猪粪和土霉素对不同肥力土壤微生物数量及活性的影响

在不施肥和施用猪粪两种情况下，采用培养试验研究了不同浓度土霉素污染(0、0.1、1、10、100和1000 mg·kg^-1)对土壤细菌丰度、酶活性和NO₃-N浓度等的影响.试验培养温度为25 ℃，培养时间为30 d，取样分析时间分别为1、4和30 d.结果表明：在不施肥条件下，土霉素污染对土壤细菌数量及微生物活性的影响较小，土壤S₁、S₂和S₃细菌数量、呼吸强度、酶活性和NO₃-N浓度下降10%时土霉素的剂量（EC₁₀）分别为36～1000 mg·kg^-1、20～1000 mg·kg^-1和4～1000 mg·kg^-1；而在施用猪粪的情况下，对应的数值分别为2～656 mg·kg^-1、2～81 mg·kg^-1和1～42 mg·kg^-1.添加土霉素对土壤细菌及酶活性的影响随土壤肥力的提高而增大,且其对土壤细菌数量和呼吸强度的影响大于对酶活性和NO₃-N浓度的影响.土霉素污染对土壤微生物数量和活性的影响随时间变化而变化，一般在培养4 d时的影响最为明显.土霉素对土壤微生物的影响总体上表现为抑制作用.

Effects of pig manure and oxytetracycline on microbial number and activity in soils with different fertility levels

An incubation test was conducted to study the effects of antibiotics oxytetracycline on the microbial number and activity in three soils varied with fertility level under the conditions with or without pig manure application.The soils were injected with six concentrations(0,0.1,1,10,100,and 1000 mg·kg~(-1)) oxytetracycline,and incubated for 30 d at 25℃.Soil samples were collected on the 1st,4th,and 30th day of incubation to measure the bacterial number,respiratory activity,and enzyme activity.Under no pig manure application,oxytetracycline had little effects on the soil bacterial number and activity.The EC10 values of oxytetracycline based on a 10% decrement of bacterial number,respiratory activity,enzyme activity,and NO-3~--N concentration in treatment without pig manure were 36-1000 mg·kg~(-1),20-1000 mg·kg~(-1),and 4-1000 mg·kg~(-1) for S_1,S_2 and S_3,while those in treatment with pig manure application were 2-656 mg·kg~(-1),2-81 mg·kg~(-1),and 1-42 mg·kg~(-1) for S_1,S_2 and S_3,respectively.Soil fertility level had obvious effects on the dose-response relations between oxytetracyeline and soil microbial number and activity.The effects of oxytetracycline on soil microbial number and activity increased with increasing soil fertility level,and the effects on microbial number and respiratory activity were higher than those on enzyme activity and NO-3~--N concentration.The effects of oxytetracycline on soil microbial number and activity were time-depending,being the greatest on the 4th day of incubation.Overall speaking,oxytetracycline could exert temporary inhibition on soil microbes.