Effect Of Metsulfuron-methyl On The Microbial Ecology In Rhizosphere Soil And Its Degradation

Effect of metsulfuron-methyl, a herbicide, on microbial populations and enzymes activities in rhizosphere and its degradation was reported. The results for the research can be summarized as follows:The microbial ecology in rhizosphere was influenced to a certain extent by metsulfuron-methyl:1. The wheat rhizosphere stimulated the growth of bacteria, and also increased their degradation and tolerance capability;2. Rhizosphere fungi were the dominant organisms, which had strong tolerance and degradation capability on metsulfuron-methyl, this may provide bases for repairing the soil polluted by metsulfuron-methyl with combination of microbes and plants;3. Actinomyces were the inferior organisms, which may be taken as the sensitive indicator for assessing the ecological effect of metsulfruon-methyl in soils;4. The domestication of metsulfruon-methyl and the wheat rhizosphere62stimulated the growth of rhizosphere aromatic compounds-decomposing bacteria;5. The population of rhizosphere azotobacter in soil was changed significantly when metsulfruon-methyl was added, and the secretion of rhizosphere was not the energy source to azotobacter group.6. The population of nitrite bacteria reduced significantly while the wheat growth period prolonged. Meanwhile the population of denitrifying bacteria increased, which was propitious to denitrification in soil.7. The population of sulfur-oxidizing bacteria was low, and it was even lower while the wheat growth period prolonged. The sulfur-reducing bacteria were sensitive to metsulfruon-methyl toxicity, while the inhibition was weakened by the wheat rhizosphere.The activities of enzymes in rhizosphere were influenced to a certain extent by metsulruron-methyl:8. The activities of the catalase and the polyphenol oxidase in rhizosphere were higher than those in non-rhizosphere, which showed they were stimulated by the wheat rhizosphere.9. The metsulfuron-methyl inhibited the activities of catalase, polyphenol oxidase and dehydrogenase to a certain extent in rhizosphere.10. In non-rhizosphere soil, the activities of catalase and polyphenol oxidase could be inhibited significantly by metsulfuron-methyl.11. The activity of dehydrogenase didn't change significantly in rhizosphere and non-rhizosphere.The degradation of metsulfuron-methyl was clearly different in the soils under different treatment:12. Metsulfuron-methyl degraded sooner in rhizosphere than in non-rhizosphere because of the abundant microbes in the wheat rhizosphere; the combination of microbes and plants can accelerate metsulfuron-methyl degradation effectively, the soil polluted by metsulfuron-methyl can be repaired with the growth of crops such as wheat;13. The toleranc microbes had much more degradation capability on the low63concentration metsulfuron-methyl in rhizosphere soil, but the degradation was not effective on the high concentration metsulfuron-methyl;14. The degradation capability on metsulfuron-methyl was high in domesticated rhizosphere soil than in the common soil; cooperated with the roots, the soil polluted by metsulfuron-methyl can be repaired by the dominant microbes;15. The degradation rule of metsulfuron-methyl accorded with decaying exponential, that meant there was inverse linear correlation between the logarithm of metsulfuron-methyl concentration and the time; the half-life period of metsulfuron-methyl ranged 17.7d~45.9d, the shortest was in domesticated rhizosphere soil when the metsulfuron-methyl concentration was 5mg/Kg, and the longest was in domesticated non-rhizosphere soil when it was 2mg/Kg.