The results are in - and our soil is good!

A dozen or so budding soil scientists joined Ecologist, Geologist and Palyntologist Dr Steve Boreham from the Geography Department at the University of Cambridge on World Soil Day, 5th December 2019 to carry out CoFarm Cambridge’s first community soil survey.

Although it was quite a chilly and misty December morning, we all had a great time and learned a lot from Dr Boreham about not only how to survey soils and record the data but also the rich industrial history of the area. (Our field, and Coldhams Common next to it, was once an important site for mining coprolite - fossilised dinosaur poo - to produce agricultural fertilisers in the mid 19th century.)

To access the results of our first ‘baseline’ study of CoFarm Cambridge soils, please click here to download a PDF document of the results. Steve’s interpretation of those results is included below.

• Soil depth (cm) - this is the thickness of the ploughsoil before an abrupt change was detected. There is a zone of thin soils over chalk across the western part of the site, and an area of deeper soils, often on clay, to the east. 

• In most places beneath the ploughsoil there was a layer of orange chalky sand, which we took to be a disturbed layer from the coprolite workings.  The orange sand was thicker in the western part of the site and absent to the southeast.

• Chalk bedrock was contacted in the western part of the site and clay was found to the southeast.

• Most of the site had a slightly alkaline pH (c.pH 8).  To the southwest there were some clear differences with two boreholes reaching c.pH 8.5 and two much lower at c.pH 7.5.

• Electrical Conductivity (EC) showed some higher values to the southwest of the site, suggesting mesotrophic conditions (>600µS/cm).  To the north, there were much lower EC values (<350µS/cm) suggesting oligotrophic conditions.  EC is a proxy for all ionic solutes (nutrients) present in the soil.

• Phosphate vales were moderate (c.15 ppm) across the site.  Phosphate tends to be retained in soils attached to organic material and clays.  There were two discreet areas with higher phosphate values (>20 ppm) to the east and west of the site.  

• Nitrate N values were below the limit of detection by the dipstick method across much of the site.  Nitrate is very soluable and is readily washed out of agricultural soils.  However, there were two areas where nitrate could be detected.  These are probably attributable to ’spot eutrophication events’.

The good news is that this means our soil is good and that there is also room for us to improve it by showing it some love over the coming years and planting the right things at the right times.

Huge thanks once again to Dr Steve Boreham for sharing his expertise, enthusiasm, equipment and time with us. We’ll use this baseline data to monitor changes in the soil over time as we focus on improving our most precious resource.