Arable News

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Soils – a back to basics approach?

Spring cultivations and planting programmes are well underway, but many growers are still waiting for saturated land to dry out before they can proceed with more work

Spring cultivations and planting programmes are well underway, but many growers are still waiting for saturated land to dry out before they can proceed with more work. With the subject of soils fresh in most people’s minds, now may be a good time to go back to basics where drainage, compaction and cultivations are concerned. Dominic Kilburn writes.Growers have been urged to wait for soils to dry out prior to spring cultivations and drilling so that they will be structurally stronger and more able to withstand vehicle weights.Bigger kit, more extreme weather and the forgotten art of drainage – a combination that has crept up on us over the past 20 or 30 years, and one which has caused considerable havoc across the land in recent months.While there is little we can do in terms of changing the weather, and big kit is here to stay to help deliver the economies of scale required, have you really thought about the drainage status of your land recently?That’s the question posed by ADAS senior researcher and soil scientist, Dr Martyn Silgram (left), who says that drainage has dropped off the radar following the removal of grant funding in the ’80s, and regular drainage implementation and maintenance has been lost to a generation of farmers. “It’s only when you have extremes in weather like in 2012 that these things start to become a focus again,” he comments. “But with more extremes likely in the future, farmers need their soils to be more resilient,” he adds.Martyn says that he understands the urgency felt by growers at the moment who are keen to get on the land in the time left available to them this spring, but enthusiasm to get on should be curbed with an element of pragmatism.
“Having a lot of horsepower in the shed can create the illusion of versatility,” he points out. “It means that growers can probably force the issue and get on and work the land when soil conditions are not yet suitable, but if soils are too wet then cultivations risk smearing soils at depth creating ‘plough pans’ and subsoiling will not create the fracturing required while subsoils are still plastic. “It’s not always possible, but if you can wait a while for soils to dry out a little, then they will be structurally stronger and more able to withstand vehicle weights, while subsoiling will create the fissures we want to open up subsoil structure.”He accepts that farmers will be only too aware that poor drainage affects crop yields, as was seen in abundance last season, causing either water-logging on the surface or high perched water tables in the subsoil, but he is adamant that drainage should be back on every grower’s agenda.
“It really could be a case of going back to basics with this; find those old farm drainage maps and get out there and walk the ditches where the outfalls are. If they’re not running after heavy rainfall then there must be a problem. Cultivating at the wrong time can cause smearing which can create cultivation ‘pans’ at depth and hinder both crop root development and subsurface drainage.”It could mean installing a new drain or simply cleaning out an existing one, maintaining or repairing it,” he adds.
Martyn also suggests that simple investigations with a spade or a penetrometer in water-logged areas of fields will reveal where the impermeable layer is and the best management solution required to deal with it. Spring soil advice at a glance:

  • Review old farm drainage maps
  • Carry out basic outflow, drain and ditch maintenance
  • Sample soil profile for signs of impermeable layer where water-logging occurs
  • Don’t start cultivating until the soil is sufficiently dry
  • Use shallower cultivations where possible
  • Remember; the first pass causes the most compaction, so timing is critical
  • Use low ground pressure tyres or tracks where possible
  • Any Farmers Guide readers requiring more information on this subject can contact ADAS’ Dr Martyn Silgram by email: [email protected].

 Vehicle compaction
In terms of compaction, Martyn notes that research has shown that 75 per cent or more of vehicle compaction is typically caused by the first vehicle pass in the field – with subsequent passes adding little additional compaction to the same wheelings. “The message to growers is that compaction is more about where you travel and when, rather than about how many times. Wet soils won’t support modern heavy machinery without causing damage, and so the time you decide to go on the land is crucial,” he stresses.In addition, he says it is vital to choose the right vehicle tyre pressure as over-inflation can cause very high levels of compaction.
He points out that correctly inflated low ground pressure tyres such as Michelin’s Xeobib are a practical option. ADAS has trialed low ground pressure (LGP) tyres for spraying operations in research funded by Defra, LINK and Scottish Government. Such tyres are specifically designed to run at low pressures – often 50 per cent of the pressure of standard tyres for the same axle weight.Specifically manufactured with stronger sidewalls, they create a more rectangular, shallower imprint in the soil. This compares with standard tyres which create a deeper concave wheel imprint which can channel run-off and promote erosion, he explains.
“Where possible, low ground pressure tyre technology is a cost-effective option to protect soils as, although they may cost slightly more than conventional tyres, they typically have improved fuel efficiency and a longer tyre life, while retaining trafficability,” adds Martyn.
For those waiting to get on the land this spring he reminds growers to carefully consider the state of their soils before beginning field operations. “Cultivating at the wrong time can cause smearing which can create cultivation ‘pans’ at depth and can hinder both crop root development and subsurface drainage.” He also suggests that growers use the lightest vehicles possible, in addition to correctly inflated low ground pressure tyres, or tracks, and, rather than travelling randomly on fields, stick to the same wheelings where possible.
“It’s been exceptionally difficult for farmers recently, but the weather conditions in 2012 have raised awareness of the need for more careful cultivations, rather than too many cultivations. “We must build resilience into the farming operation. Three out of the last ten years have been unusual in terms of weather conditions and we have to adapt to it. We can’t ignore the problem as it’s not going away.”Make a difference to your drainage now
The director of Warwickshire-based drainage specialist Farm Services, says that soils have been so wet in recent months that it has been very difficult for contractors to get on the land to lay new drains. Robert Burtonshaw (left) comments that, like cultivations, the temptation is to get on the land as soon as possible but, if the soil conditions are not suitable, laying new drains could lead to further soil damage.”Even when it’s been as wet as it has, there’s no reason to have water standing on fields,” points out Robert, who has been involved in the Harper Adams-based Soil & Water Management Centre initiative (see Farmers Guide February edition). “The trouble is that many existing drainage infrastructures have been left to rack and ruin over the years and they simply haven’t even been checked.”Farmers really could make a difference right now by studying drainage plans and start digging to find any problems.”All drain outlets should also be checked to see if they are flowing,” he adds. “Often it’s just simple maintenance that is required – unblocking ditches for example – and it could just mean an afternoon’s work.”Robert, who is also a Nuffield Scholar, suggests that while land is starting to dry out in many parts of the country, there will be some areas left uncultivated this spring, remaining fallow until the autumn. “It will be a tough decision for growers to leave land fallow, but it does offer them a window of opportunity to get land drains laid where otherwise a crop would be planted.”Drainage is all about improving yields and, while it’s perceived as an upfront expense, it should be viewed as a long-term investment over 20-30 years and more, and, when you work out its cost over that period, then its value is clear.”Tyre pressure adjustment on the move
The problems of soil compaction, reduction in water and air within the soil structure and its effect on yield, drainage and other associated issues is, in its simplest form the weight of ever larger agricultural vehicles and regular field activity, often during wet periods, overcoming the soil’s natural strength and ability to withstand it, says East Yorkshire-based South Cave Tractors.The Central Tyre Inflation System can offer growers a dramatic reduction in compaction damage in the field.The Central Tyre Inflation System (CTIS) developed by Mercedes Benz 20 years ago for Unimog tractors is an electro-pneumatic system to inflate or deflate tyres while driving – the pressures at the front and rear axles can be controlled individually by axle, or together, via a console-based switch.
According to South Cave Tractors, tyre pressure is shown in a display while a security system limits maximum and minimum pressures of the tyres fitted.
The company says that due to rapid changes of internal tyre pressure, the system can offer growers a dramatic reduction in compaction damage when in the field, as well as running tyres at the correct pressure when back on the road – and all achieved while on the move. With no need to stop the vehicle and get out, and with easy regulation and control of tyre pressure from the cabin, operators’ time is saved and the system will maximise traction while also minimising rolling resistance – reducing the power required to drive the vehicle.

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