Mekelle University The School of Graduate Studies Faculty of ...

4.2 DiscussionsAddition of earthworm in mixture of the ingredients rice husk, cow dung and biosolid atdifferent C/N ratio vary in pH. The pH concentrations were significantly (P < 0.01)affected by C/N ratio and earthworm treatments (Table 1). The highest and lowest pHvalues were observed at the rate of C/N ratio of 55:1 with earthworm and 15:1 with andwithout earthworm respectively. This could be due to the materials used forvermicomposting especially the biosolid rich in active fraction of organic matter andNH + 4 , CO 2 and organic acids product of respiration and different microbial metabolismduring vermicomposting and composting may contributed to the decrease in pH as it wasdescribed by Albanell et al., (1988).On the other hand, from the result it is clearly shown that the mixture of rice husk, cowdung and biosolid treated with earthworm at the rate of 25:1 C/N ratio had significantlyincreased organic carbon (P < 0.01) as compared to control and the other treatmentsexcept 15/1 C/N ratio with earthworm (Table 1). This indicates that the continuous inputsof organic carbon to the 25:1 C/N ratio were probably from slowly miniralization of thematerial used especially rice husk and neutral of pH which favored the activity of theearthworm to release organic carbon effectively. The excrated polysaccharides in theearthworm gut could also be responsible for this increase as it was described by Lui et al.,(1991).Phosphorus is essential for plant growth. In this trial the mixture treated with earthwormat the rate of 25:1 C/N ratio had significantly (P < 0.05) increased available phosphorousas compared to 15/1 C/N ratio without earthworm (Table 1). The enhancement of53