Growers in the UK are under pressure to move away from using peat and are increasingly turning to coir - the fibre around the hard shell of the coconut - as a substitute. Every year the Dutch firm Legro imports around 30,000 tonnes of coir from Asia and sends around a quarter of this to the UK. The substrate is widely used in soft fruit production, as well as in protected crops such as peppers, cucumbers and tomatoes.
In recent years, the government has stepped up its pressure on the industry to move away from peat for production. And many of the larger supermarkets are keen to display their green credentials by promoting food crops that have been grown in "sustainable" media.
But the picture is not simple. For a variety of reasons - horticultural, economic and political - products such as rockwool and peat continue to be used, and many growers, particularly of berries, still prefer to grow crops in the soil. Jan Butterley, who owns Nynehead Fruit in Somerset, explains: "We are old-fashioned. We don't want the overheads, but it's something that we're still monitoring and in a few years time we might have to change."
Many soft-fruit firms have already made the change. Agrovista soft-fruit specialist Mark Davies told Grower that for many producers, the switch to coir coincides with their switch to table-top production. "Some growers switch to table tops when they run out of clean ground on the farm," he says. "They can set up table-top production close to the packhouse - and coir fits in nicely.
"It does not seem to me like there's been a great deal of pressure on them to move onto coir. They do it because of the benefits - its consistency, its sterility, and the fact that it's easy to manage in terms of irrigation and fertigation."
Peter Gwynne, a partner at Freshfield Fruit based near Hereford, uses coir. "Growing on tables means that we can test the plant tissue and look at what we put in. We can use a computer to make sure that nothing is wasted. It's also light to handle when we put the bags on to the table top," he says.
At Freshfield, plants are now being grown in a combination of media including peat, rockwool and coir. Gwynne adds that during the last five years, the majority of soft fruit growers have made the switch.
Davies reckons that it costs in the region of £1.50 to £2 to buy a metre of peat, and that coir costs around 10 or 20 per cent more than this, but has the potential to last longer.
Soft fruit grower Neil Cockburn, claims this is the main reason why he has started to use coir for some of his strawberry beds. "There's a political side to this, as only two per cent of peat excavated is used in horticulture - the rest of it is burned. So I have slight doubts about the way we are supposedly saving the planet by driving half way across the world to get coir," he says.
"Saying that, we have switched to coir for some of our production, but it's only about 10 per cent of it. We're not getting a lot of customer pressure and we can get three or four seasons out of it rather than just two for peat."
Anthony Snell, of Herefordshire-based soft fruit grower AJ & CI Snell, started using coir last year. The farm still grows a large proportion of its strawberries - and all of its outdoor raspberries - in soil, but is using coir from Legro for its table-top production.
Snell says: "Last year we put in our first 4ha of table-top strawberries and we are now expanding that by another four hectares. We looked at the various options, but the reason we are using coir is that the customers prefer it to the peat option. We also know it has good longevity so it will give us a reasonable crop before we have to renew it.
"Although there's all of the implications of food miles of bringing something from the other side of the world, you are basically using a waste product," he adds. "Up until quite recently coir was not quite as sought after as it is now. But it's well-marketed and there seems to be a reasonable supply of the stuff at the moment. In a way you feel slightly better using a waste product than going down the peat route."
Dutch coir suppliers reckon that the market is growing by about 10 per cent a year. Jack van Batenburg, product specialist at MeeGaa says: "We find that there is a lot of interest from growers in buying loose material because it's a very cheap option."
Coir is also gaining popularity with tomato growers. Until a year ago, Wight Salads grew tomatoes in rockwool. Now their British operation has moved onto coir. Technical director Paul Challinor is positive about the change. "We were having difficulty getting rid of our old rockwool. Coir is easier to recycle and we're getting good results," he says, adding that Wight Salads wanted the recycled coir to improve its own soil.
Not everyone has made the transition away from rockwool. Produced from fibres spun from molten rock, the medium is not usually used for berries as it is difficult to insert a small plant into the mass of material. However, it is suitable for growing from seed and is widely used for cucumbers, peppers and tomatoes. Many firms like to use rockwool because it holds air and water and is sterile.
Kent-based Thanet Earth is a modern, high-tech, 25ha greenhouse complex, built about two years ago, and specialising in cucumbers, peppers and tomatoes, which are grown in rockwool. Even some of the small cucumber and pepper plants are supplied in miniblocks of rockwool, which can then be put into the large rockwool trays.
At the end of a season, rockwool can be cleaned and, if it is steamed properly, can last two or three seasons. However, Thanet Earth prefers to dispose of the rockwool at the end of each year, and has a contract with Dutch specialist Grodan to supply the new rockwool and take away the old material. The reasons are straightforward, says Thanet technical manager Robert James. "We were concerned about yield and security. We were worried about pests, so we change the wool every year," he explains.
Not only is there pressure to use the most environmentally friendly product, but there is also the exchange rate to take into account. Coir is usually purchased using US dollars and the biggest cost is fuel for transport. When fuel prices are high - or when the dollar is strong - coir leaps in price. By contrast, most peat is sourced in the Eurozone. Conversely, if the dollar is weak, then coir becomes the more attractive option.
This is another reason why many firms are keeping their options open. Since technical or economic changes could lead to a swing away from coir, peat or rockwool, for most growers the choice of substrate is a question of continual vigilance and careful judgement.
But the traditional growing medium of peat still remains popular and most of the firms that sell it, do so in large quantities. Legro for example, sells twice as much ordinary peat as coir.
A number of firms have stuck resolutely with the traditional medium. Northern Ireland-based Bulrush Horticulture, for example, still sells peat or mixtures of peat and wood fibre. Most of its customers growing edibles opt for 100 per cent peat, and professional products director James Hayes rejects the idea that peat is somehow worse for the environment than coir.
"There is a huge amount of peat available," says Hayes. "Most of it is simply used as fuel. The amount taken for horticultural use is very limited. Most coir has to be shipped from Sri Lanka, which means that it has a large carbon footprint. I think the opposition to peat is misplaced."
Angus Soft Fruits - a growing group based mainly in Scotland - has experimented with various growing media but still uses peat. Technical director David Griffiths explains: "We have tried green waste, coir and bark chippings. Green waste and coir were more expensive, but bark chipping can be reasonably cheap." However, he says, using a mix of peat and bark for raspberries produced relatively poor returns.
The firm also tried pure hydroponics - growing entirely in water with no additional medium. However, there was a problem with disease drifting from plant to plant, and although peat doesn't last as long as coir, Griffiths says this short life can be an advantage of using the traditional medium. "It means we get a clean start - no weeds and no contamination. I know growers who have moved onto coir and have eventually gone back to peat."
Plenty of growers are still weighing up the alternatives. Berry Gardens, for example, is trialling different growing media and is testing both black and white coir bags to see what differences in fruit they give.
Tel: +31 88 008 1800, www.legro.nl
Botanicoir Supplied to UK growers in association with Agrovista. Email Mark Davies on firstname.lastname@example.org or call 07979 703526.
Tel: 028 7938 6555 www.bulrush.co.uk
MeeGaa Substrates BV
Tel: +31 15 214 3055, www.meegaa.nl
Tel: +31 475 35 30 20, www.grodan.nl