Whatever happened to kale?

Once a staple game crop on many shoots in the UK, Tim Furbank explains the decline of kale in recent years and why he still rates it as the best conservation game cover crop going.

Up until 30 years ago, kale was the mainstay of game cover crops in the UK. Grown widely for forage, kale produced a warm and dry winter cover for game and was often strip-grazed through the winter period. As commercial shoots developed, they started to use kale as a stand-alone game cover or alongside a food crop such as a cereal or maize. Many would leave their kale for a second year, which delivered fantastic brood rearing for wild game as well as a wonderful food source for farmland birds in the second winter.

Kale is, without question, the best conservation game cover crop as it delivers winter cover, spring insects and winter food. So why does it appear to have gone out of fashion?

The main reason is that growing kale became more difficult and commercial shoots simply couldn't afford to risk a crop failing. As the acreage of oilseed rape grown in the UK increased through the '80s and '90s, the prevalence of pests that feed on oilseed rape increased dramatically. And of course, pests that feed on oilseed rape also feed on kale.

With the best will in the world, a lot of game crops are not looked after as well as they could be, so many crops of kale disappeared before shoots realised there was a problem. Forage crops such as maize were, at the same time, becoming more widely used in the dairy industry and shoots soon discovered that maize was considerably easier to grow. Combine that with the introduction of sorghum and the use of perennial crops, such as canary grass, miscanthus and chicory, and you can soon see why kale fell out of favour with shoots that rely on game crops for the bulk of their shooting.

The threatened loss of a viable seed dressing to protect the kale seedlings against flea beetle attack virtually signed the death warrant for kale. Fortunately, common sense prevailed and kale was granted a reprieve. The sugar beet formulation of Cruiser (thiamethoxam) is approved on kale until 2017 and this has meant that growers have been able to plant kale with some confidence that the seedling is protected from flea beetle.

There are a few restrictions on using treated seed – namely that the seed must be drilled and not broadcast and there is a maximum sowing rate of 3.7kg/ha. Unfortunately the treatment doesn't protect the seed from slugs, pigeons, gamebirds, hares or rabbits! However, thanks to the continued use of a robust seed dressing and the undoubted benefits of a good crop of kale, it has made a comeback over the last few years, especially in Environmental Stewardship and CFE (Campaign for the Farmed Environment) wild bird seed mixes.

Considerable time and effort is required to get the best out of a crop of kale but the rewards can be significant. If you put the work in during the establishment year, you will have a crop that will potentially last you for three seasons. The problem that we see all too often is that wild bird seed mixes are treated with suspicion (and sometimes disdain) by shoots as they expect them to fail and therefore deprive them of a drive. I would argue that a properly grown wild bird seed mix containing kale and other seed-bearing crops is hugely beneficial when trying to hold game. Diversity is not only good for all wildlife, but providing different types of cover will appeal to game on different days with different weather conditions.

So what are the keys to growing a successful crop of kale or a wild bird seed mix containing kale? The most important advice here is to grow it as you would a commercial crop, i.e. sow it at the right time, into a good seedbed, with effective early weed control and plenty of fertilizer. Failure is often blamed on flea beetle or weeds overtaking the crop but both of these are often effect rather than cause. Cruiser SB is very effective at preventing flea beetle attack in the early stages of growth (up to 1–2 true leaves) but if the seedlings are in cold, poorly structured soils then they will not have enough vigour to grow away from the flea beetle attack when it inevitably happens.

If the seedbed has not been prepared properly, as the weather breaks down the clods, more and more weed seeds will germinate and overtake the kale. Be patient! Some of the best crops of kale we have seen over the past few years have been sown at the end of June. By then the seedbed has been worked down to a fine, firm tilth, all of the weeds in the top couple of inches of soil have germinated and been killed, the base fertilizer is on and the only limiting factor to growth is moisture. Again, don't be driven by the date. If there is little or no moisture in the top few centimetres of soil, then don't drill. The seedbed should be left in a state ready to drill by the beginning of June. Wait for a decent rain (minimum 10mm) and then drill into that moisture, without moving the ground again in front of the drill, and roll after drilling. You will then get rapid, even germination and emergence, and a crop that will be more competitive with any later germinating weeds and will grow away from flea beetle attack. Another slight advantage of delayed drilling is that pigeons have usually found some peas/clover/laid barley by June, so tend to leave newly sown kale plots alone.

Kale is very responsive to nitrogen (N) fertilizer and you should budget for 120kg/ha of N in the first year with a top-up of 40–60kg in the spring of year two for maximum seed yield. If you skimp on fertilizer you will be disappointed with the crop.

A) A kale crop with 120kg N/ha applied

B) A kale crop with 60kg N/ha applied

C) A kale crop with no N applied

I often hear beaters moaning that a crop of kale is ‘too wet', and the birds therefore don't like it. If it is grown properly, in wide (40–50cm) rows, the leaves form a fantastic canopy which actually keeps it fairly dry at ground level. Of course, when you walk through it, all the water runs off the leaves and into your boots! The other advantage of wide rows is that each plant will have a thicker and stronger stem which will help keep it standing through the winter and the second year.

And what about choice of variety? Until you are confident of growing a successful crop of kale, the variety is unimportant as varietal differences are small compared to the differences that good husbandry makes. Clubroot is another oft-quoted problem for kale and it can certainly be an issue when brassica crops are grown in too tight a rotation, particularly on acidic soils. Varieties such as Caledonian and Goldeneye are shown to be resistant to some strains of clubroot but not others, so are not a solution but may add a degree of protection on sites where clubroot is more likely. Once you are confident you can grow kale, the variety is very much a case of personal preference. As long as it produces a good canopy with strong stems, that will do for me!

As one who is keen to promote the benefits that well managed shoots deliver for farm wildlife, it makes my job a whole lot easier if shoots do grow more than just maize. If people are prepared to spend a bit more time and care when establishing their game covers, then the rewards that a good crop of kale will deliver are huge for game, insects and farmland birds.