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Amplification of DNA from soil is often inhibited by co-purified contaminants. A rapid, inexpensive, large-scale DNA extraction method involving minimal purification has been developed that is applicable to various soil types (1). DNA is also suitable for PCR amplification using various DNA targets. DNA was extracted from 100g of soil using direct lysis with glass beads and SDS followed by potassium acetate precipitation, polyethylene glycol precipitation, phenol extraction and isopropanol precipitation. This method was compared to other DNA extraction methods with regard to DNA purity and size.

The dispersion and initial transport of Cryptosporidium oocysts from fecal pats were investigated during artificial rainfall events on intact soil blocks (1,500 by 900 by 300 mm). Rainfall events of 55 mm h ؊1 for 30 min and 25 mm h ؊1 for 180 min were applied to soil plots with artificial fecal pats seeded with approximately 10 7 oocysts. The soil plots were divided in two, with one side devoid of vegetation and the other left with natural vegetation cover. Each combination of event intensity and duration, vegetation status, and degree of slope (5°a nd 10°) was evaluated twice. Generally, a fivefold increase (P < 0.05) in runoff volume was generated on bare soil compared to vegetated soil, and significantly more infiltration, although highly variable, occurred through the vegetated soil blocks (P < 0.05). Runoff volume, event conditions (intensity and duration), vegetation status, degree of slope, and their interactions significantly affected the load of oocysts in the runoff. Surface runoff transported from 10 0.2 oocysts from vegetated loam soil (25-mm h ؊1 , 180-min event on 10°slope) to up to 10 4.5 oocysts from unvegetated soil (55-mm h ؊1 , 30-min event on 10°slope) over a 1-m distance. Surface soil samples downhill of the fecal pat contained significantly higher concentrations of oocysts on devegetated blocks than on vegetated blocks. Based on these results, there is a need to account for surface soil vegetation coverage as well as slope and rainfall runoff in future assessments of Cryptosporidium transport and when managing pathogen loads from stock grazing near streams within drinking water watersheds.

A rapid, inexpensive, large‐scale DNA extraction method involving minimal purification hasbeen developed that is applicable to various soil types. DNA was extracted from 100 g of soilusing direct lysis with glass beads and sodium dodecyl sulphate (SDS) followed by polyethyleneglycol precipitation, potassium acetate precipitation, phenol extraction and isopropanolprecipitation. The crude extract could be used in PCR directed at high‐copy number (bacterialsmall subunit rRNA) and single‐copy (fungal β‐tubulin) genes.

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