Evaluation of trichoderma enhanced fertilizers on growth of common beans (phaseolus vulgaris l.)

Abstract

Three Trichoderma spp. were isolated from agricultural soil in Embu district, Kenya and identified morphologically as T. harzianum, T. polysporum and T. viride. These isolates were evaluated for their effect on the growth of F. oxysporum var phaseoli. Evaluation of the effect of Trichoderma spp. on F. oxysporum var phaseoli was carried out by setting up invitro experiments and green house experiment. Invitro experiments were done by placing 5mm mycelia growth disc cut out from the growing Trichoderma spp. isolates and placed on one side of a 9 mm PDA plate, a similar disc of F. oxysporum var phaseoli isolate was cut out and placed 3 mm opposite the Trichoderma spp. mycelia disc. F. oxysporum var phaseoli without Trichoderma spp. was also cultured as a control; all the treatments were in triplicates. A green house experiment was carried out by planting common bean seeds coated with Trichoderma spp. in sterilized soil infected with F. oxysporum var phaseoli. The beans were immersed in a mixture of gum Arabic and Trichoderma spp. and left for 5 hours prior to planting so as to let the mixture attach to seed coat. Seven mixtures of Trichoderma isolates were formulated: T. polysporum; T. harzianum; T. viride and in combinations of the species; T. polysporum and T. harzianum; T. polysporum and T. viride; T. harzianum and T. viride; T. polysporum, T.harzianum and T.viride. The soil was placed in 22cm diameter pots which were then applied with manure at a rate of; 0g (control), 38g (without Trichoderma spp.) 38g, 28g, 18 g and 9 g (with Trichoderma spp.). The same procedure was followed with NPK fertilizer application except that fertilizer rates were; 0g (control), 0.76g (without Trichoderma spp.), 0.76 g, 0.57 g, 0.38 g, 0.19 g (with Trichoderma spp.). Invitro experiments of F. oxysporum var. phaseoli with T. harziunum, T. polysporum or T. viride revealed that each of these Trichoderma species inhibited growth of the pathogenic fungi. T. polysporum had the highest inhibitory (P<0.05) effect at 64% while T.viride had the least inhibitory effect (47%). On the other hand a combination of manure and the Trichoderma species improved growth of common bean when grown in F showed a highly significant effects (P<0.001) on all the bean growth parameters measured. The combination of Trichoderma spp. and fertilizers however did not show significant difference (P>0.05) among the different rates of fertilizer in root length and fresh weight. The results reveal the ability of Trichoderma spp. to control pathogens and improve plant growth