熏蒸剂威百亩对土壤微生物数量和酶活性的影响

威百亩是一种甲胺衍生物，在黄瓜、番茄、烟草等作物田采用熏蒸处理防治土传病害。为了探明其对土壤生态环境造成的影响，采用室内模拟试验方法研究了威百亩不同剂量、不同处理时间对土壤微生物数量及酶活性的影响。结果表明，威百亩对土壤细菌和放线菌均表现出抑制—激活—恢复的趋势，但对放线菌的影响程度小于细菌，恢复培养40天对放线菌的激活率达最大，为180.77%，恢复培养30天对细菌的激活率达293.61%；而对土壤真菌则表现出强烈的抑制作用，抑制程度与处理剂量呈正相关，高剂量处理(90.28 mg/kg、180.56 mg/kg)对真菌的抑制率均为100%，到恢复培养60天各处理组真菌数量与对照组之间仍存在显著性差异(P<0.05)。威百亩处理后，中低剂量处理对土壤蔗糖酶活性表现激活—抑制—激活—恢复的趋势，高剂量处理表现抑制—激活—恢复的趋势，最高激活率达213.62%；对土壤脲酶活性表现出抑制作用，处理剂量越高，抑制率越大，且这种抑制作用是不可恢复的；对磷酸酶和过氧化氢酶均表现出先抑制后激活的趋势。由此可知，威百亩对土壤真菌种群和脲酶活性的影响较大，而对土壤细菌、放线菌及蔗糖酶、磷酸酶和过氧化氢酶活性的影响是暂时性的，随着培养时间的延长，微生物种群及酶活性可恢复，不会对农作物生长及土壤环境造成潜在危害。

Effects of Fumigant Metham-sodium on Soil Microbial Population and Enzyme Activities

Metham-sodium is a methylamine derivative which is used on cucumber, tomato, and tobacco (seed bed). It can protect crops from soil-borne diseases, but it will affect soil microbial, then affect soil enzymes. This study was an attempt to evaluate the environmental ecology influence after using metham-sodium. By simulation in laboratory, the investigation studied the relationship between different concentrations of metham-sodium, different treatment time and soil microbial population, soil enzyme activities in a selected soil. The results showed as follows: metham-sodium had similar effects on soil bacteria and actinomycetes which were inhibition-stimulation-recovery, but the effect on bacteria was bigger than actinomycetes. The highest stimulation of bacteria was 293.61%, however, the actinomyces was 180.77%. While metham-sodium at each concentration inhibit soil fungi at the test; the inhibition of high concentration (90.28 mg/kg, 180.56 mg/kg) was 100%, and the level of inhibition was proper to the concentration of metham-sodium. The effects of four representative soil enzymes to metham-sodium showed different dynamic changes. The effects of metham-sodium on soil invertase were dosage-dependent. When soil was fumigated with low or medium concentrations of metham-sodium, the effects showed stimulation-inhibition-stimulation-recovery, while those treated with high concentrations of metham-sodium showed inhibition-stimulation-recovery, and the stimulation was up to 213.62%. To all of the concentrations of metham-sodium, soil urease activity presented irreversible inhibition impact, and the inhibition of metham-sodium on soil fungal were dosage-depenndent. The effects of metham-sodium on soil phosphatase and catalase were inhibited at first, and then stimulated. It showed that metham-sodium have great effect on soil fungi and urease, but to soil bacteria, actinomycetes, soil invertase, phosphatase and catalase, the effects are temporary without potential harm to soil fertility and crop growing.