Nitrogen dynamics from different tillage practices associated with application of liquid swine manure on two Ontario agricultural soils

This thesis is divided into two main components. For the first component, the first objective of the study was to compare the NH4 + concentrations measured by standard salicylate- and phenol-based methods using a set of soil samples obtained from a single-site manure application study. The second objective was to assess the use of water instead of KCI as the carrier in both methods. Therefore, for analysis of soil-extracted NH4+-N at low concentrations (below 1 mg NH 4+-N L-1 ), the salicylate-based method can be used effectively with water as a carrier instead of KCI.;For the second component of this thesis, pathways of nitrogen (N) loss were quantified at two study sites with two consecutive spring manure applications at Elora, Ontario and a single fall manure application at Ridgetown, Ontario. Treatments consisted of: a control where no manure was applied and no tillage practice, surface application without tillage, pre-tillage, incorporation and a combination of pre-tillage and incorporation. Nitrogen measurements included NH3 volatilization following application and NH4 +-N and NO3--N content in water samples for the remainder of the application year. Water samples were taken from overland flow, lysimeters, tile drains, and groundwater. The first three sources of water were monitored for concentration and total flow volume from which total annual and seasonal mass loadings were calculated. Groundwater NH4+-N and NO3--N concentrations only were determined. In addition to water samples, soil samples were taken before manure application and after harvest. At harvest, grain and stover samples were obtained for measurement of biomass and analyzed for N content. The 2007 growing season had lower than normal precipitation and 2008 had higher than normal precipitation. Volume of water showed a higher influence than N concentration for N loading results from overland flow, water captured in lysimeters, and tile drains. Few treatment differences were found and water sample data was inconclusive regarding tillage practice. Grain yield and grain N content favoured the pre-tillage and incorporation treatment while surface applied was the least beneficial. NH3 volatilization comparison also favoured the combination tillage treatment. Groundwater nitrate-N concentration averages at Elora stayed below the 10 mg L-1 drinking water standard, whereas at Ridgetown they were often 2 or 3 times higher than the limit.