Soil Lab
Soil Sample Collection
 Use a shovel to collect several small samples of soil from one area, from a depth of
2 to 6 inches, place all the samples together until you have around one cup.
pH
 Fill test bag to line C with distilled water.
 Add about ½ teaspoon of soil
 Add one soil pH test tab. Roll the top of the bag down 3 or 4 times.
Fold the yellow tabs back around the bag hold the bag and shake for 15 secondsdon’t pinch or squeeze…just shake.
 Let the bag sit for 1 minute
 Compare the color of the liquid to the pH on the poster and record your results
 Throw the water/soil mixture out in the planter then wash out your baggie
(pH is a measure of how acidic or basic something is. 7 is neutral, below that is acid and
above that is basic or alkaline. Different plants prefer different pH’s. The pH of the soil
solution determines how much nutrients are available to the plants, if a soil is too acidic or
basic, the plant can’t absorb nutrients such as nitrogen, phosphorus, and potassium. Other
elements, such as metals, can become more available and can become toxic to the plant. To
lower the pH of a soil aluminum sulfate or alum is added and to raise the pH of a soil,
limestone or “lime” can be added)
Next step: The floc-ex tabs must be used to free the soil nutrients from the soil. It is
actually a powdered form of acetic acid that is able to pull the nutrients (which are tightly
stuck to the soil) from the soil particles, this makes the nutrients (nitrogen, phosphorus,
and potassium) measurable  this is called “extraction”
Extraction
 Pour ½ cup of distilled water in a freezer bag
 Add 8 floc-x tabs. Seal the bag. Shake the bag until the tabs dissolve
 Add 5 teaspoons of soil to the bag
 Close the bag and shake it briskly for one minute (the extraction is taking place at
this time)
 Hold the bag at an angle and let the soil “settle” out
 Carefully pour off the liquid into a beaker. This liquid will be used for the remaining
tests
Nitrogen
 Fill test bag to line C with soil nutrient extract
 Add on Nitrate #1 testab, roll the bag down 3 or 4 times. Fold back the yellow tabs
and shake until the tab dissolves (~30 sec)
 Open the bag. Add on Nitrate #2, fold the bag and shake for about 2 minutes or
until tablet dissolves
 Wait 3 minutes for test results to develop, compare your results to the chart and
record your results
 Rinse out your bag
(Plants use nitrogen to make chlorophyll, which allows photosynthesis to take place.
Nitrogen is also a component of amino acids and proteins. Nitrogen is responsible for
healthy green leaves…such as those found in spinach and lettuce, and crops like soybeans
and alfalfa. Plants called “legumes” have special bacteria on their root nodules that
enable nitrogen fixation and nitrification to take place. A plant that is deficient in
Nitrogen will have yellowing of the leaves)
Potassium
 Fill your test bag to line C with soil nutrient extract
 Add one Potassium test tab, fold the bag and shake for about 2 minutes or until
tablet dissolves
 Compare the “cloudiness” of the reaction to the poster by holding the bag over the
black salamanders in the left column and see how fuzzy they look. Compare them to
the gray salamanders in the right hand column, record your result
 The potassium test results produce turbidity rather than color….the more potassium
there is, the more cloudy the sample will be
 Rinse out your bag
(Potassium comes from the weathering of minerals in the soil. A plant that doesn’t get
enough potassium will have slow growth, small size, and may have leaf edges that look
brown and “scorched”. Potassium is important for new cell growth and helps plant resist
disease and survive weather extremes, it also makes the stems strong. Crops such as
beets and potatoes, carrots, and radishes as well as asparagus, broccoli, and cauliflower
benefit from sufficient potassium)
Phosphorus
 This test is very sensitive, so the soil nutrient extract must be diluted.
 Put 7 teaspoons of distilled water into a beaker, add one teaspoon of soil extract,
stir it up
 Fill your test bag to line C
 Add one phosphorus testab, roll the bag down and shake for about 3 minutes or until
the tablet dissolves
 Wait 5 minutes for color to develop
 Compare your results to the color chart and record your results, rinse out the
baggie
(Phosphorus is changed into a useable form by soil microorganisms; it is most available to
plants at a pH between 6 and 7. A plant that doesn’t get enough phosphorus will have
purplish or deep green color on lower leaves and a poor root system. Phosphorus is necessary
for root development and growth, and helps plants grow strong and make flowers and fruit,
especially for root veggies such as potatoes, carrots, and radishes)