Soil development of an artificial soil mix: nutrient dynamics, plant growth, and initial physical changes

Abstract

An artificial soil mix made out of industry wastes and sewage sludge has been created for the revegetation of an industrial site. Physico-chemical properties were measured over time to examine soil formation in a chronosequence of 11 gardens aged 3–11 years, and in a 3-year longitudinal study of 8 replicate experimental plots. In the field plots, available nutrient content was initially high but declined quickly in 3 months. Particle weathering occurred, with an increase in the finer soil fractions after 1 year. pH was initially 7.62 and declined to 6.85 by 3 years. Native tree growth was exceptionally good over the 2 years monitored, with average trunk diameter increases of 144 mm for Corymbia maculata, 94 mm for Acacia floribunda, and 39 mm for Callistemon salignus. In the chronosequence study, there was a build- up of nutrients (C, N, and P) in the soil mix over 6–10 years, with a slight decrease by 11 years. This study has shown that soil development has occurred in the short and longer terms, with rapid changes seen in the first 12 months. High levels of N and P remaining after 11 years, and abundant organic C for microbial decomposition, indicate the potential for nutrient cycling