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

An artificial soil mix made out of industry wastes and sewage sludge has be en created for the revegetation of an industrial site. Physico-chemical pro perties were measured over time to examine soil formation in a chronosequen ce of 11 gardens aged 3-11 years, and in a 3-year longitudinal study of 8 r eplicate experimental plots. In the field plots, available nutrient content was initially high but declined quickly in 3 months. Particle weathering o ccurred, 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 exce ptionally good over the 2 years monitored, with average trunk diameter incr eases 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 sligh t decrease by 11 years. This study has shown that soil development has occu rred 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 orga nic C for microbial decomposition, indicate the potential for nutrient cycl ing.