Where and how often to do soil tests
There’s a seasonal quarterly, annual and biannual schedule for each test laid out on the Sectormentor For Soils website - have a look before you get started: https://soils.sectormentor.com/soil-tests/how-often-do-i-do-tests/
Where to do soil tests
Create a W in your field: walk to one corner of the 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 tests to do in one field
The important thing is that you do the tests and repeat them over the year(s), so if the below is not do-able, then aim for a minimum of 5 in each field, although this may lead to less accurate information. Another approach is do the test 3-4 times across the W. If all the readings are the same more or less, then you can assume the field is more or less uniform on average and those readings are representative.
The Codes for the tests correspond to 3 different types of test: 1 – Spade tests, 2 – Soils tests and 3- Grass tests. Below are recommendations for the optimal number of samples you would take for each test type in a field.
1 set of spade tests per 8 acres. Equally spaced across W.
Insert spade about 20cm down. Dig out spade-full of ground, intact as possible.
1 set of soil tests per 8 acres. Equally spaced across W.
One set per acre. Equally spaced across W.
Once you reach a sample spot, throw the Quadrat a few metres in front of you and to tests at that spot to avoid any bias of which spot you choose to look at.
For Lab Tests: Take a “Compound” Sample
In the app there is the option to add in lab test readings as well, as it can be interesting to compare to these as well. In order to take a lab soil sample you want to create an average for the soils in that field.
The W is a way to create a representative average for a whole field.
Avoid: Field margins, hedges, water troughs etc
Walk a W across the field
Take 20-25 “sub samples” more or less evenly along the way
Mix sub-samples well in a bag
Label bag with field name