Effect of 2,4-Dichlorophenoxyacetic Acid (2,4-D) and Dichlorvos (2,2-Dichlorovinyl Dimethyl Phosphate DDVP) on Soil Microorganisms

Effects of 2,4-D(2,4-dichlorophenoxy acetic acid) and Dichlorvos(2,2-dichlorovinyl dimenthyl phosphate DDVP) were investigated on soil microbial population in a 4 weeks experiment. Soil samples were serially diluted and inoculated using pour plate method on different medium and incubated at 37°C for 24 and 48 hrs for enumeration of microbial diversity, colonies that appeared on plates were counted. At pre-application of 2,4-D, bacteria had the highest population (9.5x107 Cfu), followed by fungi (7.5x105 Cfu ), actinomycetes (1.6x106 Cfu) and protozoa (1.1x103 Cfu). Likewise, the pre-application of DDVP represents the population count of microorganisms in the following manner: Bacteria (8.0x107 Cfu)>fungi (5.1x105 Cfu)>actinomycetes (1.0x106 Cfu)> protozoa (1.0x103 Cfu)f The post-application of 2,4-D and DDVP also had the similar pattern of population count. With percentage difference on each of the microbial counts, 2,4-D of bacteria, fungi, actinomycetes and protozoa (99.5%, 95.3%, 99.9% and 86.0% respectively), DDVP percentage difference (99.2%, 99.4%, 99.3% and 98.6% respectively). Application of these pesticides at recommended rates was followed by the general decline in microbial counts. Therefore, the pesticides had toxic effects on microorganisms which may be beneficial to cultivated plants.