乙草胺对玉米根际和非根际可培养微生物的影响

Effects of Acetochlor on Culturable Microbial Communities in Maize Rhizosphere and Non-Rhizosphere Soil

为探明土壤-植物系统中,田间施用量的乙草胺对玉米根际和非根际微生物数量的影响,采用田间试验及室内测试方法,在玉米苗期不同阶段测定了土壤中微生物量碳的变化,并进一步用平板稀释培养法研究了玉米根际和非根际土壤中细菌和真菌数量的变化。结果表明,乙草胺施用对玉米根际和非根际的土壤微生物群落均具有一定影响。可培养的根际细菌和真菌均呈现先抑制后刺激的变化,但与真菌不同,细菌受到的抑制作用时间较短,刺激作用时间较长;而本体土壤中可培养细菌和真菌则主要受到抑制作用,但是抑制作用的强度和持续时间差别很大。乙草胺对根际土壤微生物量碳可产生一定刺激作用,但影响并不显著;由于乙草胺施用对非根际土壤细菌和真菌的影响不同步并存在群落结构的补偿作用,从而维持了非根际土壤总体微生物生物量碳的基本稳定。

Acetochlor is a kind of important pre-emergence herbicide and has been widely used for the control of annual grasses and broadleaf weeds in row crops such as corn, soybean and sorghum. As being labeled as a ＂probable human carcinogen＂, the intensive use of acetoehlor is considered to be serious threat to human health and environmental safety. Microorganisms can respond rapidly to changes in soil environments, regardless of nutrient or hazard material input. In this paper, the effects of agriculturally relevant application rate of acetochlor on cuhurable microbial communities in maize rhizosphere and non-rhizosphere soils during different stages of maize seedlings were investigated. The results showed that the response of different microbial communities in rhizosphere and non-rhizosphere soils to acetochlor was time-dependent.The cuhurable bacteria in both rhizosphere and non-rhizosphere soils were inhibited initially but those in rhizosphere were stimulated significantly afterward. The culturable fungi in rhizosphere soil were inhibited till 30 days after acetochlor application and then were reactivated; however, fungi in non-rhizosphere soil were kept inhibited within 24 days application. The soil microbial biomass in rhizo- sphere was stimulated slightly by acetoehlor application while that in non-rhizosphere exhibited no significant difference between the two treatments. It could be reckoned that the asynchronous effect of acetochlor on bacteria and fungi as well as the compensatory shift of community structure was mainly contributed to the insignificant change of soil microbial biomass carbon in non-rhizoshphere soil.