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Serial Dilutions

To learn more about our procedure.

Chemical Testing 




  Steps with pictures for Serial Dilutions Instructions for how to test for these items can be found here
  1. Select three equally-sized sites in your area in which you want to test for the effects of water on the nitrogen cycle.
  1. From each of the sites take one equal-volume sample of soil (e.g. 2 cm wide and 15 cm deep). Be sure that you are able to distinguish between your different samples (e.g. label plastic bags).
  2. Weigh each of the samples to determine their mass and write these numbers down in a data table.
  3. Place the samples on a window or other dry space in order to remove to water (If available, use an oven to dry overnight).
  4. Once dried, mass the samples again to determine how much water each sample contained.
  5. Cut fifteen squares out of trash bags (e.g. 20 cm by 20 cm).
  6. Take five samples from each of the sites, each soil sample being about 15 cm deep by 2 cm wide.
  7. Based upon the amount of water that each soil sample contained, hydrate it with the corresponding amount of water in order to make all of the samples have the same hydration value (which you determine based on your area) and cover with one of the trash bag squares to control the amount of sunlight each sample receives. Make sure the trash bag squares are secured to the ground (use marker flags if available).
  8. Perform ammonia, nitrate, and nitrite chemical test using the LaMotteŠ test kit on all of the soil samples. If you do not have access to a LaMotteŠ  test kit refer to this page for instructions on how to perform the tests.


  1. Perform serial dilutions on all of the soil samples; refer to this page for pictorial instructions on performing serial dilutions.
  2. Twenty-four hours later collect a second soil sample from where you took the first and pick up the trash bags.
  3. Perform ammonia, nitrate, and nitrite chemical tests on the samples. Testing
  4. Perform serial dilutions on the samples. Dilutions
  5. Wait at least twenty-four hours to count the bacteria from the serial dilutions.