Professional growing media

As interest in bark and wood fibre-based products grows, Sally Drury reports on latest developments.

Melcourt Industries: offers its customers quality, consistency and cost-effectiveness - image: Melcourt Industries
Melcourt Industries: offers its customers quality, consistency and cost-effectiveness - image: Melcourt Industries

Whatever materials we use, in any aspect of our industry, there will be an impact on the environment. In this respect, growing media is one material that continually draws attention. Version 1 of the industry calculator for assessing the responsible sourcing of material used in growing-media products is now being tested by the Growing Media Association.

Feedback from the trials is expected at a launch event at the end of the month (30 June). For now, we can report a continued growing interest in the use of bark and wood fibre products, in part due to peat prices, which are related to peat harvesting and the weather.

Last year was a relatively good one for harvesting peat, says ICL (formerly Everris) technical manager Dr Jim Smith. "Good harvesting conditions equate with good weather and therefore a good year for growers. This reflects growing media requirements for the following season," he explains.

In contrast, the previous two years saw challenging peat harvest periods that he says resulted in an industry-wide trend to dilute peat with bark, coir and wood fibre to ensure sufficient growing media to satisfy demand. With higher processing and transport costs, these alternative raw materials cost more than peat.

Price sensitive

"In 2015 some growers have seemed more price sensitive, preferring peat-based growing media," says Dr Smith. "Some returned to wanting the lowest-cost, most consistent materials in which to grow plants. For those wanting reduced-peat products the favoured alternative bulky raw material was wood fibre."

Responding to this demand, earlier this year ICL launched its own wood fibre material, Fibagro. Said to be a more economical alternative to fine bark, it helps to reduce peat use while keeping overall growing-media costs in check. With a relatively short fibre length, it is suitable for smaller celled bedding plant packs as well as larger pots for nursery stock.

Wood fibre is made from woodchips that are processed to separate out the fibres. While there are several different methods for achieving this, the process chosen can affect the consistency of the end material. Fibagro is manufactured by the PF3 disc defibration process method, while other wood fibre tends to be made by extrusion.

"It is important to incorporate the wood fibre evenly with raw materials to avoid clumping," says Dr Smith. "This requires specialist machinery. Another important factor is material stability. As with all wood-based products, nitrogen must be added to combat bacterial breakdown. We stabilise Fibagro during its production. As to crop management, when growing in media containing wood fibre, growers need to take into consideration how open the material is when irrigating."

ICL recommends up to 25 per cent addition of wood fibre to other materials, such as peat, bark or coir. "If wood fibre products are added at a higher rate the fibres may align and allow the growing media to shrink," warns Dr Smith. "A growing media with uniform particles will hold the fibre apart, keep the product open and prevent shrinkage."

While wood fibre is proving a popular peat dilutant, he points out that price is likely to vary according to woodchip requirements for fuel and pressed board production. For growers wanting a peat-free growing media, ICL now has a full range of products manufactured from coir, bark and Fibagro.

Specialist supplier

Melcourt industries has specialised in the supply of barkand wood-based growing media for three decades. At this year's RHS Chelsea Flower Show, 10 growers who use Melcourt Sylvamix were awarded medals, seven of which were gold.

"Given that this is one of the highest accolades of quality possible in UK horticulture, it goes a long way to dispelling forever the myth that top-quality plants cannot be grown without the use of peat," says Melcourt technical director Catherine Dawson.

But it is not only at Chelsea that the quality of Melcourt growing medium is being recognised. Of the plants on offer at the National Trust's new garden centre at Morden Hall Park, there are few not growing in Sylvamix, and like many grower retailers the National Trust is also offering the retail version of the same mix, called SylvaGrow.

Although many of its customers use Sylvamix for its technical merits, one the challenges Melcourt sees is that of being pigeonholed as a supplier of peat-free products. "Our growing media are second to none in terms of quality, consistency and cost-effectiveness, with customer service to match," says Dawson.

"Happily there are many growers who have seen that whether or not their customer base is asking for peat-free plants is not the main issue. A raft of benefits is available to users apart from the growing of very good-quality plants. Customers report faster potting times, less wastage, cleaner tops, significantly reduced moss, liverwort and weed growth and ease of handling - all of which have a cost saving attached. The fact the mix is peat-free is just another benefit."

It is not just in the ornamentals sector that peat alternatives have shown benefits. Strawberry growers who are considering the longevity of growing are investing in high-quality substrate that will benefit short-term varieties and offer the opportunity to reuse bags should their cropping plans dictate.

According to Stephen McGuffie, production director at Staffordshire-based New Farm Produce, investing in a quality growbag can save money and ensure a better crop. He uses Botanicoir's Precision Plus.

"It's important to think about investing in a quality product to get enhanced results on a short crop and also for reuse on a long-term basis if required," he says. "This will ensure better growing conditions and will mean you don't have to purchase more bags year after year."

McGuffie has worked with Agrovista and Botanicoir on the development of the Precision Plus strawberry growbag. Botanicoir pioneered the development of the dehydrated strawberry slab.

"I've done a lot of work on Precision Plus with Botanicoir to develop a product with adequate drainage that also retains enough water to support strong growth," says McGuffie. "The bags have all the benefits needed - sufficient drainage, AFP and water/nutrient holding capacity as well as excellent structural integrity and longevity."

He is now using the same bags for the fourth year running. "To extend the life, we crush the bag on the sides - not on the top and bottom," McGuffie explains. "This helps to break up the root fibres and provide even greater AFP in the bag. It's also easy to flush the bag of negative elements such as sodium and sulphates. New bags should be flushed and crushing is done from two years onwards."

Growing demand

Botanicoir works closely with Agrovista. "The demand for our Botanicoir substrate is growing dramatically," says Agrovista commercial head of fruit Mark Davies. "Existing customers are using it more and new growers are coming on board. This is down to a loss of soil sterilants, planning restrictions and a desire to grow on tabletops, which reduces picking costs.

"Ultimately growers are understanding the benefits of purchasing the best grade coir initially for many reasons, most importantly for better results on a short crop, but also capitalising on the potential to use the same growbags year after year without compromising yield or fruit quality."

Jiffy's factory

Fargro supplies growing media on behalf of major European suppliers, from propagation to container mixes. One of these suppliers is Jiffy, which in April opened its substrate factory in Estonia.

The upgraded facility is ready to produce high-quality Baltic peat mixes. Now it is possible to deliver, right from the source, substrates with new raw materials such as white peat blocks fraction 0 and 1, Coco Pith fine.

In addition, a big-bale machine and 70-litre bags are now available as a new packaging option. All this makes it possible to produce consistent quality, match the needs of growers and produce innovative and environmentally sound products.

New Green-tree products utilise Carbon Gold's biochar

Landscaping supplier Green-tech and biochar firm Carbon Gold have joined forces to launch three new products. Green-Tree Topsoil, Green-tree Amenity Tree Soil and Green-tree Roof Garden substrates are available pre-blended with Carbon Gold's enriched biochar Tree Growth Enhancer to increase survival rates of trees and plants.

Biochar is a highly purified form of charcoal that is created by pyrolysis - low-oxygen baking of woody waste. To maximise the beneficial effects of adding biochar to soils, Carbon Gold's biochar is enriched with mycorrhizal fungi, seaweed and worm casts, which are essential for healthy root systems.

Biochar acts like a sponge, improving the water-holding capacity of soil or compost. It minimises drought stress for newly planted trees, reducing the frequency of irrigation and raising survival rates.

Green-tech communications manager Lesley Spence says: "If rootstock or containerised plants or trees are planted into poor soil with limited biology and fertility, it will create stress and ultimately losses. Green-tree soils are manufactured to BS3882:2007 and already have high nutrient content, fertility value and structural components.

"With the added Carbon Gold biochar these products will provide drought and disease resistance, providing customers with reduced losses, long-term cost-savings and confidence in planting."

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