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2.Usage of Microbial Community Structure Analysis as an Indicator of Compost Management and Its Maturity

Kotaro Kato, Nobuaki Miura, Hiroyasu Tabuchi, Ichio Nioh(Institute for Agro-Microbiology)

Two types of poultry manure compost, PHP (bulk density; 260 kg m-3) and PHW (bulk density; 190 kg m-3) were made from same volumes of same raw materials, and their decomposition processes were compared. Throughout the composting periods, changes in temperature, inorganic nitrogen contents, and germination indices (GI) were slower in PHP than in PHW. Development of microbial community structure in PHP was shown to be later than that in PHW by the principal component analysis of phospholipid fatty acids (PLFA) analysis. Proportion of biomarker fatty acids for gram-positive bacteria reached a plateau (about 50 mol%) after day 134 for PHP and day 91 for PHW. Concomitantly, the proportion of the straight hydroxyl and saturated fatty acids that were contained in anaerobe as Bacteroides and aerobe as Acetobacter or Thiobacillus decreased to less than 2 mol%. These days coincided with the time we determined as the maturity stage based on the changes in physicochemical and biological parameters. Linear simple regression analysis with additional data of other composts showed that GI had positive and negative correlations for the proportions of biomarker fatty acids for gram-positive bacteria and straight hydroxyl and saturated fatty acids, respectively. Cluster analysis of PLFA proportion indicated that the microbial community structures were classified into exclusive clusters according to the differences of the nitrogen contents in compost feedstock, of the composting method, and of the turning frequency. These results suggested that PLFA analysis was used as an indicator not only to detect the succession of microbial community structure but also to assess compost management and its maturity.

Keywords:Nature Farming, Soil diagnosis, Organic matter, Paddy field, Ordinary upland field, Greenhouse field