Spatial variability of deep leached nitrate as related to denitrification in a prairie landscape
van Kessel, C.
Denitrification is an anaerobic process that converts NO3- to N2 and N2O, and is considered one of the most highly variable soil processes within a landscape. Moisture acting in response to hillslope hydrological processes controls rates of denitrification and leaching at the landform level. In 1991, a field study was conducted in the Black Soil Zone of an undulating landscape (3-5% slope) at Blaine Lake, Saskatchewan to determine the amount of nitrate leached below the rooting zone and its possible relationship to denitrification. Nitrate has been leached and translocated in the upper regolith in response to water movement where significant leaching of soluble components occurred in depressional areas to depths beyond 3 m. The amount of nitrate at depth was greatest in shoulder and upper level elements where it reached a maximum of 95 ug g-1 at the 1.5 m depth. Footslope and lower level elements contained the lowest nitrate levels (<1 ug g-1) within the 3m sampled area. High rates of denitrification occurred in footslope and lower level elements, compared to significantly lower rates on divergent shoulder and upper level elements. Nitrate content at depth was inversely correlated with denitrification activity (-0.485 ***). High mean concentrations of nitrate were therefore, spatially related to low rates of denitrification activity in response to hydrological spatial variation.
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