WO2022112446A1

WO2022112446A1 - An apparatus and method for seeding and crop establishment

Info

Publication number: WO2022112446A1
Application number: PCT/EP2021/083052
Authority: WO
Inventors: Leslie Francis May; David Howard Holloway
Original assignee: Russet Technology LLP
Priority date: 2020-11-30
Filing date: 2021-11-25
Publication date: 2022-06-02
Also published as: GB2601371A; GB202018787D0

Abstract

The invention provides a method of suppressing weed growth on an underlying soil substrate, which method comprises: (i) providing a moving carriage (2) having mounted thereon; a soil collecting device (4); a soil sterilizer device (30, 36); a sterilized soil dispensing device (50, 52); and a weed barrier laying device (54); (ii) moving the carriage (2) along or close to a path on which a weed barrier is to be laid; (iii) collecting soil from an underlying soil substrate using the soil collecting device (4); (iv) passing the soil through the soil sterilizer device (30, 36) to kill weeds present in the soil and provide a stock of sterilized soil; (v) laying the weed barrier onto the underlying soil substrate using the weed barrier laying device (54); (vi) depositing sterilized soil on to the laid weed barrier using the sterilized soil dispensing device (50, 52) so as to cover the weed barrier and hold it in place on the substrate; and optionally (vii) irrigating the dispensed sterilized soil and weed barrier. The invention also provides a method of suppressing weed growth as above but wherein the weed barrier is seed-bearing, as well as an apparatus for use in suppressing weed growth on an underlying soil substrate.

Description

AN APPARATUS AND METHOD FOR SEEDING AND CROP ESTABLISHMENT

This invention relates to a method of seeding into a weed free environment, and an apparatus for use in the method.

Background of the Invention

The range of herbicides available for weed control in close-spaced row crops such as carrots and onions has become significantly diminished as a result of the withdrawal of key herbicides following changes in pesticide regulations. Mechanical weeding methods such as mechanical hoeing can be used between crop rows but effective in row weed control has become a significant problem. Even crops grown at wider spacings, such as lettuce and brassicas, are affected. Automated mechanical hoeing between plants (particularly within a row) damages root systems and disturbs the soil (stimulating further weed emergence) while manual labour to hoe crops is excessively expensive and is becoming increasingly difficult to source. Attempts to automate the selective identification of weeds from the crop and individually treat them with herbicides, compressed air, heated fluids or laser beams has not been cost effective and therefore an alternative system of weed control is urgently needed by commercial growers.

The use of soil-sterilizing apparatus to kill weeds in soil is known and soil sterilizers that use steam as the sterilizing agent have been known for several decades but fell out of favour as more cost effective solutions became available. Commercially available examples of such soil sterilizers include the sterilizers available from Alvan Blanch (http://www.alvanblanchgroup.com/soil-sterilisation-systems) of Malmesbury, United Kingdom.

Steam sterilizers for sterilizing soil are also known from CN 109673341 (Univ. Kunming Science & Tech.) and WO2018/073718 (Marco Scotta),

W02005/022983 (Alee Garden S.R.L) discloses a trailer-mounted apparatus for sterilizing soil in situ on the ground using a sterilizing or weed-killing substance which is typically steam, optionally in combination with calcium oxide. The apparatus breaks up the soil and lifts it into the air where it is contacted with the sterilizing substance.

W09927779 (Cope) discloses an apparatus for sterilizing a top layer of soil in situ in an agricultural situation. The Cope apparatus works by cutting through and breaking up a top layer of soil which is then directed through a sterilization chamber where the soil is sterilized by the heat generated by gas burners. A water injection system is used to spray water on to the soil before it exits the apparatus and is returned to the environment.

Swiss patent CH563102 (Paul Wuligrocki & The Raymond Lee Organization) discloses an apparatus which can be towed by a tractor and which scoops up earth from the ground, sterilizes it by passing it through a rotating oscillating drum which is heated by gas burners, and then returns the sterilized soil to the ground. The sterilizing of the soil is intended to be carried out before sowing.

All these systems rely on sterilisation of very significant quantities of soil, enabling sterilisation of a sufficiently deep seed bed, otherwise weeds are liable to emerge from below the treated soil layer. Any later disturbance of the sterilised layer, including the planting of crops, can result in similar issues.

The use of seed-tapes and seed mats for weed control is known and examples of seed mat products are described in WO-A-OO/67549, WO-A-2005/099431 and WO-A- 00/67549. Seed tapes and seed mats can be used to prevent weed germination from below the seed mat or tape, while encouraging crop establishment from seed sown in the tape or applied above the tape or barrier film.

However, a problem with seed mats and tapes is that they need to be covered in a substrate substantially free of weeds and weed seeds in order to hold the mats or tapes in place and prevent them from being blown away. Typically weed-free coarse sand is used but this is heavy to transport which makes it very expensive to use.

JP 2018027055 discloses a method of seeding which involves laying a mulch mat, forming a shallow groove (about 2 cm wide by 3 cm deep) in the soil beneath the mulch mat by using a compression roller, laying a water-soluble seed tape into the shallow groove, covering the seed tape with weed free soil (carried in a hopper on the laying apparatus); and compressing the weed free soil down onto the seed tape. The weed free soil is not stated to be sterilised soil but appears instead to be soil taken from a source (volcanic ash soil or “mountain” soil) that is naturally low in “organic contaminants” and is most probably therefore unsuitable for supporting plant growth.

Therefore, there exists an urgent need for an improved apparatus and method for sowing seeds and protecting germinating seedlings from competition by weeds.

The Invention The present invention provides a solution to the above problem by using sterilized soil to hold the seed tapes or mats in place. The sterilized soil is prepared in situ by mounting a soil collector, soil sterilizer, and soil dispenser on the carriage from which the seed tapes or mats are laid. The collector is mounted on or near to the front of the carriage and/or to the side of the carriage and scoops or throws up soil which is then fed into the on-board sterilizer. As the seed tape or seed mat is laid from the rear of the carriage or carriage train, sterilized soil is dispensed onto the seed tape or seed mat to cover the tape or mat and hold it in place.

An advantage of the method of the present invention over known methods of soil sterilization, for example as described in the references given above, is that it makes use of much smaller quantities of sterilised soil. Thus, it is not necessary to sterilize the soil over a large area and to a large depth; instead, it is merely necessary to sterilize enough soil to cover the seed tape or seed mat. This means that the soil sterilizer can be more compact and is likely to consume much less energy than the soil sterilization apparatuses described above. The need to sterilise smaller quantities of soil also allows the seeding process to take place more quickly, creating a significant commercial advantage over previous in situ sterilisation methods. The method of the present invention is also advantageous over known methods of laying seed tapes and seed mats in that it avoids the need to carry sand on the tape or mat-laying apparatus in order to deposit on the tape or mat to hold it in place and prevent it from being blown away. A further advantage is that the method of the invention results in the depositing onto the seed tape or mat of a substantially weed-free soil medium in which seedlings can readily grow.

Accordingly, in a first aspect, the invention provides a method of suppressing weed growth on an underlying soil substrate, which method comprises:

(i) providing a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil dispensing device; and a weed barrier laying device;

(ii) moving the carriage along or close to a path on which a weed barrier is to be laid;

(iii) collecting soil from an underlying soil substrate using the soil collecting device;

(iv) passing the soil through the soil sterilizer to kill weeds present in the soil and provide a stock of sterilized soil; (v) laying the weed barrier onto the underlying soil substrate using the weed barrier laying device;

(vi) depositing sterilized soil on to the laid weed barrier using the sterilized soil dispensing device so as to cover the weed barrier and hold it in place on the substrate; and optionally

(vii) irrigating the dispensed sterilized soil and weed barrier.

The weed barrier can contain seeds or it can instead function primarily as a weed barrier and not contain seeds.

Where the weed barrier does not contain seeds, the method of the invention typically includes an additional step of introducing seeds into the sterilized soil covering the weed barrier. In one embodiment, the seeds are introduced into the sterilized soil after the sterilized soil has been deposited onto the weed barrier. In another embodiment, the seeds are deposited onto the weed barrier and the sterilized soil is then deposited onto the weed barrier so as to cover the seeds. In a further embodiment, a first charge of sterilized soil is deposited onto the weed barrier, then seeds are deposited onto the first charge of sterilized soil, and then a second charge of sterilized soil is deposited onto the weed barrier so as to cover the seeds and at least part of the first charge of sterilized soil.

Where the weed barrier does contain seeds, typically it takes the form of a seed tape or seed mat.

In one embodiment of the invention, there is provided a method of suppressing weed growth on an underlying soil substrate, which method comprises:

(i) providing a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; and a seed-bearing weed barrier laying device;

(ii) moving the carriage along or close to a path on which a seed-bearing weed barrier is to be laid;

(iii) collecting soil from the underlying soil substrate using the soil collecting device;

(iv) passing the soil through the soil sterilizer to kill weeds present in the soil and provide a stock of sterilized soil; (v) laying the seed-bearing weed barrier onto the underlying soil substrate using the weed barrier laying device;

(vi) depositing sterilized soil on to the laid seed-bearing weed barrier using the sterilized soil depositing device so as to cover the seed-bearing weed barrier and hold it in place on the substrate; and optionally

(vii) irrigating the dispensed sterilized soil and seed-bearing weed barrier.

In another embodiment of the invention, there is provided a method of suppressing weed growth on an underlying soil substrate, which method comprises:

(i) providing a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; and a weed barrier laying device;

(iv) passing the soil through the soil sterilizer to kill weeds present in the soil and provide a stock of sterilized soil;

(v) laying the weed barrier onto the underlying soil substrate using the weed barrier laying device;

(vi) depositing sterilized soil on to the laid weed barrier using the sterilized soil depositing device so as to cover the weed barrier and hold it in place on the substrate; and

(vi-a) introducing seeds onto the weed barrier prior to and/or during and/or after deposition of the sterilized soil onto the weed barrier so that the seeds are embedded in and preferably covered by the sterilized soil; and optionally

(vii) irrigating the dispensed sterilized soil and weed barrier.

The term “moving carriage” as used herein is intended to cover any moving vehicle, platform, trailer or other support structure upon which the soil collecting device, soil sterilizer device, a sterilized soil depositing device; and weed barrier laying device can be mounted. The moving carriage may comprise one or more than one component. For example, it can comprise a trailer, or a train or two or more trailers, that can be towed behind a tractor, or it can be self-propelled (i.e. it has its own propulsion unit). The moving carriage can comprise, for example, a self-propelled driverless (e.g. robotic) vehicle. The soil collecting device is typically mounted at or near a front end of a carriage or carriage component upon which are mounted the soil sterilizer device and the sterilized soil depositing device. The term “front end” refers to the direction of travel of the carriage. Thus, where the carriage is a self-propelled vehicle, the soil collecting device is typically mounted at a near a front end of the carriage. Where the carriage comprises a trailer or train or two or more trailers towed behind a towing vehicle such as a tractor, the soil collecting device is typically mounted at or near a front end of the carriage or, where there is a train of two or more carriages, at or near a front end of a leading carriage.

Thus, the soil collecting device is typically mounted on the carriage or carriage component forwardly of the sterilized soil depositing device and weed barrier laying device. The soil collecting device is also typically mounted forwardly of the soil sterilizer device.

The soil collecting device may be configured to collect soil such that one or more furrows are created in the underlying soil substrate, into one or more of which the weed barrier is laid by the weed barrier laying device. In this embodiment, the soil collecting device functions also as a furrowing device.

Alternatively, the moving carriage or carriage component(s) may have separate soil collecting and furrowing devices.

Where there are separate soil collecting and furrowing devices, the soil collecting device may be disposed forwardly of the furrowing device, rearwardly of the furrowing device, or laterally with respect to the furrowing device.

In one embodiment, the soil collecting device is disposed forwardly of the furrowing device.

In another embodiment, the soil collecting device is disposed laterally with respect to the furrowing device.

The soil collecting device can take various different forms. It can for example take the form of a scoop or ploughing device which cuts into the underlying soil substrate to remove soil which is then conveyed to the soil sterilizer device. In this embodiment, the soil collecting device can function also as the furrowing device. Alternatively, it may comprise a flail or rotating cultivator head which cuts and/or scrapes the underlying soil substrate to create an airborne stream of soil particles which is directed to a soil-receptacle. By creating an airborne stream of soil particles, the particles can be graded or classified by gravity before they reach the soil-receptacle such that only the lighter and/or smaller particles are collected by the soil-receptacle while heavier and/or larger particles such as clods and stones are not collected, thereby further aiding the efficiency of the soil sterilisation process.

When the furrowing device is a separate entity from the soil collecting device, it can, for example, comprise a ploughshare or blade or an array of one or more (typically a plurality) of coulter discs or pairs of coulter discs.

The furrowing device is typically a device that cuts through the underlying soil substrate rather than simply compacting it. Whereas light pressure may be applied to a furrow to level the floor of the furrow to make it easier to lay the seed barrier into the furrow, the use of heavy pressure to compact the soil is typically avoided as the resulting compacted soil may have poorer plant-growth supporting properties. Thus, the furrowing device cuts through the underlying soil substrate to form a furrow either by displacing soil to one or both sides or by scooping up soil (when the furrowing device is also the soil collecting device).

In one embodiment, the furrowing device is configured to create a single furrow in the underlying soil substrate.

In another embodiment, the furrowing device is configured to create a plurality (e.g. two, three, four, five or six) of furrows in the underlying soil substrate.

The furrow(s) may have a flat floor, or a curved (e.g. concave) floor, or an undulating floor, depending on the nature of the furrowing device. For example, where the furrowing device comprises one or more pairs of coulter discs, each furrow may comprise two-sub-furrows linked by a land of lesser depth, such that the edges of the weed barrier may be more deeply buried.

The moving carriage may have mounted thereon a furrowing device, or it may have mounted thereon a plurality (e.g. two, three or four) furrowing devices, each of which may be configured to create one or a plurality of furrows (e.g. two, three, four, five or six). The moving carriage may be provided with one or more (e.g. one either side) lateral extensions upon each of which is mounted a furrowing device. In this way, a much greater area may be covered in a single pass of the moving carriage.

The furrows can vary in width and spacing depending on the width of the weed barrier and the type of seeds to be sown, but are typically of a width in a range from 1 to 30 centimetres, for example from 2 to 10 centimetres. The furrows are typically shallow; i.e. have a maximum depth of no more than about 0.5 to about 5 centimetres, and more typically in a range from about 1 to about 3 centimetres.

Prior to entering the soil sterilizer, the soil collected by the soil collecting device can be pre-treated by one or more pre-treatment devices to remove stones and other unwanted materials from the soil and/or to break down lumps of soil into smaller soil particles.

Thus, the soil-collecting device can be linked to or comprise a pre-treatment device in the form of a separator device for separating stones and other unwanted materials. The separator device can take various forms and, in a simple form, can comprise one or more sieves. The sieves can be static or moving and, in one embodiment, are arranged to vibrate or oscillate to facilitate separation. A moving sieve can also take the form of a moving belt formed from a mesh material whereby soil of a required size can fall through the mesh to be collected for onward conveyance to the soil sterilizer device.

When the soil-collecting device comprises a flail or rotating cultivator head which cuts and/or scrapes the underlying soil substrate to create an airborne stream of soil particles, a baffle (e.g. a baffle plate) may be provided which acts as a barrier to larger soil particles (e.g. clods and stones) but which allows smaller and/or lighter particles to pass to the soil-receptacle.

The soil-collecting device and, when present, the separator device, can be linked to a further pre-treatment device in the form of a size-reducing device for breaking lumps of soil down into smaller soil particles. The size reducing device can be, for example, a pulverising device which crushes lumps of soil to form smaller-sized particles. Thus, in a simple form, the size reducing device can be a percussive pulverising device and/or a pulverising device which comprises moving jaws that crush lumps of soil into smaller particles, or contra-rotating rollers.

A pre-treatment storage container may be provided for storing collected soil prior to passing it through the sterilizer device. The pre-treatment storage container is typically arranged downstream of any pre-treatment devices when present. The pre-treatment storage container acts as a buffer to help ensure that there is a continuous supply of soil during the weed barrier laying process.

Alternatively, after collection and size grading, soil of a desired particle can be conveyed directly to the sterilizer device without intermediate storage.

After collection and, typically, pre-treatment to provide soil of a desired particle size range, the soil is fed into a soil sterilization device.

The term “sterilization” as used herein is not intended in an absolute sense to imply that all living organisms in the soil are killed but rather is used to mean that the soil is substantially free of weeds and propagatable weed materials such as viable seeds or other propagatable matter such as propagating root fragments. The sterilization process represents a balance between eliminating weeds and other propagatable materials such as seeds on the one hand, and destroying the organic structure of the soil on the other hand. Thus, the soil sterilization methods of the invention will typically destroy the great majority of weeds and propagating matter such as seeds and root fragments present in a given soil sample but without completely destroying the structure of the soil. Following sterilization, there may be small remnants of propagating matter from which weeds may grow but the levels of such propagating matter will be too low to be problematic in practice. In this application, the soil sterilizer may also be referred to as the “soil sterilizer device”, and these two terms are used interchangeably herein.

The soil sterilizer device can take various different forms. For example, the soil sterilizer device can comprise a sterilization chamber along which soil is advanced from an inlet to an outlet, whereby the soil is exposed to a sterilizing heat source as it advances along the chamber. The sterilizing heat source can be steam which is introduced into the container, or it can be a dry heat provided by heaters mounted in or on the walls of the sterilization chamber, or it can be heat provided by a flame from a burner mounted in or at an end of the sterilization chamber.

The soil can be advanced along the sterilization chamber by a mechanical advancing device or by means of gravity. For example, where a mechanical advancing device is used, this can comprise an auger or Archimedes screw, or a conveyor belt.

In one embodiment, the mechanical advancing device is an auger which moves the soil from the inlet of the chamber along to the outlet of the chamber. In another embodiment, the sterilization chamber is inclined so that the soil advances through the chamber from the inlet to the outlet under the influence of gravity.

In one embodiment, the soil sterilizer device comprises a rotating drum which is arranged at an incline so that soil entering an inlet end of the drum is gradually carried downhill to the outlet end of the drum. The rotating drum is typically provided with one or more internal baffles to assist tumbling of the soil. In this embodiment, the sterilizing heat source can be a burner mounted at one end of the rotating drum (typically the downhill outlet end), such that soil moving down the rotating drum is tumbled through the hot gases from the burner on route to the outlet.

The device can be constructed so that the angle of inclination can be varied thereby to vary the residence time of the soil in the rotating drum. The residence time of the soil in the drum can also be varied by adjusting the speed of rotation of the drum. Thus, the temperature to which the soil is heated can be controlled by varying any one or more of: (i) the gas flow to the burner; (ii) the angle of inclination of the drum; and (iii) the speed of rotation of the drum, thereby allowing selection of the degree of sterilisation of the soil.

The soil sterilizer device is typically configured and used to heat the soil to a sterilizing temperature of at least 65 °C, for a period of at least 30 seconds. For example, the soil can be heated to a temperature in the range from 65 °C to 120 °C for a period in the range from 60 seconds to 180 seconds, preferably with agitation. In order to heat the soil to such temperatures, the interior of the sterilization chamber can be maintained at a temperature of from 100 °C to 300 °C, more usually from 150 °C to 250 °C. The period of time over which heat is applied to the soil will typically depend on the degree of agitation of the soil and the moisture content of the soil.

In a further embodiment, sterilization can be carried out by use of microwave heating.

Microwave treatment of soils has previously been investigated as a means of destroying weed seeds - see the Chapter by Graham Brodie, Muhammad Jamal Khan and Dorin Gupta, entitled Microwave Soil Treatment and Plant Growth, October 15^th 2019, DOI: 10.5772/intechopen.89684, the contents of which are incorporated herein by reference. Damage to a weed seed is achieved by a combination of direct absorption of microwave energy by the seed and the heating effect on moisture within the seed. Where the soil around the seed contains appreciable amounts of water, heating of the water can provide an additional mechanism for destroying the viability of the seed. The sterilizer device may be configured so as to allow batch sterilization or continuous sterilization.

In a batch sterilization process, the soil can be introduced into a sterilization chamber which is then closed and then subjected to microwave irradiation for a period of time sufficient to bring about sterilization, before reopening the sterilization chamber and removing the sterilized soil from the chamber.

In a continuous sterilization process, the soil may be advanced through the apparatus in or on a moving conveyer (such as a conveyer belt or auger) and may pass through a microwave sterilization station where the soil is subjected to microwave irradiation. The moving conveyer may operate in an incremental or stop-start manner, stopping at the sterilization station while the soil is subjected to irradiation and then moving on to allow an untreated volume of soil to enter the sterilization station, or the microwave irradiation may be directed at a continuously moving mass of soil. The sterilisation station may be stationary or permitted to rotate or vibrate such that the soil contained therein is more uniformly exposed to irradiation.

In each of the foregoing embodiments, additional moisture may be added to the soil to facilitate the sterilization process by, for example, generating steam within the soil. The additional moisture can be added by means of a water inlet such as a spray located upstream of a sterilization station or sterilization chamber, or in the sterilization station or sterilization chamber.

In order to safeguard the health of the operator of the apparatus of the invention, the microwave sterilization chambers or sterilization stations will be provided with sufficient shielding to prevent stray microwave radiation from reaching the operator. For example where a batch sterilization process is used, the sterilization chamber can be provided with a sealed closure such as a door which prevents the escape of microwave radiation while the sterilization process is in operation. Once the irradiation has stopped, the door or other closure can be reopened to remove the sterilized soil. Where a continuous sterilization process is used, the sterilization station may be also provided with seals and baffles to shield a user from the microwaves.

A combination of steam treatment and microwave irradiation may be used to bring about sterilization. Thus, a steam generator outlet may be located within a sterilization chamber or sterilization station, or may be located upstream or downstream of the sterilization chamber or sterilization station. Thus, in separate embodiments of the invention, the sterilization may be provided by (i) steam pre-treatment of the soil followed by microwave irradiation; or (ii) simultaneous steam treatment and microwave irradiation; or (iii) microwave irradiation followed by steam treatment; or (iv) steam pre treatment of the soil followed by microwave irradiation followed by steam post treatment of the soil.

Irradiation times and the quantities of microwave energy directed on to the soil will depend on the masses of soil involved and the amounts of moisture in the soil and can be determined empirically by trial and error. The apparatus may be provided with a moisture sensor which is linked electronically to a controller controlling the microwave sterilization device and/or a steam generator and/or steam outlet so that the amount of steam to which the soil is exposed is controlled in accordance with the pre-existing moisture content of the soil.

After passing through the soil sterilizer device, the sterilized soil can be stored temporarily in a post-sterilization storage tank before being deposited onto the laid weed barrier. The post-sterilization storage tank is preferably insulated to maintain a high temperature so as to continue with the sterilization process. At this point, a small amount of steam could be introduced into the storage tank to bring about partial rehydration of the soil after drying in the sterilization chamber. However, care would need to be taken to ensure that the soil did not hydrate to a point where it would stick together to form clumps, thereby significantly reducing the flowability of the soil and hindering subsequent depositing of the soil. Preferably, therefore, rehydration of the soil is effected by spraying water (which can optionally contain one or more additives as defined below) onto the soil as it is deposited on the weed barrier or shortly thereafter.

The post-sterilization storage tank can be a hopper provided with a soil dispensing outlet or conduit such as a tube. The outlet and/or conduit is typically provided with a valve (e.g. a sliding gate valve or flap, or a rotary valve) for controlling the dispensing of the sterilized soil. The hopper, outlet, valve and conduit can together constitute the sterilized soil dispensing device.

The weed barrier laying device can be configured to lay the weed barrier onto the underlying soil substrate as an elongate continuous strip or as a series of shorter discrete strips. The weed barrier is typically stored on the carriage in strips having a width of from 1 to 200 centimetres, more usually from 2 to 10 centimetres. The strips can be stored in folded form but more usually are provided in the form of rolls, for example having a length of up to about 1000 metres in the case of a non-seedbearing weed barrier and up to about 250 metres in the case of a seedbearing tape. The weed barrier laying device therefore typically comprises a support structure for holding a roll of the weed barrier and a mechanism for dispensing the weed barrier from the roll. The weed barrier laying device can be provided with one or more cutters for cutting the weed barrier in a lateral direction. For example, in certain circumstances and for certain types of crop plant or growing systems it may be advantageous to be able to lay the weed barrier as a series of discrete individual strips of a desired length. The cutters for cutting in a lateral direction can be used to cut through the roll of weed barrier at the end of a run, or in order to lay a series of discrete longitudinally spaced-apart strips. The cutters for cutting in a lateral direction can comprise a guillotine blade.

The carriage can have a plurality of weed barrier laying devices mounted thereon. For example, the carriage may have two, three, four, five or six weed barrier laying devices mounted thereon, each of the weed barrier laying devices being arranged to lay a weed barrier strip of from 1 to 30 centimetres, more usually from 2 to 10 centimetres in width.

The weed barrier can comprise an elongate strip formed from upper and lower layers between which are held a plurality of seeds. The upper and lower layers are typically formed from a biodegradable material, typically paper and/or a biodegradable polymer material.

Alternatively, the weed barrier can comprise an elongate carrier layer of a biodegradable material such as paper or a biodegradable polymer film, coated with a biodegradable adhesive which serves to bond seeds to the carrier layer.

In a further alternative, the weed barrier can comprise an elongate single or multi-ply layer of a biodegradable material such as paper or a biodegradable polymer film.

In each case, the lower layer, or the carrier layer, or the single or multi-ply layer, whichever the case may be, is formed so that roots from germinating seedlings can readily penetrate through into the underlying soil substrate. In a similar manner, the upper layer of the elongate strip, or the coating of biodegradable adhesive on the elongate carrier, will each be such as to permit the growth of seedlings.

A particular example of a weed barrier suitable for use in the method of the present invention is the seed-germination medium disclosed in WO-A-OO/67549 (Terraseed) which comprises an upper layer formed from a tissue paper having a weight of approximately 10-30 g/m2, the tissue paper being coated or impregnated with a waterproofing agent such that the tissue paper is permeable to gases but substantially impermeable to water in liquid form; a lower layer formed from a water-absorbent biodegradable material; seeds being disposed beneath the upper layer; and the upper layer optionally having a plurality of perforations therein to assist disruption of the upper layer to enable seedlings germinating from the seeds to grow therethrough.

Another particular example of a weed barrier is a barrier as described above, in relation to WO-A-OO/67549, but without the seed between the upper and lower layers.

The seed germination medium disclosed in WO-A-OO/67549 is typically provided in the form of a roll and can be gradually fed out from the roll as the carriage moves across a field or other agricultural site.

A further particular example of a weed barrier is a weed barrier in which seeds are held within an adhesive layer which is bonded to support layer formed from a biodegradable material such as a paper or biodegradable polymeric film.

The weed barrier can contain one or more substances that facilitate plant growth. Thus, for example, the weed barrier can contain any one or more of fertilizers, micro-nutrients (such as zinc, copper, boron, and seaweed extracts), iron (III) phosphate, soil improving agents, biological agents such as beneficial soil bacteria and mycorrhizal fungi, humic acid, sea kelp, sugars, amino acids, plant growth promoters and hormones such as gibberellins and auxins, pH-regulators such as lime and sulphur, salt binding agents such as gypsum (calcium sulphate) and adsorbents such as activated carbon can be included in the composition. The pH-controlling agents can be used to control the acidity of the immediate environment, and agents such as gypsum and activated charcoal can minimise the impact of adverse chemical contaminants and salt in the soil or medium, as well as to improve germination, and/or to aid and accelerate plant establishment. Salt binding compounds, buffering and pH regulating compounds and adsorbents typically are applied at between about 20 g/m² and 200 g/m², more usually 50 g/m² to 150 g/m², for example approximately 100 g/m². In the case of the adsorbent, activated carbon, lower concentrations are typically used.

A range of microbiological additives can be incorporated into the weed barriers of the invention to assist germination and plant establishment. These are typically mycorrhizal fungi. Mycorrhizae are a group of about 400 fungi that form symbiotic relationships with plants. They live in or on the roots, extend their hyphae into the soil and make phosphate, nitrogen other nutrients and water available to the host plant. They extend the effective root area many hundreds of times so plants grow faster, larger and stronger with less fertiliser and water. Other commercially available biological and chemical agents that stimulate plant defences and encourage beneficial symbiotic mycorrhizal associations may also be included.

The buffering and other chemical organic agents provide a means of counteracting the impact of adverse chemical contaminants in the soil or medium, as well as improving germination, and/or aiding and accelerating plant establishment. Thus, for example, lime provides a buffer against low pH, gypsum provides a means of counteracting high salinity, whereas clay minerals such as zeolite, kaolinite, calcium bentonite and montmorillonite (which may form part of the binding agent) counteract high levels of fertiliser or chemical contamination in the soil.

The weed barrier may also include one or more pesticides, e.g. fungicides and/or insecticides. An advantage of incorporating the pesticide in the weed barrier is that the pesticide is applied only to the areas of the field where the seeds are being sown; and therefore it is not necessary to treat the whole field.

As an alternative to including the above substances in the weed barrier, any one or more of the substances can be mixed with the sterilized soil prior to deposition. For example, any one or more of the above substances can be introduced into the post sterilization storage tank, when present, and mixed with the soil, care being taken to ensure that the soil does not form clumps that are difficult to dispense.

More usually however the substance(s) can be applied to the sterilized soil (for example in the form of a spray) as it is being deposited onto the weed barrier, or after (e.g. immediately after) it has been deposited onto the weed barrier. Thus, any one of more of the aforesaid substances can be incorporated into an aqueous solution or suspension that can be sprayed on to the sterilized soil after it has been deposited on the weed barrier, so as to rehydrate the soil. Alternatively, or additionally, the substance(s) can be applied to the weed barrier before or at the same time as the soil is deposited on to the weed barrier.

The weed barrier laying device may comprise a roller or other pressing element for applying light pressure to the upper surface of the weed barrier as it is laid onto the underlying soil substrate in order to bring it into firm contact with the substrate. When the weed barrier is laid into shallow furrows created by the soil collecting device or another furrow-forming element mounted on the carriage, the pressing element is used to gently but firmly press the weed barrier into the furrow. The pressing element may also serve as a guide roller around which weed barrier from a roll is directed so that the weed barrier is brought into contact with the furrow.

Once the weed barrier has been laid on to the underlying soil substrate (for example into one or more furrows), the sterilized soil depositing device then deposits soil on top of the weed barrier, typically to give a depth of about 3-30 mm, and more usually 5-15 mm of soil. During or after the depositing of the soil, an irrigation device mounted on the carriage can be used to spray water onto the soil to dampen it and thereby provide more mass for holding the weed barrier in place, as well as providing moisture to facilitate germination of seeds carried by the weed barrier. The irrigation water can contain any one of more the plant growth promoting substances, microbiological substances or pesticidal substances referred to above.

When the weed barrier does not carry seeds, seeds can be introduced (for example using a seed drill) into the layer of sterilized soil covering the weed barrier, for example by depositing seeds onto the layer of sterilizing soil and optionally covering the seeds with a further charge of sterilized soil, or by depositing seeds onto the weed barrier before depositing the soil thereby to cover the seeds with sterilized soil.

In addition to providing a method for the suppression of weed growth in an underlying soil substrate, the invention also provides an apparatus for use in the method.

Accordingly, in another aspect, the invention provides an apparatus for use in suppressing weed growth on an underlying soil substrate; which apparatus comprises:

(i) a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; a weed barrier laying device; and optionally an irrigation device; wherein optionally either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(ii) the carriage being capable of being moved along or close to a path on which a weed barrier is to be laid;

(iiia) the soil collecting device being arranged to collect soil from the underlying soil substrate and direct the soil towards the soil sterilizer device; (iiib) the furrowing device when present being configured to create a furrow in the underlying soil substrate as the carriage moves along a chosen path;

(iv) the soil sterilizer being operable to kill weeds present in the soil and provide a stock of sterilized soil;

(v) the weed barrier laying device being arranged to lay a weed barrier onto the underlying soil substrate (e.g. in the furrow);

(vi) the sterilized soil depositing device being arranged to deposit sterilized soil on to the laid weed barrier so as to cover the weed barrier and hold it in place on the substrate; and optionally

(vii) wherein the irrigation device when present is arranged to irrigate the sterilized soil deposited on to the weed barrier.

In one embodiment, the invention provides an apparatus for use in suppressing weed growth on an underlying soil substrate, which apparatus comprises:

(i) a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; a seed-bearing weed barrier laying device; and optionally an irrigation device; wherein either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(iiia) the soil collecting device being arranged to collect soil from the underlying soil substrate and direct the soil towards the soil sterilizer device;

(iiib) the furrowing device being configured to create a furrow in the underlying soil substrate as the carriage moves along a chosen path;

(v) the seed-bearing weed barrier laying device being arranged to lay a seed bearing weed barrier onto the underlying soil substrate (e.g. in the furrow);

(vi) the sterilized soil depositing device being arranged to deposit sterilized soil on to the laid seed-bearing weed barrier so as to cover the weed barrier and hold it in place on the substrate; and optionally (vii) wherein the irrigation device when present is arranged to irrigate the sterilized soil deposited on to the seed-bearing weed barrier.

In another embodiment, the invention provides an apparatus for use in suppressing weed growth on an underlying soil substrate; which apparatus comprises:

(i) a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; a weed barrier laying device; and optionally an irrigation device; wherein either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(v) the seed-bearing weed barrier laying device being arranged to lay a weed barrier onto the underlying soil substrate (e.g. in the furrow);

(vi) the sterilized soil depositing device being arranged to deposit sterilized soil on to the laid weed barrier so as to cover the weed barrier and hold it in place on the substrate;

(vi-a) a device for introducing seeds onto the weed barrier prior to, during or after deposition of the sterilized soil onto the weed barrier so that the seeds are embedded in and preferably covered by the sterilized soil; and optionally

(vii) wherein the irrigation device when present is arranged to irrigating the sterilized soil deposited on to the weed barrier.

Particular and preferred features of the apparatus of the invention are as set out above in relation to the method aspects of the invention.

Brief Description of the Drawings

Figure 1 is a plan view showing an apparatus according to a first embodiment of the invention, having multiple soil collection devices. Figure 2 is a side view of the apparatus of Figure 1 showing the soil collection devices mounted on the front of the apparatus.

Figure 3 is a front view of the apparatus of Figures 1 and 2.

Figure 4 is a sectional view along line A-A in Figure 2.

Figure 5 is a sectional view along line B-B in Figure 2, but omitting the soil sterilisation drum and associated hoppers for clarity.

Figure 6 is a side sectional view of the soil sterilisation drum.

Figure 7 is a view from one end of the soil sterilisation drum.

Figure 8 is a series of schematic views showing use of the apparatus in creating a furrow in the soil followed by the laying of a weed barrier, and the laying of soil and seed on top of the weed barrier, and the subsequent germination of the seed.

Figure 9 is a plan view of an apparatus according to a second embodiment of the invention, having a single soil collection device.

Figure 10 is a front view of the apparatus of Figure 9.

Figure 11 is a plan view of an apparatus according to a third embodiment of the invention having separate soil collection and furrowing devices.

Figure 12 is a side view of the embodiment of Figure 12.

Figure 13 is a series of schematic views showing the use of the apparatus of Figures 10 and 11 in creating a furrow in the soil followed by the laying of a weed barrier, and the laying of soil and seed on top of the weed barrier, and the subsequent germination of the seed.

Detailed Description of the Invention

The invention will now be illustrated but not limited by reference to the accompanying drawings 1 to 13.

Figures 1 to 7 illustrate an apparatus according to a first embodiment of the invention. The apparatus comprises a moving carriage (2) which, in this embodiment, is a tractor.

A soil collecting device (4) is mounted on the front of the tractor. The soil collecting device (4) comprises a support structure on which are mounted a plurality (in this case four) of soil scoops (6), each scoop being connected to an associated auger (8) or other conveying device for conveying soil from the scoop (6) towards outlets (10) and (12) for fine and coarse materials respectively. The auger is enclosed within a tubular casing which has arrays of holes that act as sieves; holes of a smaller diameter providing a sieve through which fine materials can fall out through outlet (10) but coarser materials (e.g. clods and stones) cannot pass. One or more holes of a larger diameter enable coarser materials to fall out through outlet (12). In the embodiment illustrated, there are four scoops (6) and four associated augers. The outlets (12) are positioned and oriented so that the stones and other coarser materials fall between the furrows rather than into them.

Mounted transversely on the support structure is a continuous (closed loop) transfer belt (14) and associated drive mechanism (not shown). The transfer belt (14) is positioned beneath the outlet (10) for fine materials and the direction of travel of the transfer belt (14) is shown by the arrows.

Mounted at the end of the transfer belt (14) is an open topped hopper (16) for receiving fine materials from the transfer belt (14). The hopper (16) has an outlet which connects to an elevator conveyor (18) which carries the fine soil materials to a milling and crushing unit (20) containing a pair of contra-rotating rollers (21) (see Figure 2) which crush the soil particles to a desired particle size range (for example up to 1-2mm). The outlet of the milling and crushing unit (20) is connected to a sieve (22) which separates smaller particles so that they fall through holes (not shown) in the sieve down an angled chute (not shown) onto another elevator conveyer (26) which is offset laterally with regard to the elevator conveyor (18). Larger particles do not fall through the holes but instead are conveyed to the end of the conveyer elevator where they fall down through outlet (24) onto the ground between the furrows. The smaller particles of soil are then conveyed by elevator (26) up to a storage hopper (28) mounted on the rear of the tractor (2).

As can be seen more clearly in Figure 2, the storage hopper (28) is positioned above a sterilizer device which comprises a rotating drum (30) having an array of inwardly projecting baffles (32). The storage hopper (28) has a discharge outlet (34) through which metered amounts of soil can be introduced into the higher end of the drum (30). The flow of soil through the discharge outlet is controlled by a flow-controlling device (29). The flow controlling device (29), which can be for example a rotary valve or a gate valve, or other metering device, can be seen in Figure 4.

As can be seen from Figure 6, the rotation of the drum (30) is driven by a mechanism comprising a motor-driven gear (31) which engages a toothed sprocket (33) extending around the outer surface of the drum. The drum (30) rotates about an axis which is inclined at an angle (Q) from the horizontal which can range from about 5° to about 25°, typically about 10 to 20°.

A gas- or diesel-fuelled burner (36) (fuel storage and supply pipe not shown) protrudes into the open lower end of the drum. A stream of hot gases produced by the burner (36) passes along the interior of the drum and exits the drum through the opening (37) at the upper end of the drum. Soil entering the drum at its upper end is tumbled through the stream of hot gases and is churned by the baffles (32) as it moves under the influence of gravity to the opening (38) at the lower end of the drum.

The angle of inclination (Q) of the drum (30), the speed of rotation of the drum and the temperature of the gases produced by the burner (36) are selected so that a combination of the residence time of the soil in the drum and the temperature of the burner gases brings about the destruction of weeds, seeds and other plant propagating matter present in the soil.

Soil leaving the drum through opening (38) falls into a temporary storage hopper (40) which is fitted with a temperature sensor (42). The temporary storage hopper (40) is insulated and the sterilized soil entering the hopper (40) can be held in the hopper for a given period of time to allow completion of the sterilization to take place, and the temperature of the soil to fall to a desired figure, and then discharged into or onto a transfer conveyer (44) (which can be for example an auger) and conveyed to the storage hopper (46). Alternatively, the soil entering the temporary storage hopper (40) can be discharged straightaway into the transfer conveyor (44).

The storage hopper (46) can be provided with a means for adding a small and controlled amount of moisture back into the soil, but without causing clumping of the soil. The means for adding moisture can take the form of a steam jet inlet (47) as shown in Figure 5. Various additives of the type described above can also be added to the soil at this stage. Thus, the water jet inlet can be linked to a tank (not shown) containing a solution of such additives. More usually however, the soil inside the storage hopper (46) is maintained in a dry state so as to maintain flowability. The hoppers (28), (40) and (46) are mounted on a support structure attached to the rear end of the tractor. Also mounted on the rear support structure is a transversely oriented conveyor (48) (which could be for example an auger) which conveys sterilized soil from the storage hopper (46) to a plurality (four in the embodiment shown in Figures 1 and 3) of sterilized soil-dispensing openings (50) spaced apart along the length of the conveyor (48). Each of the openings has an associated sterilized soil depositing tube (52) extending downwardly therefrom (see Figures 2, 3 and 5).

A plurality of weed barrier tape dispensers (54) bearing rolls of weed barrier tape (56) are mounted on the rear support in front of the soil depositing tubes (52). A ground engaging pressure roller (58) presses the weed barrier tape into the shallow recesses created by the scoops (6).

Mounted immediately rearwardly of the soil depositing tubes (52) is a precision seeding device comprising a plurality of precision seeding heads (60) (four in the embodiment illustrated) by means of which seeds can be dispensed onto the weed barrier tape in a desired pattern and density. Many different types of precision seeding devices suitable for use in the apparatus of the invention are commercially available and examples include precision pneumatic seeders, for example the precision seeders available from Agricola Italiana of Massanzago, Italy.

The soil depositing tubes (52) and the seeding heads (60) are preferably close together so that soil deposited by the tubes (52) covers the seeds as they are laid, thereby avoiding the need to drill into and disrupt the soil layer when depositing the seeds. A plurality of irrigation spray heads (62) (not shown in Figure 1 but shown in Figure 2) are mounted rearwardly of the soil depositing tubes (52) and the seeding heads (60). The irrigation spray heads (62) are connected to one or more tanks of water (not shown) and/or solutions of suspensions of one or more of the additives (including plant growth- promoting agents and pesticides) described above.

The manner in which the apparatus illustrated in the Figures 1 to 7 is used in the method of the invention is illustrated in Figure 8.

Thus, as the tractor (2) advances across a field or equivalent agricultural surface, the soil scoops (6) at the front of the apparatus scoop up soil and, in doing so, create shallow furrows (F) in the soil as shown in Figure 8(A). The soil is conveyed through the apparatus and is sterilised as described above, before being carried to the storage hoppers (46) as shown in Figure 1. As the apparatus moves over the furrows, the weed barrier tape (which is typically formed from a paper material) is laid into the furrows and is pressed down against the floors of the furrows by the ground-engaging roller (58), as shown in Figure 8(B). Sterile soil (E) from the storage hopper (46) is then deposited onto the weed barrier tape (56) through the soil dispensing tubes (52) so as to cover the tape (56). Seeds (S) are also deposited on the weed barrier tape (56) by means of the seeding heads (60) as shown in Figure 8(D). By positioning the outlets for the seed dispensing tubes sufficiently close to the seeding heads (60), the seeds are covered in soil as they are deposited. Finally, water (which may contain one or more additives as described above) is sprayed onto the sterilized soil from irrigation spray heads (62) so as rehydrate the soil and provide it with sufficient weight and cohesiveness to resist being blown away, thereby ensuring that it can hold the weed barrier tape firmly in place.

The method of the invention creates an area of weed-free soil on top of a weed barrier through which the roots of seedlings (R) that have germinated from the seeds are able to grow into the soil beneath the barrier tape, but whereby weeds are unable to grow up through the barrier. The seeds (S) can therefore germinate to produce seedlings (R) free from competition from weeds, apart from a possible very small number of weed plants that may develop from airborne seeds that may land on the sterilized soil after it has been laid. If weeds grow in the soil either side of the furrow, these can be removed if desired by mechanical means such as hoeing.

The apparatus shown in Figures 1 to 7 has four soil scoops (6). In this embodiment, the furrows in which the weed barrier is subsequently laid are created by the action of the soil scoops. However, in a second embodiment of the invention, as shown in Figures 9 and 10, the soil collecting device (104) has a single soil scoop (106), and this is mounted on one side of the tractor (102). The soil scoop (106) in connected to an associated auger (108) or other conveying device for conveying soil from the scoop (106) towards outlets (110) and (112) for fine and coarse materials respectively. The auger (108) is enclosed within a tubular casing which has arrays of holes that act as sieves; holes of a smaller diameter providing a sieve through which fine materials can fall out through outlet (110) and into hopper (114) but coarser materials (e.g. clods and stones) cannot pass. One or more holes of a larger diameter enable coarser materials to fall out through outlet (112). Soil passes out through the bottom of the hopper (114) onto elevator conveyor (116) which carries the fine soil materials to a milling and crushing unit (120). The milling and crushing unit (120) corresponds to the milling and crushing unit (20) in the embodiment illustrated in Figures 1 to 7. From the milling and crushing unit (120) onwards, the apparatus of Figures 9 and 10 is substantially the same as the apparatus illustrated in Figures 1 to 7 and, apart from the differences in the soil collection arrangement and the consequential differences discussed below, the apparatus of Figures 9 and 10 works in substantially the same way as the apparatus of Figures 1 to 7.

One significant difference between the embodiment of Figures 9 and 10 and the embodiment of Figures 1 to 7, apart from the differences in number and location of the soil scoops and the consequent differences in configuration of the conveyors and sieves, is that the soil scoops (106) of the embodiment of Figures 9 and 10 can be made wider and/or deeper than the corresponding soil scoops (6) in the apparatus of Figures 1 to 7, so that they can scoop up much larger quantities of soil. As the deeper and wider furrows made by the scoops (106) are not subsequently used for laying the weed barrier, they can be backfilled with stones, clods of earth and larger sized materials separated by the sieves and discharged through the outlets (110) and (112). An advantage of this is that it avoids the possibility of stones and larger soil particles and clumps of soil falling into the furrows in which the weed barrier tapes are to be laid. In this embodiment, the shallow furrows (F) into which the weed barrier tapes are laid are formed by ground-engaging pressure rollers corresponding to those identified by the reference numeral (58) in Figures 1, 2, and 8.

Figures 11, 12 and 13 show the construction and use of an apparatus according to a third embodiment of the invention.

The apparatus comprises a moving carriage (102), e.g. a tractor with attached support frame (121). To the front end of the support frame (121) is attached a depth setting roller (102), the vertical position of which can be adjusted to increase or decrease the extent of engagement of the soil collecting and furrowing devices with the underlying soil substrate.

In this embodiment, the soil collecting device comprises a high speed rotating cultivator head (103) with a plurality of blades that cut into the underlying soil substrate and throw up a stream of soil particles. Located rearwardly of the rotating cultivating head is a particle size separator chamber (104), at the rearward end of which is a curved baffle plate (105). Smaller soil particles thrown up by the rotating cultivator head pass over the top edge of the baffle plate (105) and fall onto the transverse drag elevator/sieve (106). However, stones and larger particles or clumps of soil are thrown against the baffle plate (105) and do not pass over the top edge of the baffle plate (105). Instead they are discharged back onto the underlying soil substrate.

The smaller soil particles passing over the top edge of the baffle and entering the transverse drag elevator/sieve (106) are further graded so that larger particles are retained on the sieves and are then discharged to waste while finer particles of a desired size (for example particles capable of passing through a 5-10mm sieve) are deposited into the vertical auger (107). The vertical auger (107) conveys the fine particles of soil upwardly and discharges them through a conduit (107a) into a sterilizer device which comprises a rotating drum (117) having an array of inwardly projecting baffles around its inner walls in a similar manner to the sterilizer device of the first and second embodiments described above. In a similar manner to the embodiment of Figures 1 to 10 (see Figure 6 in particular), the rotation of the drum (117) is driven by a mechanism comprising a motor-driven gear (not shown) which engages a toothed sprocket (also not shown) extending around the outer surface of the drum. The drum (117) rotates about an axis which is inclined at an angle (Q) from the horizontal which can range from about 5° to about 25°, typically about 10 to 20°.

A gas- or diesel-fuelled burner (118) (linked by a supply pipe (not shown) to a fuel storage tank (120), protrudes into the open lower end of the drum. A stream of hot gases produced by the burner (118) passes along the interior of the drum and exits the drum through an opening (not shown) at the upper end of the drum. Soil entering the drum at its upper end is tumbled through the stream of hot gases and is churned by the baffles as it moves under the influence of gravity to the open lower end of the drum (117).

The angle of inclination (Q) of the drum (117), the speed of rotation of the drum and the temperature of the gases produced by the burner (118) are selected so that a combination of the residence time of the soil in the drum and the temperature of the burner gases brings about the destruction of weeds, seeds and other plant propagating matter present in the soil.

Heat-treated soil leaving the drum through the open lower end of the drum (117) falls into an auger (116) which transfers the soil to into a temporary storage hopper (115) which is fitted with a temperature sensor. The temporary storage hopper (115) is insulated and the sterilized soil entering the hopper (115) can be held in the hopper for a given period of time to allow completion of the sterilization to take place, and the temperature of the soil to fall to a desired figure. The hopper (115) is provided at its lower end with a discharge valve (114) which can be, for example, a sliding gate valve or a rotary valve. A soil depositing tube (113) extends downwardly from the valve (114).

The apparatus of Figures 11 to 13 is provided with a furrowing device comprising a plurality of pairs of coulter discs (108) (one pair of which is shown in Figure 12) which are mounted on an axle secured to the support frame (121) behind the transverse drag elevator/sieve (106). The coulter discs can be of conventional type and can be secured to the support frame (121) by a fixed link, in which case the positioning of the depth setting roller (102) will determine the depth of the furrow created by the coulter discs, or a mechanism (not shown) can be provided for varying the vertical position of the coulter discs thereby providing an additional means of varying the depth of the furrow.

Mounted on the support frame (121) behind the furrowing device are a plurality of weed barrier tape dispensers bearing rolls (110) of weed barrier tape. Also mounted on the support frame (121) (mounting not shown) are a plurality of ground engaging guide rollers (109) for pressing the weed barrier tape into the furrows created by the furrowing device (108) as the seed barrier tape is unwound from the rolls (110).

As with the apparatuses illustrated in Figures 1 to 7, the apparatus of Figures 11 to 13 is provided with a plurality of precision seeding heads (111) (four in the embodiment illustrated) but in this embodiment they are mounted forwardly of the soil depositing tubes (113). The precision seeding heads (111) deposit seeds in predetermined numbers and at predetermined spacings on to the seed barrier tape before sterilised soil from the soil depositing tubes (113) is deposited on to the tape to cover the seeds. As with the apparatus of Figures 1 to 7, a water spraying device may be mounted on the support frame to rehydrate the heat-treated soil after it has been deposited on to the tape.

The sequence of steps taking place on the underlying soil substrate is illustrated in Figure 13. Thus, in Step A, the pairs of coulter discs of the furrowing device cut profiled furrows in the soil substrate. Seed barrier tape that has been unwound from the rolls (110) is then pressed into the furrow by the ground engaging guide roller (109) (Step B), following which seeds are deposited onto the tape by the precision seeding heads (Step C) and the seeds are then covered by soil from the soil depositing tubes (113) (Step D). The seeds are subsequently able to germinate to give seedlings (Step E), the fine roots of which can penetrate the seed barrier tape. However, weeds are unable to grow up through the seed barrier tape.

The invention is further illustrated by the Examples set out below. EXAMPLE 1

In this experiment, samples of soil containing seeds were exposed to different heating regimes to investigate the effect of heating on seed viability. Cress seeds were used to mimic the effect of heating of weed seeds.

Method and materials: Soil: Pitt Hall Farm, Basingstoke, UK.

Sieved through 5mm sieve

Seeds: Mr Fothergill Cress seeds

Oven: Neff fan assisted oven with digital thermostat

Gas Torch: Butane/Propane mix hand held plumbers torch. The moist field soil was obtained from the top 10 cm layer of the field and sieved through a 5mm sieve before use. Each treatment was replicated 3 times and the control 6 times. Each treatment consisted of 30g of soil amended with 10-15 cress seeds mixed thoroughly and placed in an 11cm foil tray. The trays were then subjected either to no heating (control trays) or to oven heating or direct flame heating under the conditions set out in Table 1 below.

Oven treatments were placed in the centre of the oven for the requisite time and were not stirred during or after treatment. Gas torch treatments were stirred continuously with a metal spatula during heating.

After heating the trays were arranged randomly in a room at 21 °C and mist watered with approximately 8 mis per tray. Trays were mist watered daily until assessments at 6 and 9 days post treatment were completed.

Table 1:

Treatment Tray Heating Numbers of seeds

T (°C) Time Unit Number Number method germinated t+5 _T+9 9 day days average

1 Room None 0 minutes 3 7

2 Room None 0 minutes 4 4

3 Room None 0 minutes 10 10

4 Room None 0 minutes 7 8

5 Room None 0 minutes 10 12

6 Room_ None_ 0 minutes 9 12

7 100 Oven 5 minutes 0 0

8 100 Oven 5 minutes 3 3 9 100_ Oven_ 5 minutes 1 2

10 100 Oven 10 minutes 0 1

11 100 Oven 10 minutes 0 1

12 100_ Oven_ 10 minutes 1 2

13 100 Oven 30 minutes 0 0

14 100 Oven 30 minutes 0 0

15 100_ Oven_ 30 minutes 0 0

16 100 Oven 60 minutes 0 0

17 100 Oven 60 minutes 0 0

18 100_ Oven_ 60 minutes 0 0

19 120 Oven 5 minutes 0 0

20 120 Oven 5 minutes 0 0 21 120_ Oven_ 5 minutes 0 0

22 120 Oven 10 minutes 0 0

23 120 Oven 10 minutes 0 0

24 120_ Oven_ 10 minutes 0 0

25 120 Oven 30 minutes 0 0

26 120 Oven 30 minutes 0 0 27 120_ Oven_ 30 minutes 0 0

28 120 Oven 60 minutes 0 0

29 120 Oven 60 minutes 0 0

30 120_ Oven_ 60 minutes 0 0

31 120 Oven 120 minutes 0 0

32 120 Oven 120 minutes 0 0

33 120 _ Oven _ 120 minutes 0 0

34 High Gas torch 10 seconds 4 4

35 High Gas torch 10 seconds 2 2

36 High Gas torch 10 seconds 0 0

37 High Gas torch 20 seconds 0 0

38 High Gas torch 20 seconds 0 0

39 High Gas torch 20 seconds 0 0

40 High Gas torch 40 seconds 0 0

41 High Gas torch 40 seconds 0 0

42 High Gas torch 40 seconds 0 0

43 High Gas torch 60 seconds 0 0

The results showed an average of 9 seeds germinating in control trays (range from 3- 12). Any oven treatment in excess of 10 minutes at 100 °C resulted in complete control of germination. Any gas torch treatment in excess of 10 seconds resulted in complete control of germination.

Example 2

In this experiment, soil samples containing seeds were subjected to thermal sterilization using a rotating drum sterilizing chamber heated by a gas burner of the type shown in Figures 1 to 10. Cabbage, lettuce and mixed grass seeds were added to soil to mimic the effect of heat sterilization on weeds.

Method and materials:

Soil: Pitt Hall Farm, Basingstoke, UK.

Sieved through 5mm sieve

Seeds: Cabbage, Lettuce, mixed grass seeds Seed tray: 23 x 17.5 cm Gas Torch: SuperShrink Propane hand held pallet wrap torch Seed mixer: SIP 63L cement mixer (Tool Station)

The moist field soil was obtained from the top 10-15 cm layer of the field and sieved through a 5mm sieve before use. 15 kg of soil was placed in the mixer and mixed thoroughly with 95 g of seed mixture. Four treatments and an untreated sample were replicated 5 times.

Soil treatment was accomplished using the apparatus shown schematically in Figure 6 and comprising a 1 metre long rotating flue lined with longitudinal paddles to ensure adequate soil circulation in the hot air stream. The hot air was generated using a propane fuelled heat gun at the lower end of the flue and various treatment regimes were achieved by either adjusting the flame temperature (gas flow rate) or altering the angle of the flue to adjust the soil residence time. The soil temperatures of the heat- treated samples were measured on emergence from the rotating flue using a digital infra-red thermometer.

The treatment conditions and results are shown in Table 2 below. After heating, the trays containing the treated and untreated soil were randomly positioned outdoors, uncovered and under mist irrigation and watered twice per day. A single assessment of numbers of germinated seeds per tray was made after 56 days.

Table 2

In the untreated trays, an average of 47 germinated seeds per tray was observed after 56 days. By comparison, in the trays containing soil heated to 105 °C over a period of 105 seconds, no germinated seedlings were observed in the trays after 56 days. In the trays containing soil that that had been subjected to a temperature of 88 °C and heating time of 80 seconds, an average of 1 germinated seed was observed after 56 days whereas, for the trays containing soil that had been heated to 75 °C, the number of germinated seeds observed at 56 days depended on the length of time for which the soil had been heated. In the trays containing soil that had been heated at 75 °C for 60 seconds, an average of 6 germinated seeds per tray was observed whereas, in the trays containing soil that had been heated at 75 °C for 80 seconds, an average of only 1 germinated seed per tray was observed.

The results indicate that the apparatus shown in Figures 1 to 10 should provide an efficient means of sterilizing soil and preventing germination of unwanted seeds for a prolonged period of 56 days, which is more than enough to allow for the germination and growth of crop seeds planted in the sterilized soil.

It will readily be apparent that numerous alterations and modifications could be made to the compositions, apparatus and methods shown in the accompanying drawings and described in the Examples without departing from the principles underlying the invention and all such modifications and alterations are intended to be within the scope of this application.

Claims

1. A method of suppressing weed growth on an underlying soil substrate, which method comprises:

(vii) irrigating the dispensed sterilized soil and weed barrier.

2. A method of suppressing weed growth on an underlying soil substrate, which method comprises:

(i) providing a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil dispensing device; and a weed barrier laying device; wherein either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(ii) moving the carriage along or close to a path on which a weed barrier is to be laid; (iiia) collecting soil from the underlying soil substrate using the soil collecting device; (iiib) creating a furrow in the underlying soil substrate;

(v) laying the weed barrier onto the furrow in the underlying soil substrate using the weed barrier laying device; (vi) depositing sterilized soil on to the laid weed barrier using the sterilized soil dispensing device so as to cover the weed barrier and hold it in place on the substrate; and optionally

(vii) irrigating the dispensed sterilized soil and weed barrier.

3. A method of suppressing weed growth on an underlying soil substrate, which method comprises:

(i) providing a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; and a seed-bearing weed barrier laying device; wherein either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(iiia) collecting soil from the underlying soil substrate using the soil collecting device;

(iiib) forming a furrow in the underlying soil substrate; (iv) passing the soil through the soil sterilizer to kill weeds present in the soil and provide a stock of sterilized soil;

(v) laying the seed-bearing weed barrier into the furrow in the underlying soil substrate using the weed barrier laying device;

(vii) irrigating the dispensed sterilized soil and seed-bearing weed barrier.

4. A method of suppressing weed growth on an underlying soil substrate, which method comprises: (i) providing a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; and a weed barrier laying device; wherein either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(iiia) collecting soil from the underlying soil substrate using the soil collecting device; (iiib) forming a furrow in the underlying soil substrate;

(v) laying the weed barrier into the furrow in the underlying soil substrate using the weed barrier laying device;

(vi-a) introducing seeds onto the weed barrier prior to, during or after deposition of the sterilized soil onto the weed barrier so that the seeds are embedded in and preferably covered by the sterilized soil; and optionally

(vii) irrigating the dispensed sterilized soil and weed barrier.

5. A method according to any one of claims 1 to 4 wherein the soil-collecting device is configured to collect soil such that one or more furrows are created in the underlying soil substrate, into one or more of which the weed barrier is laid by the weed barrier laying device.

6. A method according to any one of claims 1 to 4 wherein the moving carriage has mounted thereon a furrowing device, which furrowing device is separate from the soil collecting device.

7. A method according to claim 6 wherein the furrowing device is mounted rearwardly of the soil-collecting device.

8. A method according to claim 5 or claim 6 wherein the furrowing device comprises one or more ploughshares or blades or one or more coulter discs or pairs of coulter discs.

9. A method according to any one of claims 6 to 8 wherein the soil-collecting device comprises a flail or rotating cultivator head which cuts and/or scrapes the underlying soil substrate to create an airborne stream of soil particles which is directed to a soil- receptacle

10. A method according to any one of the preceding claims wherein prior to entering the soil sterilizer, the soil collected by the soil collecting device is pre-treated by one or more pre-treatment devices to remove stones and other unwanted materials from the soil and/or to break down lumps of soil into smaller soil particles.

11. A method according to any one of the preceding claims wherein the soil sterilizer comprises a sterilization chamber along which soil is advanced from an inlet to an outlet, whereby the soil is exposed to a sterilizing heat source as it advances along the chamber.

12. A method according to claim 11 wherein the soil sterilizer comprises a rotating drum which is arranged at an incline so that soil entering an inlet end of the drum is gradually carried downhill to the outlet end of the drum, the rotating drum being provided with one or more internal baffles to assist tumbling of the soil; and wherein the sterilizing heat source is a burner mounted at one end of the rotating drum (typically the downhill outlet end), such that soil moving down the rotating drum is tumbled through the hot gases from the burner on route to the outlet.

13. A method according to any one of claims 1 to 12 wherein the soil sterilizer comprises a microwave sterilizing device, optionally in combination with a steam generating device.

14. A method according to any one of the preceding claims wherein the soil sterilizer is configured and used to heat the soil to a sterilizing temperature of at least 65 °C, for a period of at least 30 seconds.

15. A method according to claim 14 wherein the soil is heated to a temperature in the range from 65 °C to 120 °C for a period in the range from 30 seconds to 180 seconds.

16. A method according to any one of the preceding claims wherein, after the weed barrier has been laid on to the underlying soil substrate (for example into one or more furrows), the sterilized soil depositing device then deposits soil on top of the weed barrier to give a depth of about 3-20 mm, and more usually 5-10 mm of soil.

17. A method according to any one of the preceding claims wherein, during or after the depositing of the soil, an irrigation device mounted on the carriage is used to spray water onto the deposited soil and/or weed barrier.

18. An apparatus for use in suppressing weed growth on an underlying soil substrate, which apparatus comprises: (i) a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; a weed barrier laying device; and optionally an irrigation device; wherein optionally either the soil-collecting device also acts as a furrowing device or the moving carriage has mounted thereon a separate furrowing device;

(iiib) the furrowing device when present being configured to create a furrow in the underlying soil substrate as the carriage moves along a chosen path;

(iv) the soil sterilizer being operable to kill weeds and propagatable weed materials present in the soil and provide a stock of sterilized soil;

(v) the weed barrier laying device being arranged to lay a weed barrier onto the underlying soil substrate (e.g. in the furrow when present);

(vi) the sterilized soil depositing device being arranged to deposit sterilized soil on to the laid weed barrier using so as to cover the weed barrier and hold it in place on the substrate; and optionally

19. An apparatus for use in suppressing weed growth on an underlying soil substrate, which apparatus comprises:

(iiia) the soil collecting device being arranged to collect soil from the underlying soil substrate and direct the soil towards the soil sterilizer device; (iiib) the furrowing device being configured to create a furrow in the underlying soil substrate as the carriage moves along a chosen path;

(v) the seed-bearing weed barrier laying device being arranged to lay a seed bearing weed barrier onto the underlying soil substrate (e.g. into the furrow);

(vi) the sterilized soil depositing device being arranged to deposit sterilized soil on to the laid seed-bearing weed barrier so as to cover the weed barrier and hold it in place on the substrate; and optionally

(vii) wherein the irrigation device when present is arranged to irrigating the sterilized soil deposited on to the seed-bearing weed barrier.

20. An apparatus for use in suppressing weed growth on an underlying soil substrate; which apparatus comprises:

(i) a moving carriage having mounted thereon; a soil collecting device; a soil sterilizer; a sterilized soil depositing device; a weed barrier laying device; and optionally an irrigation device;

(iiia) the soil collecting device being arranged to collect soil from the underlying soil substrate and direct the soil towards the soil sterilizer;

(v) the seed-bearing weed barrier laying device being arranged to lay a weed barrier onto the underlying soil substrate (e.g. into the furrow);

(vi-a) a device for introducing seeds onto the weed barrier prior to, during or after deposition of the sterilized soil onto the weed barrier so that the seeds are embedded in and preferably covered by the sterilized soil; and optionally (vii) wherein the irrigation device when present is arranged to irrigating the sterilized soil deposited on to the weed barrier.

21. An apparatus according to any one of claims 18 to 20 wherein the moving carriage has mounted thereon a furrowing device which is separate from the soil- collecting device.

22. An apparatus according to claim 21 wherein the soil-collecting device comprises a flail or rotating cultivator head which cuts and/or scrapes the underlying soil substrate to create an airborne stream of soil particles which is directed to a soil-receptacle

23. An apparatus according to any one of claims 18 to 22 wherein the soil sterilizer device is as defined in any one of claims 11 to 15.