Collaborative project demonstrates benefits of outdoor pigs for land management

Thursday, 13 July 2023

The ‘Swaffham project’ began in 2016 with the aim of safeguarding the outdoor pig industry. This followed an increase in environmental incidents related to outdoor pig rearing and their potential impact on water sources, both above and below ground.

Pig producers, landlords and key stakeholders, including Norfolk Rivers Trust, Anglian Water, Catchment Sensitive Farming, the Environment Agency and Kings Crops, came together to look at how the relationship between pigs and the environment could be improved.

A series of workshops over the next few years focused on topics such as protecting water, preserving soil health, minimising nitrate pollution and preventing erosion. This culminated with a final event in June 2023.

As most outdoor pig herds are kept on rented arable land, collaboration between pig keepers and their landlords is crucial. A better understanding of site location and source protection zones, along with manure heap locations, were some of the early areas of focus. Herd managers were encouraged to become more adept at land management, and most outdoor pig producers can now include grassland management among their skills.

The focus then moved on to including pigs in arable rotations and the emerging environmental schemes. Along with national environmental scheme payments, project stakeholders funded specific activities to reduce run-off from fields, such as including buffer strips, sediment traps, and gateway relocation infrastructure.

As a result of this work, the pig producers and landlords involved are more aware of and in a position to implement best practices when planning which fields to occupy and for how long. This resulted in more proactive conversations between producers and landlords and an improvement in overall site management.

Grass trial

In 2019, we joined forces with Norfolk-based LSB Pigs, Norfolk Rivers Trust, Anglian Water, and Kings Crops as part of a trial to move LSB Pigs away from stubble paddocks and onto grass. Rob McGregor, Farm Manager at LSB Pigs, said:

“Anglian Water and the Norfolk Rivers Trust wanted to study what was going on in outdoor pig units in terms of rainfall, where the water was ending up and what it was taking with it into watercourses.”

The trial involved looking at how different grass mixes could improve soil management while withstanding the pressure of an outdoor commercial pig unit. Regular site visits were conducted for visual evaluation of soil structure (VESS) , worm counts and other general observations to assess progress.

Find out more about the trial and the different grass mixes

The two main grass mixes used were a traditional pig mix and a more legume-based mix, which were drilled post-harvest. Pigs moved onto the land the following spring. Establishment is important for the success of the grass sward and the introduction of new environmental schemes, and working more closely with landlords means it is now possible to establish a sward two years in advance.

Trial results

At the meeting in June, Rob provided a full picture of what the trial involved and shared the results with attendees.

Both mixes started well, but as the impact of the hot, dry summer in the second year took effect, it was the legume mix that suffered, with traditional weeds taking hold. The other grass mix did suffer in the heat but soon recovered after rainfall.

Read more about how the grass fared during summer heatwaves

LSB Pigs also introduced a new approach to paddock management. This involved resting a third of the occupied dry sow paddock for 6–9 weeks, enabling the sward to recover and providing us with an insight into the longevity of the different swards.

The grass mix was significantly more resilient to pig grazing than the legume mix. However, the legume mix produced a floral display in early spring, which was beneficial to pollinators. Rob is considering planting this mix around the unit perimeter of his paddocks or using it in the farrowing paddocks, which have a lower stocking rate.

Further wildlife benefits were also seen within the paddocks, with regular visitors including skylarks, linnets, shelducks, kites and kestrels.

Testing to assess soil nitrogen levels was conducted before and during the trial. This demonstrated a build-up of soil nitrogen under both mixes, although the visual impact of this varied depending on the mix over winter.

The grass mix helped store nitrogen in the soil and plant matter and is likely to have reduced leaching into water courses and aquifers over the winter. The weedy cover that developed with the legume mix produced more volatile soil nitrogen, with significant amounts being lost over winter.

The initial concern that the legume mix would fix even more nitrogen into the soil was not realised, as conditions did not enable the legume root nodules to develop sufficiently for this to happen.

On average, the increase in soil mineral nitrogen (SMN) was calculated to be worth 50 kg/ha, with an additional 30–40 kg/ha measured across the site as potentially available nitrogen. This is valuable for the following crop. We hope to do some follow-up work regarding the crops that are sown after pigs have been on the land to collect further data.

Another factor to consider is not leaving cultivated ground bare for too long, especially during the winter. If the land is worked too soon after pigs move on, nutrients could leach out, reducing the available soil nitrogen for the following crops. It is, therefore, advisable to cultivate the land in spring.

In addition, dung sampling showed higher levels of organic matter in the grass mix samples compared with those from bare paddocks. This supports observations around sow contentment, feeding behaviour and the reported use of less straw. An increase in potassium was also noted across both the mixes, compared with the bare paddock samples.

Worm counts were higher across both mixes, and the VESS also improved under the grass mix, as expected, since soil below 50 mm was not disturbed over the two-year period.

These findings highlight the improvements made above ground during the trial as well as those made below the surface, which has benefitted soil health.


During the second part of the meeting, we discussed future opportunities, as grants and environmental rotation mixes are becoming more readily available and accessible for outdoor producers.

We agreed that while this might be a closing meeting for the project, we will continue to work together and share the findings with the wider industry. The impact of the work is beginning to pay off, and we want to encourage more people within and outside of the region to consider and implement some of the learnings.

While not all outdoor units have the luxury of being able to establish a grass sward before moving onto the land, an increasing number of environmental schemes is making the inclusion of pigs in the rotation more attractive to landowners.

Hopefully, we will start to see more pigs being kept on grass as pig producers and landlords begin to work more closely together to benefit not only each other but the environment as well.

Find out more about this project

Read the Kings case study

Image of staff member Andrew Palmer

Andrew Palmer

Knowledge Exchange Relationship Manager (East) - Pork

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