Gagliardi J V, Karns J S
USDA, Agricultural Research Service, Soil Microbial Systems Laboratory, Beltsville, Maryland 20705, USA.
Appl Environ Microbiol. 2000 Mar;66(3):877-83. doi: 10.1128/AEM.66.3.877-883.2000.
Application of animal manures to soil as crop fertilizers is an important means for recycling the nitrogen and phosphorus which the manures contain. Animal manures also contain bacteria, including many types of pathogens. Manure pathogen levels depend on the source animal, the animal's state of health, and how the manure was stored or treated before use. Rainfall may result in pathogen spread into soil by runoff from stored or unincorporated manure or by leaching through the soil profile. Steady rainfall consisting of 16.5 mm h(-1) was applied to 100-mm disturbed soil cores that were treated with manure and inoculated with Escherichia coli O157:H7 strain B6914. The level of B6914 in leachate was near the inoculum level each hour for 8 h, as was the level of B6914 at several soil depths after 24 h, indicating that there was a high rate of growth. Bacterial movement through three different types of soil was then compared by using disturbed (tilled) and intact (no-till) soil cores and less intense rainfall consisting of 25.4 mm on 4 consecutive days and then four more times over a 17-day period. Total B6914 levels exceeded the inoculum levels for all treatments except intact clay loam cores. B6914 levels in daily leachate samples decreased sharply with time, although the levels were more constant when intact sandy loam cores were used. The presence of manure often increased total B6914 leachate and soil levels in intact cores but had the opposite effect on disturbed soil cores. Ammonia and nitrate levels correlated with B6914 and total coliform levels in leachate. We concluded that tillage practice, soil type, and method of pathogen delivery affect but do not prevent vertical E. coli O157:H7 and coliform transport in soil and that soluble nitrogen may enhance transport.
将动物粪便作为作物肥料施用于土壤是回收粪便中氮和磷的重要手段。动物粪便还含有细菌，包括许多种类的病原体。粪便病原体水平取决于来源动物、动物的健康状况以及粪便在使用前的储存或处理方式。降雨可能导致病原体通过储存或未掺入土壤的粪便径流或通过土壤剖面淋溶而扩散到土壤中。以16.5毫米/小时的稳定降雨强度施加于100毫米经扰动的土壤柱体上，这些土壤柱体已用粪便处理并接种了大肠杆菌O157:H7菌株B6914。在8小时内，渗滤液中B6914的水平每小时都接近接种水平，24小时后在几个土壤深度处B6914的水平也是如此，这表明其生长速率很高。然后，通过使用经扰动（耕作）和完整（免耕）的土壤柱体，并以连续4天25.4毫米且在17天内再进行4次的强度较小的降雨，比较了细菌在三种不同类型土壤中的移动情况。除了完整的粘壤土柱体之外，所有处理的B6914总水平都超过了接种水平。每日渗滤液样品中B6914的水平随时间急剧下降，不过使用完整的砂壤土柱体时其水平更稳定。粪便的存在通常会增加完整柱体中B6914渗滤液和土壤中的总水平，但对经扰动的土壤柱体则有相反的影响。氨和硝酸盐水平与渗滤液中B6914和总大肠菌群水平相关。我们得出结论，耕作方式、土壤类型和病原体输送方法会影响但不能阻止大肠杆菌O157:H7和大肠菌群在土壤中的垂直迁移，并且可溶性氮可能会增强这种迁移。
