Tropical and Subtropical Agroecosystems (Oct 2009)
SPATIAL DISTRIBUTION OF TRICHODERMA SP. IN EMBU AND TAITA REGIONS, KENYA
Abstract
The distribution of Trichoderma species in soils of Embu and Taita regions in Kenya with relation to land use practices was investigated. The study areas were chosen because of their significant land use intensification and for being biodiversity hot spots. Soil washing and dilution plate techniques were used to recover Trichoderma spp from the soil samples collected from different land use types. The fungal isolates were identified and assigned to nine species from Embu soils and eleven species from the Taita soils. Greater populations were however observed in Embu than in Taita. Geographic differences between the regions mostly explain the differences in ecological niches of the two regions that result to different soil assemblages and plant types in the regions and therefore variation in available substrate for the fungus. Land use at each site affected the distribution, richness and abundance of Trichoderma with Napier grass having the highest abundance in both Embu and Taita while coffee had the lowest richness and abundance. Trichoderma favoured plants with shallow and widely spreading rooting systems, compared to the deeply rooted perennial coffee and tea trees. This underpins the importance of plant type and in effect land use system in the abundance of Trichoderma. The unevenness in the distribution of Trichoderma within the LUTs suggests yet another factor influencing the distribution of Trichoderma apart from the LUTs. Unevenness was greater in Embu than in Taita. The differences could mostly be attributed to soil management practices employed by different farmers while managing their land and crops differently. Trichoderma harziunum was the most frequently isolated species and the most abundant in both Embu and Taita. The presence of Trichoderma species in some land use types and the absence in others, provides a clue on the most preferred habitats, plants and/or crops. Considering the beneficial aspects of Trichoderma such as being antagonistic to the pathogenic fungi, crops or plants such as napier grass that induce high abundance and richness of Trichoderma can be used in crop rotations or in combinations with other crops to maintain high levels of the fungus in the soil.
