Ploughing and subsoiling in one pass
While ploughing inverts and refreshes the top layer of soil, the use of heavy tractors and ploughshares that smear can cause problems at greater depths. Andy Collings takes a look at plough pan busting – while ploughing.
You may not be able to see it, but the presence of an impermeable plough pan can be responsible for numerous yield sapping problems. Poor drainage, inadequate root development and increased susceptibility to drought are just three of them.
Although ploughing may not be every grower’s first choice for a crop establishment system, there are more than a few who rely on the plough to cultivate at least a percentage of the farm’s arable area each year.
For Louth, Lincolnshire-based Paul Bennett, the plough remains an essential implement, although the acreage it now covers has reduced significantly in recent years as cost-cutting controls were implemented. “We farm about 800 acres, of which 700 acres are down to arable cropping,” he says. “The crops comprise winter wheat, oilseed rape, winter barley and spring beans.”
With a soil type which is predominantly heavy clay land, there is an annual battle to control black-grass. Mr Bennett says he is keen to plough as much as he can – particularly for the ground destined for barley and beans.
“This means we now plough about a quarter of the farm each year,” he says. “Which I hope will help keep the black-grass under control.”
He adds, however, that with the ruts his combine harvester made this year, he may have to rethink how he is going to handle his min-till operation.
Mr Bennett is no stranger to the effects of compaction and plough pans and, like many other growers on similar land, he recognises the benefits of subsoiling.
“It’s essential to keep this sort of ground open and prevent it becoming sealed,” he says. “In a wet time, the water has no chance of making it into the drains and, during a dry time, the roots cannot penetrate deep enough to find water.”
However, subsoiling is not a cheap operation and it was clear that greater economy could be achieved by combining the operation with plough.
Fitted to his Gregoire Besson five-furrow plough are subsoiler tines, which are attached to the base of the second and fourth furrow. These work the soil down to a depth of about 35cm (14in) which, while not being quite so deep as a purpose-built subsoiler, breaks into the plough pan and causes some shattering of the soil below ploughing depth.
“Like subsoiling, it works best when the ground is dry and an element of shatter and lift can be achieved,” says Mr Bennett. “But on the other hand, if the ground is being ploughed, you might as well run with the subsoilers – it is only one pass.”
On the subject of power and fuel consumption, he says the two tines take as much pulling as an extra furrow.
“There have been times when our 200hp MF6499 has struggled to cope and we have been forced to take the tines off – which is quicker than dropping a furrow, but not perhaps the right thing to do. On areas where the subsoiling tines were removed, it is possible to see the crops looking decidedly worse than in areas which have received the full treatment.
“It seems to be most obvious in times of drought,” he says. “The plant roots seem to really struggle to find the level where they can find adequate moisture.”
Mr Bennett reckons on replacing the tines every 80 hectares (200 acres), although this is dependent on soil type and conditions. The tines are shearbolt protected from snagging on large boulders or tree roots although, on occasions, the main beam shearbolt has broken rather than the tine shear bolt.
“It’s essential that they are protected, if only to stop the beams being over stressed,” he says. “But I have no worries about running the plough with the subsoiler tines.”
In terms of cost, the tines and their assembly unit costs about £350/pair – the replacement tines cost about half of this initial outlay. Other costs which need to be considered include the extra fuel used and the reduction in output.
And on matters of fuel consumption, Mr Bennett concedes he has not undertaken any specific fuel consumption tests but says he does not believe it is excessive and, on output, he maintains that there is very little difference, whether the subsoiler tines are fitted or not.
“The important point is that we are ploughing and subsoiling in one pass, which must be more economic than doing it as two separate operations,” he says.