Doctor of Philosophy (PhD)


Plant, Environmental Management and Soil Sciences

Document Type



Phosphorus (P) is an essential nutrient for all life forms, including plants, but is a limited agricultural resource whose future availability is in question. Therefore, identification of alternative forms of P fertilizers is important. Poultry litter ash (PLA), a byproduct of bioenergy production, contains high concentrations of P comparable to conventional fertilizers. Forms of P contained in PLA have been characterized as having low water solubility. Nutrient losses during containerized plant production are high due to excessive inputs of water and nutrients and low nutrient sorption capacities of common horticultural substrate components. Environmental concerns over reduced water quality intensify this problem. Use of low soluble P sources has been recommended as a potential means of reducing P losses. Experiments were conducted to determine effects of PLA application on growth, quality, and nutrient uptake of two greenhouse crops (Verbena canadensis Britton ‘Homestead Purple’ and Lantana camara L.‘New Gold’), substrate chemical properties, and P losses during greenhouse crop production. In the first experiment, substrate leachate-pH increased 25% when PLA was applied instead of superphosphate (SP). Foliar P concentrations of verbena and lantana also increased 27 and 62%, respectively. Application of PLA did not reduce biomass of verbena or lantana. In a subsequent experiment, leachate-dissolved reactive phosphorus (DRP) and effluent-total phosphorus (TP) concentrations were reduced >92% and 69%, respectively, through PLA application, however, plant growth and landscape establishment was not deleteriously affected. Water solubility of PLA-P decreased markedly as combustion temperature increased. Finally, in a third experiment, concentrations of DRP were reduced 24% through reduction of PLA rate, but were reduced 134% when PLA was topdressed instead of incorporated. Plant quality was improved with PLA incorporation. These results indicate that, while P loss reduction can be achieved through PLA application, lower substrate P concentrations do not necessarily reduce plant growth or quality.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Bush, Edward