Caring For Samples
After collecting the sample, proper care is essential to obtaining reliable results. Very small amounts of contaminants can have large effects on analytical results obtained at the laboratory. It is recommended that plastic pails be used for compositing the subsamples in the field. Metal pails often contaminate the sample rendering it useless for zinc and iron analysis. Plastic pails with rounded surfaces are also easier to keep clean.
If available nitrate-N and sulfate-S is requested for analysis, the samples should be delivered to the laboratory immediately after collection in order to minimize microbial mineralization of organic nutrients. If the samples cannot be delivered to the laboratory in a timely manner, the samples should be air-dried or frozen. Normally, spreading samples on a clean surface and air drying the samples overnight will be adequate, although very wet samples may take longer. All samples should be submitted to the laboratory as soon as possible to minimize the potential for contamination.