Bacteriological Quality of Surface and Subsurface Runoff from Manured Sandy Clay Loam Soil

Abstract

AbstractThe bacterial quality of surface waters determines their acceptability for both drinking and recreational uses. Since livestock activities have been implicated as sources of fecal contamination, information on the bacterial quality of runoff from manured cropland is required. Bacteriological parameters (total coliform [TC], fecal coliform [FC], and fecal streptococcus [FS]) were monitored in spring surface and subsurface discharge from continuously corn‐cropped sandy clay loam that was amended with either liquid dairy manure, chemical N‐P‐K fertilizer at about recommended rates, or no fertilizer. Liquid manure was applied for 6 years at three rates, which averaged 105, 263, and 420 m3 ha−1 year−1, plowed under after harvest, in spring prior to seeding, or split between spring and fall. Liquid manure was also applied directly to snow or frozen ground.With the exception of winter‐applied treatments, neither rate nor time of manure application significantly affected organism contents in spring surface or subsurface discharge. Winter manure applications resulted in significantly higher FC and FS counts in surface runoff and FS counts in subsurface discharge when compared with other application times. Fecal coliform and FS counts did not increase with increased winter application rates. Fecal streptococcus populations of winter‐applied manure changed little during the first 100 days after application, while both TC and FC counts declined in the manure to low levels 24–40 days after spreading.