GB2549453A - Wood fibre - Google Patents

Abstract

The present invention relates to the use of microporous wood fibre particles as a mulch, to a method of preventing or reducing weed growth in a plant growing medium comprising the step of locating microporous wood fibre particles over the plant growing medium, and to microporous wood fibre particles when used as a mulch. Microporous wood fibre particles are able to bind to each other or 'bind together'. The microporous wood fibre particles may be obtained by defibration of the particles. The particles may provide greater light-blocking and protection from surface drying out when compared to conventional mulches.

Description

WOOD FIBRE

The present invention relates to the use of microporous wood fibre particles as a mulch, to a method of preventing or reducing weed growth in a plant growing medium comprising the step of locating microporous wood fibre particles over the plant growing medium, and to microporous wood fibre particles when used as a mulch.

Mulch is matter conventionally placed on soil surfaces to prevent weed growth. Many mulches are known, including organic-base mulches such as straw and wood barks chips. However, such mulches only provide irregular or intermittent soil coverage, so that ‘effective’ weed growth is really only achievable with either excessively heavy layers of such materials, or plastic sheeting or the like which is not organic.

According to one aspect of the present invention, there is provided a use of microporous wood fibre particles as a mulch.

According to another aspect of the present invention, there is provided a method of preventing or reducing weed growth in a plant growing medium comprising the step of locating microporous wood fibre particles over the plant growing medium.

Optionally, the plant growing medium is one or more of the group comprising: soil, compost, culture medium, or a combination of same.

The term “plant growing medium” as used herein relates to a medium generally comprising a mixture of minerals, organic matter, gases, liquids and possibly organisms. They can supply plants with nutrients that are held in place by the content of the medium. Many types and qualities of plant growing media are known, and the present invention is not limited by the plant growing medium, other than it has the required nutrients etc. to allow weed growing .

Optionally, the plant growing medium is pre-treated to clear or minimize weeds therein, so that the use of mulch as described herein is to prevent or reduce any remaining weeds (e.g. their seeds) from germinating or reaching the soil surface.

The term “weed” as used herein relates to any embryonic plant matter that can grow into an unwanted plant. Examples commonly are plants unwanted in human-controlled settings, such as farm fields, gardens, lawns, and parks. The term also is applied to any plant that grows or reproduces aggressively, or is invasive outside its native habitat. Weeds generally include mosses, lichen, grasses, clover, etc. More particularly, weeds include various ‘common annual and perennial weeds’ including dandelion (Taraxacum spp.), daisies (Beilis spp.), docks (Rumex spp.), groundsel (Senecio vulgaris), Shepherd’s Purse (Capsella bursa-pastoris), procumbent pearlwort (Sagina procumbens), willowherbs (Epilobium spp.), common poppy (Papaver rhoeas), speedwells (Veronica spp.). Buttercups (Ranunculus spp.), cleavers (Galium aparine), nettles (Urtica spp.), sow thistles (Sonachus spp.), thistles (Cirsium spp.), fat hen (Chemnopodium album, knot-grass (Polygonum spp.) bindweeds (Convolvulus spp.), chickweed (Stellaria spp.), and grasses.

Thus, the term “mulch” as used herein relates to the use of microporous wood fibre particles to cover plant growing medium as defined herein relative to the atmosphere.

Optionally, microporous wood fibre particles are useable on a plant growing medium having one or more plants growing therein or therefrom not being weeds as defined herein. For example, the microporous wood fibre particles are useable around the stems of plants already extending from the plant growing medium, so as to prevent the growth of weeds therewith, or for plants able to grow through the microporous wood fibre particles covering such as tulips or daffodils, i.e. bulb-derived plants.

The microporous wood fibre particles may be obtained from any suitable source, including but not limited to mechanical shearing of wood chips.

Optionally, the mechanical sheared wood chips are steamed at an elevated temperature. For example, the Wood chips or other suitable wood pieces can be steamed at pressures of about 6 bar to 10 bar, and at temperatures of about 150°C to 180°C.

Optionally, the steamed wood chips are subsequently sheared. After cooking, the chips or particles become brittle and grinding can be carried out by means of rotating discs (for example a rotor disc and stator disc) which shears the chips into fibres.

Optionally, the fibres provided by the above process are subsequently agitated, preferably stirred, for a time, and at a slightly elevated temperature such as between 30-50°C, until they at least partially curl.

By varying the process conditions, it is possible to provide microporous wood fibre particles having diameters in the range of 10-100 micron, or 0.1-1mm, or greater than 1mm.

Optionally, the present invention further comprises drying the wood fibre particles prior to use. The wood fibre particles may be dried using any suitable drying process or dryer, generally involving an elevated temperature and optionally a vented fluid such as air thereacross.

Optionally, the drying process avoids complete drying of the fibres, and uses hot air at a temperature between 160°C to 180°C for a few seconds, optionally in a drum or a rotating cylinder. EP0947130 describes a culture medium for plants based on wood fibres obtained by grinding and steam cooking the fibres so that they at least partially roll up on themselves as the beginnings of twists or spirals, and are thus capable of hooking into one another.

Because of the nature of the microporous wood fibre particles formed in this way, they are able to bind to each other or ‘bind together". As such, the microporous wood fibre particles are able to provide greater light-blocking coverage over a plant growing medium such as soil, compared to conventional mulches. The binding microporous wood fibre particles are also able to reduce further the water evaporation from the plant growing medium, generally due to wind and sun, etc. Thus the microporous wood fibre particles better protect the plant growing medium surface from drying out compared with conventional mulches.

Furthermore, as they bind together, the microporous wood fibre particles are less likely to be disturbed by animals and birds, ruining the coverage achieved by the use.

Meanwhile, because of the spaces between the so-formed microporous wood fibre particles, the coverage provided by the microporous wood fibre particles is also water porous. That is, the microporous wood fibre particles do not prevent water from rainfall or artificial irrigation from reaching the soil surface.

Thus, the microporous wood fibre particles used in the present invention provide an organic material that can wholly or substantially prevent weed growth, that can reduce water evaporation, and can still allow natural watering therethrough, and usually at only a small depth of material required compared to conventional mulches.

Optionally, the microporous wood fibre particles are obtained by defibration of the wood fibre particles. Defibration maybe carried out in saturated water vapour and relatively high temperature atmosphere.

Optionally, the microporous wood fibre particles are at least partially rolled up on themselves.

Optionally, the microporous wood fibre particles form a web wherein the fibres are simultaneously both entangled with each other, and spaced from each other.

According to another aspect of the present invention, there is provided a microporous wood fibre particles as defined herein when used as a mulch.

According to another aspect of the present invention, there is provided a plant growing medium insulator wholly or substantially comprising microporous wood fibre particles as defined herein.

Optionally, the insulator is able to reduce the difference or variation between the minimum and maximum temperatures in the soil over time, compared to the same soil without any covering. In this way, there is a smaller temperature variation in the soil, which prevents stress to the plant root system from excessively hot or cold temperatures, which could in many plants make the difference between survival or death.

The density and/or depth of the mulch provided by the microporous wood fibre particles are intended to provide a barrier effect. This can include, but is not limited to, wholly or substantially preventing light passage.

Optionally, the depth of the mulch provided by the microporous wood fibre particles is in the range 2-20cm, such as in the range 5-10cm.

In one embodiment of the present invention, there is use of binding microporous wood fibre particles formed from mechanical shearing of wood chips that are steamed, sheared and optionally dried, as a layer of mulch in the range 5-10cm over a plant growing medium such as soil.

In general, the present invention can be in or for an industrial, commercial or domestic environment, over plant growing medium being ‘the ground’, or in containers, optionally already seeded with or growing one or more desired plants (i.e. notweeds).

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings in which;

Figures 1A-D are four photographs showing weed density in Treatment areas A, B, C and D respectively; and

Figure 2 is a temperature versus time graph.

In the growing of any plant in soil, etc., especially in outdoor conditions, all plant growers and gardeners are aware of the ubiquitous presence of a range of plants generally termed ‘weeds’, that are not desired to be grown at the same time in the same area. Hence, many so-termed ‘weed killers’ and methods of trying to minimize or rid the presence of weeds or their seeds and roots are known, a typical exercise for many plant growers and gardeners in the time ahead of seed planting.

Many weed killers are chemical-based products known in the art, which may have some effect. However, many plant growers also seek to at least minimise the growth, or new growth, or further growth, of weeds in a plant growing area by covering the area a permanent or temporary covering. This can include sheeting, such as plastic sheeting, or mulch. Such coverings can also be used to try and retain soil moisture and regulate soil temperature. Mulches are typically formed from organic residue such as leaves, hay, and straw, but include bark products, in particular shredded bark or bark chips which are relatively inert and their decay does not take away the demand for soil nitrates from the plant growing medium.

The present invention is a surprising new use of microporous wood fibre particles as a mulch, which has been found to provide a method of method of reducing weed growth in a plant growing medium by improving the barrier between the plant growing medium and the atmosphere thereabove.

Figure 1A shows a first plot 10 of soil defined by a wooden border 12. Under Treatment A, there has been no covering over the soil over a set time period, which has lead to a proliferation of weeds 14 within the plot 10. Any plant grower or gardener will known and recognise that even after any ‘weed killing’ action or method, the ‘regrowth’ of weeds, either from roots, etc., still in the soil, or borne on the wind, or brought in by animals or birds, will inevitably occur.

Figure IB shows a second plot 20 of soil defined by a wooden border 22. Under Treatment B, the plot 20 microporous wood fibre particles 24 are located over the soil in the plot 20 to an approximately depth of 5cm. The microporous wood fibre particles 24 thereby form a barrier across the soil, wherein sunlight is wholly or substantially prevented from passing there through, preventing the propagation of weeds.

Because the microporous wood fibre particles 24 are at least partially rolled up on themselves in the form of twists or spirals, possibly behaving in the form of small springs, this promotes their hooking into each other, resulting in a structure which forms a web, wherein the fibres are simultaneously both entangled with each other, and spaced from each other.

Figure 1C shows a third plot 30 of soil defined by a wooden border 32, wherein the soil is covered by a conventional landscape bark 34, and in which a number of weeds 36 can be seen. Landscape bark does not create a substantial light barrier, allowing weeds to grow or regrow. Bark is also not able to form a web, and to bind to itself. As such, the bark cannot prevent movement by weather or animals or birds, causing breakages in the intended coverage of the soil, which allows weeds to grow.

Figure ID shows a fourth plot 40 of soil defined by a wooden border 42 wherein the soil has been covered by a decorative mini bark 44, which still shows the presence of a number of weeds 46.

Figure 2 shows the average 24 hour temperature of each of the treatment plots A-D and the ambient temperature between June and September in the South of England. It can be seen that the ambient temperature ranges between 12-13°C, to a maximum of near 30°C in the middle of July. Naturally, the ambient temperature is higher in the afternoon and dips in the evening and at night time.

In treatment A with the plot 10 having no soil covering, it can be seen from line ‘TA’ that the soil temperature is typically significantly above ambient temperature in the afternoon/evening, at one point hitting a high temperature in mid-July of 40°C.

The coverings provided in treatments C and D show in lines TC and TD form much smoother lines, having less extremes, but still at one stage allowing the soil temperature to reach 25°C, and a minimum of 15°C.

The covering provided by the present invention shown by line TB in treatment B can be seen as having the least maximum and minimum deviation, able to provide a much shorter temperature variation in the soil, which therefore prevents stress to the plant root system from excessively hot or cold temperatures, which could in many plants make the difference between survival or death.

The present invention provides an organic mulch able to insulate against excessive moisture loss form a plant growing medium such as soil, whether being soil in ‘the ground’, or in any container such as small or large pots, by preventing sun and dry wind from reaching the plant growing medium surface and drying it out. This again helps plants as it reduces water stress.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined herein. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as defined herein should not be unduly limited to such specific embodiments.

Claims (13)

1. Use of microporous wood fibre particles as a mulch.

2. A method of preventing or reducing weed growth in a plant growing medium comprising the step of locating microporous wood fibre particles over the plant growing medium.

3. A use or method as claimed in any one of the preceding claims wherein the microporous wood fibre particles are formed from mechanical sheared wood chips.

4. A use or method as claimed in claim 3 wherein the the mechanical sheared wood chips are steamed at an elevated temperature.

5. A use or method as claimed in claim 4 wherein the steamed wood chips are subsequently sheared.

6. A use or method as claimed in claim 5 wherein the steamed wood chips are subsequently dried.

7. A use or method as claimed in any one of the preceding claims wherein the microporous wood fibre particles are obtained by defibration of the wood fibre particles.

8. A use or method as claimed in any one of the preceding claims wherein the microporous wood fibre particles are at least partially rolled up on themselves

9. A use or method as claimed in any one of the preceding claims wherein the microporous wood fibre particles have a depth in the range of 2-20cm over the plant growing medium.

10. A use or method as claimed in any one of the preceding claims wherein the plant growing medium is one or more of the group comprising: soil, compost, culture medium, or a combination of same.

11. Microporous wood fibre particles when used as a mulch.

12. A mulch wholly or substantially comprising microporous wood fibre particles.

13. A plant growing medium insulator comprising microporous wood fibre particles.