Soil Texture and Nutrients Lab Activity
Soil Texture Procedure: (NOTE: Before beginning, prepare the soil sample for the
nutrient testing portion of the lab)
1. Obtain the 3 soil separation tubes OR 3 50 mL graduated cylinders. Label the
cylinders A, B and C
2. Add 15 mL of the soil sample to tube A. Gently tap the bottom of the tube on a
firm surface to pack the soil and eliminate air spaces.
3. Use a pipet to add 1 mL of “Texture Dispersing Reagent” to the sample. Dilute to
45 mL with tap water.
4. Cap (or cover in the case of the cylinders) and gently shake for two minutes,
making sure the soil sample and water are thoroughly mixed.
5. The sample is now ready for separation. The separation is accomplished by
allowing a predetermined time for each fraction to settle out of the solution. Be
sure to continue to gently shake the separation tube up to the time of the first
separation.
6. Allow tube A to stand undisturbed for exactly 30 seconds.
7. Carefully pour off all the solution (what hasn’t sedimented out) to tube B.
8. Allow tube B to stand undisturbed for 30 minutes. (During this time, you should
work on the Nutrient testing portion of the lab)
9. Carefully pour off the solution from Tube B into Tube C.
10. Due to the colloidal nature of clay in solution and its tendency to swell and form
a gel, the portion of clay remaining in Tube C is not used to determine the clay
fraction present in the soil. The clay fraction is calculated by adding the sand and
silt fractions and subtracting this total from the initial volume of soil used for the
separation.
11. Read tube A at the top of the soil level. To calculate percentage sand in the soil,
divide the reading by 15 and multiply by 100.
12. Read tube B and the top of the soil level. Calculate the percentage silt in the soil.
13. Calculate the volume of clay and the percent clay.
Soil Nutients:
Extraction
1) Fill the round extraction tube or a test tube with 30 mL of distilled water.
2) Add two Floc-Ex tablets. Cap and mix until the tablets have disintegrated
3) Remove the cap and add one heaping teaspoon of soil
4) Cap the tube and shake for one minute
5) Let the tube stand until the soil settles out.
Nitrogen
1) Use a pipet to transfer the clear solution above the soil to a test square tube or a
test tube. Fill with about 10 mL of solution.
2) Add one Nitrate WR CTA tablet. Cap and mix until the tablet disintegrates.
3) Wait 5 minutes for the color to develop. Compare the pink color of the solution to
the Nitrogen Color Chart.
L= 40 lb A/6” soil
M= 160 lb A/6” soil
H= 320 lb A/6” soil
Phosphorus
1) Use a pipet to transfer 25 drops of the solution above the soil sample to a test
tube.
2) Fill the tube to about 10mL
3) Add one Phosphorus Tablet. Cap and mix until the tablet disintegrates. Wait 5
minutes for the color to develop.
4) Compare the blue color of the solution to the Phosphorus color chart.
L= 8 lb A/6” soil
M= 20 lb A/6” soil
H= 64 lb A/6” soil
Potassium
1) Use a pipet to transfer about 10 mL of solution about the soil to a test tube.
2) Add one Potassium Tablet. Cap and mix until the tablet disintegrates.
3) Compare the cloudiness of the solution in the test tube to the Potassium color
chart. Hold the tube over the black boxes in the left column and compare it to the
shaded boxes in the right column.
L= 40 lb A/6” soil
M= 80 lb A/6” soil
H= 160 lb A/6” soil
Report: Write a paragraph on the make up of your soil sample. Explain the texture
and how you would describe the soil (ie sandy loam or loamy sand). Explain the
nutrient level. What is your soil sample good for? Can you grow plants in it? If so,
what kind?