Effects of bulk and nano-forms of copper oxide (CuO) and zinc oxide (ZnO) to soil fungal community
Jonathan Jaime G. Guerrero1.2*, Teresita U. Dalisay2, Irineo B. Pangga2, Nolissa D. Organo3
1University of the Philippines Los Banos Graduate School
2 University of the Philippines Manila, College of Medicine
3University of the Philippines Los Banos Institute of Weed Science, Entomology and Plant Pathology, College of Agriculture and Food Science, University of the Philippines Los Banos
4Division of Soil Science – Agricultural Science Institute College of Agriculture and Food Science, University of the Philippines Los Banos
Soil fungi are subject to the dynamic changes in the soil brought about by environmental factors and contaminants, such as copper and zinc oxides used in agriculture. These metal oxides are now used in nano-forms to provide better dynamics in the soil environment. In this research, the effects of copper oxide (CuO) and zinc oxide (ZnO) in bulk and nano forms on soil fungal communities was determined. Lipa clay loam soil collected from the University of the Philippines Los Baños were placed in polypropylene bags and amended with 300 ppm of CuO or ZnO in either forms. Colony-forming units (CFU) as well as average well color development (AWCD), functional richness and stress index were determined on day 1, 8 and 15 via indirect viable plate count method and community – level physiological profiling (CLPP). Fungal isolates from the same soil samples were likewise identified and tested in vitro in terms of radial growth when treated with varying concentrations of the metal oxides. Results indicated no significant difference in CFU, AWCD, functional richness and stress index among treatments. In vitro, responses of fungal isolates differed. Specific species were more sensitive to the metal oxides than others. In general, CuO was more toxic than ZnO. In both cases, the nature of the compound, not size, was the primary determinant of toxicity. It is recommended that the use of nanotechnology in agriculture be promoted with caution to limit the harmful effects to the soil microbiota and to the environment in general.