Role of Microorgainsms and Their Enzymes in Composting Process From Plant Residues

Abstract

Newly reclaimed sandy soils are considered one of the main items of agricultural expanding policy in Egypt. Therefore we need to continuous addition of organic matter to increase soil fertility and agricultural production. For this reason, eight heaps were prepared each heap involves four plant residues. One set of four heaps was supplemented with organic manure. Another set was supplemented with cellulose decomposers. Some physical, chemical and microbiological properties were determined during composting process. The important obtained results are as follows: Temperature inside the compost heaps began to rise from the third day of composting and reached maximum values at the third week of the process. From the fourth week there was a gradual decrease in temperature till the end of composting. The pH values of the eight heaps tended slightly to acidic at early intervals of composting process till the 20 th day, then the pH values increased to reach neutral or slightly alkaline by the end of the process. The Gradual increases in EC and bulk density values during the process. The obtained results showed a gradual decrease in organic carbon and organic matter by time and increase in total-N of all composted heaps during the different intervals of composting process. The results showed remarkable decrease in C/N ratio with the progress of the composting process.At the beginning of the composting, total number of mesophilic bacteria was increased, however it was markedly decreased in the third week of composting. Then it was highly increased at the end of composting. The same pattern of the results was also observed with mesophilic fungi and actinomycetes. On the other hand, thermophilic bacteria were sharply increased at the third week and then obviously decreased at the end of the composting process (cooling phase). The same trend was also observed with thermophilic fungi and actinomycetes. It has been also observed that no marked differences were obtained in the total microbial counts of different compost heaps for both mesophilic and thermophilic organisms.In concerning the enzymes activities of common selected fungal, bacterial and actinomycets strains the obtained results were: In regarding to Cellulase enzyme activity, it was obvious that Trichoderma reesei, Bacillus stearothermophilius and Streptomyces antibioticus recorded the highest activity in culture filtrates. In regarding to dehydrogenase enzyme activity, Trichoderma reesei, Bacillus subtilis and Streptomyces roseus exhibited the highest activity. In case of protease activity and also soluble protein the fungus Trichoderma ressei, Bacillus subtilis, and Streptomyces antibioticus showed high protease activity and also high soluble protein content.