Introducing cattle to grass when it’s nearly 1m high, allowing them to selectively graze and then trample in the remaining stalk, has helped one drought-prone farm boost grassland performance.
At St Paul’s Walden Bury Estate in Hertfordshire, herd manager Tom Chapman has been successfully mob grazing the herd of 125 suckler cows for nearly four years.
Using his experience as a Nuffield Scholar to draw on global grazing practices, he has been able to extend the grazing season by about two months and in doing so reduce feed and labour costs.
He believes getting cattle to graze off the best parts of the plant and then trample the remaining stalk into the ground is helping to improve soil organic matter and water holding capacity on the estate’s grassland.
“In the past, as soon as the farm dried up in June we struggled to get any grass re-growth,” explains Mr Chapman. “That meant we were forced to feed silage in September and house from October to April. We were building a lot of costs by having to feed cattle silage, rather than grazed grass.”
In 2010, the suckler herd were set stocked on the estate’s 121ha (300 acres) of grassland. “At the end of June there was hardly any grass and the soil was grey and lifeless – it was almost like concrete,” he says.
As a result, Mr Chapman began investigating different ways he could reintroduce soil organic matter. After reading about mob grazing in the US and South America, he decided to experiment on farm. In May 2010 he started by grazing 80 cows at a time on half an acre with stock moved twice a day. However, he quickly realised he was grazing too heavily and struggling to get regrowth.
In 2011 he began a Nuffield Scholarship looking at the concept of mob grazing and started addressing herd management. The herd of Simmental cross Holstein cows was gradually replaced with Sussex cattle that would be better forage converters, and they moved towards spring calving.
Grazing management has been tweaked and now cows are mob grazed from April on 97ha (240 acres) of the primarily low-input grassland.
The principle of mob grazing is to introduce cattle to pasture when grass has fully matured and pushed up a seed head. This allows a long recovery time between grazings. Cattle then selectively graze the seed heads and leaf tips.
Although overall grass silage quality is said to reduce if you cut when the plant has matured, Mr Chapman believes because cows are only selecting the best bits of the plant and not the stalk, they are eating the most nutritious elements.
The cows trample in the stalk, leaving a grass “mat”. This dries off, with the new grass growing through about three to four weeks later.
The primary aim is for the stalks to break down and provide organic matter to feed the soil. The “mat” also provides a protective layer, preventing the soil from drying out on a hot day and allowing friendly bacteria and worms to thrive. It also provides protection from cattle poaching, which means ground can handle high stocking densities.
Mr Chapman says the type of grass affects at what height cattle at East Hall Farm can be introduced to the swards, with leys made up of Cocksfoot or Timothy grazed at about 0.91m [3ft] high.
“In ryegrass fields, the grass tends to fall over so it’s probably about 0.6m [2ft] deep when cattle go in,” he says.
Currently, about 125 cows along with about 90-100 calves and four bulls are being grazed on about one and a half acres at a time. The fence is then moved and cattle introduced to a new break every 24 hours.
By adopting such a policy, the estate has been able to build up more grass cover moving into autumn and extend the grazing season.
“Since we started mob grazing in 2010 we’ve reduced the housing period. We used to have to feed silage outside from about September and house in October. Last year we didn’t feed silage or house until November.” And he hopes this year this will be extended until December.
“If cattle are harvesting their own grub, spreading their own dung and don’t need housing as early, it’s got to be cheaper,” says Mr Chapman.
The farm is currently just mob- grazing suckler cows and followers, but the intention is to extend it to all stock.
“I saw one farmer in Saskatchewan, Canada, who was grazing store cattle at about 1,000 head/acre, with cattle moving to a new break up to eight times a day. They were seeing good growth rates and fattening cattle over 24 months just by mob grazing.”
Mr Chapman is also looking at ways to incorporate the concept of mob grazing into the arable rotation. The hope is by using cattle to improve the estate’s 404ha (1,000 acres) of cropped land, they will be able to reduce fertiliser inputs.
Over the next five years, the farm will experiment by mob grazing cattle on mixed forages. Last spring 2ha (5 acres) was drilled with coxfoot, Timothy, red and white clover, lucerne, birdsfoot trefoil, sainfoin and chicory.
The initial mixture also included stubble turnips, sunflowers and maize. However, because of last year’s poor season, Mr Chapman wasn’t able to graze the ley until this year, which meant he was unable to make the most of these annual plants.
Cattle will be weighed on and off the field to calculate how much meat the area produces, along with gross margin. At the moment 12 heifers are being grazed on the mixture with the aim to get three grazings, starting in May, with a six-week break between each.
Mr Chapman explains how his Nuffield scholarship showed that the more diverse the plants in the mixture, the greater the benefits to soil fertility.
“There are a range of different plants that are either cool- or warm- season grasses, which means they photosynthesise differently. My findings showed you need to mix cool and warm grasses with broadleaf plants to bring maximum benefit to the soils.”
The experiment will have to show the gross margin of the cattle is comparable to a conventional break crop. But if the mix proves viable, the plan will be to include it in an eight to 10 year arable rotation – possibly two crops of wheat, followed by the mixed ley – which will be mob grazed and then two more crops of wheat.
“This will help put the organic matter back into the soil, which will increase its water holding capacity. This will mean there’s no check in grass growth rates due to lack of water or too much water and it will hopefully lower fertiliser costs.”