Dissolved organic carbon concentration and denitrification capacity of a hill country sub-catchment as affected by soil type and slope

Characterising the dissolved organic carbon (DOC) concentration and denitrification capacity of the soils and slopes in hill country is important in order to manage the leaching and availability of nitrate in ground and surface waters. This study investigated the DOC concentration and denitrification capacity of the soils and slope classes of a sub-catchment within a hill country farm, in Palmerston North, New Zealand. Fifty locations comprising of 2 soil orders (Pallic, Brown), 8 soil types (3 drainage classes) and 3 slope classes were sampled from different soil depths down to 1 m. The results suggest that compared to slope, soil type had a greater effect on denitrification capacity within the sub-catchment. The Ramiha soil had the highest DOC concentration (105 mg kg(-1) within 0.3-0.6 m depth) and moisture content, and hence the highest denitrification capacity (10 mu g kg(-1) h(-1)). This suggests that farms or catchments with similar soil types may have a greater capacity to attenuate nitrogen losses to the environment.