I am quite regularly asked by colleagues and farmers to offer an opinion on some more complex soil analysis reports. It may be a soil audit that includes Cation Exchange Capacity and total nutrients or a REAMS test. These results can be illuminating and help in preparing fertiliser and soil management plans. The tests for soil health or the biological activity of the soil that go beyond the organic matter level are notoriously inaccurate.
A simple infiltration test is probably as good as an indicator as any of the soils’ health. These can be carried out very quickly at almost no cost and involve no more equipment that a short piece of 6 inch pipe, a known volume of water (450 ml in the case of a 6 inch pipe) and a stop watch, or phone. The infiltration rate is a good indicator of the health of your soil, the quicker the better. It is worth comparing the infiltration rate of the field and that of the uncultivated field margin. In most cases the results are alarmingly different, highlighting the poor structure and compacted nature of most soils within the field.
To work out your infiltration rate in inches/hr, divide 3,600 by the time in seconds it took for your water to infiltrate, for example 20 seconds is 3,600/20 = 180 inches/hr.
For a complete guide to carry out an infiltration test read on.
1. Locate your chosen sample site – you can use the GPS mapping feature on the app to do this if you’ve recorded the sample locations previously.
2. It is very important to remove all debris, weeds and vegetation on an area of 150mm x 150mm square – either trim these down or cut through with a knife.
3. Insert the cylinder/tin into the bare ground to 85mm depth.
4. Firm soil gently on the inside of the tube.
5. Measure out exactly 450ml of water from your pre-marked water bottle.
6. Pour water into cylinder and start timer.
7. Stop timer when all the water has disappeared into the ground and the surface is just glistening.
8. Repeat steps 5-7. Record this second time. This is because often the second time gives a better indication of the real infiltration rate that is less dependent on recent weather, as the first test just wets the soil. If the soil is already quite saturated, you may find there is very little difference in the first and second times.
9. You can stop here, or if you want to be very confident in your infiltration rate reading or if it has been particularly dry, then it’s worth repeating steps 5-7 again a couple more times to ensure you are getting a representative infiltration rate.
10. If it is happening very slowly, carry-out other tests nearby and check back on it every few minutes.
See This video https://youtu.be/PYvfTxQhbOQ
Contact William at firstname.lastname@example.org or your local FCG office, for more information on interpreting soil infiltration results and soil management in general.