Effects of Istanbul metropolitan municipality compost product on plant growth, mineral nutrients and heavy metals in plant and soil

Official URL: http://192.168.1.20/record=b1225703 (Table of Contents)

Large scale municipal solid waste (MSW) production is a common environmental problem in metropolitan areas of the world. Converting the organic fraction of MSW obtained from residential areas into environmentally acceptable products is possible through composting process. Composting of MSW is widely accepted as an environmentally friendly and sustainable solution for recycling large amounts of MSW collected by metropolitan municipalities. The final product "compost" can be further utilized in agriculture, horticulture, landscaping, erosion control, reclamation and landfill applications. In this study, the compost product of Istanbul metropolitan municipality was characterized to reveal its potential on plant growth and mineral nutrition. The two common problems of MSW composts, heavy metals and high salt content, were also assessed by greenhouse pot experiments using different plant species. In a series of incubation experiments, the long term effects of compost amendments to soil was tested to understand the changes in plant nutrient concentrations, nutrient bioavailability and levels of salt and heavy metal accumulation in soils. Chemical analysis performed on the compost product showed that it is rich in organic matter (i.e. %46) and various plant macro and micro nutrients. Although not comparable to strict EU legislation for eco-compost, concentrations of heavy metals were similar or even lower than typical MSW composts. In greenhouse experiments compost applications to soil up to 5% (w/w) promoted plant growth, particularly at low productivity conditions with limited basal fertilizer rates. Using soils with inherent problems such as zinc (Zn) deficiency and born toxicity, it was demonstrated that compost applications can totally eliminate Zn deficiency and decrease accumulation of B to safer limits in plant shots. However, higher application rates resulted in occurrence of salt toxicity symptoms which could be alleviated to a certain extent by the use of zeolite amended compost during processing. Shot concentration of heavy metals, particularly Cd and Pb, were also increased at higher application rates. It was concluded that MSW compost produced by Istanbul metropolitan municipality can be beneficial in agricultural production with some limitations. Although it was shown to enhance plant biomass production particularly at low productivity and Zn deficient conditions, there is the need for on-site and long-term field trials to acquire cost-benefit relations and ensure safe heavy metal limits in harvested plant parts.