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Nitrogen & carbon transformations in conventionally-handled livestock manure Vol. 1

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Title: Nitrogen & carbon transformations in conventionally-handled livestock manure Vol. 1
Author: Kachanoski, R. Gary; Barry, D. A. J.; Stonehouse, D. Peter; Beauchamp, E. G.
Abstract: One objective of this project was to investigate various manure storage and handling systems with respect to nitrogen (N) and carbon (C) changes during storage and handling. A literature review found few definitive studies done specifically on this topic. These transformations determine the nutrient content and losses from the handling system. Thus, a primary goal of the project was to measure C and N of the animal feed, fresh faeces, and the various states of transformation of the manure as it moved through the handling system. The magnitudes of the various losses of C and N between the handling stages were also measured. Thus, methods of estimating the mass balance had to be devised. Since the economics of the systems also had to be assessed the study was done on operational sized units. Six manure handling systems were chosen to track the mass balance of C and N for a defined set of inputs and outputs. The systems included(1) solid poultry manure, (2) solid top-loading beef, (3) liquid swine (high water use), (4) liquid swine (low water use), (5) solid dairy, and (6) liquid alley-flush dairy. The study allocated considerable resources to chemical analysis, to form a reference database of chemical composition of manure from as many components of the different systems as possible. This characterization included aerobic incubation of sand-soil-manure mixtures in the laboratory to measure mineralizable C and N. Full nutrient analysis (N, P, K, C) are given along with selected analysis of C and N compounds (lignin, acid digestible fibre, volatile fatty acids, etc ). The data given are average values for major time periods (fall, winter, etc ), but sampling was usually done on a weekly or bi-weekly basis. Measurements of greenhouse gas flux rates were made to rank stages of the handling system with respect to their potential to generate these gases. Usually the greenhouse gas losses (except CO2 ) were negligible with respect to mass balance of C and N. However, the magnitudes of the losses are important from an environmental perspective. The fate of the C and N inputs varied depending on the manure, but there were also many similarities. The amount of N excreted as fresh faeces was consistently 70-80% of applied feed N. Final plant available manure NH4-N amounts as a percentage of N inputs were (1) solid poultry manure = 7.5 to 10%, (2) solid top-loading beef = 8%, (3) liquid swine (high water use) = 38%, (4) liquid swine (low water use) = 40%, (5) solid dairy = 19%, and (6) liquid alley-flush dairy = 40%. Additional amounts of organic N were in the manure, but it varied from 1% (liquid swine) to 45%(solid dairy) of input N. Gaseous loss of N from NH3-N volatilization was the major pathway of N loss. The loss occurred very quickly from fresh manure leaving few management options for reducing N loss. A second major objective of this research was to provide a comparative benefit-cost assessment of the six manure-handling systems. A questionnaire was designed for collection of bio-physical and economic data from farmers, through on-farm interviews or mailing out. A spreadsheet system was developed to analyse the farm data and produce a profile of total annual manure production, total capital investment in manure-handling facilities and equipment, annual costs of ownership and operation of manure-handling, economic benefits from manure, and total net costs or benefits from manure operations. Five of the six farms displayed net costs of manure operations (i.e. costs exceeded benefits) ranging from $4.13 to $124.28 per tonne of manure applied per year. The sixth farm showed a net benefit of $0.06 per tonne of manure applied per year. These results concurred with previous research results, which typically showed a net cost for manure operations. Results from this study are being used by a manure systems team at the University of Guelph to aid in development of an expert system for managing animal waste. The final manure generated from the different systems was used in a different study evaluating plant uptake of the manure nutrients. This study is a separate AAFC Green Plan report (Principle Investigator, Dr. E. Beauchamp, Univ. of Guelph), but the combination of the studies gives a complete summary of the fate of C and N and other nutrients.
Date: 1998
Rights: In Copyright - Non-Commercial Use Permitted
Rights Holder: Agriculture Canada

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