Soil carbon event: Delivering higher returns
Sam Adams - 24 June 2013
Over thirty farmers attended a Low Carbon Farming event in north Cornwall that focussed on soil carbon, ways to increase it and the potential knock-on benefits. The event that was supported by the SWARM Hub project, managed by Duchy College, was held at Martin Howard’s farm near Launceston. I introduced the Low Carbon Farming project and referred to “the four pillars of low carbon farming”; nutrient management, soil and grassland management, livestock management and renewable energy.
Dr Jennifer Dungait, a senior research scientist from Rothamsted Research North Wyke, gave an animated talk on ‘The benefits of carbon for soil quality.’ She emphasised that soil organic matter typically contains 57% soil organic carbon (SOC) as well as other beneficial nutrients including nitrogen and phosphorus, and stressed that SOC should be protected/enhanced because of its wider role in promoting and maintaining soil quality and crop production.
Dr Dungait covered everything from what soil carbon is and ways to increase it, to the impact of SOC on food security, referring throughout to long term experiments being run at Rothamsted Research, and the new North Wyke Farm Platform aimed at optimising the sustainability of livestock agriculture. For the farmers present there were plenty of things to consider such as the importance of annual manuring and good fertiliser management as ways of increasing SOC. Dr Dungait also referred to the direct relationship found between levels of SOC and biological activity.
“When asked how I can make a rough assessment of soil quality and soil carbon levels, I suggest that earthworms are an excellent indicator of soil organic carbon.”
Farmers heard how SOC can be increased through adding manures, bio solids and biochar to the soil, using reduced tillage methods such as green mulches and crop residues and through introducing deep rooting plants to increase SOC in deeper soil horizons and reducing erosion. However, Dr Dungait emphasised that the addition of carbon to the soil can cause production of greenhouse gases such as nitrous oxide so farmers need to be mindful.
The messages were reinforced by Martin Howard explaining the techniques he has been using on his farm as part of his quest to increase SOC.
“On an organic farm it’s difficult to produce enough organic matter so I’ve been building it in with root crops.”
Mr Howard explained that he is particularly interested in what he perceives to be the direct relationship between yield increase and high SOC. He took the group in to a field which he had sub soiled as part of his quest to increase the SOC and explained that he has been looking at how he can get more oxygen in to the soil and is now starting to find that he can get deeper roots. Deep rooted plants can have a significant benefit on soil hydrology as well as increasing SOC.
The group were also shown a pasture field with steers that have been managed using mob grazing (grazing cattle on a small acreage of land for a short time then moving them on) to help increase organic matter. The system creates a deeper, more extensive root system below ground through maximising on the root zones of the different herbs in the field which are treaded in by the cattle.
Also speaking was John Morgan from the Farming Advice Service who talked about managing emissions from soils, nutrients and manures. He urged farmers to sample and analyse typical samples of slurry and FYM, review yard infrastructures and target applications to spring where possible.
Adapted from original article by Janie Caldbeck, Duchy College.
Thanks to Janie for words and photos.
Sam Adams is Low Carbon Farming Advisor at the Soil Association. Farmers can find out more about low carbon farming and use the Soil Association's Farm Carbon Assessment Tool (FCAT) here: www.soilassociation.org/lowcarbon