Measurement of environmental impacts from the land application of raw and digestion manure
Authors: Crolla, A, C Kinsley, A Thiam
Description: The overall objective of this study was to quantify the environmental impacts associated with the land application of anaerobically digested dairy manure. Land application trials were conducted on twelve hydraulically isolated plots, where soil and subsurface drains were monitored for fate of pathogens and nitrate migration. Odour emission and crop yields were also quantified. A suite of four pathogen indicator species (E.coli, Salmonella, Enterococci, C.perfringens) were selected to evaluate pathogen migration to surface and subsurface drains. Average geometric mean bacteria counts of 2.8 log E.coli, 1.7 log Salmonella, 0.9 log Enterococci and 1.1 log C.perfringens were observed in the subsurface drainage waters. These values could be considered as indicative of background levels found in clay soil agricultural drainage waters. Bromide and E.coli NAR (nalidixic acid resistant) tracers have been implemented to track pathogen migration in soil and sub-surface waters. Flow-weighted mean nitrate concentrations in drainage waters 60 days after the land application of raw and digested manure were measured over the past 4 years. Although the drainage water concentrations were observed to be typically below 10 mg/L, the digested manure plots did have higher flow-weighted mean nitrate concentrations in both surface and subsurface drains. This could be attributed to the higher concentration of ammonium-nitrogen typically attributed to digested manure. Lab simulation studies were conducted to determine surface odour fluxes from the land spreading of raw and digested manure. Using this criterion it was determined that digested manure had a low odour nuisance potential. Standard flux chamber and wind tunnel protocols and odour measurements will be presented.
Keywords: anaerobic digestion, pathogens, nitrogen, subsurface drains, odours, land application
Technical field: technical_fields_app7
Session name: Soil and water