Side Effect of three Herbicides on Soil Microorganism

Abstract

Field experiment was carried out to study the side effect of 3 herbicides, namely; atrazine, ametryn and paraquat, on population dynamics of beneficial and non- target soil microorganism in sugarcane field at Central Laboratory and Greenhouse Complex, Kasetsart University, Kamphaeng-saen Campus. Soil samples were collected before and at 0, 7, 14, 30, 60 and 90 days after application of herbicides. The soil samples were air dried, sifted and divided into two parts. One was used for microorganism isolation on selective media, the rest was used for toxic residues analysis by gas chromate-graph. Forty isolates of bacteria and forty-six isolates of fungi were obtained. It was found that the total population of microorganisms decreased during the first week after application. Accordingly, the amount of residues detected in soil reached the maximum quantity (1774.08 ppb and 112.3 ppb of detected Atrazine and Ametryn, respectively) Half life of atrazine and ametryn in these soil samples were 35 and 6 days, respectively. The isolated soil microorganism that showed antagonistic effects to Fusarium moniliforme, the causal agent of root and foot rot of sugarcane also studied for residual toxicity under laboratory under laboratory condition. The result showed that atrazine and ametryn gave higher inhibitory effect on growth than paraquat.