Sample preparation and storage depend on the type of samples and the desired analysis.  It is best to always check with the laboratory technicians who will be doing the sample analysis to find out what is required in terms of sample processing, transport, and storage.  Preparation of air-dried, less than 2 mm samples is standard for many nutrient analyses.

References and Resources:

• Carter, M.R., and E.G. Gregorich (eds). 2008. Soil sampling and methods of analysis. 2nd ed. Canadian Society of Soil Science, CRC Press and Taylor & Francis Group. Oxford, UK.
• Soil Survey Staff. 2009. Soil Survey Field and Laboratory Methods Manual. Soil Survey
  Investigations Report No. 51, Version 1.0. R. Burt (ed.). U.S. Department of Agriculture, Natural Resources Conservation Service. Version 2.0 (2014) available at: https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052226.pdf
• Sparks, D.L. (ed). 1996.  Methods of soil analysis: chemical methods. Part 3. Soil Sci. Soc. Am. Book Series No. 5. ASA-SSSA, Madison, WI.Sheppard, S.C., and J.A. Addison. 2008. Soil sample handling and storage. In Carter, M.R., and E.G. Gregorich (eds). Soil Sampling and Methods of Analysis. 2nd ed. Canadian Society of Soil Science, CRC Press and Taylor & Francis Group. Oxford, UK.
• Westerman, R.L. (ed). 1990.  Soil testing and plant analysis. 3rd edition. ASA-SSSA, Madison, WI.