Effects of sewage sludge application on vegetation and soil macrofauna recovery in Soratama Sand Quarry, Bogota, Colombia

Effects of sewage sludge, used as an organic amendment, on vegetation recovery and soil macro-fauna re-colonization, were studied in Soratama quarry restoration. For this purpose, mixtures of mining residual soil and sewage sludge in different proportions (T1 8:1; T2 4:1; T3 2:1) and a control (C1:0) were used. Plots were arranged in a complete randomized design. Vegetation cover was recorded using permanent subplots. Data of macro fauna was collected digging three monoliths of 20 x 20 x 30 cm. Results showed that vegetation height and cover on treatments were significantly greater than on control plots; nevertheless this pattern was not proportional to sewage sludge addition. Floristic composition was dominated by Poaceae and Asteraceae families, especially of perennial species. Diversity and richness of plant species increased along time and were higher in T1, however it was not dependent from sewage sludge addition. Results for soil macro fauna revealed that adult’s re-colonization started after 3 months, while larvae re-colonization occurred after 6 months in the majority of treatments. Enchytraeidae and Staphylinidae were the most abundant families. T1 and T2 proportions showed to promote vegetation growth, diversity and species richness. T3 was the treatment with the fastest soil macro fauna re-colonization. A soil analysis evidenced that the greater the proportion of sewage sludge, the greater the contents of organic carbon, nitrogen, phosphorus and moisture, however, treatment with 2:1 proportion (T3) presented similar characteristics with the nearest forest soil.