|
E
<br />SENCINDIVER & AMMONS
<br />tles and mixed colors are related
<br />result of parent material weath-
<br />rocess of sulfuricization (pyrite
<br />;t al., 1993). Dark colors of sur-
<br />>anic matter accumulation and
<br />igh -C rock fragments produces
<br />materials often result in erratic
<br />f the backfilling and topsoiling
<br />1978). In situations where soils
<br />ors from pre- existing soils with
<br />;oils may no longer be in poorly
<br />ias may develop with time.
<br />yr old, have weak to moderate
<br />zons. This structure is primarily
<br />1985; Daniels & Amos, 1981;
<br />but sometimes it is platy (Bus -
<br />ity structure often results from
<br />;tion. Structure developed since
<br />)ment also has been observed in
<br />'iolkosz et al, 1985; Daniels &
<br />1980; Thomas & Jansen, 1985).
<br />new type of structure in Illinois
<br />cure has a similar appearance to
<br />aggregates loosely compressed
<br />;d structure is formed in materi-
<br />transported on a conveyor belt.
<br />nois minesoils with fritted struc-
<br />inesoil subsurface horizons that
<br />POROSITY
<br />iesoil bulk density values to be
<br />1984; Dunker & Barnhisel, 1997;
<br />., 1971; Thurman & Sencindiver,
<br />al bulk density, whereas others
<br />:s, as well as total bulk density.
<br />ijusted bulk densities of surface
<br />ian the native soils, but the bulk
<br />nilar to the unmined soil.
<br />ages (Schafer et al., 1980), bulk
<br />or less than the native soil. New
<br />MINESOIL GENESIS AND CLASSIFICATION 599
<br />minesoils had a slightly higher bulk density than the native soils. The authors
<br />attributed the differences to mining method rather than to pedogenic processes.
<br />The old minesoil had been dumped in place by horse - pulled wagons, while the
<br />new minesoils were constructed with large dozers and scrapers. Another study on
<br />different -aged lignite minesoils in Texas showed bulk density of 20- to 50 -yr -old
<br />minesoils to be significantly lower than 1- to 15 -yr -old minesoils (Skousen et al.,
<br />1990). These bulk density differences were attributed to mining equipment and
<br />organic inputs on older sites.
<br />In a study of topsoiled and nontopsoiled minesoils (Thurman et al., 1985),
<br />adjusted bulk density values were significantly higher for all depths in minesoils
<br />that had been topsoiled. Equipment used to place topsoil may have compacted the
<br />soil. Most studies have shown that surface horizon bulk density is lower than sub-
<br />soil bulk density (Short et al., 1986a; Strain & Evans, 1994; Thurman et al., 1985;
<br />Varela et al., 1993). The lower density of the surface soil may be the result of bio-
<br />logical activity, organic matter incorporation, root penetration, and/or freeze -thaw
<br />cycles.
<br />Compaction of minesoils negatively affects water movement, aeration and
<br />plant root extension. Minesoil compaction has been identified in Illinois as a
<br />major limiting factor to successful row crop production (Dunker et al., 1992).
<br />However, some investigators (Smith et al., 1971; Ammons, 1979) have sug-
<br />gested that minesoils with no physical barriers to root growth, such as massive,
<br />compacted layers, extremely acid layers or thick fragmental layers, are com-
<br />monly deeper than native soils developed over bedrock. Therefore, these mine-
<br />soils have a greater depth for plant rooting and a higher total water - holding
<br />capacity. Texas studies (Bearden, 1984) showed coastal bermudagrass [Cynodon
<br />dactylon (L.) Pers.] roots extending to depths of 4 m in unconsolidated loamy
<br />sediments of the Wilcox Group, considerably deeper than in native clay pan soils
<br />of the area.
<br />VIII. SOIL GENESIS
<br />On undisturbed landscapes, soil profiles are the function of climate, organ-
<br />isms, relief or topography, parent material, and time. These five factors are called
<br />factors of soil formation (Jenny, 1941) or state factors (Jenny, 1980). As Indorante
<br />and Jansen (1981) have observed, this soil genesis model applied in the usual way
<br />does little to help perceive the spatial order of minesoils. Time is so short that the
<br />active factors of soil formation have had little impact on the process of soil for-
<br />mation. Parent material variability cannot be explained by applying the usual geo-
<br />morphic models. Grube et al. (1982) reported that the "aggregation of geologic,
<br />pedologic, and chemical information. . . . is the basis for predicting the nature
<br />of soils that form in specific rock environments." Freeze -thaw, shrink - swell, dis-
<br />solution, leaching, oxidation, organic matter decomposition and incorporation,
<br />and aggregation of soil particles into peds are major pedogenic processes that dif-
<br />ferentiate minesoil properties and horizons (Daniels & Amos, 1981; Roberts et
<br />a1., 1988a).
<br />
|