Soil Erosion: An Advisory Leaflet for Preventing Soil Erosion by Outdoor Pigs (PB5820c)

Soil Erosion: Preventing erosion by outdoor pigs

PB5820C
2001, rev. 2005

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This chapter shows how sows and growing pigs can cause soil erosion when reared outdoors. It provides information on how to avoid soil erosion and damage to the land, and how to reduce pollution by preventing soil, dung, and urine being washed into watercourses.

To prevent soil erosion from outdoor pigs:

  • Plan the overall system to avoid run off and erosion.
  • Select appropriate sites.
  • Plan paddock layout to suit site topography.
  • Site water troughs and feeding areas away from ditches and water courses.
  • Manage the paddocks to avoid poaching and minimise run off.
  • Manage farm tracks to avoid polluting watercourses.

Topography, soil type and rainfall

Site selection has a major impact on the risk of soil erosion. The factors that need to be considered are topography, rainfall, and soil type. The ideal site for outdoor pigs consists of flat or gently sloping, freely draining land in low rainfall areas. Pigs can be kept on sites which are less than ideal but these will require particularly careful management. Not all sites within the UK are suitable for outdoor pigs and a combination of sloping land, heavy soils and high rainfall will lead to damage to the soil and run off.

To reduce soil damage and pollution risks:

  • Select sites which have free draining soils.
  • Avoid high rainfall areas, ideally pigs should be sited in areas were rainfall is less than 800mm.
  • Always avoid steeply sloping fields.
  • Avoid moderately sloping fields in medium to high rainfall areas.
  • Where conditions are less than ideal provide green cover, rotate the stock or reduce stocking rate to protect the soil.

Paddock management

Ground cover, which would normally be grass, will improve the integrity of the soil surface and aid drainage through the soil profile, thus reducing soil erosion. Outdoor herds often utilise arable stubbles with little or no ground cover. In these circumstances great care is needed to minimise erosion, as there is no vegetation to hold together the soil surface and “catch” soil particles carried in run off.

To reduce soil damage and pollution risks:

  • Use grass or encourage natural regeneration where this can be efficiently incorporated into the rotation.
  • Allow as long a period as possible for ground cover establishment before pigs are moved on.
  • Manage stocking rates to prolong grass survival.

Nose ringing is used by some farmers to minimise paddock damage and promote grass survival. Although nose ringing can protect ground cover and has environmental advantages, there are serious welfare concerns over this practice, and it should be avoided wherever possible. Where it is necessary to nose ring pigs, it should only be carried out by a suitably trained and competent operator. All equipment should be cleaned and disinfected between pigs.

Stocking and rotation

Stocking rate has a major influence on soil damage, run off and thus erosion. High stocking rates, for example 25 or more sows per hectare, can lead to poaching and may reduce the longevity of vegetation cover in the paddocks. Higher stocking rates are less of a problem on free draining soils.

To reduce soil damage and pollution risks:

  • Select stocking rate appropriate to site conditions.
  • Avoid stocking at more than 25 sows per hectare.
  • Incorporate spare paddocks into the system to allow rest periods for paddocks on marginal sites.
  • Where paddocks show signs of damage reduce stocking rates or remove animals to fresh paddocks to limit damage.
  • Re-establish ground cover and good soil structure as soon as possible after pigs are moved off the land.

Conventional outdoor pigs are typically stocked on land which is dedicated to pigs for 1 to 2 years. Soil erosion can be reduced by using a ‘wave motion’ stocking policy where the outdoor pigs are more integrated into the farm rotation with paddocks being moved across the land every 3 to 4 months.]

Weaner rearing areas

Where weaners are reared in outdoor kennels, high numbers of animals can be concentrated in relatively small areas. This can result in high volumes of farm traffic to move and feed stock and resultant soil damage.

  • Locate weaner sites away from slopes and watercourses.
  • Relocate the site if it becomes heavily damaged.

Feeding, watering and wallows

Within paddocks the most heavily used areas are the feeding and watering points.

  • Spread feed over a wide area.
  • Vary the area on which feed is distributed.
  • Move any ad-lib feeders regularly to prevent soil damage.
  • Avoid excessive overflow from water troughs.
  • For sloping paddocks site water troughs and wallows at the top of the slope.

Trackways

Access tracks for feeding and movement of stock are vulnerable to soil damage and erosion.

To reduce soil damage and pollution risks:

  • Site tracks to maximise the use of hard road ways where available.
  • Plan layout of paddocks so access does not rely on a single trackway.
  • Minimise traffic when soil is very wet or waterlogged.
  • On sloping land try to make the trackway follow the contours.
  • Avoid routes which slope steeply.
  • Allow for wide trackways e.g. 10m to avoid repeatedly having to travel across the same ground when conditions are unsuitable.
  • If trackways become badly damaged relocate where feasible.
  • Divert run off from tracks into field margins or soak away areas where it can be intercepted and filtered.

Gateways

Gateways into individual paddocks are frequently crossed by farm traffic.

  • Site gateways where the land is least vulnerable to damage.
  • Position gateways at the top of a sloping paddock so any run off will be retained within the paddock.
  • Move gateways if the land becomes badly damaged.

Buffer zones

As a last resort it can be beneficial to create buffer strips – vegetated areas of land of perhaps 5 to 50 metres wide – at the bottom of sloping fields containing pig paddocks. The stabilising effect of the root systems reduces erosion and the vegetation cover intercepts soil particles carried in any run off. The buffer zones should be managed separately from the rest of the field, normally by fencing to exclude livestock. They should be as wide as necessary to be effective.


DEFRA PB5820C, 2001, revised 2005
(C) Crown Copyright. Reproduced for ADLib under Licence.

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