Tropical Grasslands (2000) Volume 34, 254–262

Effects of pasture cover on soil erosion and water quality on central Queensland coal mine rehabilitation

CHRIS CARROLL1 and ANDREW TUCKER2

1Queensland Department of Natural Resources, Rockhampton, and
2Emerald, Queensland, Australia

Abstract

To determine the impact of vegetative cover and slope on runoff, erosion and water quality, a field study was commenced in 1993 at 3 open-cut coal mine sites in the Bowen Basin. Field plots of 0.1 ha with slope gradients of 10, 20 and 30%, along with catchments of 0.1 ha, were used to measure runoff, sediment loss and water quality from rehabilitated land. Pasture and tree treatments were imposed on soil and spoil material, while 2 soil and spoil plots were left bare as the control for the study.
The greatest soil erosion risk occurred before pasture cover established, when a large surface area of the soil (> 50%) was exposed to rainfall impact and overland flow. Once grass species, such as buffel (Cenchrus ciliaris), colonised soil plots, there were negligible differences in soil erosion between slope gradients. On spoil plots, rhodes grass (Chloris gayana) reduced in situ soluble salt content and runoff electrical conductivity levels. Where spoil crusted, there were poor vegetative growth and unacceptably high runoff and erosion rates throughout the study. Average electrical conductivity of water leaving the catchments also declined with the increase in vegetative cover. Where burning was conducted, runoff and erosion rates increased. After one month and following rainfall, buffel biomass had regenerated to 1.1 and 1.7 t/ha on the two catchments.

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