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Fate, Transport, and Ecological Effects of Livestock Antibiotics in Manure-Amended Agroecosystems
Department of Plant and Soil Sciences
Arsenic and other antibiotics are widely fed to broiler chickens, and high concentrations of these compounds are commonly found in poultry litter. While poultry litter is considered a valuable fertilizer source when applied to agricultural soils, repeated and intense applications of litter can also contaminate surface and groundwater with arsenic and other livestock antibiotics, which poses health risks to people living in areas where poultry manure is used as a soil amendment. Little is known about the factors that regulate the occurrence and effects these compounds in the environment (e.g. bacterial diversity, development of antibiotic resistant bacteria, carbon and nutrient cycling, etc.).
Under certain environmental conditions, human and animal pathogens can acquire antibiotic resistance by genetic mutation and gene transfer from ARB. Objective 1 of this project will show whether livestock antibiotics affect soil bacteria diversity at different topographic positions (soil catenas) in the landscape. Results from this project will be useful for making improved management decisions about when and where to apply manure in order to maximize the benefits and minimize the ecological/health risks. Thus, the proposed research has a direct impact on both production agriculture and natural resource management in Kentucky and the nation.
Information about As levels and speciation in poultry manure determined in Objective 2 is critical for assessing health risks associated with applying large amounts of manure to the environment.
Information about the effect of tillage and manure application timing on As migration to the subsurface as addressed in Objective 3 would be useful for (i) predicting the fate and ecological effects of As and (ii) developing widely applicable best management practices that will maximize the benefits and minimize the health/ecological consequences of land application of manure wastes.
Results from the project will be disseminated through several outlets in order to inform scientists, Kentucky agricultural producers, and the public about the ecological and health consequences of applying poultry manure with As to agricultural fields. Results from the project will be (i) published in two refereed scientific journals, (ii) published as a Ph.D thesis, (iii) presented at local, regional, and national scientific conferences (e.g. American Society of Agronomy), (iv) published as two extension publications (e.g. Soil Science News and Views) and (v) posted on the extension Plant and Soil Sciences department web site.
2009 Project Description
Studies were conducted to determine whether arsenic in poultry litter and applied to soils is transported to the groundwater or is taken up by corn leaves and grain that are growing in litter amended soils. Additional studies were conducted to determine the mechanism of arsenic sorption in soils, using a selective chemical extraction procedure that was developed in our laboratory.
This project has resulted in a change in knowledge about the fate and health effects associated with the application of arsenic in manure to soils. Using a highly sensitive instrument acquired by the University this year, it was discovered that higher amounts of arsenic were in groundwater underlying manure amended soils, however, the levels were much lower (<1 ppb)than allowable amounts in drinking water (10 ppb). In addition, it was discovered that arsenic levels were similar in corn plants and grain grown on manure amended and unamended soils.
Results from this study suggest that there is little health risk associated with applying manure containing arsenic to soils. However, it is possible that results may not be transferable to other sites whose soils have different physical and chemical properties than those used in this study.
Elisa D'Angelo. Impacts of Poultry Litter on Human and Environmental Health. Environmental & Natural Resource Issues Newsletter. Summer, 2009.
Elisa D'Angelo. Understanding Antibiotics in the Soil. The Magazine. Fall, 2009.