Ed Bramham-Jones, operations director at Norfolk Rivers Trust, says having livestock in an arable rotation definitely benefits cropping and soil health. They return organic matter and plenty of nutrients to the ground, but experience shows that the light, free-draining land typically used for outdoor pigs, has limited water and nutrient holding capacity which can cause problems.

"Pigs do bring plenty of organic nitrogen back to the soil, but retaining those valuable nutrients can be challenging when herds move straight onto stubble or are managed on bare earth. This project was initially set up to try and control some of the environmentally damaging aspects associated with excessive run-off, during the winter and following episodes of high rainfall, which many outdoor pig units and land owners were struggling to manage in this area the soil loss on some units could be quite considerable. But we've all learned so much more from growing grass, with benefits that extend beyond water protection and reducing run off," he explains.

Rob McGregor says the having grass cover has altered drainage patterns and the unit does not experience as much waterlogging it used to during the winter months, which makes it easier for staff to navigate when feeding and moving stock. The run-off during torrential storms - which seems to be occurring more frequently - is now also more controlled, there fewer water gullies and ruts and the site's low-lying areas, no longer flood excessively.

Having a thriving sward with an active root system improves the moisture and nutrient holding capacity of the free-draining land and the growing grass will also lock in and utilise the nutrients (mainly nitrates, phosphorus, potassium and trace minerals) deposited in pig manure, which helps reduce the risk of leaching. And, when the pigs move off and the land is cultivated those valuable 'locked in' organic nutrients are released and are readily taken up by the next crop.

Protective benefits
Fiona Wood, catchment scientist with Anglian Water, has been monitoring soil structure and nutrient concentrations on LSB's Coxford site across all seasons for a number of years. So far, data collected from the pig mix comparison trial indicates that maintaining cover in pig paddocks protects soil structure and how, when the conditions are extreme as they were during last summer's drought, an established root system can 'survive' below the surface and help preserve soil health and nutrient levels.

"We have some more data to collect before this trial is complete and hope to have some conclusive results this Spring, but anecdotally, looking at what's been happening with the pig-specific ley and the flip-grazing routine, we can see it's influencing soil structure and ecology. The soil looks well, with plenty of worm activity and a robust root system keeping it all together. Our observations certainly suggest that rest and re-establishment during pig production does helps to maintain green cover and promote deeper root development, which is important as it will lessen nutrient loss and help protect ground water quality," she explains.

These are critical issues for catchment sensitive areas, particularly those that rely on aquifers for fresh water supplies. A significant number of Anglian Water's boreholes are located on light land in pig producing areas and the company is keen to encourage more farmers to explore how green cover crops and sward management can protect soil and water quality and benefit outdoor pig production. Financial support and grant funding is available to farm businesses via water companies and associated agencies to sponsor trails, training, equipment, technical innovation/development projects aimed at improving water management and soil/protection. Such partnerships are worth consideration as the pressure to reduce costs and become more environmentally responsible will denote a new mindset for primary food producers.

UK agriculture must strive to minimise impacts at every stage and mixed farming systems do offer opportunities to optimise resources. Working collaboratively, with other sectors and industry stakeholders, should enable the pig sector to reach carbon neutral, or certainly come close.

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Useful links: https://norfolkriverstrust.org/project/green-cover-outdoor_pigs/ https://www.anglianwater.co.uk/business/help-and-advice/working-with-farmers/ https://www.kingscrops.co.uk/services