5.9 Soil Structure Test
Does your soil sip, or slump and spill?
 A
well structured soil can drink in rainfall. A poorly structured soil will
tend to slump blocking soil pores and cause water to run-off.
Even a high
quality soil will eventually break down after several storms. The aim is
to improve soil structure to maximise infiltration and minimize run-off.
In the paddock rainfall infiltration can be estimated
using the following simple test.
You will need:
-
150mm of metal exhaust pipe or plastic down pipe about
100mm diameter
-
2-3 litres of rainwater
-
300-500ml measuring cup, or a beer can with the top
removed
-
Plastic bag and rubber bands
-
Sheets of paper towel
-
Stop watch, ruler, note book and pen
In the shed
-
Sharpen one end of the pipe to make it easier to push
it into the soil.
-
Secure the plastic bag on the bottom of the tube to
form a water tight base.
-
Stand the pipe on a flat surface.
-
Fill your measuring cup and pour into the pipe.
-
Measure the depth of water in millimetres.
-
Discard the water and remove the bag.
In the paddock
-
Press the sharpened end of the pipe into the soil
until it is a tight fit.
-
Place the cloth on the soil inside the pipe (to
protect the soil as you pour the water in).
-
Fill your measuring cup to the top with rainwater.
-
Note the time and pour the water into the pipe.
-
When the last bit of water disappears check the time
again and see how many minutes it took for the water to soak in.
The infiltration rate
The infiltration rate. measured in mm/minute, is the depth
of water the measuring cup puts into the pipe divided by the time it took
to soak in. Values of 1 or 2 mm/minute are okay, smaller infiltration
rates than this means that large storms will cause runoff.
Rule of thumb
If you capture an additional 25mm rain, it can mean 1/2
ton/ha extra in yield.
5.9 Soil Structure Test
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