Spatial pattern of soil properties in an irrigated field
van Kessel, C.
Denitrification from agricultural ecosystems is regarded as a major contributor to atmospheric N levels, but the actual rates of denitrification and the controls on these rates remain poorly understood. This study was conducted to examine landscape-scale patterns of denitrification and the soil properties that control these patterns. Two sampling grids (11 x 11 m and 110 x 110 m) were established in an irrigated field in an aridic Boroll (Brown Chernozemic) soil in southern Saskatchewan. The measured soil properties (denitrification rate, respiration rate, volumetric moisture content, bulk density, soluble organic and inorganic carbon, total and mineral N, in situ pH, and in situ redox potential) were correlated to slope properties and derived landform elements at the site to determine landscape-scale patterns and relationships. The soil properties occurred in one of three spatial patterns: (i) a random pattern for mineral N; (ii) a diagonal pattern for pH, soluble organic and inorganic carbon, and total N; and (iii) a depression-centered pattern for denitrification, bulk density, moisture, respiration and redox potential. Statistically distinct rates of denitrification were associated with the different landform elements: rates were lowest in the shoulder elements, intermediate in the footslope and level-convex elements, and highest in the level-concave elements. Hot-spots of denitrification activity, i.e., sampling sites with denitrification rates statistically identified as outliers, were all associated with the level elements and, predominantly, the level-concave elements.
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