How did grass cover mixes fare during summer heatwaves?

The trial stemmed from collaboration between East Anglian pig producers, their landlords and organisations including Norfolk Rivers Trust, Anglian Water, Catchment Sensitive Farming (CSF), the Environment Agency and Kings Crops, which were established through a series of AHDB meetings.

Rob McGregor, unit manager at LSB Pigs, Norfolk, where the trials are taking place, looks after two outdoor units producing weaners for BQP. On the first site, eight hectares was planted with a standard pig seed mix, which is hardy and grows back well, and a further eight hectares with a fallow mix, including rye, vetch and other pollen and nectar-producing species.

The second site has a total of 20 hectares, with 10 hectares of the standard pig mix and 10 hectares of herbal mixes, which include non-legume species, such as chicory and plantain.

Trial mixes

Tough pig mix: Strong creeping red fescue, intermediate perennial ryegrass, late perennial ryegrass, late perennial ryegrass (35 kg per ha)

Fallow/pollen and nectar mix: Italian ryegrass, vetch, birdsfoot trefoil, red clover (20 kg per ha)

Pig herbal mix: Tall leaved fescue, festulolium, perennial chicory, plantain, agricultural burnet, yarrow (28 kg per ha)

Aim of trial

The aim of the trial, which is ongoing, is to investigate which mixes are good to establish on light soil and to see how they perform in the following key areas:

• Establishment and longevity/persistence
• Ability to cope with pigs (grazing and potential poaching)
• Pig productivity and economics
• Soil structure
• Soil nutrient retention – minimising phosphate and nitrate losses through surface run-off and leaching to groundwater

Below, Andrew Palmer, Knowledge Exchange Relationship Manager and project lead, provides an update on the trial and how the grass is holding up during prolongeddry periods.

Impact of drought and heatwaves

In spring, the cover crops looked tremendous and there were signs that the mixes had great potential for the summer months. Roll on a few months and we’ve experienced prolonged dry periods that have resulted in the cereal harvest starting earlier than normal and a changing picture with the cover crops as well.

The fallow mix, that contains the likes of clover and vetch, are starting to struggle, and the common arable weeds of fat hen and mayweed are returning to the paddocks. For those of us who have worked outdoors, these are common weeds that often appear during a pig rotation. However, in this case they’re returning because of the clover and vetch starting to struggle in the dry conditions.

The traditional grass mix seems to be coping relatively well with the drought but, as with all grass, it is showing signs of stress. However, even with the mixes showing signs of needing rain, there is sward cover that is helping to prevent the traditional dust clouds that we often see on outdoor units at this time of year.

The biodiversity seen across the mixes has been encouraging, with sightings of red kites and kestrels. This suggests that there is a population of small mammals within the mixes supporting these predators. Moths and bees were also seen in abundance during the early part of the season, but as the dry weather impacts the green cover, number seem to be dropping.

Sow behaviour

During the early part of the project, it was reported that sows across the different mixes seemed exceptionally content, spending much of the day grazing. Rather than dominant sows commanding first dibs at the morning feed, there seemed to be less jostling and sows seemed much calmer. This suggests that they are more content, possibly due to increased gut fill from grazing the grass mix.

As sward mixes have deteriorated during recent weeks, there seems to have been a slight regression to old behaviour patterns, highlighting the impact the grass was having on sow contentment.

Next steps and drone imagery

So where does that leave us with regards to which is the best cover mix? It’s difficult to say. At this stage, the dry weather has had a more noticeable negative impact on the greener fallow mix than the grass mix. But do we take this summer as an exception or the start of a new normal?

What we’ll need to consider is when the rain does come, how quickly the paddocks recover in readiness for the winter. After all, our lawns seem to come back from the brink every year, but will the paddocks with grazing pigs on them do the same?

Rob’s management practice of flipping and resting a third of the paddocks with each batch has supported the recovery of swards to an extent, even through the prolonged dry weather. As a result we know that ground cover can return and this will only be bolstered by rain. It will be interesting to watch how the mixes perform over the next few months.

The trial still has a year to run, which gives us plenty of time to collect more data and we will be using drone imagery to get a bird’s eye view of the paddocks. This will help us get a better feel for how the mixes are recovering as we move into autumn and winter.

Added benefits to soil composition?

In addition to determining the establishment and durability of the different sward mixes, we have also been looking at the impact the mixes have on dung composition. In April 2021 we sampled dung from each of the trial paddocks, recording the N, P and K levels, as well as the dry matter and organic matter content. We will be repeating the sampling over the next few weeks to see whether the results are similar and, if so, what this could mean for fertiliser application and future cropping.

If the results indicate that there is a noticeable difference between the composition of the dung sampled across the three mixes, a more in depth, scientific study may be proposed as this could have an impact on fertiliser requirements for crops that follow outdoor pigs.

Look out for more information about this project or get in touch with Andrew Palmer for more details.