Quality Assessment of Commercially Produced Composts in Saudi Arabia Market

摘要

A variety of stability and maturity indices were evaluated for 14 commercially produced composts in Saudi Arabia in order to acquire a comprehensive image of local compost quality and its compliance with local and international compost standards. Theses indices include chemical parameters such as Electrical Conductivity (EC), ammonium and nitrate concentrations, heavy metals and biological parameters such as Germination Index (GI), pathogen indicator and selected pathogens. Other important compost characteristics were also analyzed. Results revealed wide variations among samples in respect to all parameters examined. About 64 percent of tested compost exceeded the upper limit of EC set by most compost associations. The C/N ratio for compost samplesranged from 10.90 to 39.30 and 36% of samples were above the maximum value (1:25) set by various compost nations. Ten compost samples (71 percent) exceeded the maximum value set for nitrification index (NH_4/NO_3 ratio). Heavy metal contents in almost all compost samples were lower than the permissible levels set by local and international standards. GI test indicated that 64% of examined samples were below 80% and therefore could exhibit phytotoxicity. Microbiological analysis showed that 5,4 and 10 compost samples were contaminated with faecal coliform, Salmonella and Staphylococci, respectively at levels above the suggested limit proposed by regulatory agency. Stability and maturity indices tested in this study have shown that most compost samples had a poor quality and should have no access to the market. The high variability of most important parameters of local composts suggests an urgent need for developing local compost quality standards in order to assure a good quality for land application,environment and public health.