COMPARATIVE ANALYSIS OF THE MICROBIOLOGICAL AND PHYSICOCHEMICAL CHANGES ON COMPOSTING RICE HUSK WITH MIMOSA PUDICA AND LEUCENA LEUCOCEPHALA.

AUTHOR: MBANU, CHERYL IFEANYICHUKWU 

DEPARTMENT: APPLIED MICROBIOLOGY AND BREWING 

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

Analysis of the microbiological (bacterial and fungal) and physico-chemical modifications in the controlled biological decomposition of rice husk with two different leaves was carried out. The standard 4:1 carbon to nitrogen substrate ratio and out-door semi-circular heap method of composting were employed. Heap I contained husk and Mimosa pudica leaves (touch and die plant) while heap II contained husk and leaves of Leucena leucocephala (Ipil ipil). The degradative process was effected by factors like temperature, pH, moisture content, particle size and microbial population. Ambient temperature (270C) increased to a 570C maximum for heap I and 580C for heap II and gradually returned to 270C as both heaps matured. Alkalinity set in from the 7th week, reaching a maximum pH of 9 for both heaps, and then returning to neutral at the end of the experiment. A moisture content of about 30% was observed for both heaps throughout the study. A mixed population of mesophilic and thermophilic bacteria and fungi effected the degradation to humus. Total aerobic bacterial counts decreased throughout the study while total aerobic fungal counts decreased with increasing temperature and then increased as heap returned to ambient values. Bacterial genera identified were Bacillus, Alcaligenes and Pseudomonas, all of which were mesophiles. The only thermophilic bacterium identified was Bacillus. Mesophilic fungal genera identified were Aspergillus, Fusarium, Mucor, Penicillium, Rhizopus, Scopulariopsis and Trichoderma while Aspergillus and Trichoderma were the thermophiles identified. Bacteria reached a peak value of 30.0 x 107cfu/g for heap I and 32.0 x 107cfu/g for heap II at 5th week while fungal peak value was 15.0 x 105cfu/g for both heaps. The compost attained stability at 140 days as carbon to nitrogen ratio reached 13:1 for heap I and 14:1 for heap II while the ash content increased from 12% to 19% in heap I and 12% to 23% in heap II, indicating compost maturity. Organic matter content decreased for both heaps from 23% to 3.8% and 4.4% in heaps I and II respectively. Other macronutrients analyzed were potassium, phosphorus, calcium and magnesium with values within standard range of less than 2% each. 

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