Effects of Organic and Inorganic Fertilizer on the Population Dynamics of Soil Microorganisms in Tea Rhizosphere at Kericho, Kenya

Aim: The long-term cultivation of tea (Camellia sinensis L.) alters microorganism communities in the rhizosphere; it can increase saprotrophs, pathogenic microorganisms and reduce symbiotrophs. Fertilizers are sources of plant essential nutrients and can influence the activity and population of soil microorganisms. This study aimed to determine the effect of fertilization regimes on the population dynamics of soil microorganisms in the tea rhizosphere for its management.

Place and Duration: The study was carried out at the Tea Research Institute, Kericho, Kenya during the dry (February-March) and wet season (June-July).

Methodology: Two main fertilizer types; organic (Phymix) and inorganic (Nitrogen, Phosphorus and Potassium- NPK) and foliar fertilizer (Tecamin Max, Tecnokel Amino Mix) as sub treatments application at the rate of 0, 75 and 150 kg N ha-1), were applied in four replications. Sampling of soil was done before treatment application, during the dry season (February-March) and the wet season (June-July). The fungal and bacterial populations for both seasons were characterized. The data collected was analyzed using SAS (version 9) Statistical Software.

Results: The study showed that the fungal colony units varied significantly (P≤0.05) between the types of fertilizer both during dry and rainy season. The interactions of fertilizer type and rate also varied significantly (P≤0.05) for fungal populations during both seasons. No significant variation was noted for the bacterial population (cfu) for both seasons regardless of fertilizer type and rates. The fungi identified included; Cylindrocarpon spp., Trichoderma spp., Penicillium spp., Aspergillus spp. Colletotrichum spp., Pestalotiopsis spp., and Fusarium spp. The bacteria included; Pseudomonas spp., Bacillus spp., Rhizobium spp., and Xanthomonas spp.

Conclusion: Organic fertilizer increased fungal populations significantly, an indication of enhanced soil health and may be recommended for use.