Die‐off of Fecal Indicator Organisms Following Land Application of Poultry Manure

Abstract

AbstractLand‐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.