Different methods of assessing, improving and maintaining soil health were discussed at the ‘Soil Health and Circular Economy’ Agri-Tech East event hosted by NIAB on Friday.
The function of a healthy soil to receive, retain and release was discussed by Prof Jim Harris, Professor of Environmental Technology at Cranfield. He explained there were two main components of soil health: its quality (physical, chemical and biological) and its quantity.
Unstable soils lose heat
As an ecologist he views the soil as an interrelated system. When a system is inefficient it releases energy. In a project he has used this as a proxy for measuring the health of the soil and indeed found that balanced, stable soils released less heat. Additionally, soils that have inorganic inputs create twice as much heat as those that receive organic inputs. This is a metric that could be measured remotely, potentially creating a new way to look at soil health.
There are broadly four ways to improve soil:
- Method of cultivation
- Use of cover crops
- Soil additions
- Field engineering
Jim described some of the methods use by conservation farmers to maintain soil health, such as strip-tillage and showed how microbial activity declined in the areas impacted by soil cultivation, suggesting that no-till systems (although not widely applicable) could maintain soil structure and function.
Rewilding – quality meat and birdsong
His last comments were about a rewilding project at Knepp Castle, where an area of heavy clay was left to return to forest and was grazed by longhorn cattle, tamworth pigs and Exmoor ponies. The farming was subsidised by other sources, such as holiday rentals, but the results had been positive in terms of meat production, with only minimal supplementary feeding required in winter.
Other benefits had been an increase in biodiversity and the return of wildlife – in particular BTO had identified a concentration of nightingales.
Soil biology the missing dimension
Dr Elizabeth Stockdale, Head of Farming Systems Research, NIAB is heading up a project ‘Soil biology and soil health partnership’ which is looking at the tools available to assess soil health.
Physical and chemical measurements can be made using current technology, but the biology, the living element is poorly served.
Guidance coming out of the project, which has trials across six farms, includes advice on the use of manure.
- Know the nutrient content
- Estimate the crop available nitrogen supply
- Minimise nitrogen losses
- Spread evenly and accurately
- Build into farm nutrient management
Elizabeth warned that although manure is a valuable source of organic material and can help improve soil quality there is considerable variation between manures
So it needed be applied within a wider framework.
The project is looking at the use of scorecard that can be used by farmers
Optimising use of manure
Dr Lizzie Sagoo, Principle Soil Scientist, ADAS, described some of the ways to maximise value of organic matter and described MANNER-NPK as a useful tool to estimates the fate of organic manure N following land application (details on the AHDB site) She said that use of organic matter increased microbial activity as the lignin was slow to decompose, releasing food over a long period.
Dr Lydia Smith, Head of NIAB Innovation Farm talked about the synergy between roots and mycorrhizal fungi and how this can extract more nutrition from the soil.
She commented that early results from the digestate trial demonstrated the benefit of cover crops in retaining nitrogen in the soil when compared with digestate alone.
Other trials underway with Agri-Tech East members include the introduction of sheep into the arable rotation as ‘flying flocks’ on a temporary basis. This project on Honingham Thorpe farm has just started.
AgriGrub offering crop protection and source of nutrients
Dr Joe Halstead, MD of AgriGrub Ltd based at the Eastern Agri-Tech Innovation Hub.
AgriGrub is using chitosan, a natural stimulant for a plant’s defence system to create a potent active ingredient crop protection. The chitin comes from insect frass produced by the larvae of black soldier flies. The frass also provides a soil improver – offering a slow release nitrogen, source of high organic carbon and many micronutrients. Joe is currently looking for trial sites.
Two farmers also spoke. Organic farmer Nik Tonev of James Foskett Farms and Conservation farmer David White, Hawk Mill Farm who discussed the benefits of their approaches.
In summary – what to measure to assess soil health
- Soil nutrients, pH and VESS
- Earthworms – species and abundance
- Soil microbial activity
- Organic matter
- Aggregate stability
- Soil strength
- Porosity and bulk density.
National Soil Map Cranfield has launched a National Soil Map showing soil types across England and Wales. It was created to give non-soil scientists the evidence they need to understand and manage land-based risks and opportunities.
Soil Biology and Soil Health Partnership Farmers and growers have taken the initiative to understand the health of their own soils and a great deal of work is being done on-farm to experiment with ways to optimise soil biology. The Partnership will work closely with farmers, growers and advisers to draw together and build on knowledge and experience to create accessible guidance and tools to help farmers improve soil health.