Why it is key to know what your cover crop options are – Farmers Guardian
Now in its fourth year, Hutchinsons' Sustainable Farming Incentive trials site at Warboys, is starting to reveal some of the long-term impacts of agri-environment mixes. Teresa Rush finds out more...
- Putting mixes in extends the benefit
Providing a run through of the pros and cons of cover and compan- ion cropping alongside Sustainable Farming Incentive (SFI) options, North Lincolnshire-based Hutchin- sons agronomist and cover crop lead Alice Cannon’s take-home message was ‘if you are going to do it, do it properly’.
As cover crops become more important within rotations, how they are managed-and terminated-will matter in terms of the benefits they can deliver, but also the problems they may cause.
“Picking the right species is the first thing you need to do, and then managing them out at the end is the next thing you really need to consider,” said Ms Cannon.
Commenting on individual species, she said tillage radish had a long, strong root that would go deep -unless there was soil compaction.
“It is not the magic bullet; it is not going to solve all your compaction problems in one go. You may still have to go down there with some metal to solve the problem first, especially if it is deeper than about four inches.
“Once you have done the metal work, put the cover crop in; it will reinforce the cultivation that you have done, but it will not solve all your problems in one pass,” said Ms Cannon.
Diversity in terms of cover crop species was key, she added.
“That is what gives you the benefits. Growing lots of cereals in an already cereal-dominant rotation will not give you diversity. What it might do is give you a yield loss,” she said.
Ms Cannon highlighted phacelia as a species she liked to use in cover crop mixes.
On the Warboys site’s heavy clay, high-magnesium soil – which tends to be tight and sticky – phacelia’s rooting action helped open up the top two inches, creating a well-aerated layer with good crumb structure. Phacelia is also good for beneficial insects, ‘fantastic for bees’ and, as a herb, will tick the requirement for a herb in several SFI options.
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Hutchinsons’ Environmental Trial Site is hosted by P.F. England and Son, a 180-hectare family farm growing cereals and sugar beet, with land rented out for vining peas.
The farm’s soil types are split roughly 50/50 between Grade 1 fenland and heavy clays.
Linseed
Linseed and Gold of Pleasure are similar in terms of the benefits they bring, with their rooting systems binding together sandy soils but opening up clays.
When it comes to companion cropping, however, linseed would not be the first choice, said Ms Cannon.
“I am getting a lot of questions on-farm: ‘Can we put linseed in as a companion crop with cereals?’. Yes, you can; it does fit for the small applicator seed box that potentially is easier to put on your drill than spinning some beans and peas on.
“But if you are trying to battle black-grass [then] the linseeds, the Gold of Pleasure, the vetches, [they] will not compete with the chemical. You will find that you have zero establishment, and then you are not achieving your SFI goal and you are in for a fine if you do that.”
Ms Cannon said white mustard was cheap and good for ground cover, but was not particularly favoured by pollinators, and there may not always be a below-ground benefit, which would be wanted from a soil health perspective.
She said: “It is also high in carbon – its carbon:nitrogen ratio is high. If you have put in a large stand of mustard and another equally high carbon:N ratio crop, such as oats, barley, or any of the cereals, and then you try and put spring barley after this, be pre- pared for a significant yield loss.
“It will take all the N out of your seedbed to break [the cover crop] down. That N is then not going into your spring barley crop.
“Spring barley grows for a lot shorter period of time than any of the winter crops; it needs a good start. The first three weeks of a spring barley crop’s life determines its yield- do not hold it up at the start.”
Ms Cannon’s advice was to use white mustard in small quantities.
“You only need 5kg to give a full stand,” she said.
Buckwheat
Buckwheat is a good companion crop and will tolerate drier condi- tions, but it needs drilling early.
“It works well as a companion crop and for the spring and the summer cover crop options that have come in with the 2024 SFI,” said Ms Cannon.
Another benefit of buckwheat is that it is an effective scavenger of phosphorus, especially in high pH soils, and it works well as a companion crop with oilseed rape.
“It will solve all your cabbage stem flea beetle problems and it will help your rape to establish. It is very reliable and will grow in the summer quite happily, but as soon as the frost comes you can wave it goodbye,” said Ms Cannon.
Vetch, as a legume, fixes N, and so is useful in a cover crop mix and has quite strong roots.
She added: “People are asking if vetch can work as a companion with wheat, but it will not cope well with the chemicals we like to use [in wheat] and it grows like a cleaver; it will be up through the top of the crop.
“Be careful with what you are putting in. These ideas and options for SFI are fantastic, but think about what you are doing and do not give yourself a headache fur- ther on down the line.
“Single species are great, and a lot of them have individual traits that are desirable, but what we really need to be doing is putting mixes in because that extends the benefits and gives us more diversity.
“Let us put a mix in and get all the benefits from the top growth and the bottom growth, and farm more sustainably,” said Ms Cannon.
Original AB15 two-year sown legume fallows, available in Countryside Stewardship Mid and Higher Tier schemes, were de- signed to provide food for farmland birds and pollinators, plus be a us ful part of the rotation in terms of reducing black-grass populations. But as these fallows begin to be removed, problems are becoming apparent.
Legume fallows
Hutchinsons technical manager Dick Neale said: “We are starting to see a real problem behind these high legume content fallows, and that is that the aggregates we are building in the soil are collapsing into a solid lump.”
As the fallow reaches the end of its life, the N accumulated in its root nodules is released rapidly into the soil and is ‘supercharging’ the soil biology, which then uses the N to consume carbon, said Mr Neale.
Pointing to evidence of this pro- cess on the Warboys site, he said: “All this lovely soil aggregation we are seeing, all of that is built around carbon. The microbiology is con- suming the carbon; the aggregates that we have built up over three years are just collapsing and it is proving a real problem.
“It is something we need to take into account; if we are leaving legumes in for a long period of time, it could be quite costly on heavy soils,” Mr Neale added.
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