Abstract: Soil organic matter has been considered an important indicator of soil quality because it is a nutrient sink and source, not only enhances soil physical and chemical properties and promotes biological activity but also maintains environmental quality. Two laboratory and one greenhouse experiments were conducted to study the decomposition of different organic debrises and their effects on soil chemical, microbial count and succession and plant growth. In both the experiments, six treatments; 1-turf (T), 2-mixed leaves (ML), 3-mixed leaves+stem and wood chips(ML+CW), 4-stem and wood chips(CW), 5-mixed leaf and stem of trimmed Evonynous latifolia (ELS) and 6-Control (soil only), each with three replications were used. The organic debrises used in treatments 2-5 belonged to common trees of city and recreational parks (Plantanus orientalis, Morus alba, Acer pseudoplatanus, Robinia pseudacacia, Populus spp., Salix sp., Alianthus altissima, Catalpa speciosa, Fraxinus rotundifolius) which were mixed on an equal w/w bases and kept between the two soil layers in plastic pots undisturbed (soil: organic debris ratio was 8:1). The results from laboratory experiment showed that the maximum bacterial counts in treatments were T>ELS>ML+CW>ML>CW, whereas, incase of fungal counts the trend was ML+CW>ML>CW>ELS>T. The ratio of bacteria/fungi and bacterial population were found to be similar as T>ELS>ML+CW>ML>CW. Comparing the initial and final ratios of C/N, OM/TN and lignin/TN in treatments, the initial and final lignin/TN ratios found to be similar (CW>ML+CW>ELS>ML>T) compared to fungi/bacteria ratio (CW>ML+CW>ML>ELS>T). In this study, the ratio of lignin/TN in treatments found to be the most suitable ratio to estimate microbial succession.The microbial succession was fungi/bacteria/actinomycetes. Phytotoxins produced by microbs in two months old (under greenhouse) treatments totally inhibited germination of snap dragon. Water extracts prepared at different concentrations from treatments induced poor germination, plumule and radicle growth of wheat.

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