The fate of nitrate in soil treated with hog manure

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Flynn, Colleen P.
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The investigation of the fate of manure nitrogen after the application of hog manure was composed of three main components; a field study, a laboratory study and a mathematical model. The field study examined NO$\sb3\sp{-}$ distributions in the soil profile to a depth of 3 m on an Emerson silty clay loam and a Poppleton loamy sand. The effects of precipitation and irrigation were considered in the analysis and interpretation of NO$\sb3\sp{-}$ distribution. Nitrate levels were highest at the surface and decreased with depth. The addition of water, through irrigation or precipitation, resulted in leaching or disappearance of NO$\sb3\sp{-}$ through denitrification. Nitrate levels that exceeded the Canadian drinking water guidelines were found in the groundwater at the Poppleton site. In the laboratory study, denitrification intensities of the two soils in saturated anaerobic environments were examined with respect to depth, temperature and treatment. Results from the laboratory study indicated that the disappearance rates of NO$\sb3\sp{-}$ were a function of temperature and soil depth. The rate was shown to be highest at the higher temperature. However, under constant temperature, the O$\sb3\sp{-}$ disappearance rate was highest at the surface and decreased with soil depth. The magnitudes of the rates for N disappearance of surface samples ere similar between the Emerson and the Poppleton soils, with slightly higher values for the Emerson soil. However, as the soil depth increased, the NO$\sb3\sp{-}$ disappearance rate ecreased with a much greater rate in the Poppleton sand than with the Emerson silty clay loam. (Abstract shortened by UMI.)