Procedure

Water Difference

1a. Get one soil sample from both site three and four 15 cm in length in a 2 centimeter wide soil core.

2a. Place the soil samples into an incubator.

3a. 24-48 hours later, weigh the samples and calculate the difference between the weight of the soil samples before and after being placed in an incubators, to find the amount of water in the soil samples. Then find the difference between the amounts of water in each sample

 

Positive Control

1b. Get three soil samples from various locations from both site three and four.

2b. Perform tests to check nitrogen and bacteria levels. (see “Lab Tests”)

  Calculating the Amount of Water to Use in Your Experiment

1c. Find how many soil cores can fit within a 50*50 cm2 area.

      Formula: 50*50/ 3.14* 1cm2 = 2500/3.14 = 795.8

2c. Multiply the water difference from 4a by the number of cores. This number is how much water difference in ml there is per 50cm2 (ml/50cm2).

3c. If appropriate to the found water difference, convert ml to liters and/or to gallons for easier transportation of water.

  Setting up the Experiment

1d. Hydrate a half square meter of land in three quadrates of site three, using the amount of water you calculated earlier. Do not forget to use flags to find this location easily.

2d. Take soil samples 4 – 24 hours later from site 3 (artificial wet and dry) and site 4 (negative control).

3d. Return with the soil samples to the laboratory to test for nitrate nitrogen and bacteria levels (see “Lab Tests”).

4d. Repeat steps 1d. – 3d. as many times as feasible.

  Lab Tests

  Bacteria Serial Dilutions

  1. For each soil sample, fill a test tube with 10 ml of water and 1 ml of the soil sample. Shake.
  2. Fill a new test tube with 9 ml of water and 1 ml of the first solution.
  3. Fill a new test tube with 9ml of water and 1 ml of the previous solution.
  4. Continue doing this until you have 5 test tubes of solution. Each one should be more diluted than the previous.
  5. Then, plate each test tube on a separate Petrifilm plate. To do so, use a micropipet to transfer 100 micro liters from each individual tube. Label the plates.
  6. The bacteria need 24-36 hours to grow. Leave them in a cool dry location for this period.

  Nitrate Nitrogen Test 

*This test is taken from the LaMotte STH instruction manual and is used with the LaMotte STH Series of professional soil testing outfits.

Making the Extractions

  1. For each soil sample, fill an Extraction Tube to the 14 mL line with Universal Extraction Solution.
  2. Use a plastic soil measure to add two level measures of the soil sample. Cap and shake for one minute.
  3. Use a piece of filter paper and a plastic funnel to filter the soil suspension into a second extraction tube. (Fold the filter paper in half and then in half again to form a cone, which is fitted into the funnel.) The filtrate in the second extraction tube is the general soil extract that will be used in the Nitrate Nitrogen Test.

  Nitrate Nitrogen Test

  1. Use a 1 mL pipet to transfer 1 mL of the general soil extract to one of the larger depressions on a spot plate.
  2. Add 10 drops of Nitrate Test Reagent #1.
  3. Use a 0.5 g spoon to add one level measure of Nitrate Reagent #2.
  4. Stir thoroughly with a clean stirring rod. Allow to stand five minutes for full color development.
  5. Match sample color with Nitrate Nitrogen Color Chart. Record as pounds per acre nitrate nitrogen.

  Repeat the extraction and nitrate nitrogen test for each sample.

 

 

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