Soil could play a key role in delivering public goods such as clean air, non-polluted water and a range of wildlife, the Hutchinsons Farmer Conference heard. Abby Kellett reports.
»Different thinking on soil structure required
In light of Defra Secretary Michael Gove's pledge to replace subsidies with 'public money for public goods' post-Brexit, there was a need for farmers to better engage with the environmental features they influenced, according to speakers at the conference at Buston Barns Farm, Alnwick, Northumberland.
Soil was not only a key environmental asset in its own right, but when managed well it could help improve the quality of other natural features including water, air and wildlife.
Hutchinsons' technical manager Dick Neale said: "Currently, about 2.9 million tonnes of topsoil is washed from fields annually in the UK, but if we can stabilise the soil by improving soil structure through cover cropping, shallow tillage and by encouraging worm populations, we are going to reduce the amount of topsoil leaving our fields, while at the same time preventing nutrients and pesticides from entering our watercourses."
Since worms form burrow networks within the soil, which allows roots to grow to depth, infiltration was often greatly improved where earthworms were present, said Jacqueline Stroud, soil scientist at Rothamsted Research. When they exist at 16 worms per spade of soil or more, they could also significantIy improve crop performance and act as an important protein source for farmland birds.
Dr Stroud said: "To maximise the benefits associated with earthworms, it is important not only to have sufficient numbers of earthworms but to have each of the three different types - the surface dwellers, the deep burrowers and the topsoil earthworms."
Providing worms with an adequate source of organic matter on the soil surface was said to be crucial for boosting populations.
The improved infiltration associated with earthworm activity was helpful in preventing surface water run-off, which could lead to contamination of nearby water sources with crop protection and fertiliser products, according to Hazel Leah, catchment team manager for Northumbrian Water Group.
She said: "Metaldehyde is still the worst offender - in a six-month period metaldehyde exceeded drinking water standards 309 times. We have not yet developed a technique which is 100 per cent effective in removing metaldehyde from our water supplies. While they are not frequent offenders, we often see a big spike in carbetamide and propyzamide in autumn, which correlated with when farmers would typically be applying blackgrass products.
"Nitrate contamination can be a big problem where there is surface water run-off. A removal method does exist but it is very expensive, so anything farmers can do to retain nutrients and chemicals in the soil would improve the sustainability of the water treatment process."
To best deliver the 'public goods' the Government was likely to reward going forward, Mr Neale suggested reducing cultivations to a depth of no more than 5cm (two inches).
He said: "We have to think very differently about what good soil structure is because soil structure off the back of a plough is not very good, it is soil which has been de-structured by a major cultivation process which burns a lot of fuel and releases a lot of carbon into the atmosphere. We can get the benefits associated with high worm populations, better infiltration and ultimately better crop yields if we take a 'top-down' approach to cultivation."
To adopt this type of system, he said it was important glyphosate remained within the chemical armoury.
"Farming without glyphosate is difficult in any farming system, but especially this one. But the noises from Government suggest it is keen to address soil health, which would have to mean a move towards shallower tillage and the use of glyphosate."
Ms Leah said Northumbrian water was in favour of relicensing glyphosate as it was an easy compound to remove from water, whereas the active which could replace it may prove more challenging to breakdown.
By making changes to benefit the wider environment, Mr Neale said farmers would be in a better position to influence new policies going forward.