Mulch, in either organic or inorganic forms, will help maintain soil moisture by reducing evaporation from the soil surface. Clearly, it’s a good way to reduce the need for watering. A layer of mulch, or a piece of appropriate film or matting, can also help weed control. That means a reduction in pesticide usage. And where organic mulches are used there can be an improvement in soil structure and possibly drainage, plus increased fertility, as the material slowly decomposes. That means a saving in soil conditioners and fertilisers.
There are more benefits, such as keeping the soil warmer in winter and cooler in summer — witness the mulching sheets covering the fields to warm the soil in spring for early planting or sowing. Then there is disease suppression. By preventing the foliage and fruits of spreading or trailing plants from coming into contact with the soil, a number of soil-borne diseases could be avoided and plant losses or pesticide applications further reduced — but only if the material is clean and free of plant diseases in the first place.
There is a long list of materials suitable for use as mulch. There are those in sheet form, such as polypropylene or natural-fibre matting, and loose materials such as stone chippings, bark and woodchip. The best material for a site will depend on many factors.
Bark remains a preferred choice by landscape architects. According to Green-Tech general manager Mark Shaw, sales of bark for use as mulch and surfacing are already up on last year. The company, based near York, is a main distributor for Melcourt Industries of Tetbury, Gloucestershire. Shaw confirms that sales currently stand 20 per cent higher than the first quarter of 2005, but says that much of the supply is going to a large number of small jobs rather than a few big ones.
Although varying with species, bark has the colour everyone expects to see under trees and shrubs. Its performance has been tried and tested over the years, it is gradable, consistent and available throughout the UK.
“Bark can actually set off a scene and that is one reason why it is popular in the landscape,” says Melcourt sales and marketing director Andy Chalmers. Bark also gives you choice. “There are different species and a range of grades; by using the right one, bark can give best value over time,” he adds. The company has supplied 20,000cu m of bark for mulching at Heathrow’s new Terminal 5.
Having built a business over many years, Melcourt has expertise on its side. It offers technical advice on choice of material and the writing of specifications. Some of its products have been fire tested to BS4790 — a big advantage if mulching beds in car parks and other situations where a smoker could toss a smouldering cigarette butt.
Melcourt recently completed a major investment at its Tetbury headquarters. The £250,000 worth of improvements include the installation of a new Doppstadt bark-grading machine, while the refurbished yard infrastructure has speeded up collections and deliveries.
“Demand for our products is continuing to grow across the entire range of landscape, play, grower and other areas,” says Chalmers. “The new yard layout vastly increases the speed at which we can turn round deliveries as well as other efficiencies. The Doppstadt machine — the first of its kind in the UK — ensures better consistency in our bark products and also reduces handling, so keeping costs down.”
A material reportedly gaining in popularity for use as planting-bed mulch is recycled woodchip. Made from post-consumer wood waste such as old pallets, woodchip also finds uses as surfacing for paths and, in some instances, play areas. Following a local authority study, the Waste & Resources Action Programme (WRAP) points out that woodchip could have far wider applications.
Like bark, woodchip was found to have a variety of potential uses and offered benefits such as marking picnic sites under trees, reducing erosion on slopes and banks and mopping up mud around car parks or by the edge of water. Areas that may previously have been unsuitable for public access may become usable, maintenance is reduced because of the product’s effectiveness as a weed suppressant and its long lasting properties mean less topping up may be required.
WRAP material development manager Julia Turner says: “This study demonstrates the extent to which local authorities can use recycled woodchip.
“As well as helping councils meet their sustainable and environmental obligations, recycled woodchip is a durable, cost-effective surfacing product that reduces maintenance requirements such as weeding or watering.”
Other research by WRAP indicates that only three per cent of specifiers, purchasers and professionals are aware of the potential use of recycled woodchip as a loose surfacing material. WRAP says that because woodchip knits together well, it adheres effectively to steep slopes. It can be used in locations where some loose surfacing materials are washed downhill, although it should be noted that the choice of grades means bark that is sufficiently heavy to stay in place can also be selected.
Woodchip does offer the advantage of colours. Organic dyes can be used to produce woodchip in a variety of colours, including natural shades that highlight foliage and others that are suitable for more decorative and domestic sites.
Turner says: “The demand for recycled woodchip in landscaping has grown in the past few years with more organisations using the material and an increasing number of suppliers entering the market. But we need to build on this and demonstrate how it can be used as an effective and versatile solution in a variety of landscaping applications.”
The cost of removing nails and other contaminants, plus the reduction to chips, means woodchip materials may not be as cheap as you might think. Expect to pay between £8 and £18 per cubic metre for woodchip from recycled timber. Bark averages about the same price, depending on grade. For cheapness, there is composted organic material. This may come in at under £8 per cubic metre, but make sure it is matured and expect to top it up regularly.
Cost will be an important issue for most specifiers but, perhaps this year more than any other, the focus needs to be on the retention of soil moisture. And if parched summers and hosepipe bans are here are stay, we need research into which materials are most effective at keeping water where it is needed — at the roots.
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