Effects of composted green waste on soil quality and tree growth on a reclaimed landfill site

The addition of composted green waste (CGW) into soil-forming materials during land reclamation can benefit tree growth by improvement of soil properties and provide an effective waste management solution. CGW addition may also assist the establishment of earthworm populations, which in turn aid soil development through their burrowing and feeding activities. An experiment was set up on a reclaimed landfill site, to measure the effects of CGW addition on soil physical and chemical quality and subsequently on the survival and growth of two tree species (Acer platanoides and Alnus cordata). A further objective was to measure the influence of earthworm (Aporrectodea longa) addition on the above. CGW addition led to significantly greater A. cordata growth (height and diameter) and increased survival rate. No benefits from CGW addition were observed on A. platanoides growth or survival, although this is likely due to soil drought conditions during establishment. CGW addition significantly increased levels of organic carbon and essential plant macro-nutrients in the reclaimed soil. Soil pH rose slightly across all treatments, with highest final pH under the control treatment. Earthworm inoculation, as used, was unsuccessful at increasing population density of A. longa. This experiment showed that CGW application can effectively improve tree establishment and soil quality on reclaimed landfill; however tree species selection is an important consideration, based on individual species tolerance and sensitivity to certain soil conditions. These findings will be informative to decisions on soil amendment and afforestation activities on similar reclaimed landfill sites.