Effect of animal manure on population dynamics of indigenous soil Bacillus spp.

Abstract

Bacillus spp. are soil inhabitants, many of which play vital roles as biofertilizers and biopesticides in plant production. These bacteria derive their nourishment from soil organic carbon and nitrogen provided by organic matter. Reports indicate that animal manure increases the population and diversity of Bacillus spp. in the soil.  However, there is limited information on which of the three commonly used animal manure (cattle, goat, and chicken) is more effective in multiplying Bacillus cells. This study evaluated the effectiveness of cattle, goat, and chicken manures, standard nutrient broth, and soil, as growth media, on the multiplication of 22 indigenous soil Bacillus spp. strains previously isolated from the cabbage rhizosphere. A Completely Randomized Design with five treatments replicated three times was used and the conditions were kept at room temperature. Both standard nutrient broth and sterilized soil media were used as controls. Colony-forming unit counts of Bacillus spp. were subjected to Log (x+1) transformation. One-way analysis of variance was used to generate mean differences and means separated using Duncan’s LSD test (p = 0.05). Linear curves were drawn to compare the growth trends for each Bacillus strain. The findings indicate that the growth of Bacillus spp. strains in animal manure were significantly higher than in the soil media. Growth in the soil media was significantly lower than in standard nutrient broth media growth. Results further show that the growth of the Bacillus spp. in all the media followed the normal growth curve of bacterial cells. Results from this study, therefore, suggest that amendment of soil with cattle, goat, and chicken manures enhances the growth and multiplication of soil Bacillus spp. and this has a positive effect on soil fertility. These manures can also be used in the commercial production of the bacillus bacteria as a biofertilizer and biopesticide. Biofertilizers are cheap, have long-term effects on soil fertility, and are health-friendly to the environment and the user.