wastewater-recovered struvite in multiple plant-less soil incubations with multiple soil textures in a moist- and flooded-soil environment. Fertilizer-P sources including electrochemically precipitated struvite (ECST), chemically precipitated struvite (i.e., Crystal Green; CG), triple superphosphate (TSP), diammonium phosphate (DAP), monoammonium phosphate (MAP), and RP, were added to plastic soil cups at an equivalent fertilizer rate of 24.5 kg P ha-1 containing three or four agricultural soils of varying soil texture [i.e., loam, silt loam, and silty clay loam, but the loam was not used in the flooded-soil incubations] from various agricultural field sites throughout Arkansas. Soil cups were destructively sampled six times over a 9-month period in the moist-soil incubation and five times over a 4-month period in the flooded-soil incubations to examine the change in water-soluble (WS) and weak-acid-extractable (WAE; i.e., Mehlich-3) nutrient (i.e., P, K, Ca, Mg, and Fe) concentrations from the initial over time. In the moist-soil incubation, after 0.5 months of incubation, WS-P concentrations increased the most in the ECST treatment (41.6 mg kg-1), which did not differ from that from DAP. Throughout the remaining 8.5 months of incubation, the WS-P concentrations numerically decreased in most treatments, but still were greater than the initial and were generally similar among ECST, CG, MAP, DAP, and TSP treatments. In the flooded-soil incubation, after 0.5 months, WAE-P concentrations increased the most from the initial in the ECST treatment (82 mg kg-1), which did not differ from DAP. After 1 month of incubation and throughout the remaining three months of incubation, WAE-P concentrations increased the most from the initial and were similar among ECST, CG, and DAP treatments. The comparable WS-P concentrations among ECST, CG, MAP, DAP, and TSP in the moist soil incubation and similar WAE-P concentrations among ECST, CG, and DAP treatments under flooded-soil conditions further support struvite’s agronomic potential as a potentially sustainable, fertilizer-P source, thus warranting further investigation of the plant response to struvite use as a fertilizer-P source.

Included in

Hydrology Commons

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