丁草胺污染对高产水稻土微生物区系的影响

土壤微生物多样性是表征土壤质量最有潜力的指标，与农田生态系统的稳定性和生产力密切相关。云南永胜涛源乡是保持我国水稻小面积超高产纪录的特殊生态区，常年施用丁草胺作为选择性芽前除草剂，因此，了解丁草胺对其土壤微生物物种多样性的影响意义重大。采用平板菌落计数法，研究了模拟条件下不同丁草胺剂量（有效成分质量分数0.15、0.30和1.5 mg·kg^-1）对高产水稻土中好氧细菌（aerobic bacteria）、放线菌（actinobacteria）和真菌（fungi），以及功能微生物自生固氮菌（nitrogen fixing bacteria）、磷酸盐溶解菌（phosphate solubilizing bacteria）和硅酸盐细菌（silicate dissolving bacteria）数量的影响。结果表明：施药7 d，中、高质量分数（0.30和1.50 mg·kg^-1）丁草胺处理好氧细菌数量比CK分别高出78.6%和153.8%，而后数量逐渐下降，表现出先刺激生长、后抑制活性的作用，低质量分数（0.15 mg·kg^-1）丁草胺对好氧细菌的生长和增殖影响不明显；施药7 d，高质量分数处理放线菌数量超过CK 75.1%，表现出明显的刺激作用；施药15 d，中等质量分数处理放线菌数量比 CK 高出125.0%，丁草胺浓度越高，刺激作用越迅速，低浓度丁草胺对放线菌则主要表现为抑制作用。低浓度丁草胺对真菌的生长和增殖基本没有影响，中等浓度有先抑制后刺激的作用，施药30 d后其真菌数量超过CK 56.9%，高浓度丁草胺则表现为抑制作用，施药7、30和45 d其真菌数量始终显著低于CK；不同浓度处理丁草胺均能刺激自生固氮菌的数量显著增加，施药7 d，低、中、高质量分数处理自生固氮菌数量分别高出CK 237.1%，179.9%和138.1%，刺激作用显著，但随培养时间延长，高浓度开始表现出抑制作用；不同浓度丁草胺均能抑制磷酸盐溶解菌的生长和增殖，低浓度处理抑制作用微弱，中、高浓度处

Effects of butachlor-contamination on population of microbial communities in high-yield paddy soils

Soil microorganism is the most potential indicator of soil quality evaluation, and is closely related to the stability and productivity of agricultural ecosystem. Taoyuan, Yunnan province is a special eco-site which keeps the highest yield records of rice cultivation in small planting areas, and butachlor is applied at the pre-emergence stage of rice year in and year out in Taoyuan. Therefore, it is significant to understand the ecological effects of the herbicide butachlor on microbial communities in high-yield paddy soils. Effects of butachlor-contamination on population of aerobic bacteria, actinobacteria, fungi, nitrogen fixing bacteria、phosphate solubilizing bacteria and silicate dissolving bacteria in high-yield paddy soils were investigated under laboratory conditions, and the microbial communities structures under different butachlor concentrations （calculated by active ingredient 0.15, 0.30 and 1.5 mg·kg^-1） were evaluated using plate count. The results showed that the number of aerobic bacteria were higher than CK 78.6% and 153.8% after application of butachlor at high or middle concentrations （0.30 and 1.50 mg/kg dried soil） 7d later, and then declined significantly, while the number did not change significantly at low butachlor concentration （0.15 mg·kg^-1 dried soil）. The number of actinomycetes was higher than CK 75.1% after application of butachlor at high concentrations 7 d later, and 125.0% at middle concentrations 15 d later, butachlor at high or middle concentrations accelerated the growth of actinomycetes, while showed an inhibition at low concentration. The proliferation and growth of fungi did not change significantly at low butachlor concentration, while stimulated first and then restrained at middle butachlor concentration, and showed a sustained inhibition at high butachlor concentration. The number of fungi was higher than CK 56.9% after application of butachlor at middle concentrations 30 d later, and the number were lower than CK at high concentrations throughout. Butac