In an attempt to reverse the gradual decline in soil organic matter, one arable farmer looks to regain the benefits associated with livestock in a landscape largely dominated by arable production. Abby Kellett reports.
With a firm belief that soil organic matter is key in driving crop yields, one Cambridgeshire farmer has chosen to reintegrate livestock into his arable system, ending a 40-year spell without animals on the farm.
Thriplow Farm, south of Cambridge, consisted of a beef and dairy herd, as well as a sheep flock, in the 1970s. But like many farms in the area, a need to become more specialised in order to increase production meant all 900 hectares (2,223 acres) were put into arable production.
Having assessed the health of the soil across much of his acreage in recent years, arable farmer David Walston noticed fields which were most recently in grass were proving the most fertile and, as a result, were boasting the highest yields on average. He believes that is due to the higher organic matter content of fields which had historically been pasture.
Therefore, as well as taking several measures to try and elevate the organic matter levels of his soil, including a move towards no-till and use of cover crops, more recently he has established a three-year grass ley as part of an experiment involving ADHB and ADAS.
He says: “Perennial plants are the gold standard when it comes to increasing organic matter. Annual plants have to get everything done in one year, so they puts all its energy into above ground growth. Perennial plants are pretty much the opposite so they put a lot more energy into rooting.
“But it is not just about the physical roots being there. As plants grow they exude sugars and carbon out of the roots to feed the soil microbes, which all becomes organic matter.”
With little desire to own his own livestock, a neighbouring farmer paid to have Mr Walston look after his cattle for around six months of the year, from mid-autumn to mid-spring depending on the season.
Leys were split into several paddocks, or ‘cells’, using electric fencing and were rotated daily to make most efficient use of the land available and to encourage the stock to trample a proportion of the forage.
Trying to keep both land owner and tenant happy can be a challenge with this type of arrangement, says Mr Walston, since arable farmers are typically striving for crops with a large biomass to maximise organic matter build-up. However, these types of crops can be unpalatable and difficult to graze.
Therefore, to incentivise Mr Walston to sow a highly nutritious and energy dense ley, he was paid a premium if the cattle met previously agreed liveweight gains. High rents can also be a barrier to adopting this kind of system.
“You are not going to be doing this kind of system on a five-year FBT – I am lucky enough to own this land,” he says. “It costs around £150/ha for the seed alone. Some people around here pay £500/ha just to rent land.
“But if we could boost yields by 20 per cent, while also creating a more sustainable system, that could mean an extra 2t/ha of wheat, which equates to between £300-£400 extra income per year, depending on the season.”
The experimental field was returned back to arable production in the autumn of 2016, having been sprayed off with glyphosate and direct drilled with winter beans in early November.
Mr Walston says: “The beans established, but were fairly uneven. They were still germinating in the spring, several months after drilling. The yield was fairly poor, about 3.5t/ha, which was in line with our other beans that were not drilled after grass.”
This season, the field was sown with winter wheat in mid-October and has established well despite wet conditions at drilling. However, Mr Walston says it will take a few years before he notices significant improvements in crop performance.
“It is difficult to say whether there has been any improvement in the soil yet,” he adds. “The first soil organic matter tests showed an increase from 3 per cent to 4.5 per cent, which is encouraging, but I feel it will take four to five years to get a handle on any yield improvements, so it is still early days.”
The grass ley was direct drilled into stubble in early autumn, although Mr Walston says he may consider altering his establishment strategy in the future.
He says: “Next time, I may cultivate the ground and spread the seed on top and either roll it or disc it in lightly, rather than actually drill it.”
Rye-grass, cocksfoot, timothy, white clover, red clover, birdsfoot, sainfoin and chicory are just some of the species which made up the ley. He chose not to include fescue species as their waxy leaves can make them difficult to control in an arable situation.
By using a diverse range of plant species, Mr Walston was able to maximise rooting and ground cover and extend the grazing season length.
“The peak production of each species is different, so by using a wide variety of species, you are lengthening the time in which the ley is productive, so it can be grazed for longer,” he says.
Fence posts every 20 metres and three lengths of wire were used to stock proof the field boundaries, while electric fencing is used to create several ‘cells’ within the field. Stock were moved daily into a new cell to encourage new plant growth, but this was dependent on the sward length, size of the cell and number of stock.
To save on costs, Mr Walston created his own water troughs using tractor tyres and alkathene pipes, which remained on the soil surface so they could be easily connected and disconnected. Each water trough was shared between two cells.
The mixture of species and the cell grazing system meant the ley received little in the way of inputs.
“We used a lot of legumes and hence we use no fertiliser,” he says. “We could not use any herbicides even if we wanted to because we have such a range of plants within the sward and you would end up killing something. But because we were grazing every cell pretty hard and then leaving it to recover, we were not overgrazing any areas and so there is nowhere for the weeds to come in.
“Undergrazing is a problem with this system because firstly, it means you obviously don’t have enough animals and secondly it means there will be a lot of biomass left and not trampled in, which really hinders the regrowth.”