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- Select three equally-sized
sites in your area in which you want to test for the effects of water
on the nitrogen cycle.
- 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).
- Weigh each of the samples
to determine their mass and write these numbers down in a data table.
- Place the samples on a
window or other dry space in order to remove to water (If available,
use an oven to dry overnight).
- Once dried, mass the
samples again to determine how much water each sample contained.
- Cut fifteen squares out of
trash bags (e.g. 20 cm by 20 cm).
- Take five samples from
each of the sites, each soil sample being about 15 cm deep by 2 cm
wide.
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- 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).
- 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.
- Perform serial dilutions
on all of the soil samples; refer to
this page
for pictorial instructions on performing serial dilutions.
- Twenty-four hours later
collect a second soil sample from where you took the first and pick up
the trash bags.
- Perform ammonia, nitrate,
and nitrite chemical tests on the samples.
Testing
- Perform serial dilutions
on the samples.
Dilutions
- Wait at least twenty-four
hours to count the bacteria from the serial dilutions.
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