Characterization of Municipal Solid Waste Compost as a Soil  Amendment and Development of a Management Strategy for  Selected Potential Constraints

Urbanization and industrialization, especially in developing countries, has accumulated huge amount of municipal wastes. Incineration of solid waste is not suitable for countries  like Sri Lanka because it needs a high requirement of energy owing to the low calorific value high moisture contents. Waste recycling to produce municipal solid waste compost (MSWC) and application to agricultural lands has been successfully used around the world. Although agriculture-based waste compost (AWC) is highly popularized, the use of  MSWC in agriculture sector of Sri Lanka is still in subordinate level, where farmers are reluctant to use them due to the negative impressions such as toxic effects and low nutritive values. This is mainly caused by the lack of knowledge and limited research. The major objective of the proposed study is to assess the effectiveness of Municipal Solid Waste Compost (MSWC) as a soil amendment. The study considers physicochemical and biological aspects of MSWC and development of management strategy for selected potential constraints, basically related with pH and EC.  Thirty-two MSWC samples were collected from compost-producing plants distributed over the country and three AWC that are commonly available in the local market were  purchased. Particle size fractionation and determination of organic matter content, pH, EC, N, P, K, and selected heavy metal (Zn, Mn, Cu) levels were conducted for all samples. After basic characterization in the laboratory for basic properties, eight MSWC and two AWC samples were selected for the further experiments including field studies. Phytotoxic effects using Germination index (GI) and the impacts of organic amendments (biochar, Gliricidia, gypsum) on pH and EC levels of MSWC, were determined in the laboratory.  Field experiment I was conducted to assess the impacts of MSWC on soil properties (pH, EC, and short-term crop yield response for two consecutive years using bush bean and maize as the test crops. At present, farmers use both biochar and compost in their crop  fields. However, the knowledge lacks on the effects of combined application of biochar and compost. Therefore, a pot experiment was conducted to evaluate possible impacts of mixing biochar with MSWC on soil pH, EC, and crop yield using tomato. The total OM% of the compost samples were in a range of 23–30%, where that of the fractionated samples (>2 mm, 2-1.4 mm, 1.4-1.0 mm, 1.0-0.5 mm,