Cover crops could be a key driver in delivering public goods to improve water quality, according to Brian Barker, an AHDB strategic farmer who chaired the crop establishment seminar at this year’s CropTec.
Mr Barker told the audience how working alongside AHDB he had nitrate levels tested from the drain water coming off each of his fields, which are under different management systems.
“In a field that had been ploughed over and left the nitrate levels were averaging about 130 milligrams per litre which is over double the allowance,” said Mr Barker.
The EU directive for nitrate in water is 50mg/l. “Where we had water coming out underneath the cover crop it was just 3mg/litre. Nitrate is mentioned in the environmental plan and this is something that we need to be prepared for. If you can reduce the amount of nitrate to 3mg/l, considering rainfall is 5mg/l, then we have a really easy win with public goods if we can reduce the amount of nitrate leaving our farms.”
Speaking of his experience with cover crops, Lincolnshire farmer Andrew Ward MBE, told how his first cover crop subsequently saw a total crop fail, but perseverance has made key improvements to soil health.
“I’ve got one field that I changed to no-till five years ago and in the first year had a total crop failure. This had very heavy soil and a high clay content - to direct drill cover crop was fine, but then direct drilling spring barley was like going into concrete. Since then we cultivate straight after harvest to work the cover crop three or four inches deep, broadcast the cover crop, roll it and then leave it to direct drill the cereal crop in the spring. We’ve had four years of cover crop on that field and there’s no doubt that soil structure has changed. When you go into that field you can see the soil is in a better condition and despite the lack of moisture this autumn, the cover has got going. I’m now in a position to try not cultivating the cover crop and see what happens in the spring with direct drilling. It highlights that there isn’t one size fits all and for all soil type there is a different system.”
Cambridgeshire farmer and speaker Russell McKenzie started with 40ha of cover crops and now grows 200-300ha each year. “We are capturing around 37-47kg of nitrogen in those cover crops. That nitrogen will be given back to the following crop about two or three years later so that field will take a little while to come back into the equation. There’s a lot of options there to keep the soil in order. We introduced sheep a few years ago which gives us natural form of recycling and helps someone else.”
Velcourt farmer Adrian Whitehead of Norfolk bales straw to manage herbicide residue for high value crop like onions and potatoes, using the straw income to buy in organic matter.
“We don’t have cover crop, but we’re more concerned about organic matter and returning as much as we can through poultry litter or farmyard manure. Some of these soils have been beaten to death and we need to look at how we can improve structure.”
Also on the panel was Stephan Haefele, systems agronomist at Rothamsted Research who predicted that it may become a requirement for farmers to incorporate cover crops into their systems similar to the French model whereby there are strict rules about leaving soils bare.
The potential loss of glyphosate was also high on the agenda because it would have a substantial impact on the way cover crops are managed.
Mr Barker, who has trialled cover crop destruction using a combination of rib rolls and so far unsuccessfully without glyphosate said: “There are cultural methods to control cover crops but the choice of species is going to be critical. It’s a conundrum that we don’t want to have.”
Mr Ward reflected these views saying: “Glyphosate is the safest product on the market and we need to hold onto it. What will happen to cover crop destruction if we lose it?”
Adrian Whitehead highlighted concerns over the loss of glyphosate and cooch grass. “For those who remember how difficult cooch grass can be, without glyphosate it will return. It’s an essential component of what we do.”