Influence of textural layering on field capacity of coarse soils

Zettl, J. D., Barbour, S. L., Huang, M., Si, B. C. and Leskiw, L. A. 2011. Influence of textural layering on field capacity of coarse soils. Can. J. Soil Sci. 91: 133-147. The current method of designing reclamation covers for land disturbed by oil sands mining in northern Alberta, Canada, relies on an estimate of the field capacity (FC) of both natural soils and reclamation soil prescriptions. The objective of this research was to examine the influence of layered, textural heterogeneity on FC. Field testing was performed on seven natural sites with coarse-textured soils that support a range of ecosite classes. Double-ring infiltration and drainage tests with real time monitoring of water content were undertaken along with test pit excavation and detailed profile sampling. The measured water storage at FC following drainage demonstrated that higher water storage at FC values are associated with increased textural heterogeneity, and these sites reflected more productive ecosite class. Rigorous, physically based modeling illustrated that a texturally heterogeneous site can have water storage at FC within 1 in profile that is between 110 to 330 mm higher than a homogeneous profile with the same average texture. These higher values of water storage at FC in texturally heterogeneous sites could account for the differences in observed ecosite productivity. This work highlights the importance of textural layering in designing reclamation covers in coarse-textured soils to maximize FC.