Going under the surface

Once a year I spend a morning walking around the farm with a soil auger, taking little cores of soil about 12″ deep from across the whole farm. The purpose is to understand what is happening in the farm’s soils, in particular the soil organic matter.

It sounds idyllic, though is not quite as lazy and romantic as it sounds. I sample 10 fields, each one having at least 10, sometimes 20 sub-samples. Each sub-sample gets put in a bucket, and mixed together so that there is a representative sample from one field (or one set of fields that are sampled together). Each sample is put in a bag, labelled clearly and put in a box.

Mixing soil before bagging

When all the samples are bagged and labelled they are put in a box. I then walk quickly to the Post Office (to catch the 1.00 post deadline) and send them off to the lab. I use Forest Research, and have done for years. They will receive the samples, process them and analyse the percentage of soil organic matter.

This is an annual process I’ve done since 2009, so there’s an interesting sample of data. A master spreadsheet contains all the data – SOM percentages across all fields, which we then convert to carbon sequestration using a recognised calculation.

Using a soil auger to take soil samples

The upshot is that, on the whole, soil organic matter is building across the farm year on year, and carbon is being sequestered. This also means soil is getting heathier and more productive. However there are some variations between years and fields – some going up, some going down, some staying stable. Understanding why this happens is really important, and it’s not always straight forward.

Taking SOM samples give us the evidence and understanding of what’s happening – both specifically in each field, and the bigger picture across the farm. Linking that to management practice is the next important step, and a process we’re constantly learning more about. When it comes to SOM, generally the more data you have, the better.

For anyone wanting to know more about how to take soils samples, where to send it and what it means, this excellent guide from Farm Net Zero is really worth a read https://farmcarbontoolkit.org.uk/2021/11/11/new-guide-on-monitoring-soil-carbon/

Jonathan Smith

I started Scilly Organics in 2003, and it was the first certified organic farm on the Islands. We continue to supply the highest quality fruit and vegetables, available fresh on our stall and at certain eateries on Scilly.