Bacterial Quality of Runoff from Manured and Non-Manured Cropland

Abstract

ABSTRACT INDICATOR bacteria concentrations in non-snowmelt runoff from adjacent manured and non-manured watersheds were monitored for 4 years. Significant differences in the quality of runoff from the manured and non-manured cropland were not consistently observed. Hydrological conditions greatly affected bacterial concentrations. Heavy runoff under wet weather conditions resulted in water quality degradation irrespective of cropping or manuring activity. Under relatively dry weather conditions, runoff from both the manured and non-manured cropland often met the recommended bacterial quality criteria for water to be used for recreation or as a source of public water supplies. The relatively better quality of manured cropland runoff in our study compared to other studies was attributed mainly to the management practice of dry weather manure application followed by immediate plowdown and the mostly level topography of the watersheds. Much lower indicator bacteria concentrations in long-term stored manure than in relatively fresh manure suggested a lower potential for runoff pollution from land application of the former.