UVM Theses and Dissertations
Format:
Print
Author:
Johnson, Nicholas Russell
Dept./Program:
Civil and Environmental Engineering
Year:
2011
Degree:
MS
Abstract:
Excessive application of phosphorus (P) rich animal manure onto agricultural fields will increase the amount of P available to run-off and potentially accelerate eutrophication in receiving waters. Accelerated eutrophication may impair water quality by encouraging harmful blooms of cyanobacteria. Current P recommendations rely on standard soil test P methods that measure extracted reactive orthophosphate. Organic phosphorus compounds in soil and manure systems often represent a majority of total P and are not measured using standard soil test P methods. Much ofthis organic P is enzyme-labile and will be hydrolyzed to plant-available reactive orthophosphate by phosphatase enzymes commonly found in soil and manure systems. Enzymatic hydrolysis (EH) is an emerging method that can be used to measure and classify enzymelabile organic P.
In this thesis, several EH techniques, first developed by Dr. Zhongqi He (USDA, Orono, ME), were combined into one method capable of measuring the two largest classes of organic P found in soil and manure systems: P monoesters and P diesters. This new EH method was rendered high-throughput by adapting it to a microplate reader format and up to 96 samples were processed simultaneously. A time series of manure-amended soil samples was measured by both enzymatic hydrolysis and phosphorus-31 nuclear magnetic resonance spectroscopy (³¹P-NMR) -- a standard method capable of measuring different P species in soil and manure samples. Enzymatic tracking of P species in manure amended soil extracts was robust; 25 to 36 % of P extracted by NaOH-ethylenediaminetetraacetic acid was liberated as orthophosphate after incubating samples with enzymes. In a separate study, a 30 % decrease in the relative abundance of monoester P species was measured in samples held at 25° C over a 64 day study period. Only a 10 % decrease in monoester P relative abundance was measured in identical control samples held at 4° C over the same 64 days. This temperature dependence of P mineralization suggested the mineralization process measured in this study was biologically-mediated.
The objectives of this thesis are to: (i) describe the development of a highthroughput EH method for measuring and classifying enzyme-labile P in soil and manure systems; (ii) present verification of this EH methods accuracy by making parallel P measurements on identical samples using both traditional and state-of-the-art P assessment tools; (iii) present several applications of this new EH method in order to demonstrate its utility for measuring and classifying enzyme-labile P in soil and manure systems.
In this thesis, several EH techniques, first developed by Dr. Zhongqi He (USDA, Orono, ME), were combined into one method capable of measuring the two largest classes of organic P found in soil and manure systems: P monoesters and P diesters. This new EH method was rendered high-throughput by adapting it to a microplate reader format and up to 96 samples were processed simultaneously. A time series of manure-amended soil samples was measured by both enzymatic hydrolysis and phosphorus-31 nuclear magnetic resonance spectroscopy (³¹P-NMR) -- a standard method capable of measuring different P species in soil and manure samples. Enzymatic tracking of P species in manure amended soil extracts was robust; 25 to 36 % of P extracted by NaOH-ethylenediaminetetraacetic acid was liberated as orthophosphate after incubating samples with enzymes. In a separate study, a 30 % decrease in the relative abundance of monoester P species was measured in samples held at 25° C over a 64 day study period. Only a 10 % decrease in monoester P relative abundance was measured in identical control samples held at 4° C over the same 64 days. This temperature dependence of P mineralization suggested the mineralization process measured in this study was biologically-mediated.
The objectives of this thesis are to: (i) describe the development of a highthroughput EH method for measuring and classifying enzyme-labile P in soil and manure systems; (ii) present verification of this EH methods accuracy by making parallel P measurements on identical samples using both traditional and state-of-the-art P assessment tools; (iii) present several applications of this new EH method in order to demonstrate its utility for measuring and classifying enzyme-labile P in soil and manure systems.