GLOBE III - Soil Fertility

Design and Learning Approach

Hands on activity. Material will be developed to illustrate the critical ties between soil fertility and plant productivity, which strengthens the integration of multiple GLOBE units.

Cost Impact

• Kit cost:
• Cost of reagents:

Training Impact

• Requires extra time during the soil characterization training, before or after explaining how to measure pH.

Systems Impact

• Adds one field to soil profile characterization data
• What is danger associated with chemicals - what can be done for elementary students?

PURPOSE
To measure the amount ofnitrogen (N), phosphorus (P), and potassium (K), 3
soil macronutrients, in each of the soil horizons within the soil sampling
sites.Soil fertility information is a key component for linking properties
of the soil with biometry and land cover, as well as stream chemistry
within a watershed.

OVERVIEW
Soil samples taken from the GLOBE study sites will be analyzed by
colorimetric methods (in triplicate) for N, P, and K in the classroom,
after the soils have been air dried.

TIME REQUIRED
Part of the class period devoted to measuring pH and particle size
distribution.  Extraction is started in one class period (requires 5
minutes to perform, 24 hours t settle).  Analysis requires 1 class period
to complete all 3 test on all samples

SKILL LEVEL   All (For elementary students, teacher can perform procedure,
and students can interpret results)

MEASUREMENT FREQUENCY
Three subsamples from each soil horizon are measured and reported once for
each soil profile characterized.


KEY CONCEPTS AND SKILLS
Concepts: soil nutrients, soil fertility, chemical reactions
Skills: observing color, preparing sample, pipetting, determining relative
	nutrient content

MATERIALS AND TOOLS
Soil testing kit with reagents to measure N, P, and K
Distilled water
enough 30mL graduated cylinders for extraction procedure of each sample
	(only one is included in the kit)

DESIGN AND LEARNING APPROACH
Hands on activity. Material will be developed to illustrate the critical
ties between soil fertility and plant productivity, which strengthens the
integration of multiple GLOBE units.

COST IMPACT
Kit cost: $20-$30 which includes 1 30 mL vial and lid, 3 analysis vials and
lids, 1 pipet, color charts, and enough reagents for 50 tests for N, P, and
K

TRAINING IMPACT
Requires extra time (about 10-15 minutes) during the soil characterization
training, before or after explaining how to measure pH.

SYSTEMS IMPACT
Adds one field to soil profile characterization data
 Reagents are non-toxic.  Elementary students can read color charts and
make interpretation of levels of N, P, and K

ASSESSMENT REQUIREMENTS


WHAT TO DO AND HOW TO DO IT

Part1:  Extraction

1.Prepare the soil samples you obtained from the soil sampling sites by
drying and sieving them (required for particle size analysis and pH
measurements as well).  You should have 3 samples for each horizon at each
of the 2 soil sampling sites.

2.Fill the extraction tube (in the Soil Test Kit) or a 50mL graduated
cylinder to the 30mL line with distilled water.  Add 2 "Floc-Ex" tablets to
the water, and cap the tube or cylinder.  Mix until all of the tablets have
disintegrated.

3.Remove the cap and add one heaping teaspoon of sieved, dry soil.  This
should be performed for each of the 3 samples of each horizon.

4.Cap the tube or cylinder again, and shake for one minute.  Be sure all of
the soil has been mixed thoroughly with the water.

5.Let the tube stand until the soil settles out (this may take 24 hours in
very clayey soils!). The clear solution above the soil will be used for the
Nitrogen, Phosphorus, and Potassium tests.

Part 2:  Nitrogen

1.Use the pipet to transfer the clear solution above the soil to one of the
test tubes in the Soil Test Kit until the tube is filled to the shoulder.

2.Add one Nitrate #1 Tablet and one Nitrate #2 CTA Tablet.  Cap with the
red cap and mix until both tablets disintegrate.  Wait 5 minutes for color
to develop.  Compare the pink color of the solution to the Nitrogen Color
Chart in the Soil Test Kit.  Record your results (High, Medium, Low) on the
GLOBE Data Entry Page.  Discard the solution and wash the tube and the
pipet with distilled water

3.  Repeat this procedure with the liquid from  each of the soil samples.
Be sure to rinse the pipet and tube with distilled water after they are
used.

Part 3: Phosphorus

1.  Use the clean pipet to transfer 25 drops of the clear solution above
the soil to a clean test tube.

2.  Fill the tube to the shoulder with distilled water.

3.Add 1 Phosphorus Tablet to the tube and cap it with a blue cap.  Mix
until the tablet disintegrates.

4.Wait 5 minutes for color to develop.  Compare the blue color of the
solution to Phosphorus on the color chart in the Soil Test Kit.  Record
your results (High, Medium, Low) on the GLOBE Data Entry Page.  Discard the
solution and wash the tube and the pipet with distilled water.

5.  Repeat this procedure with the liquid from  each of the soil samples.
Be sure to rinse the pipet and tube with distilled water after they are
used.

Part 4: Potassium
1.  Use the clean pipet to transfer the clear solution above the soil to a
clean test tube until it is filled to the shoulder.

2.  Add 1 Potassium Soil Tablet to the tube.  Cap with the white cap and
mix until the tablet disintegrates.

3.  Compare the cloudiness of the solution in the test tube to the
Potassium Color Chart in the Soil Test Kit.  Hold the tube over the black
boxes in the left columna dn compare it the shaded boxes in the right
column.  Record your results (High, Medium, Low) on the GLOBE Data Entry
Page.  Discard the solution and wash the tube and the pipet with distilled
water.

4.  Repeat this procedure with the liquid from  each of the soil samples.
Be sure to rinse the pipet and tube with distilled water after they are
used.

Back to UA/GLOBE Soil Moisture home page