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Soils: poaching

Course: Soil Management | Last Updates: 7th January 2016

 
Mark Tripney
Biography >>
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What is poaching?

Poaching is the damage caused to turf or sward by the feet of livestock. Hooves cause compaction of the soil surface, leaving depressions which can be 10cm to 12cm deep. This can form an almost continuous layer of grey anaerobic soil, where natural activity, carried out by soil micro-organisms, is low.

Poaching lowers sward productivity, with knock-on consequences for meat or milk yield. It also has welfare issues, causing lameness, while mastitis and somatic cell counts can rise when dairy cows are up to their udders in mud. Severe cases of poaching may lead to an increased risk of run-off as water is unable to permeate soil, and can give farming a poor image.

How is it caused?

Typically the cause is not enough grass in front of animals. It may be the field or paddock is too small, or Cows on poached landinsufficient fresh grazing is available when strip grazing.

Highly-stocked fields in wet conditions or cattle having access to wet areas, particularly around inappropriately-placed or overflowing water troughs, will cause poaching. Feeding rings left in the same position also cause problems.

Frequent movement of livestock along the same routes, such as cows to milking parlour, also puts pressure on fields closest to farm buildings.

Poorly-drained soils, badly-maintained ditches and blocked drains create a sward prone to poaching. Grazing new leys too early in the season or when excessively wet should be avoided.

Surface compaction, caused by cattle or machines, can lead to poaching of the top surface while the substrata remain dry. Water becomes trapped as it cannot drain away quickly because it cannot permeate soil.

What soil types and situations are vulnerable?

Heavier clay soils are more prone to poaching. However, lighter soils, such as sandy loams with a clay subsoil, can act like a heavy soil because water is trapped by the relatively impermeable layer, leading to perched water.

Where this is the case, soil will become waterlogged in wet weather quicker, with the critical factor being depth of topsoil before the clay is hit.

Damage from poaching is dependent on rainfall and ideal grazing conditions can quickly turn into a quagmire. Soils supporting dairy enterprises suffer from frequent movement to parlour. Poor management of strip grazing on winter forage crops can also lead to poaching.

What are the signs?

Increased waterlogging and water standing in pockets, such as hoof imprints are classic signs. Dirty undersides of animals indicate conditions could be deteriorating. Poor grass growth or increased weed growth are signs of past damage and anaerobic soil tends to smell.

What can I do to reduce poaching?

Poaching in grass

Plan and manage grazing to suit grass cover. Vary this through the season when conditions and cover dictate and watch for sensitive fields or field areas. Look at longer-term grass leys for grazing so root structure can develop and provide support for grazing animals.

Maintaining correct pH and nutrient status of soils promotes good root development and grass growth, which in turn helps maintenance of soil structure.

When reseeding don't overwork the seedbed and subsoiling will help to break pans and improve rooting. Shallow moling may be appropriate in permanent pasture.

Keep an eye out for compacted areas – use a spade to investigate suspect patches. When grazing pans in the top 50-100mm are apparent use aeration to help eliminate them and prevent perched water.

Keep traffic damage down by ensuring good tracks to fields, and use potential for multiple access routes where possible.

Why Has Tom Rawson's system worked?

Tom has introduced a good system of tracks, which he rearranges if he thinks they are not quite right. He has multiple access points from most of the tracks, which he uses to help manage the grazing.

He also manages the grass coverage of the farm well. He knows how much grass he has in front of him and how much he may have to balance with silage. He monitors compaction levels closely and aerates where necessary.

The longer term eight-year grazing leys, sown at optimum times, also contribute to a system that can sustain an impressive level of productivity.

Case study

Tom Rawson – Dewsbury, West Yorkshire

Tom Rawson with a cow

Every blade of grass on Tom Rawson's Yorkshire dairy farm is geared towards maximum production. An organic unit of 178ha, its 260 dairy cows are kept on grass for 10 months of the year.

"Through paddock-grazing we're harvesting 50t/ha of fresh grass, which is no mean feat for an organic farm," notes Mr Rawson. "Cows are scalping the sward, eating pure leaf with no stalk of at least 11.5 ME, 27% protein. It means we're getting extra milk and fields are so finely grazed you could see a golf ball in them."

As well as extended grazing, Mr Rawson, who farms the unit with his wife Catherine and his parents, has introduced a few simple but ingenious ways to keep the turf in tip-top condition.

The farm converted to organic in 2001. "In the first year cows were sinking up to their udders in mud. We had problems with cell counts and mastitis," he recalls. So he developed a system that maximised grazing, but minimised travelling on the grass.

Some 3000ft of concrete sleepers now form a hardstanding which fast-tracks the herd to and from the dairy. The electric fencing on either side is used to steer cows to the choicest sward. And once there, a close eye is kept on the weather, with the herd pulled back on to hardstanding when wet conditions start to blacken the green turf.

"They spend just 12 hours in each paddock, but cows can get everything they need from four hours' grazing," explains Mr Rawson.

Track

Surface compaction is reduced with a soil aerator – steel blades set on a solid steel shaft that is pulled over the field like a roller in autumn and spring. "When you dig down, you find the top couple of inches can be wet, but underneath it's dry. The aerator gets water down to the roots where it's needed." It also improves air spaces within the soil, aiding drainage and aerobic activity.

The benefits are now stacking up from the improved sward productivity and silage use has been cut by up to 2.5t a day. Less concentrates, which start at a pricey £300/t, are consumed, but milk yield consequently has gone up. All-in-all Mr Rawson has deduced the extended grazing system put £8000 straight on the bottom line for February alone.

"There are health and welfare benefits, too. Cell counts are down and we have much less digital dermatitis – our vet bill for August was just £23." And the surprise benefit has been time – the tracks speed the cows to and from the dairy, adding vital minutes of available grazing time to each day.

Golden Rules

  • Lay tracks and make them as straight as possible – cows just can't do corners. The benefit of using concrete sleepers is that you can move them.
  • Conditions have to be perfect to get the best from a soil aerator – the soil shouldn't be too wet or dry.
  • Regularly measure grass with a plate meter – you've got to keep dry matter intake up.
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