He’s seen great success with overwintering cattle on Scottish units and, more recently, new varieties that have softer and more digestible stems have further improved the feed value and utilisation of the crop.
“Poor stem quality has limited the feed value of forage kales in the past and could have accounted for between 60% and 70% of total crop yield,” says Mr Heaphy. “But new varieties have been bred for improved stem digestibility that supports better feed value.”
He adds that, in the past, farmers could face a bit of a dilemma. “A well-grazed kale crop shows good utilisation, but liveweight gain could be limited as the feed value in this stem is poor. But if a proportion of the stem is left, liveweight gains are better but crop utilisation is poor.”
Marrow stem kales, like Limagrain UK’s Bombardier, which are highly digestible and have improved dry matter yields and utilisation potential, can overcome this dilemma. “Farmers like to see fields grazed clean and cattle perform well,” says John. “Many farmers are delighted with these new kale varieties.”
Bombardier was introduced in 2018. In trials it showed a digestibility of 72% and a relative dry matter of 18% above the control – worth an extra 1.74 tonnes per hectare.
He explains that kale is best drilled in May or early June at a seed rate of 5kg per hectare. Farmers are encouraged to opt for varieties that are club-root tolerant and where a seed treatment can be applied. A fine-seed bed is also important, to help the crop germinate, establish and achieve good ground cover as quickly as possible.
“The sooner the crop gets to the ‘rough-leaf’ stage, the less prone it is to pest damage, predominantly from flea beetle and pigeons,” he says.
He adds that kale is proving popular because it helps to reduce the costs of production on Scottish beef units, as well as offering a break crop on units that may also grow cereals in their rotation. “But the big attraction is its high yields. Average dry matter yields for kale are twice that of stubble turnip crops and it’s also ready for grazing from late October.”
One Fife-based suckler beef producer has been growing kale, on and off, for the past 20 years and has consistently grown the crop on his unit since 2011. Bob Howat overwinters half of his 150 Saler cross cows on kale, at his 500-acre (202-hectare) unit, based between Cupar and St Andrews, which is also home to 1,000 breeding ewes.
The farm is predominantly grass, for grazing and silaging; but also grows barley, for cattle feed and kale, for overwintering suckler cows.
“Kale’s large leaves and stems are ideal for grazing cattle and it’s ready at a time of year when we need it,” he says, adding that he sees dry matter yields of at least 10 tonnes per hectare. “And nothing is wasted either. Leaf, stem – it’s all eaten. And the cows look well on it too.”
Bob grows 5.5 hectares (14 acres) of Limagrain kale varieties Bombardier and Grampian – a variety bred at the James Hutton Institute– a 50:50 split – each year, which is supplied by East Linton-based Watson Seeds. The crop follows grass – Bob selects a ‘tired’ ley that’s also on a suitable and relatively free-draining site. And he says that seedbed preparation is key to success.
“Achieving good establishment and fast early growth is vital,” says Bob. “Once the crop has grown to the rough-leaf stage and good ground cover has been achieved, it looks after itself. So I give it plenty of attention early on.”
He drills the kale, in early May, into a fine seed bed, created by first rotovating the old ley, ploughing and then power harrowing. “We may make two passes with the power harrow if the seed bed isn’t quite fine enough. It’s well worth the effort to achieve the ideal tilth. And after sowing, to improve soil-to-seed contact, we’ll make a pass with a roller.
So far, so good. But Bob says there are two more hurdles or ‘problems’ he must look out for and quickly tackle to ensure the crop’s success.
“The first is flea beetle. We keep a close eye out for it and if we see if, we spray straight away. It’s important to control this pest as it can significantly check growth and yield.”
The second challenge faced by the crop is pigeon damage. “Pigeons really like young kale plants. So we use bird scarers until the crop is a little more robust. Once good ground cover has been achieved, and the pigeons can’t see space to land, they lose interest in it.”
Bob applies 80 units of liquid nitrogen with the bulk of it put on post emergence, once he can see rows started to emerge, and a second dressing when he can still see space between the rows, just prior to total ground coverage.
“Once we get to a good ground cover stage, we know that we can close the gate and walk away, until it’s time to graze it in the autumn. The crop really does look after itself.”
He says that when he goes in with the electric fencing in October, he’s always pleased to see how well and how consistently it’s grown. “We aim for chest height – we’re happy with that.”
Cows are strip grazed on the kale and the fence is moved every 12 hours. As nothing else is fed to this block, except some big bales of straw sitting on a trailer on a hard standing, Bob saves on the cost of grass silage and home-grown rolled barley, as well as the additional labour required to feed housed cattle.
“I don’t know what we did in 2020, but some plants stood six feet high and the entire crop – both varieties – yielded better than usual. We grazed 83 cows on it, 10 more than usual, from late October to late January. This was an extra two weeks compared to a more typical year.
“The bigger the yield, the more we save on other feed costs,” adds Bob. “And if I get the crop off to a good start, it’ll be trouble-free during the growing season.”