Influence of soil chemical and physical properties on occurrence of trichoderma spp. in Embu, Kenya

Abstract

Soil samples were collected from eight land use types in Embu to assess the effects of land use on soil chemical and physical parameters and their impact on occurrence of Trichoderma spp. The fungus was recovered from the soil using the dilution plate and soil washing technique while soil samples were analysed for pH, total nitrogen (N), phosphorus (P), potassium (K), sodium (Na), calcium (Ca) and magnesium (Mg). Land use type (LUT), plant cover, and soil physical and chemical properties influenced Trichoderma occurrence. The frequency of isolation of Trichoderma spp. was highest in soils under napier (Pennisetum purpureum) followed by indigenous forests. Carbon, N, Mg and Fe were high in soils collected from forests thus influencing fungal diversity. The forests had clay loam soils with higher porosity and water retention capacity compared with the cultivated LUTs which had clay texture and high bulk density. Soils from the napier and cultivated plots had low Mn and Cu levels which may have resulted from leaching and nutrient transport. This implies land use and plant type were major determining factors for the high population of Trichoderma recorded in napier LUT. The diversity of soil factors observed in the fallow plots explained the influence of land management on soil physical and chemical characteristics which in turn determined the fungal distribution. The age of the fallows and usage varied from farmer to farmer causing the variations observed. Soil depth (0-20cm) did not influence soil factors though fungal diversity, abundance and evenness varied with depth suggesting the influence of other drivers.The plough/top layer of a soil profile is high in organic matter including litter and has potential to support high fungal abundance and sometimes diversity. Occurrence of Trichoderma spp. and distribution in soil is determined by a number of interacting biotic and abiotic factors.