The key uses field morphological properties (texture, pedality, colour, coarse fragment
content) to map the spatially diverse materials that strongly affect plant growth and the success of mine pit rehabilitation (Tables 1 and 2).
content varied from 40 to 55 percent (by volume) and rooting depth extended up to 30 cm (12 in) (Lord, 1984).
Carbon stock for a layer of soil is the product of organic carbon content (C%), bulk density (BD, g/[cm.sup.3]), coarse fragment
content (CF, %), and thickness (cm), representing the mass of carbon per area over a specified depth (t/ha of carbon) (Ellert et al.
where ROKF is the coarse fragment
factor as defined by Simanton et al.(1984), [C.sub.e] and [P.sub.e] are event values for the USLE C and P factors, and [X.sub.e] is selected from:
Percentage weight of the coarse fragments
was measured, and percentage of coarse fragment
by volume was calculated as described by Delgado (1998).
The shapes of the coarse fragments
(d [greater than or equal to] 9.5 mm), medium fragments (4.75 [less than or equal to] d < 9.5 mm), fine fragments (0.075 mm [less than or equal to] d < 4.75 mm), and tiny fragments were plate, flake, sand, and power, respectively.
Soil samples were analysed to determine particle-size distribution (hydrometer method), calcium-carbonate equivalent (HCI treatment or titrimetric method), organic matter content (Walkley-Black method), soil reaction (saturated paste), percentage of coarse fragments
(by volume), and bulk density (by cylinder method) (Soil Survey Staff 1996).
Fine spoil was a silty material from lagoon sedimentation resulting from the process of coal washing, without coarse fragments
. Coarse spoil was the sieving remnant, containing 89% by weight coarse fragments
(93% of these 2-6 cm), mainly limestone mixed with gypsum and lignite (this is the same spoil employed by the mine company to construct the banks).
(diameter > 2 mm ) within the sample were screened out and weighed.
The coarse fragments
were measured and used to correct the bulk density.
Some of these coarse-textured soils have a significant amount of coarse fragments
, which usually increases with depth (USDA-SCS 1973; USDA-SCS 1988).