Impact of Trifluralin and 2,4-D on Soil Microbial Biomass and Enzymatic Activities

Abstract

An experiment was laid out in randomized block design with three replications under laboratory conditions to investigate the impacts of 2,4-D and Trifluralin applied at 0, 0.1, 1, 10 and 100 mg/kg soil on total organic carbon (TOC), carbon dioxide release, microbial biomass carbon, enumeration of aerobic heterotrophic bacteria, fungal population and cellulose decomposers and enzymatic activities of fluorescein diacetic acid (FDA) and dehydrogenase activities in “kovarvany” brown forest (KBF, Nyiregyhaza) and meadow chernozem (MC, Szeged) soil types incubated for 7 days at temperature 28°C. Results indicated that Trifluralin was more toxic than 2,4-D at higher concentrations. The findings of investigated parameters in MC soil type were higher than those obtained from KBF soil type under the stress of two tested herbicides. It was found that 10 mg/kg concentration more effective on the aerobic heterotrophic bacterial population and cellulose-decomposers than fungal population, FDA and dehydrogenase as well as TOC and CO2 production. Results showed that the application of herbicides at the tested levels were not drastic enough to be considered harmful to soil microbial and enzymatic activities which are important to soil fertility. This study has shown that the microbial activity increased as a result of adaptation to the herbicides during incubation period; also, demonstrates a potential capacity for adaptation of the microorganisms in soils when large amounts of herbicides are added. Dehydrogenase can consider as sensitive bioindicator of the microbial activity response to herbicidal amendment. More investigation can be done with different soil types under various ecological parameters.