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Latest drills have it covered


Cover crops potentially offer a wide range of applications and benefits in arable rotations, but require careful establishment and management, including use of appropriate machinery, Jane Carley reports.

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As growers consider the various cover crop options and ways of growing and managing them, one point to take into account is whether existing machinery in the fleet can be used or adapted, or whether new equipment is required, both for establishing the cover crop itself and when preparing the land and sowing the following crop.


The purpose and type of the cover crop being used will have an influence on the machinery needed, explains Agrovista technical manager Chris Martin, who has been running trials at the company’s Project Lamport site, in Northamptonshire, where the emphasis is on grass-weed control, as well at other sites across the country.


See also: Cover crops: How are they best used?


“At Lamport, we are establishing the cover crop in a seedbed aimed at encouraging grass-weeds to germinate, so we cultivate the top 5cm and carry out any deep restructuring work needed in autumn. Depending on the cover crop used, it may also perform some restructuring work of its own. A cultivator drill is a good choice to establish the cover crop, especially as it will produce the level stale seedbed which is needed by a no-till drill in spring,” says Mr Martin.


Destruction methods and timing also vary depending on the goal, and the carbon/nitrogen ratio of the cover crop, he adds.


“A lower carbon/nitrogen ratio means you can burn the cover crop off later to get the benefits of the nitrogen for the following crop, but a higher carbon ratio cover crop needs destroying earlier. Similarly, brassica mixtures need burning off early to ensure the soil is clean for the following crop.”


Three years into the seven-year trial at Lamport and January-February has proved to be preferable timing for burning-off cover compared to March.


“If it’s a dry spring you can get away with going later, but remember cold temperatures also affect the ability of glyphosate to work,” Mr Martin says.


He adds when using cover crops for grass-weed control, spraying off with glyphosate is the ideal method of destruction, but mechanical destruction to produce a mulch can be effective in other applications.



“Aim to cultivate the crop as early as possible to allow winds to dry out the residues – leaving it too late can produce a mushy layer which is tricky to drill into. It can also make it difficult to get into the seedbed to close the slots after drilling.”


The condition of the residue and weed pressure are factors in choosing a drill to establish the following crop.


“For grass-weed control we are looking to place the seed at a consistent depth and consolidate well, but with minimal soil disturbance,” says Mr Martin. “Disc drills are ideal for this but bear in mind the concept ‘less is more’ – the less you can do the better.”


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“Aim to cultivate the crop as early as possible to allow winds to dry out the residues – leaving it too late can produce a mushy layer which is tricky to drill into. It can also make it difficult to get into the seedbed to close the slots after drilling.”


The condition of the residue and weed pressure are factors in choosing a drill to establish the following crop.


“For grass-weed control we are looking to place the seed at a consistent depth and consolidate well, but with minimal soil disturbance,” says Mr Martin. “Disc drills are ideal for this but bear in mind the concept ‘less is more’ – the less you can do the better.”


See also: Machinery in Practice: CTF and cover crops working hand in hand


He adds if ‘all the boxes are ticked’, including cover crop destruction at the optimum timing, a straightforward no-till drill such as the Moore Uni Drill can work well.


“We also found the Great Plains drill useful, as the modular design means it can be used as a cultivator drill to established the cover crops in autumn and then with disc coulters added for spring crops.”


Spring 2016 was especially demanding, he says, due to the wet conditions which made it difficult for drills to close the slots after seeding.


“The Weaving GD drill with its angled coulters was effective in closing the slots, but did produce more soil disturbance.”


Drill developments

Drill developments


Great Plains has taken part in Agrovista’s Lamport trials as well as long-term trials in France, and general manager David Holmes agrees establishment approaches vary depending on the purpose of the cover crop.


“We have seen a dramatic increase interest in cover crops, and the range of applications means farmers need machinery which is versatile.


“When establishing cover crops in autumn, the aim is full width shallow disturbance, but when putting spring cereals into the over-wintered crop it is low disturbance, so in many cases two drills will be needed.”


However, Mr Holmes points out the Great Plains Centurion drill is fitted with full width cultivation modules, which can then be swapped for a low disturbance disc drill unit.


“It’s effectively two drills in one, which gives flexibility,” he says.


Working into residues is always a challenge for no-till drills, so the Great Plains Saxon low disturbance drill has been fitted with a ‘turbo coulter’ which works ahead of the double disc seeding unit.


“The turbo coulter creates a 5-30mm wide seeding zone for the discs to sow into, so it handles the residues while minimising disturbance. Great Plains has plenty of experience in retaining residues from its history of developing drill to counteract erosion, so the design is well-proven.”


See also: Video: Gaining experience with cover crops in the North


Vaderstad has also participated in a number of industry cover crop trials, and according to marketing manager Andy Gamble, opinions are polarised on the subject of machinery.


“Some farmers prefer to establish cover crops by broadcasting them on a cultivator such as our Carrier disc harrow using the BioDrill, while others have successfully drilled them with the Rapid drill.”


The Carrier is designed to chit grass-weeds and create the level seedbed needed for the cover crop, and can also be used ahead of the Rapid.


“We also offer the TopDown cultivator which has adjustable soil loosening legs if deeper work is needed, but would always advise digging soil pits to establish where the compaction is and loosen only the problem areas rather than the whole field.”


Establishing spring crops after a cover crop presents some challenges as the drill is working into stalks or dead material where the cover crop has been chosen to boost organic matter and root structure, he says.


“We fit our System Disc Aggressive toolbar at the front of the drill and the three rows of tines give sufficient clearance for the residues to pass through.”


Where the aim is low disturbance drilling the Rapid can be used as a direct drill, he adds, by removing the leading coulters and harrow.


“The issue with this is without closing the slots fully, the crop is vulnerable to slugs, and further restrictions on slug pellets would mean min-till is the better option.”


Case study

Case study

Squab Hall Farm, near Leamington Spa, Warwickshire, trialled cover crop plots for the first time in 2015/16.


Manager Robert Fox says: “We are on mainly medium/heavy soils with some very wet land, so I am interested in the ability of cover crops to improve soil structure and increase organic matter. There is also a certain amount of black-grass in some parts of the farm, so the possibilities for improved grass-weed control are also an attraction.”


With 350 hectares in-hand and a further 350ha in a joint machinery venture, spring barley has recently joined spring beans in the rotation, which also includes wheat, oilseed rape and linseed.


Spring crops are traditionally established by cultivating with a Sumo Trio in autumn and leaving the land to weather and green up before spraying off. Beans are usually put straight in with a Horsch Sprinter, while a pass with a power harrow or Vaderstad Carrier disc cultivator precedes drilling the barley.


Cover crops were direct drilled with the Horsch Sprinter on August 25, 2015, into chopped straw in the field destined for spring beans, while the field for the spring barley had been baled.


“I chose a few mixes from DSV for the first year with two trial fields of 3ha each split into three, ahead of spring barley and beans,” says Mr Fox. “It is still early days with the mixtures and there is little independent data on organic matter or nutrients provided by them, but I selected N Fixx, designed to fix nitrogen, Biomaxx DT, a high biomass mixture to increase organic matter and Rigol DT, an oil radish mix to break up compaction.”


He says establishment was good, although N Fixx was the weakest of the three, and no fertiliser was used.


“The mild winter meant the cover grew well, and as the fields were on slightly higher ground they did not suffer from flooding. By December Biomaxx was one-metre tall and the Rigol DT very thick.”


The cover was sprayed off at the end of February and had eight weeks to die back before drilling; soil pits dug by soil specialist Philip Wright as part of an AHDB monitor farm visit two weeks before drilling revealed good root structure from the high biomass mixtures.


“We noted away from the plots the rest of the field showed more friable soil where the Sumo had worked, although it was wet underneath. When it came to drilling, the Horsch Sprinter’s leg dragged through the cover crop plots and left an open slot; on the Sumo-cultivated land the drill could pull the friable soil into the slots,” says Mr Fox.


“The drill coped with the residues although drilling conditions were not ideal; the sunflowers in the Biomaxx tended to wrap round the legs.”


He adds the spring beans went into the moisture well and established strongly, despite the lateness of the season, although by late spring they looked better on the Sumo-cultivated land.


“However, the barley has really struggled – it went in at a shallower depth as the harrow could not pull it in as deep as would have been ideal. We have had to use slug pellets for the first time as slug pressure was much worse than usual.”


Mr Fox says the combine yield monitor will be the best indication of how successful the cover crop trials have been, although he accepts their effects are often more noticeable in subsequent years, and wheat after the spring barley should benefit.


“We will trial half fields this year to give a larger area, although we won’t roll them out across the farm yet. I also want to try a black oat/vetch mix for soil structure; the oats also offer reduced disease carry over.”


Another variation will be to create more of a tilth for ahead of cover crop establishment using the Carrier.


“I didn’t expect to see definitive results in year one and will look at the options over the next three to four years. One consideration is where black-grass is an issue, the loss of the opportunity to spray off in the autumn while it is under the cover crop may outweigh the benefits.”


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