Abstract
Elevated atmospheric NH3 levels near intensive livestock operations can add significant N to local agroecosystems. In this study, the potential atmospheric NH3 sorbed by soil and water was assessed over a 2-year period starting October 2000 in an intensive livestock production area in southern Alberta, Canada. Fifty-two uneven grid sampling sites were selected in the 53,905 ha study area. The sorption rate of atmospheric NH3 was estimated weekly by exposing distilled water and air-dried soil samples to the atmosphere at the sampling sites. The increases in NH4–N content in the samples after 1-week exposure was regarded as an index of the atmospheric NH3 sorbed for that week. The NH3 sorption rates were highly variable across the 52 sites, with water ranging from 4 to 125 kg ha−1 year−1 with a mean of 22 kg N ha−1 year−1 and soil from 5 to 84 kg N ha−1 year−1 with a mean of 20 kg N ha−1 year−1. Considerable variation in NH3–N sorption across the study area reflects the effects of size, direction (upwind or downwind) and proximity of nearby livestock operations or other NH3 sources and operators’ activities around the sampling sites. The NH3 sorption rate at each site also varied considerably in response to weather conditions. The high rate of NH3 input poses a direct risk of surface water eutrophication in intensive livestock operation areas. If fertilizer recommendations are not reduced to account for NH3 sorption by soil, excess N may also contribute to eutrophication through runoff and leaching.
Published Version
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