Soil Characterization of Mined-Out Soils at Mahdia
By
Courtney Bullen1 and Vernon Burnett2
ABSTRACT
Soil physical and chemical analyses were carried out on samples obtained from a mined-out site at St.
Elizabeth, Mahdia, in Guyana’s rainforest region. In order to determine changes in soil properties
resulting from open-pit mining, samples were taken from undisturbed sites in the two main soil types
occurring in the area and from disturbed but undeveloped land. A fourth sampling site was located within
an Acacia mangium plantation established in 2008, as a pilot project in the rehabilitation of mined-out
soils in Guyana’s gold and diamond bearing districts.
The predominant feature of the St. Elizabeth landscape was the varied effects of water erosion as
evidenced by mounds and gullies. It was also evident that there was separation of the particle size
fractions as the lighter, less dense clay particles had largely been washed away leaving newly formed,
coarse textured soils.
These observations were in large part supported by data provided from soil physical and chemical
analyses. On both the disturbed, undeveloped sites and the within the A. mangium plantation, the sand
particles were disproportionately and significantly higher than in undisturbed sites. Soil organic matter
content was significantly lower in the undeveloped area but within the A. mangium plantation, there was
evidence of contribution to this parameter from the newly established vegetation as well as from biochar
which had been used as a soil ameliorant in agroforestry plots.
Fertility levels declined significantly as a result of changes induced by mining activity. More importantly,
there was evidence of Al toxicity in all the samples obtained from mined-out soils. Al toxicity adversely
affected attempts at the establishment of cowpea and hot peppers but did not affect the establishment and
growth of A. mangium, indicating that this exotic plant species exhibited tolerance to Al toxicity.
1. Lecturer II, Faculty of Agriculture and Forestry, University of Guyana
2. Final Year Student, Faculty of Agriculture and Forestry, University of Guyana, 2012