Lasting Weed Control
Strulch inhibits weed germination and growth by blocking out light. The mineralisation process inhibits the rate at which the straw breaks down and depending on the application rate and local conditions, can act as an effective barrier to light for up to two years.

Reduced Watering
Mulching is widely recommended as a good gardening practice. It reduces water loss from evaporation especially during summer periods. Strulch has a low capacity to hold water, allowing rainfall to soak through to the soil.

Adds Organic Matter
Strulch is biodegradable and will break down over time, adding valuable organic matter and nutrients to the soil. Strulch encourages earthworm activity by acting as a long term food source for surface feeding species.

Environmentally Friendly
Strulch is made from renewable and local resources which do not harm the environment.

Benefits of mulching
Mulching is good gardening practice because it provides a protective covering for the soil. Mulches assist retention of soil moisture so that nutrients are more easily absorbed by plant roots and also protect roots from heat stress. Mulches reduce the need for watering in dry periods and suppress weed growth. Plants are stronger and healthier as a result.

Mulching in the global context
With the exception of rocky mountain and desert habitats, exposure of bare soil is quite rare in natural ecosystems. Normally the soil surface will be fully covered by a complete protective layer of plants and litter. Bare soil surfaces can quickly become compacted and crusted through exposure to rainfall and drying, requiring frequent cultivation to remove weeds and maintain a fine tilth.

Mulches are essential when adopting no-till (or zero-cultivation) growing practices. No-till farming methods are becoming increasingly popular in developed and developing world agriculture as a sustainable system for land management. Ploughing and tilling soils stimulates soil organic matter breakdown whereas, no-till farming can enable soil organic matter levels to recover toward the levels found in natural ecosystems. Good soil structure and drainage will actually improve under a no-till mulch through the burrowing actions of earthworms.

Strulch Mineralised straw garden mulch Information sheet

What is Strulch?

Strulch is a new garden mulch developed specifically for long lasting weed control and water saving in herbaceous borders, raised beds, fruit and vegetable plots. Strulch is a light easy to handle mulch made from good quality home grown wheat straw. The straw is milled and treated with iron minerals to provide the best possible characteristics for general purpose garden use.

Why use Strulch?

Key Benefits

• Effective weed control. Strulch inhibits weed germination by blocking out the light required for weed germination and growth.
• Lasting protection for up to 2 years, but Strulch can be worked into the soil at the end of the season to improve soil structure and drainage.
• Ideal for establishing low maintenance beds and restoring severely weed infested plots without using herbicides.
• Saves water by providing a barrier to evaporation, thus protecting the soil from drying during periods of drought.
• The coarse textured upper surface of the mulch dries rapidly after rainfall which acts as a deterrent to snails.
• Increases in plant growth and yield can be expected compared to bare soil.
• Strulch is suitable for use as a temporary surface cover during garden establishment or to provide over-winter frost protection.
• Strulch can be incorporated into compost, and will particularly improve the structure of material made from grass clippings and other nitrogen rich plants.
• Strulch’s colour blends in well, providing an aesthetically pleasing textured surface which can be used in all areas of the garden.

 Why is Strulch different than conventional straw mulches?

Strulch retains all the benefits of traditional straw mulches but without the disadvantages. Straw was once a very popular mulch with both amateur and professional gardeners, but it tends to rot down fairly quickly, particularly when wet. If rotting occurs when the plants are young, nitrogen is removed from the soil causing reduced growth. During the manufacture of Strulch, the straw is treated with mineral iron which binds strongly to polymers in the straw and acts as a preservative and slows the rate of breakdown by cellulose degrading enzymes. This mechanism is called ‘physical and chemical protection’ by Soil Scientists. When spread as a covering layer, Strulch will last longer than conventional plant composts, hay or grass cuttings and yet it is fully biodegradable in the long term, returning beneficial humus and plant nutrients to the soil. Unlike some wood and bark based mulch products, Strulch does not leave a residue of woody fragments. 
When straw is being prepared for use in Strulch, special care is taken to remove seeds and dust. It is then chopped and milled to an optimum particle size so that it will bed down to form a matted surface. This improves stability for use on sloping and exposed areas.

How does the mineralisation treatment work?

The reason why the treatment is so effective relates to the behaviour of the mineral precipitates at the biochemical level. Mineral oxides and hydroxides deposited from solution gradually form polymerised gelatinous layers. The physical presence of this deposit and chemical binding make it more difficult for bacteria and fungi to break down cellulose. The product was called mineralised straw from the Oxford Reference Dictionary definition of mineralise: ‘to impregnate with a mineral substance’. When the product is first unpacked there may be residual traces of ferrous iron (easily detectable by the slightly rusty smell) but these will precipitate out as harmless iron hydroxide minerals after a few days of exposure to air and moisture.

If Strulch is a new product has it been adequately tried and tested?

Trials were conducted between 1999 and 2002 at the University of Leeds Experimental Gardens, followed by independent external trials in 2002-3 and 2003-4 at The Helmsley Walled Garden, The Earth Centre, The Eden Project and latterly at the RHS Harlow Carr Gardens.

The University trial compared three alternative mineralised straw treatments with a bare soil control. The tables below show results of a standard mineralised straw treatment against a bare soil control. In the tables, low refers to a low iron application rate comparison, and; +N refers to an alternative experimental treatment (not used for making Strulch) with added nitrogen and a very low conductivity. No benefit was found from adding nitrogen and, of course, this would go against the concept of a simple whole straw product. Wheat straw mulches will add soluble potassium to the soil soon after application and contain in the region of 1% N and 0.5% P that will be released more slowly as the mulch decomposes.

Longevity
Open bed plots containing shrubs were given a 10-cm (4-inch) mulching layer. More than 50% of the original volume remained on the plots after 12 months and about 40% after 24 months. This longevity far exceeds that attainable with either farmyard manure or spent mushroom compost.

Weed control
Trial plots were rotivated without herbicide treatment prior to shrub planting and mulching. Weeds were then only removed from plots after 12 and 24 months. After recording the 12-month figures, all plots were weeded manually once. The test plots were deliberately located next to fallow ground to allow maximum exposure to weed invasion.

The very high level of weed suppression can be explained by the formation of a dense mat of fibres that prevents light penetration. The retention of an open fibre structure means the mulch surface dries out very quickly after rainfall (although the soil below remains moist and well protected from evaporation). There was no evidence at all of any inhibition to plant growth other than that attributable to shading (tests with four species of shrub - mulched immediately after transplanting).

A side effect that is very noticeable in mineralised straw mulches is that perennial weeds are much easier to remove from under mulch than bare ground. Low light intensity at the base of the mulch layer stimulates proliferation of lateral roots, in dandelion for example, or rhizomes in couch grass and these are much easier to lift than when anchored into mineral soil.

Benefits for plant growth
Increased plant growth was recorded after 2 years following application. Figures based on canopy volume calculated from height and diameter of bushes: Growth was substantially better in the mulched plots - mostly due to the reduced weed competition. Of course, the other benefit is that the treatment greatly reduces nitrogen immobilisation. Mulches also reduce water loss from bare soil, which is particularly beneficial in periods of drought.  

In addition to the microbial stabilisation effect, iron impregnation makes the mulch less palatable to earthworms than ordinary straw and so is more slowly incorporated into the soil. However, earthworm activity was still higher under mulched plots than bare soil due to the additional food supply and the moister topsoil conditions during the summer.

Is Strulch wildlife friendly?

The University’s experimental gardens in Headingley are located within a conservation area of importance to urban wildlife. The dry and soft surface to the mulch made the plots the preferred resting place for neighbourhood cats and even the occasional urban fox! Over the 3 years, Strulch was also frequently observed in bird’s nests in surrounding trees.

Microcosm studies have also been conducted on the effect of Strulch on earthworm activity and populations. Strulch is a food supply for earthworms and can significantly increase earthworm populations compared with inorganic membrane mulches. Inorganic sheet membranes were effective for weed control but they did not promote earthworm populations. A membrane will also prevent access to birds foraging for worms and other wildlife in the food chain. 

Feeding choice chamber experiments showed that earthworms incorporated Strulch more slowly than untreated straw. This goes some way to explain the reason for the observed longevity of the mulches in the field trials. Contrary to a common misconception, most worm species gain little direct nutritional value from the cellulose based straw but feed principally on fungal and other microbial colonisers on the straw fragments. As fungal colonisation is inhibited in Strulch it is naturally less palatable. Apart from food supply, water is a major determinant of earthworm population size and activity. Retention of moist conditions below a mulch can significantly increase absolute earthworm populations and make existing populations more visibly active by encouraging the worms to move and feed at the soil surface during dry periods.

What is meant by environmentally friendly?

Strulch is sustainable product manufactured from a renewable resource with no harmful chemicals, namely, fresh wheat straw grown locally in the United Kingdom.

Should I be concerned about increasing the levels of iron minerals in the soil if Strulch is used regularly?

No, not at all. Strulch contains less than one percent mineral iron and this is in the form of mineral hydroxides and organic-iron complexes that are similar to naturally occurring soil iron compounds. Iron and aluminium silicates are amongst the most abundant minerals that make up all rock and soil minerals. When these minerals weather in the formation of top soils, they release iron and aluminium sesquioxides which are of vital importance in binding the soil and retaining humified soil organic matter. These iron minerals are responsible for the brown and reddish brown colours we associate with good fertile soils.

Should I be concerned about other harmful chemicals when using a product made from an agricultural crop?

Only good quality wheat straw (currently from selected known sources in Norfolk) is used to make Strulch. The straw is harvested under contract by our processor and taken on the day of harvest to processing plant where it is stored indoors until needed. Wheat straw is harvested at the same time as the grain which we all eat in bread and other food products. Therefore, there is not expected to be any harmful agrochemical residues. It is perhaps not generally realised, but when UK farmers grow winter wheat, herbicides are normally only used pre- or post-emergence (which means that herbicides are applied after planting the wheat seeds and either just before or just after the young seedlings have emerged above the ground in September). No further herbicide applications are needed during the long period of growth through to harvest the following August because, once established, the canopy of wheat leaves shades the ground for most of the year. In addition, these herbicides are biodegradable and will not be present later in season. It is perhaps a reflection on the low public esteem of our home grown cereals industry and agriculture in general that concerns about herbicide residues are so commonly raised.

Use of organic straw for mulching is not always required even when following guidelines for organic gardening and crop growing.  Organic growers often use non-organic straw for mulching. However, for customers requiring guaranteed organic straw, we supply an alternative version of Strulch made with Soil Association certified organic wheat straw. 

Is Strulch a valuable source of plant nutrients?

Yes, but the nutritional value of Strulch comes from the straw itself, there are no added nutrients. When growing to specific fertilizer management regimes it is safe to assume that the nutritional value of Strulch, over the long term, will be the same as ordinary wheat straw.

Where and how can Strulch be used?

For effective weed control in garden beds, mulch should be spread to give a deep uniform surface covering of 4 cm. Deeper layers can be applied to help in the control of tough perennial weed problems but, as with most loose mulches, over-deep layers should be avoided. It is recommended that layers are tapered away from lawn edges where hover mowers are used and some types of beds will benefit from raised edging for additional containment. When installing new raised beds, remember to leave sufficient space for a mulch layer between the soil level and the upper edge of the bed wall.

Areas to be treated should be cultivated and persistent perennial weeds should be dug out before application. For annuals, Strulch is best applied in late spring or early summer around established plants, allowing the soil to warm up and full benefit from early spring rainfall. It is advisable to leave a space around the stems of some plants to enable drying air to reach the stem base at soil level.

When applying Strulch the surface can be levelled and firmed after spreading. It is recommended that the mulch is watered in to bind it together.