土壤中乐果与微生物的相互作用研究

The interaction between dimethoate and microorganisms in soil

采用室内模拟实验,研究了土壤中乐果与微生物的相互作用。结果表明:(1)50、500、5000mg·kg-1的乐果在灭菌土中的降解速度十分缓慢,加药后15d,50mg·kg-1的降解率为69.3%,500mg·kg-1的降解率为26.7%,5000mg·kg-1的降解率为19.6%。在施过乐果的土壤中的降解速度非常迅速,加药后15d,50mg·kg-1的降解率为99.7%,500mg·kg-1的降解率为78.4%,5000mg·kg-1的降解率为54.6%。在未施过乐果的土壤中的降解速度则介于二者之间。说明微生物在乐果的降解中起着非常重要的作用,同时,施药可以诱发乐果降解菌的生成从而加速乐果的降解。(2)在各处理的土壤中,50mg·kg-1的乐果对细菌数量有一定的刺激作用,500、5000mg·kg-1的乐果抑制细菌的生长。且随质量浓度的升高,抑制作用增强。但随加药时间的延长,又有所恢复。3种不同质量浓度的乐果对土壤真菌和放线菌种群数量的影响均表现为明显的抑制作用,且随药剂质量浓度的提高和加药时间的延长抑制趋势越明显。因此,可以选择真菌和放线菌作为土壤受乐果污染的敏感指示菌。(3)在同样处理条件下,施过乐果土壤中的微生物种群数量并不比未施过乐果土壤中的占优势,表明乐果在施过药的土壤中降解速度的加快并不是由微生物的数量决定的,而是由它们的降解能力决定的。

The interaction between dimethoate and microorganisms in soil was investigated in an indoor simulation experiment. The results showed that： （i） The degradation rate of dimethoate with levels of 50 mg·kg^-1, 500 mg·kg^-1 and 5 000 mg·kg^-1 was very slow in sterilized soil, which were only 69.3%, 26,7% and 19.6% respectively. And in soil previously treated with dimethoate, the degradation rates with same concentration gradient were 99.7%, 78.4% and 54.6%. The medium degradation rate occurred in soil un- terilized and untreated, which indicated soil microorganisms played an important role in the process of dimethoate degradation and dimethoate application could induce the dimethoate degradation ability of soil microorganisms and accelerate the degradation rate.（2） Compared to the soil un-treated with dimethoate, the bacteria were stimulated to some extent in the dimethoate application soil with a level of 50 mg·kg^-1, meanwhile, the growth of bacteria was inhibited under the concentrations of 500 mg·kgt and 5 000 mg·kg^-1. The inhibitory effect was increased with the concentration, then gradually recovered to normal level in 60 days. The populations of fungi and actinomyces in soil were remarkably inhibited at the three different concentrations of dimethoate. With the increase of concentration and prolonging application time, the inhibition was more and more obvious. Accordingly, fungi and actinomyces may be used as sensitive indicator in the soil contaminated by dimethoate. （3） In addition, under the same condition, the amount of microorganisms was not significantly different in soil previously treated and untreated with dimethoate, which suggested that enhanced degradation rate of dimethoate was not determined by the amount of microorganisms, but by their degradation capability.