Effects of Coffee on the Growth of Bacteria, Fungi and Plants

Coffee has been used several times in soil amendment to increase the soil organic matter contents, which has led to improvement in crop yield and quality. However, limited information exists on the effect of coffee on soil bacteria and fungi. This study aimed to assess the effect of coffee on the soil bacteria and fungi. Soil samples were amended with concentrations of coffee (0%, 0.5%, 1% and 2%) in triplicates with the plant. Bacteria and fungi were isolated from each microcosm at seven-day intervals for four weeks. The abundance of bacterial genes (16S rRNA) and fungal genes (28S rRNA) from the soil as well as the pH of the soil and plants parameters were determined. The data collected were analysed statistically using R programme. The population of bacteria in soil microcosms decreased from 7.0 x 107 to 2.0 x 106 cfug-1 while the population of fungi increased from 5.0 x 106 to 8.0 x 108 cfug-1 with an increase in the concentration of coffee. Additionally, the bacteria 16S rRNA genes decreased from 4.0 x107 to 5.0 x106 geneg-1 while the fungi 28S rRNA genes increased from 2.0 x106 to 5.0 x107 geneg-1 of soil with an increase in the concentration of coffee. The pH of the soil decreased from 7.6 at day 0 to 7.3 after 28 days of treatment. The increase in concentration of coffee reduces the measured plant (Phaseolus vulgaris) parameters, while the highest concentration of coffee (2.0%) tested completely inhibited the plant growth. The amendment of soil with coffee inhibits the growth of the soil bacteria but stimulates the growth of soil fungi. The addition of a low concentration of coffee to the soil reduces the soil pH.