Date of Graduation

12-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Dynamics (PhD)

Degree Level

Graduate

Department

Environmental Dynamics

Advisor

Kristofor R. Brye

Committee Member

Trenton L. Roberts

Second Committee Member

Lauren F. Greenlee

Third Committee Member

Edward E. Gbur

Keywords

Fertilizer, Field, Phosphorus, Plant, Struvite, Wastewater

Abstract

Phosphorus (P) is an element that is crucial in many biological processes in all forms of life and is not substitutable. Excess P in wastewaters leading to the degradation of receiving waters or eutrophication once released is a major environmental concern. Removal of excess P from wastewater as the mineral struvite (MgNH4PO4·6H2O) could be a promising solution to reduce P discharge into receiving waters and can potentially provide a valuable fertilizer-P source for agricultural production. The objectives of this project were to evaluate the effects of: 1) chemically precipitated struvite (CPST), compared to triple superphosphate (TSP) and an unamended control (UC) treatment, and irrigation (irrigated and non-irrigated/dryland) on soybean [Glycine Max (L.) Merrill] and wheat (Triticum aestivum L.) response in a wheat-soybean, double-crop production system on a silt-loam soil (Aquic Fraglossudalf) in eastern Arkansas in 2018 and 2019 and 2) evaluate two struvite materials [electrochemically precipitated struvite (ECST) and CPST] relative to several other common fertilizer-P sources [TSP, monoammonium phosphate (MAP), diammonium phosphate (DAP), and RP] on the response of a pureline rice (Oryza sativa L.) cultivar grown under flood-irrigation in a P-deficient, silt-loam soil (Typic Glossaqualfs) and corn (Zea mays L.) and soybean grown in a P-deficient, silt-loam soil (Aquic Fraglossudalfs) in eastern Arkansas in 2019 and 2020. Aboveground dry matter, yield, and P, nitrogen, and magnesium tissue concentrations and uptake were measured. Results from the double-crop study showed that soybean seed yield were unaffected by fertilizer-P treatment and irrigation (P > 0.05), but differed between years (P < 0.01). Seed yield was 1.4 times greater in 2019 than in 2018 when averaged across irrigation and fertilizer-P treatments. In 2019, wheat yield did not differ (P > 0.05) among fertilizer-P sources. In 2019, rice grain yield did not differ (P > 0.05) among fertilizer-P sources. In 2020, rice yield was numerically largest from TSP (9.8 Mg ha-1), which did not differ from that from DAP, MAP, RP, and the UC, and was numerically smallest from ECST (8.2 Mg ha-1), which did not differ (P > 0.05) from that from CPST, and was lower (P < 0.05) than that from TSP, DAP, MAP, RP, and the UC. Averaged across years, corn yield from ECST was at least 1.2 times greater (P < 0.05) than that from CPST, TSP, MAP, DAP, RP, and UC. Soybean seed yield differed among fertilizer-P sources between years (P = 0.03). In 2019, seed yield was numerically largest from ECST (4.1 Mg ha-1), which did not differ from CPST, TSP, MAP, DAP, or RP, and was 1.2 times greater than that from UC. In 2020, soybean seed yield was numerically greatest from CPST (2.8 Mg ha-1) and numerically smallest from ECST (2.2 Mg ha-1). Results showed that wastewater-recovered struvite materials have the potential to be a viable, alternative fertilizer-P source for wheat-soybean, double-crop production system, flood-irrigated rice, and furrow-irrigated corn and soybean in P-deficient, silt-loam soils in eastern Arkansas.

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