Air-drying soils

Principle:

Soils are typically air-dried as preparation for sieving, for archiving samples or for other uses where the starting moisture content of the soils is not important for the analysis.  Air-drying affects nutrient availability and microbial biomass measurements, so do these measurements on field-moist samples (or subsamples).  For some analyses, you may need to re-wet and incubate the samples prior to analysis.

Equipment:

  • Baking trays, one for each soil sample
  • Labels, one for each tray
  • A whole lot of counter space in the sample prep lab

Note:

Before you start, make sure that no one is going to be using the sample prep room for anything really messy, like running the rock saws, for the next three days.  Your samples will be exposed to the air and you don't want foreign material getting in them.  You may want to put out a note with your contact information, so that people can let you know if they will be putting a lot of dust in the air.  Otherwise, consider using an alternate lab space.

By the same token, try to get your samples put away in bags promptly after 3 days, to let other people use the lab space.

Procedure:

  1. In the sample prep lab, make a label for your trays so you don't forget which sample is which.
  2. Spread out a soil sample on one of the trays, breaking up large clumps by hand.  Make sure your sample is small enough that the soil layer is no thicker than 2-3 cm on the tray.  If you have a larger sample, you will need to use multiple trays.
  3. Leave the samples undisturbed, in a place where they will not accumulate too much dust, for 3 days.
  4. Move the samples to sample containers.  At this point you may store them at room temperature in porous containers such as paper lunch bags.