Biostimulatory Effect of Cassava Peel Waste on the Indigenous Fungi in Atrazine-impacted Soil

The biostimulatory effect of cassava peel waste on the indigenous fungi in atrazine-impacted soil was assessed over a period of seven (7) weeks. The study site was at the Teaching and Research Farm of the institution. The herbicide used in this study was atrazine (Atraforce) while the organic waste used was the cassava peel waste (CPW) of Manihot esculenta. The fungal and physicochemical characteristics of the soil treated with cassava peel waste (CPW), cassava peel waste and atrazine (CPW+ATZ), atrazine alone (ATZ), and the CONTROL (no treatment) were assessed using culture-dependent and standard analytical techniques respectively. The influence of the treatments on soil organic carbon content, total nitrogen content and available phosphorus was investigated and recorded. The study provided adequate evidence that the study site was naturally endowed with requisite fungi (Rhizopus sp., Aspergillus sp., Penicillium sp., Saccharomyces sp., Fusarium sp., Candida sp., and Trichophyton sp.) with potential enzyme repertoire for atrazine degradation. All the seven isolated indigenous fungi except Saccharomyces sp. showed evidence of atrazine degradation potential. The addition of organic amendments improved the physicochemical status of the impacted soil which culminated to significant (P<0.05) increase in soil’s fungal population. For example, CPW+ATZ showed a high mean fungal population (week 2 =30.00x103 CFU/g, week 4 =35.00x103 CFU/g, week 6 =81.00x103 CFU/g) which was significantly higher (at P<0.05) than impacted but unamended soil, ATZ (week 2 =9.50x103 CFU/g, week 4 =12.50x103 CFU/g, week 6=46.50x103 CFU/g). This study has shown that, although fungi are excellent degraders of herbicides in the soil, some amendments may need to be brought in place in order to stimulate them to degrade pollutants. This work also revealed that the organic waste (CPW) used was a potential stimulatory substrate that enhanced the growth of indigenous atrazine-degrading soil fungi; hence can serve as improved method of waste management and potential soil remediation approach.