pH
Organics
have
contain
have
contain
Moisture
SOILS
Temperature
have
Texture
END
SHOW
Soil is Important!
Soil is the link between the
rocky crust of the Earth and
all life on the Earth’s surface.
It is a subsystem of the Earth
that is very important,
because all life on Earth
depends on soil (directly or
indirectly) for food. All soil
contains minerals, organic
matter, water, and air.
www.dpi.vic.gov.au
Organics
http://tiee.ecoed.net/vol/
v3/experiments/soil/img
/soil%5BHR%5D.jpg
• Bacteria and fungi in the soil will break down dead plants
and animals. This makes organic matter to the soil.
• Organic matter dissolves in the water in the soil to provide
nutrients to plants.
TO LAB
• Soils with less than 2% organic matter are rated “low”;
“medium” soils have 3-10%, and “high” soils have over 10%
organic matter.
Measuring Organics
THIS IS DONE AFTER SOIL MOISTURE!
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Mass a crucible.
Add the 2 spoonfuls of dry soil from the other part of
your team and mass again.
Set up a ring stand with a clay triangle and Bunsen
burner like in the diagram.
Start the Bunsen burner on low, and gradually
increase the flame until the crucible glows red.
Heat for 5 minutes at red-hot. This will burn off all the
organic matter.
Turn off the Bunsen burner and let the crucible cool.
Mass the crucible and burnt soil. Calculate the mass of
the dry soil & the burnt soil.
Calculate how much organic matter was burnt away.
Calculate the % of organic matter in your soil by:
% = (mass of organic matter)/(mass of dry soil) x 100
Moisture
• Plants need water, and they also need the nutrients that
dissolve in water.
• We can measure both how much water is in the soil when
we collect it (moisture content) as well as how much water
your sample can hold onto (moisture holding capacity).
• Soils with less than 5% water content are rated “low”,
“medium” soils have 6-20% water, & soils over 20% water
are rated “high”.
background www.dpcprints.com
TO LAB
Measuring Moisture: Part 1
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Get a small metal can.
Use a rubber band to fasten a filter paper over one end of the can.
Mass the can-and-filter.
Add the soil and mass again.
Put the can-and-soil into a drying oven set at 100°C for at least 24
hours.
Mass the soil and can again.
Calculate the mass of the original and the dry soil.
Calculate how much water was lost while the soil was dried in the
oven.
Calculate the moisture content of the soil as follows:
moisture content(%) = (mass of lost water/mass of dry soil)x100
Measuring Moisture: Part 2
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Put the can with the dry soil into a large beaker.
Add water until its halfway up the sides of the can.
Let it sit for at least 24 hours.
Put the can and wet soil on a wire gauze screen on a
ring stand (see diagram) and let it drain into a sink for
30 minutes.
Mass the can and wet soil.
Calculate the mass of the wet soil.
Calculate the mass of water the soil absorbed.
Calculate the moisture holding capacity of the soil by:
(mass of water absorbed)/(mass of dry soil)x100
Temperature
• Temperatures below 5°C are too
cold for plants to grow, and at
these temperatures even soil
bacteria and fungi are barely
active.
• All plants grow best at
temperatures from 16-22°C.
• Between 5-16°C some plants
will grow.
• Above 22 °C its too hot for
almost all plants to grow.
www.bcfd3.com
TO LAB
pH
• pH is a measure of how acidic or basic the soil is.
• This depends on the kind of rock the soil is made from, the kinds of plants
that decay, and the amount of rainfall.
• Lots of rain usually removes calcium and makes the soil acidic. Decaying
oaks and maples make soil basic, while decaying evergreens (except pines)
make the soil acidic.
• Most plants prefer soils with a pH between 6.5-7 but will tolerate a range of
6-8. When the soil becomes too acidic (lower than 6) bacteria don’t grow
well.
Which
would make
an acidic
soil?
www.transparenciesinc.com
www.geo.msu.edu
Measuring pH
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Measure out 2.0 grams of soil for
pH into a small beaker.
Add 10 mL. of distilled water.
Stir well with a clean glass stirring
rod.
Set up a funnel and filter paper
like the diagram.
Stir up the soil-and-water mix
and pour it quickly into the filter
paper.
Test the filtrate (the liquid that
goes through the filter paper into
the beaker) with pH paper.
TO LAB
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Texture
Good soil has both air spaces and
solid particles.
The air spaces provide room to store
and move water & air as well as room
for root hairs to grow.
The solid particles provide nutrients for
plants and water storage.
Soil texture describes the sizes of the
particles in the soil. Soils are usually a
mixture of pebbles (2-6 mm), sand
(0.06-2 mm), silt (0.004-0.06 mm) and
clay (under 0.004 mm).
Sandy soils let water flow and drain
quickly. Clay soils absorb water slowly
and don’t drain well.
How many textures do
165.234.175.12/
you see?
Dendro_Images.h
tml
Measuring Texture
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Look at your soil sample with your eyes and also with a magnifying
glass. Do you see mostly clay, sand, or pebbles?
Get the sieve set. Make sure the largest screen size is on top, and that
the sizes decrease from top to bottom.
Put your sample of soil in the top sieve. Hold the sieves upright and
shake hard for 30 seconds.
Pour out the soil from each sieve onto a separate pieces of paper,
recording the sieve’s screen size. The particles in each sieve are larger
than the screen size for that sieve, but smaller than the next biggest
screen.
Give the sieve set to another group.
Mass each portion of soil.
Calculate the total mass of your soil sample.
Calculate the % of soil in each size range by:
% = (mass of soil of this size)/(total mass of soil)x100