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E. coli and enterococci re-growth and decay patterns in cowpats applied to pasturelands were monitored during the spring, summer, fall, and winter. First-order approximations were used to determine die-off rate coefficients and decimal reduction times (D-values). Higher-order approximations and weather parameters were evaluated by multiple regression analysis to identify environmental parameters impacting in-field E. colt and enterococci decay. First-order kinetics approximated E. colt and enterococci decay rates with regression coefficients ranging from 0.70 to 0.90. Die-off rate constants were greatest in cowpats applied to pasture during late winter and monitored into summer months for E. colt (k = 0.0995 d-1) and applied to the field during the summer and monitored until December for enterococci (k = 0.0978 d-1). Decay rates were lowest in cowpats applied to the pasture during the fall and monitored over the winter (k = 0.0581 d-1 for E. colt, and k = 0.0557 d-1 for enterococci). Higher-order approximations and the addition of weather variables improved regression coefficients to values ranging from 0.82 to 0.96. Statistically significant variables used in the models for predicting bacterial decay included temperature, solar radiation, rainfall, and relative humidity. Die-off rate coefficients previously reported in the literature are usually the result of laboratory-based studies and are generally higher than the field-based seasonal die-off rate coefficients presented here. To improve predictions of in-field E. colt and enterococci concentrations, this study recommends that higher-order approximations and additional parameters such as weather variables are necessary to better capture re-growth and die-off trends over extended periods of time. [ABSTRACT FROM AUTHOR]

The article analyzes the effects of phosphorus-based manure applications on total suspended solids and nutrient losses from dairy manufacture and poultry litter surface applied to pasturelands. The authors also compare the nutrient losses transported to the edge of the field during overland flow events. A set for the study of in-field release and another set for the study of edge-of-the-field nutrient transport were established. Based on the results of the study, it was suggested that a buffer zone between pastureland, streams and other appropriate management practices is needed to decrease nutrient losses to waterbodies.

Land applications of manure from confined animal systems and direct deposit by grazing animals are both major sources of bacteria in streams. An understanding of the overland transport mechanisms from land applied waste is needed to improve design of best management practices (BMPs) and modeling of nonpoint source (NPS) pollution. Plots were established on pasturelands receiving phosphorus-based livestock waste applications to measure the concentrations of Escherichia coli ( E. coli), fecal coliform (FC), and Enterococcus present in overland flow at the edge of the field. The flow-weighted bacteria concentrations were highest in runoff samples from the plots treated with cowpies (1.37×105 colony forming units (cfu)/100 ml of E. coli) followed by liquid dairy manure (1.84×104 cfu/100 ml of E. coli) and turkey litter (1.29×104 cfu/100 ml of E. coli). The temporal distribution of fecal bacterial concentrations appeared to be dependent upon both the animal waste treatment and the indicator species, with peak concentrations occurring either at the beginning of the runoff event or during peak flow rates. BMPs could be selected to reduce peak flows or first flush effects depending upon the litter or manure applied to the land. The commercial Biolog System was used to identify the dominant species of Enterococcus present in the cowpie source manure ( Enterococcus mundtii 55%) and in the runoff collected from the transport plots treated with cowpies ( Enterococcus faecalis 37%). The identification of predominant species of Enterococcus that are associated with specific sources of fecal pollution could greatly assist with identifying the origins of NPS pollution. [ABSTRACT FROM AUTHOR]