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More than 70 farmers and agronomists took the opportunity of another washout day for fieldwork to explore highly topical aspects of seedbed management at the second Soil and Water Management Centre event at the Lincolnshire showground. Compaction, black-grass management and organic matter levels were all on the agenda.


Counting the cost of compaction
Soil compaction costs the UK around £400-500 million every year, cutting wheat yields by 10-15 per cent, increasing tillage energy, time and costs by up to 300 per cent and reducing soil infiltration to almost zero, significantly
increasing run-off and flooding.

This was the harsh, economic reality highlighted by Professor Dick Godwin (left) of Harper Adams University at the Soil & Water Management Centre Day from a 2011 Canfield report for Defra.

Estimating that arable farming is responsible for 70 per cent of these costs, he set out a number of things growers can do to save themselves and the country at large this major wastage by addressing the twin drivers of compaction vehicle loading and pressure.

"There are a number of things growers can do to reduce the main causes of compaction by better choice and use of tyres and tracks," he insisted. "They are not without their cost. But this is small compared to the economic benefits they can give.

"For instance, the £1/ha that using the latest Ultraflex tyre technology is calculated to add to the annual tractor bill  is well offset by fuel savings of around 20 per cent and reductions in working time, let alone soil damage. Equally the £3-4/ha cost of tracks on a combine over a 5-7 year life is offset by improvements in trafficability, harvest timing and harvesting efficiency.

"Studies show both low ground pressure systems and controlled traffic farming (CTF) can increase typical wheat yields by 1.3-1.7t/ha. And reducing the area of land exposed to traffic through CTF has particular extra benefits in improved soil structure and reduced operating costs."

While prevention is always better than cure, Professor Godwin also pointed out there are plenty of ways for growers to alleviate compaction. He stressed there is a real advantage to both winged sub-soiling tines and leading shallow tines, urging particular care with both equipment set-up and traffic on freshly loosened soil.

"Man has only a thin layer of soil between himself and starvation," he said, quoting an anonymous sage. "So if we have to tread on it at all, it's vital we tread lightly."

Soils holding excessive amounts of either water or air have a very poor load-bearing capacity.

Keeping soils in the best condition
Compaction may create problems but growers must be aware that soils that are too loose can also be highly problematic, warned Harper Adams soil scientist, Dr Nigel Hall.

"Apart from having less soil material for roots to exploit, soils holding excessive amounts of either water or air have a very poor load-bearing capacity," he explained. "This can lead to serious trafficking difficulties and rutting, not to mention sheet and gully erosion. So it's important to appreciate that looser is not always better."

Dr Hall advised everyone to use a spade to examine their ground as the basis for their cultivation decisions, stressing that if a soil looks OK to the eye it will generally have a good enough structure.
He also pointed out that soil density will invariably change over the season - from a low point after cultivation to a naturally more dense equilibrium level, depending on soil type and levels of organic matter, among other factors.

"For the greatest resilience our ideal should be to maintain the best possible structural balance over the long-term as well as throughout the season," he recommended.
 
"We need to encourage biopores from worms and old root runs to ensure good drainage and provide channels for new root growth. Equally we need to avoid disconnected voids that trap water or air and give no access to roots, and voids or
cracks that just run roughly parallel to the soil surface. These sorts of structures tend to be produced by working the soil too wet or compaction.

"Tightening rotations and the atrocious sort of weather we've seen this autumn add significant risk to modern cropping systems," insisted Dr Hall. "We're increasingly finding that soils which are just about able to handle reasonable conditions simply can't cope when the 'going gets tough'. This underlines the work that must be done to improve soil structure in many cases, as well as the need for research and extension to quantify more 'critical thresholds' for soil condition as an aid to farm decision-making."

In Agrii latest trials with Lemken, ploughing stood out as the best way of reducing black-grass in a single season, giving nearly 100 per cent control in 2010/11 wheat through effective seed burial, said David Langton.


Focus on black-grass management for black-grass control
Appropriate soil management can play a major part in controlling your black-grass before it controls you, growers and agronomists were advised.

Agrii technical manager, David Langton (left) warned that a strictly limited chemical arsenal, growing weed resistance and increasing climatic uncertainty make it vital to manage soils and tillage as effectively as possible to minimise the pressure on in-crop herbicides.

Armed with latest results from the company's long-term system trials on fields with serious multiple herbicide resistance near Huntingdon, he highlighted cultivation flexibility, multiple stale seedbeds and delayed drilling as particular opportunities for tackling problem fields.

"We've conducted carefully controlled trials on the same challenging heavy land fields at Stow Longa for more than 10 years now," he explained. "Not surprisingly with a marsh weed like black-grass, these have shown that rectifying drainage issues and cultivating to facilitate water infiltration are key areas for improvement.

"In our latest trials with Lemken, ploughing stood out as the best way of reducing black-grass in a single season, giving us nearly 100 per cent control in our 2010/11 wheat through effective seed burial. Indeed, with 100 black-grass ears/m2 taking almost exactly 1t/ha off wheat yields, we recorded a net benefit of £100/ha over our shallow min-till regimes after accounting for the extra £45/ha cost.

"It's important to stress, though, that ploughing needs to consistently bury the seed below three inches in the profile. And ploughing two years in a row can lead to greater problems by bringing up non-dormant black-grass seed buried the previous year.  Ploughing after direct drilling wheat the year before, for instance, resulted in an average of just six black-grass plants/m2  in our OSR compared with 123 plants/m2 from ploughing after ploughing."

Where rotational ploughing is not a viable option, extensive studies at Agrii farm trial sites with particular grass weed problems show some reduced tillage regimes can be almost as effective in controlling black-grass, while generating higher margins over establishment and chemical costs; providing they are accompanied by effective stale seedbeds.

"If we are to rise to a black-grass challenge which is just as great for many today as it was before the advent of Atlantis, we really need to know our weed," David Langton concluded. "As well as its resistance status, we should identify where it is both in the field and in the soil profile. That way we can utilise the tillage and other soil management tools at our disposal in the most cost-effective, integrated control approaches."


Ploughing two years in a row can lead to greater problems by bringing up non-dormant black-grass seed buried the previous year.


Organic matter management to improve seedbeds
Morley Farms manager, David Jones set out a clear 'ideal field' specification for delegates, before explaining ways he is trying to increase the resilience of his 750ha (1,850 acres) at Wymondham with extra organic matter to move towards
this.

The ideal field:

  • Good water infiltration
  • Good water holding capacity
  • Good holding and cycling capacity of nutrients
  • Lack of slumping and erosion risk
  • Good support for machinery
  • Reliable seed germination environment
  • Less effort required to cultivate
  • Less wear on machinery

"Our soil type may be fixed, but there's a lot we can do to change the 50 per cent or so of its bulk that's water, air and organic matter," he pointed out. "Although a long-term field trial at Morley has shown 25 years of incorporating straw may only increase the organic matter content by 0.2 per cent, it has demonstrated this can bring about a highly encouraging 35 per cent increase in microbial activity and a 10 per cent reduction in penetration resistance.

"We're routinely spreading turkey muck ahead of oilseed rape these days. Quite apart from its other benefits, at £8/ha it's well-priced NPK. At the same time, we've got straw for muck arrangements with local cattle and pig farmers which add value to our crop residues."

Following positive trials showing yield increases and soil structural improvements from cover crops, especially with shallow cultivations, David Jones is also experimenting with mustard and vetch and autumn peas and volunteer barley sprayed off and incorporated ahead of sugar beet.
 
"I strongly believe we need to be looking at halting the decline in our soil's heart by adding organic matter wherever we can in the rotation," he said.

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