Where do I do Each Test and How Many Times per Field?

In each field you need to decide where you want your sample sites to be. The idea is that you come back to within a 5m circular area of that spot each time you do the tests again. By going back to more or less the same spot you are able to see how that soil is changing with time and as you change management practices. If you’re using the Soilmentor app, save the GPS locations of your chosen sample sites.

  1. Best spot
  2. Worst spot
  3. An ‘average’ spot in the field

You can choose more sample sites if you like – it’s all about how much time you have! You can also just do one sample site in a field and use that spot as an indicator site for changes in that field.

For Platemeter or Sward Stick readings you need to get many more than 3 readings, but these are much quicker to do. Generally you do this by walking a W (a guide of how to do this is at the bottom of the page).

The most important thing is that you do the tests in a similar manner in each field and repeat them over the year(s).

How to do a W Walk

You’ll need to know how to do this for some of the soil tests!

Walk to one corner of your field, walk 20 steps away from the corner towards the middle of the field.

This is the start of your W.

Don’t get closer than 20 steps from the edge of your field.

Aim for the other end of the W to be in a similar spot in the other corner of the field either to your right or left.

How Many Times do I Need to do Each Test in a Field?

1.Spade and Probe Tests

Choose three points in each field to do spade (e.g. VESS, Earthworms etc) and probe tests (e.g. probe depth). Follow the same protocol for infiltration rate tests and taking samples from soil blocks for slake tests back at home – so for each field you do three tests.

For spade tests dig out a 20cm block, digging the spade down on three sides and lever out the soil block from the dug side opposite to the undisturbed side. Try to keep the soil block as intact as possible. Put the soil block on a tray or bag and if there is any left in the pit going down to 20cm dig this out and put it on the tray too. Use the undisturbed side to do your VESS top/bottom depth assessment and don’t forget to take a photo.

In the Soilmentor app you record information for each spade test by selecting which sample site you are: Sample 1, Sample 2 or Sample 3 for each field. Make sure you label soil sample bags for the slake test with 1, 2, and 3.

You can save the GPS location of each of the three sample points on the Soilmentor app, so it’s very easy to get back to that exact area next time.

2.Grass Tests

Do 1 grass test every 1 acre along your W walk (see instructions above) or a minimum of 6 grass tests, depending on how much time you have.

At each spot you test along your W throw your quadrat a few metres and take the readings.

In the Soilmentor app record information for each grass test using W Walk Sample for each field.

For Lab Tests: Take a “Compound” Sample

In the Soilmentor app there is the option to add in lab test readings too. If you’ve created a sample for W walk tests, it can be interesting to add your lab results to this sample to compare to other W walk tests. In order to take a lab soil sample you want to get a sense of an average for the soil in that field.

Taking samples to combine into a compound sample across your W is a way to create a representative average for a whole field.

Avoid: Field margins, hedges, water troughs etc

  1. Walk a W across the field (instructions above)
  2. Take 20-25 “sub samples” more or less evenly along the way
  3. Mix sub-samples well in a bag
  4. Close bag
  5. Label bag with field name