ABSTRACT

 This study was carried out to evaluate the fungal species associated with a combination of composted cattle rumen content and food waste digestate derived digestate supplemented with different concentrations of biochar. The digestates were treated differently as exposed (dried), solid (closed) and liquid digestates. Standard microbiological methods were employed to isolate and enumerate fungal isolates from different digestive treatments within eight weeks. Cultural and microscopic features of the fungi were used for identification, and their plant growth-promoting capacity was evaluated by exploring their phosphate solubilizing capacity and production of indole acetic acid. The results revealed that the fungal counts for exposed dried digestate at week 0 ranged from log₁₀ 2.22±0.02 cfu/g for digestate supplemented with 5g biochar to log₁₀ 2.444±0.06 cfu/g for 10 g biochar digestate. The control (without biochar supplementation) count was log₁₀ 2.28±0.00 cfu/g. The fungal counts observed in the control increased as the weeks of composting grown. Due to the increase in the fungal count from week 0 to the 8^th week, negative log reduction values were obtained which signifies the actual increase in the fungal population for all exposed digestates. The isolated fungi obtained from the organic amendments and control include Aspergillus, Trichoderma, Penicillium and Rhizopus species. The plant growth-promoting capacity obtained from fungal species isolated from the different organic amendments revealed that they were active phosphate solubilizers and potent producers of indole acetic acid. These properties of the isolates are advantageous to plants whenever they are found in the root zones or around the plants as they achieve the herculean tasks of making phosphate available and producing a growth promoter (auxin). Digestates, therefore, contain plant growth-promoting fungi, hence their success in agriculture.