Die-off of Fecal Indicator Organisms Following Land Application of Poultry Manure1
- S. R. Crane,
- P. W. Westerman and
- M. R. Overcash2
Land-applied animal manure can be a major contributor of agricultural nonpoint source pollution. For surface-applied manures the time period prior to the first runoff is of greatest concern, because most enteric species initially exhibit rapid die-off rates. The objectives of this investigation were to follow the die-off of indicator organisms after manure application to a bar? soil surface and to ascertain if die-off could be accurately modeled by first-order-kinetics. Poultry manure was surface-applied at approximately 36.5 and 164 metric tons/ha on Davidson clay loam and Norfolk sandy loam plots in a controlled environment chamber at a constant temperature (24.5°C). Soil samples were analyzed at intervals during a 30-day period for fecal coliforms and fecal streptococci. Modeling die-off of fecal coliform during the first 7 days gave good agreement with experimental data showing an average die-off rate constant of 0.29/day. After 7 days, regrowth of fecal coliform populations was seen on all plots. Fecal streptococcal numbers declined steadily after the first 3 days of the 30-day study and exhibited an average first-order rate constant of 0.093/day. Neither soil type nor manure application rate seemed to influence the decline in organism populations. First-order kinetics did not explain all aspects of die-off, but it appears this model could be successfully employed as a first approximation for estimating bacterial kinetics in a larger nonpoint source pollution model for agricultural lands.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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