Expected Outcomes

• Every school should be able to dry soils; not all schools should report their results

Prefered drying standard:

• Laboratory Oven: 105-110 degC, 10 hours or more, ~ 100 g sample in soil tin
  • Toaster ovens and Household stoves are NOT recommended!

Where to find ovens:

• Universities, Community Colleges, and High schools, ...
  • Departments of Soil Science, Agriculture, Biology, Chemistry, ...
• Government Laboratories
  • Ag extention, Natural Resources Conservation Service (SCS), EPA, ..
• Anyone with a kiln used for making pottery or ceramics

Alternative soil drying options (I have now formally approved these):

• Microwave Oven: high power, 30 minutes, ~ 100 g sample in pyrex beaker, rotating stage (a better procedure is to dry for 5 min, cool for 2 min, weigh, dry for 5 min, cool for 2 min, ... until consecutive weights are within 1 g).
• Home-made popcorn can oven: 75-85 deg C, 24 hours: (gif format)

  Unapproved drying methods (please report your experience to me):
  (before reporting, you must certify these procedures, see below)

• Incubating oven or dehydrator: 60-80 deg C, 36 hours, 100 g sample, disaggregated
• Open air: only has a chance where the humidity is low and the sample does not blow away

Certification

• Mix your sample and divide into two subsamples
  1. dry one subsample in a laboratory oven (forced air prefered)
  2. dry one subsample using an alternative approach
• Re-weigh your sample at regular intervals, until consecutive weights vary by less than 5%
• Repeat with at least 10 samples
• Compare the Soil Water Contents derived from your split sample, they must agree to within 5%
• Contact the GLOBE Soil Moisture PI (jwash@hwr.arizona.edu) to certify your results before reporting data to the GLOBE data archive.