Influence of soil chemical and physical properties on Trichoderma spp occurrence in Taita region

Abstract

Agricultural intensification has been cited as one of the causes of loss of biodiversity. Taita Taveta, a coastal highland region is such like area which has experienced land conversion from forest cover into farmlands with high soil intensification. Soil samples were collected across seven land use types and analysed for Trichoderma occurrence. The fungus was recovered from the soil using the dilution plate and soil washing technique. The remaining soil samples were used to analyse for pH, acidity, organic carbon (C) total nitrogen (N), organic matter (OM), calcium (Ca) phosphorus (P) sodium (Na), potassium (K), magnesium (Mg), Manganese (Mn), Iron (Fe), and Zinc (Zn), and copper (Cu). Soil texture, bulk density, porosity and available water capacity was also determined. 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 indigenous forests followed by fallow and horticulture LUTs. Maize and Coffee LUTs recorded the least. The most frequently occurring species was T. harziunum which was isolated from all land use types LUTs. Carbon, N, organic matter and Fe were high in soils collected from forests thus suggesting they influenced fungal diversity. The forests had clay loam soils with higher porosity and water retention capacity compared with the cultivated LUTs and fallow which were characterized with clay soils and high bulk density, pH, Na, P, K, Ca, Mg, Cu showing the effect of land conversion on soil properties and Trichoderma occurrence. The influence of plant type and land anagement is also seen in the cultivated LUTs with the same soil properties but with different diversity and abundance of Trichoderma. The diversity of soil factors observed in the maize plots explained the influence of land management on soil physical and chemical characteristics which in turn determined the fungal distribution. Soil depth (0-20cm) did not influence soil factors though fungal diversity, abundance and evenness varied with depth suggesting the influence of substrate availability. Occurrence of Trichoderma spp. and distribution in soil is determined by a number of interacting biotic and abiotic factors.