CHANGE IN CHEMICAL-PROPERTIES OF CONSTRUCTED MINESOILS DEVELOPING UNDER FORAGE GRASS MANAGEMENT

There is a need to better understand the effects of selection, placement, and management of coal-overburden materials on subsequent development and agricultural productivity of constructed minesoils. This field study sought to determine chemical changes that occurred in several minesoils during the early stages of soil formation and to evaluate these changes relative to the continued suitability of the soils for cropping. Four constructed minesoil profiles were compared with an undisturbed Axtell fine sandy loam (fine, montmorillonitic, thermic Udertic Paleustalf). The minesoil profile configurations included a 1.8-m depth of low-pyrite dragline spoil, and 0.3, 0.6, and 1.2 m of mixed Axtell soil placed over 1.5, 1.2, and 0.6 m of spoil, respectively. Kleingrass (Panicum coloratum L.) was established on each soil and harvested periodically. Soil materials were sampled for chemical analysis at construction in 1980 and again in 1986. Changes in profile chemistry of the undisturbed Axtell soil were attributed mainly to increased management. Changes in the minesoils were also strongly influenced by weathering processes. Incorporation of fertilized crop residues increased total C, N, and P and extractable N and P, particularly in the near-surface layers of all profiles. Both fossil C and pH decreased in the minespoil. Electrical conductivity increased with depth as salts leached from the surface soil. Differences in minesoil configuration caused differences in the magnitude and direction of chemical change during the 6-yr study period. While there were year-to-year differences in total forage yield due to variation in water stress, negative effects of chemical properties on crop growth were not generally evident. Crop production was, in fact, greater for the last harvest than for any preceding harvest since stand establishment.