What are the benefits of switching to coir?

Growers report sustainability, high-quality crops and better productivity from switching to coir, says Gavin McEwan.

Cocogreen: coir is an increasingly popular choice for growers of tabletop berries
Cocogreen: coir is an increasingly popular choice for growers of tabletop berries

Switching to coir-based growing media offers sustainability as well as productivity benefits, according to Place UK, recently-crowned not only Soft-Fruit Grower of the Year but also overall Edibles Grower of the Year at last month's UK Grower Awards.

Part of Berry Gardens, the UK's largest soft-fruit marketing group, the Norfolk-based firm sells around three million punnets of fresh strawberries and 2.5 million of raspberries a year, with Driscoll varieties Amesti, Jubilee, Solaro, Elizabeth and the raspberry variety Maravilla predominating.

While still rotating many of its fruit crops in the ground, the company has been increasingly switching to tabletop growing. This year 18 of its 64ha of strawberries, along with seven of 52ha of raspberries, will be grown in coir, all supplied by Cocogreen.

"Having worked with different coir suppliers and trialled several competing products, Cocogreen has become our sole supplier," says Place UK production manager John Blazey. The products are well buffered and highly consistent, and the price competitive."

He explains that the transition "proved quite a steep learning curve" because irrigation management "is much more involved" in coir than in field-grown crops. "However, we soon got to grips with it and it is delivering plenty of benefits."

Place UK puts great emphasis on maximising water efficiency and it has won two Environment Agency awards - one for irrigation monitoring and scheduling and the other for water recycling. Blazey and his team were therefore keen to trial H2CoCo, Cocogreen's new wetting and water conservation and management agent for coir.

"Using H2Coco at the beginning of the season, we can wet up the growbags and pot systems in just 24-48 hours instead of five days," he says, not only reducing water and labour costs but also avoiding waterlogging the fields.

Cocogreen sales and marketing director Thomas Ogden says: "High-performance, competitively priced Cocogreen substrate products are helping growers like Place UK deliver the highest-quality berries while optimising productivity and sustainability."

Dry XD: offers freer drainage for crops that prefer a drier growing environment 

Pre-formed discs

In the Netherlands, several strawberry growers are switching to pot-grown strawberries on tabletops, for which UK-based Botanicoir now supplies pre-formed coir discs of customisable dimensions, compressed flat and with an optional pre-drilled hole for wetting.

Small and light, the discs are easy and quick to put in the pots. They expand easily on wetting to create a growing medium of optimum porosity. One early adopter, Ton Groot of Hoogwoud near Alkmaar, says he can have all 12,500 pots filled within a day of taking delivery.

"Before the discs, the warehouse was full of loose cocopeat and the whole team was wheeling, filling and inserting. Now we just put in a disk as we walk past," says Groot. Once the plant is established "you can clearly see it's got an even spread of roots", he adds. "The substrate is coarser with a more consistent quality compared to what we've used before."

Nearby grower Hans Bakker was among the first Dutch growers to switch to the discs. "I've had the strawberries in the same coir for two seasons now and we're going to buy new discs again next year because they've been so successful," he says. "Even though I'm quite generous with the water, the coir maintains its integrity and doesn't become mushy. Any superfluous water is drained very quickly."

Botanicoir managing director Kalum Balasuriya says: "We're pleased with the success the Botanicoir discs are having in the Netherlands. In the UK we can supply discs with customised dimensions and volumes and we offer a range of mixes, both washed-only and washed and buffered."

Product for glasshouses

For glasshouse growers, Botanicoir is also adding a new substrate growbag to its range, Dry XD, which offers freer drainage for crops such as tomatoes that prefer a drier growing environment with a high air fill porosity.

Flavourfresh production manager Andy Roe has been trialling the new substrate and has found that the tomato plants are visibly more generative, leading to a better-yielding, higher-quality and more flavoursome product.

"We started the 5,000sq m trial in December, which is a real test because that is notoriously a difficult time for establishment and growth due to short daylight hours, but the tomatoes are thriving," he says.

The Dry XD substrate is being tested at the Merseyside grower against Botanicoir's Breeze and Dry bags. These take a little more management than the Dry XD, which is very forgiving if the plants are overwatered, Roe has found.

"Some coco fibres can sit too wet overnight for tomatoes, but the free-draining properties of Dry XD allow the coir to remain drier overnight," he explains. "I've overwatered before and the coir has corrected itself in 12 hours."

A substrate that is too wet will yield tomatoes with poorer flavour, reduced shelf life, quality issues and a lower yield, he points out. "When testing the fruit, we look at sugar levels, kilograms per square metre, cracking of the skin and whether the soil moisture is balanced, because fluctuations in soil moisture can increase the chances of blossom end rot." In these, he says, "initial results are extremely promising".

As with many of Botanicoir's products, Dry XD comes in a dehydrated block in a polythene growbag, making it light and easy to transport. When wetted, the block expands from 20mm to 80mm deep in hours.

Areas of fresh-produce sector where peat still has a major role to play

While coir-based growing becomes increasingly the norm in some areas of fresh produce, it is still a matter of horses for courses, says ICL technical manager for growing media Jim Smith.

Crops such as lettuce with delicate leaves that cannot be handled must be grown in blocks, sufficiently compressed to hold together in a set shape but still able to absorb water and with enough air space to let the roots breathe. "The only ideal raw material available for making blocks is peat," says Smith.

For this a particular form of peat is harvested from deep down in the peat bog and rotovated, not allowed to dry, so retaining its stickiness. This peat is very dark and has a high CEC (cation exchange capacity), allowing relatively high fertiliser levels to be added without risk of restricting the roots.

However, as a growing medium this can contain up to 30 per cent of other raw materials without losing adhesiveness, including fine bark, coir, loam or perlite. The pH of the blocking peat is adjusted using dolomitic lime and a base fertiliser, either organic or inorganic, is added.

Celery, tomatoes, cucumbers and courgettes can also be grown in blocks, whose size can be tailored using different moulds, again with the block handled, rather than the plant. "Our Levington B2 growing media is the industry standard," adds Smith.

Crops such as brassicas with stronger foliage can be handled without fear of damage, and these are usually grown in modules of varying sizes, comprising a growing medium with fine enough particles to fill the cells uniformly, and also hold together as the plants are withdrawn from the cell.

"Peat is the most widely used raw material for modules, though coir and bark are also suitable provided water and fertiliser management is adjusted to suit," Smith explains.

The increasingly popular fresh potted herbs are multi seeded in pots in which they are grown to marketable plants. For this the growing medium has to be fine enough to get the seedling established, when fertiliser requirement is low, yet buffered to ensure watering and fertiliser is adequate to maintain a reasonable shelf life. Here again "peat is the cheapest and most reliable material but coir, bark, wood fibre and perlite, or combinations, can also be used," Smith points out.

Soft-fruit plants, meanwhile, are normally propagated in pots, with strawberry plants grown from root tips in buffered coir with a suitable fertiliser, while raspberries require a coarser growing medium as well as a slightly higher pH. Acid-loving blueberries, on the other hand, require a low pH and can be sensitive to certain types of phosphate, requirements which ICL's Levington special recipes can address.

Lastly, mushroom spawn is grown in manure that is "capped" with peat. "It is the contrast in conductivity between the peat and the manure that encourages fruiting bodies to form," Smith explains. The peat has lime added to give a pH as close to seven as possible and must be able to hold a lot of water.

"There is a growing media for all edible crops," says Smith. "Whether in blocks, modules, 9cm pots or large pots, ICL can provide recommendations on the initial growing media and subsequent feeding."

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