Patent Publication Number: US-2020296903-A1

Title: Soil covering and planting apparatus

Description:
FIELD OF THE INVENTION 
     This invention relates to improvements in respect of a soil bed covering and planting apparatus. In various preferred embodiments the invention may be used in a raised ridge soil bed planting application to apply and secure a layer of weed deterring cover material over a soil bed, then to subsequently pierce this cover material and deposit a plant into the soil below. 
     BACKGROUND OF THE INVENTION 
     A variety of agricultural crops are grown using raised ridge soil beds where soil is mounted into a long ridge with a crop planted at the top of this ridge. This approach is useful when bush or small tree crops are grown over several years, providing access for workers and machinery between the ridges formed. 
     As with all forms of agriculture, crops planted on such ridges can have their productivity impacted by weed growth. Although herbicides can be used, these compounds are disliked by consumers and will add to the production costs of the crop. 
     One of approach used to minimise the use of herbicides is through the application of a layer of weed deterrent cover material over the length and width of a raised ridge soil bed. For example sheets of material formed by woven plastic fibres—known generally as ‘weed mat’—are commonly used in these applications. These sheets of cover material prevent windborne seeds from accessing the soil bed and existing weed seeds in the soil bed from germinating and accessing sunlight. Generally the thicker the sheet of weed cover material used, more effective this material is in deterring the growth of weeds. 
     However on large-scale commercial plantings the installation and use of weed deterrent cover materials can be particularly laborious and time-consuming. 
     The material must be laid flat over a projecting mound of soil bed over long distances and can be secured in place by a large number of pins or staples which tension the surface of the material. Furthermore, as the thickness of the cover material increases it becomes increasingly difficult to drive pins or staples through its surface to secure it in place. In various applications there may also be a need to adjust the distance between adjacent pins or staples during installation, adding a further complication when this process is to be automated. Due to these complications it is common for such pins or staples not to be used, and instead for soil to be simply piled onto the edges of the cover material. 
     In a number of applications it is also preferable to deploy a water distribution irrigation conduit with the cover material, with best results being achieved when this conduit is sandwiched between the cover material and the soil bed. However this requirement again complicates the actions required to deploy and secure the cover material. 
     After an area to be cultivation is covered by a weed deterrent material sheet the crop to be raised will still need to be planted, and holes must be formed in the cover material to allow plants to be introduced into the soil bed. Again this planting operation requires a further action of cutting or otherwise forming planting holes, which can be increasingly difficult and require increasing levels of force as the thickness of the cover material used increases. Cutting planting holes can be particularly difficult when the edges of the cover material are only secured by a layer of soil deposited on the edges of the material. In these instances the force applied to make a cut in the cover material can instead result in the cover deforming instead of being cut. 
     In these applications it is also of advantage to perform the operations required from a continuously moving platform. Workers and the machines or tools they operate can be moved over a sheet of weed deterrent material while making holes in the sheet to receive seedling plants. However any tool used to cut or pierce the sheet will be in motion relative to the ground, dragging this tool along the length of the sheet when it is moved down into contact to the sheet. This causes problems by ripping or cutting a much larger or longer hole in the sheet that is necessary to receive a seedling plant—leaving a gap where weeds can also grow up through the sheet and compete with the seedling plant. 
     It would therefore be of advantage to have an improved soil bed covering and planting apparatus which addressed any or all the above issues, or at least that provided an alternative choice to the prior art. In particular it would be of advantage to have an apparatus which could at least partially automate the steps of applying and securing a sheet of weed cover material to a soil bed. It would also be of advantage to have improvements over the prior art which at least partially automated the installation of a water distribution conduit of an irrigation system between a soil bed and a sheet of weed cover material. An improved apparatus which allowed for the formation of planting holes in a sheet of cover material deployed and secured by the same apparatus, and/or which also could deliver plants into such holes in at least a semi-autonomous matter would also be of advantage over the prior art. It would also be of advantage to have improvements over the prior art which minimised the size of planting holes made in a sheet of weed cover material by an apparatus mounted to a continuously moving platform. 
     DISCLOSURE OF THE INVENTION 
     According to one aspect of the present invention there is provided a soil bed covering and planting apparatus adapted to be carried along the length of a soil bed by a conveyer vehicle, the apparatus including 
     a cover material reel configured to retain and supply a sheet of cover material, and
 
a compaction roller configured to feed cover material supplied by the cover material reel over a soil bed and being configured to press the cover material on to the soil bed, and
 
two spike hammers positioned adjacent to and at opposite sides of the compaction roller, each being configured to drive at least one spike through the cover material and into the soil bed to secure the cover material to the soil bed, and
 
an actuation structure associated with each spike hammer configured to urge the spike hammer against a spike, and
 
a piercing assembly arranged to form a series of holes in the sheet of cover material, the piercing assembly being engaged with a drive structure which is configured to reciprocate the piercing assembly to drive one end of the piercing assembly through the sheet of cover material.
 
     According to another aspect of the present invention there is provided a soil bed covering and planting apparatus substantially as described above wherein the piercing assembly defines a hollow bore configured to receive at least one plant to be planted in the soil bed. 
     According to a further aspect of the present invention there is provided a soil bed covering and planting apparatus substantially as described above wherein the end of the piercing assembly driven through the cover material defines a pair of jaws movable between an open configuration and a closed configuration, wherein in the closed configuration the jaws define a piercing blade and in the open configuration the jaws define a delivery port which allows a plant located in the hollow bore to exit the bore and be delivered to the soil bed through a hole formed in the cover material by the piercing assembly. 
     According to a further aspect of the present invention there is provided a soil bed covering and planting apparatus substantially as described above wherein the compaction roller defines a ground contact profile complimentary to the profile of the soil bed being prepared. 
     According to another aspect of the present invention there is provided a soil bed covering and planting apparatus substantially as described above wherein each actuation structure associated with a spike hammer includes a trigger mechanism which controls the placement distance between spikes used to secure one edge of the cover material to the soil bed. 
     According to a further aspect of the present invention there is provided a soil bed covering and planting apparatus substantially as described above which includes an irrigation conduit reel configured to retain and supply a length of irrigation conduit over the soil bed and under the cover material pressed into the soil bed. 
     According to another aspect of the present invention there is provided a soil bed covering and planting apparatus substantially as described above wherein the irrigation conduit is fed out on top of the soil bed offset from the centre of the width of the sheet of cover material. 
     The present invention provides a soil bed covering and planting apparatus configured to apply and secure a sheet of weed deterrent cover material to a soil bed. These types of cover materials are well known and commonly used in agricultural applications and can be formed from a variety of materials. One commonly used form of cover material is known as ‘weed mat’ and is formed by a woven fabric of plastic fibres. 
     Reference in general will predominantly be made to the invention being used to deploy and secure woven plastic fibre weed mat materials. However those skilled in the art will appreciate that the invention may also operate in conjunction with other forms of weed deterrent cover materials in other embodiments. 
     Furthermore in various embodiments the invention need not necessarily be configured to only deploy and secure sheets of cover material over a soil bed. For example in various embodiments the apparatus provided by the invention may also include additional subsystems which facilitate deploying irrigation conduit, forming planting holes, delivering plants into planting holes, and/or forming a ridged soil bed prior to deploying a sheet of cover material. Those skilled in the art appreciate that combinations of one or more of these subsystems may be used in combination with the invention&#39;s cover material installation components. 
     The apparatus provided by the invention is arranged to be carried by a conveyer vehicle over the length of a soil bed as the invention operates. In some embodiments this conveyor vehicle may be utilised to power or drive various components of the invention, whereas in other embodiments this vehicle may be utilised just to convey the various parts of the invention along a soil bed. 
     Reference throughout this specification will in general be made to the invention utilising a conveyor vehicle in the form of tractor, preferably with a power output of at least 200 horsepower. A tractor can move freely over uneven and wet ground and has a capacity to convey heavy loads. Again however those skilled in the art will appreciate that other types of conveyor vehicle, or potentially custom-built vehicle systems may also be used in conjunction with the present invention in other embodiments. 
     In some preferred embodiments the soil bed covering and planting apparatus may also include a ridging structure. This ridging structure can be employed to form a raised ridge of soil from a relatively flat area as the conveyor vehicle moves along the length of a soil bed. For example in some embodiments a ridging structure may incorporate at least two substantially vertically orientated soil collection blades which are angled towards an open apex region. The structure may be deployed to define an open leading throat where these blades collect and channel soil to the apex region as the vehicle moves forward along the soil bed. 
     The apparatus provided by the invention includes a cover material reel which is arranged to retain and also supply a sheet of weed cover material. A sheet of cover material may be wound around this reel, with rotation of the reel winding out the length of the sheet as the conveyor vehicle moves forward along a soil bed. Those skilled in the art will appreciate that rotation of the cover material reel may be induced through the forward motion of the conveyor vehicle in some embodiments, whereas in other embodiments an independent powered rotation system may be used to drive the rotation of this reel. 
     The apparatus provided by the invention includes a compaction roller arranged to feed out the sheet of cover material over the soil bed. The compaction roller is supplied with cover material by the cover material reel, and in some embodiments one or more spreading or translation rollers may be interposed between these elements to deliver the cover material to the compaction roller. This compaction roller is arranged to deliver cover material into the soil bed and may also compress or shape the profile of the soil bed as it rotates. In embodiments where the invention also incorporates a ridging structure the compaction roller may compress the relatively loose mounded soil ridge formed by this component. 
     In a preferred embodiment rotation of the compaction roller may be induced by the motion of the conveyor vehicle as it moves along the length of the soil bed. However in alternative embodiments a separate independent powered rotation system may be provided for the compaction roller if required. 
     The compaction roller defines a ground contact profile which is complementary to the profile or shape of the soil bed to be prepared. For example, when the invention is to be used with a flat soil bed the compaction roller may have a substantially cylindrical form which presents a regular or level ground contract profile across the surface of the roller. However in preferred embodiments when the invention is used with a ridged soil bed the compaction roller may have a cylindrical form with a tapered central waist which complements the shape of the ridged soil bed. In such embodiments the ground contact profile defined by the compaction roller can also act to shape and compact the soil used to form a ridged soil bed. 
     In some preferred embodiments the invention may also include an irrigation conduit reel which is arranged to retain and supply a length of irrigation conduit. For example, in some embodiments it may be desirable to deploy a length of T-tape formed from a conduit which defines a large number of water outlet holes along its length. Water pumped through this T-tape conduit will act to irrigate the adjacent soil bed. 
     When provided with the invention an irrigation conduit reel can be positioned on the apparatus adjacent to the compaction roller so that irrigation conduit will be delivered to the soil bed ahead of the cover material being deployed. The following compaction roller can then act to cover the conduit with cover material and then compress it into the soil bed. 
     Those skilled in the art will appreciate that in preferred embodiments an irrigation conduit reel may be induced to rotate and deploy irrigation conduit through the motion of the conveyor vehicle. However in other embodiments a separate powered rotation system may be provided if required. 
     The apparatus provided by the invention also includes two spike hammers. Each of the spike hammers is configured to drive a form of spike or projection through the cover material deployed by the compaction roller to secure the material in place over the soil bed. Spike hammers can therefore be deployed on either side of the compaction roller at positions where the spike hammers travel over cover material as the conveyor vehicle moves along the soil bed. In this arrangement the two opposed spike hammers can therefore be operated to secure the sides of the sheet of cover material in place over a soil bed as the cover material is deployed by the compaction roller. 
     Those skilled in the art will appreciate that the spikes used to secure the cover material may have different configurations or forms in various embodiments. For example staples defining two vertically orientated spikes joined by horizontal head may be driven through the cover material by a spike hammer in some embodiments. In other embodiments spikes formed by pins terminating in a horizontally orientated head may be driven through the cover material. 
     Reference throughout this specification will predominantly be made to a spike hammer provided by the invention being configured to drive a staple forming two separate projecting spikes through a cover material. Those skilled in the art will however appreciate that the spike hammers provided by the invention may also be used with other forms of spikes in alternative embodiments. 
     The apparatus provided by the invention includes an actuation structure associated with each spike hammer which is configured to urge a spike hammer against a spike. This actuation structure can be used to apply a driving force through the spike hammer and into a spike to push it through the cover material and into a soil bed. In various embodiments such an actuation structure can operate to provide the associated spike hammer with a reciprocating motion, forcefully driving the hammer downwards each time a spike is to be driven through the cover material. 
     In a preferred embodiment a spike hammer&#39;s actuation structure may be formed from a pneumatic drive system where the spike hammer forms at least part of a pneumatic ram assembly. Air pressure can then be used to forcefully drive the hammer ram into a spike and then lift the hammer back to a ready position after this action. 
     Reference in general throughout this specification will also be made to a spike hammer&#39;s actuation structure being formed from a pneumatic drive system with a spike hammer being formed from or being connected to a pneumatic ram assembly. However those skilled in the art will appreciate that a hydraulic drive system may function equally well to provide an actuation structure for a spike hammer, as could equivalent electrical drive systems. 
     Preferably each actuation structure engaged with a spike hammer includes a trigger mechanism which controls the placement distance between spikes used to secure one edge of the cover material to the soil bed. These trigger mechanisms can be used to trigger the application of a driving force by the actuation structure to a spike hammer at particular times or when the conveyor vehicle has traveled a certain distance. 
     For example in a preferred embodiment a trigger mechanism may be formed by a ground travelling wheel which is rotated by the progress of the conveyor vehicle. The completion of a number of revolutions, or rotation through a set arc of degrees by the ground travelling wheel may trigger the operation of an associated actuation structure. 
     In various embodiments a ground travelling wheel may, for example, be connected to a gear assembly connected through to a cam mechanism which repetitively trips a trigger switch operating an actuation structure. The configuration of the gears used can therefore be designed to control the distance traveled by the conveyor vehicle between successive triggers of a spike hammer&#39;s actuation structure. Furthermore this distance may also be adjusted in some embodiments by replacing various gears of the gear assembly. 
     The apparatus provided by the invention includes a piercing assembly configured to form a series of planting holes in the cover material deployed and secured by other components of the invention. This piercing assembly may be operated by a drive structure which moves at least a portion of the piercing assembly in a reciprocal manner so that one end of the assembly is driven through the sheet of cover material to form a planting hole in the underlying soil bed. For example in one embodiment a drive structure for a piercing assembly may include a pneumatic ram which acts of a hammer element configured to reciprocate within a guide channel. Alternatively, in yet other embodiments similar forms of drive mechanism may be used which can rapidity drive a hammer element through a sheet of weed cover material. 
     In a further preferred embodiment a piercing assembly may be formed from or incorporates elongate shaft which defines a hollow interior bore. This interior bore may be formed with dimensions large enough to receive a plant to be deposited into a planting hole formed when the piercing assembly pierces the overlaying cover material. For example in some embodiments such a piercing assembly may define an entry port on the side wall or at the top of the hollow bore through which a plant can be introduced. 
     Those skilled in the art will appreciate that action of gravity and/or the impact of the lower end of the piercing assembly with the cover material and soil bed will cause a plant introduced into the hollow bore to move down to the bottom of the bore. This will eventually result in a plant introduced into the hollow bore being located close to where the piercing assembly contacts the soil bed. 
     In a further preferred embodiment the end of the piercing assembly driven through the cover material may define a pair of jaws which can be moved between an open configuration and a closed configuration. When placed in this open configuration the jaws can define a delivery port which gives access to the hollow interior bore and can allow a plant inside this bore to be delivered to the soil bed. When placed in the closed configuration these jaws may define a piercing blade from their projecting leading edges which will be the first surfaces to contact the sheet of cover material. It is envisioned that the opening and closing of the pair of jaws will therefore be synchronised with the reciprocal motion of the main shaft of the piercing assembly, so that the doors are closed when the assembly is used to form a planting hole, and then opened to deliver a plant after the hole is formed. 
     In a preferred embodiment a drive system associated with the piercing assembly may include a trigger mechanism. This trigger mechanism can be used to control how frequently the piercing assembly operates and therefore how closely spaced plantings will be made in the soil bed. For example in one potential embodiment such a trigger mechanism may incorporate a ground following wheel incorporating a number of magnets mounted on its side which are positioned to rotate past a magnetic sensor. This magnetic sensor can generate a signal based on the passage of a magnet and hence provide an indication of the speed or distance being travelled by the apparatus to interment trigger the operation of the piercing assembly. 
     In a preferred embodiment a lateral adjustment mechanism may be provided as an intermediary component used to engage the piercing assembly with the support frame. For example, in one embodiment the piercing assembly and its associated drive may be cantilevered from a threaded shaft and associated drive system. Forward and backwards operation of this drive system can result in lateral translation in the cantilevered piercing assembly. This feature therefore allows for precise adjustment of the relative position of the piercing assembly to the left and right on the support frame to adjust for deviations in the soil bed being traversed by the apparatus. 
     In a preferred embodiment a resilient tilt mounting may be used as an intermediary component to engage the piercing assembly with the support frame. For example in some embodiments this resilient tilt mounting may suspend the piercing assembly from the support frame. Preferably this form of mounting may include a pivot connection between the piercing assembly and the support frame or any additional intermediary components engage with the support frame. In such embodiments the resilient tilt mounting may also include a resilient return mechanism such as a return spring which can apply force which urges the piercing assembly into a substantially vertical orientation. 
     This feature of the invention may be used to minimize the length of a cut formed in the surface of the cover material as the apparatus moves forward along the length of a soil bed. The pivoting connection provided to the piercing assembly can allow it to tilt as it is withdrawn from the soil after a planting operation, instead of being dragged along the ground as the apparatus moves forward. The resilient return mechanism can then be used to return the piercing assembly to a substantially vertical orientation ready for the next planting operation. 
     In a preferred embodiment a height adjustment mechanism may be used as an intermediary component to engage the piercing assembly with the support frame. The height adjustment mechanism may—for example—incorporate a further pneumatic ram or similar assembly which lifts or lowers the piercing assembly relative to the support frame. This feature therefore allows for precise adjustment of the relative height of the piercing assembly on the support frame to adjust for deviations in height of the soil bed being traversed by the apparatus. This feature can also be used to control the depth of the planting hole formed by the operation of the piercing assembly. 
     In a preferred embodiment the apparatus provided by the invention may also include an air pump and at least one pneumatic accumulator tank. In such embodiments various components of the apparatus may be pneumatically driven, with the air pump and accumulator tank or tanks being used to supply high-pressure air to these components. In such embodiments the air pump can be used to provide a constant supply of pressurised air, and the tank can be accumulate air at high pressures in the tank to await intermittent use by pneumatic systems. 
     In a further preferred embodiment a plurality of pneumatic accumulator tanks may be provided in accordance with the invention. In such embodiments the increased numbers of accumulator tanks are able to provide consistent or stable air pressure to the pneumatic systems provide in accordance with the invention. 
     The present invention may provide many potential advantages over the prior art. 
     The present invention may provide an improved soil covering and planting apparatus which has the ability to at least partially automate the installation of weed deterrent cover materials. This apparatus may also include a number of additional subsystems and further components in various embodiments to form a mound or ridge of soil for a soil bed prior to the application of weed cover materials, apply an irrigation conduit underneath a layer of weed cover material, and/or cut and form planting holes and potentially deliver plants into these holes. Those skilled in the art will appreciate that these various components of the invention may all be combined in some embodiments, or used in other combinations in other embodiments. 
     The staple hammers provided by the invention ensure that the edges of the cover material can be anchored in place securely and will also tension the surface of the cover material sheet. This ensures that the cover material can be cut reliability and quickly as it will resist the cutting action of the piercing assembly and not deform around it. 
     The various drive systems utilised by the invention provide high impulse forces which impart rapid motion to hammer elements and/or piercing assembly jaws. These systems allow the cover material to be anchored and for piercing and planting operations to be completed rapidly as the apparatus moves forward in use. Furthermore, the high impulse forces applied aid significantly in the cutting, piercing or otherwise penetration of relatively thick weed cover materials. 
     In various additional embodiments the invention may also incorporate intermediate mounting systems for a piercing assembly which allow for vertical and horizontal positioning adjustments, as well as for tilting of such assemblies after the completion of planting operations to minimise the size of the hole formed in the cover material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional and further aspects of the present invention will be apparent to the reader from the following description of embodiments, given in by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  shows a side view of a soil bed preparation apparatus as provided in accordance with one embodiment of the invention, and 
         FIG. 2  shows a detailed view of the ridging structure integrated in the apparatus of  FIG. 1 , 
         FIGS. 3 a , 3 b , 3 c , 3 d  and 3 e    show a number of perspective views of the cover reel, compaction roller and irrigation conduit reel provided in the apparatus shown with respect  FIG. 1 , 
         FIG. 4  shows a view of one of the two spike hammers integrated into the apparatus of  FIG. 1 , 
         FIG. 5  shows components of the trigger mechanism which operates one of the spike hammers integrated provided the apparatus of  FIG. 1 , 
         FIG. 6  shows a view of the piercing assembly provided in the apparatus of  FIG. 1 , 
         FIGS. 7 a , 7 b  and 7 c    show the range of motion and configuration of the piercing assembly of  FIG. 6  during various stages of operation, 
         FIGS. 8 a , 8 b  and 8 c    show the motion of the side mounted pneumatic rams and lever arms of  FIG. 6  as the jaws moved from their closed to open positions, 
         FIG. 9  shows components of the trigger mechanism which triggers the actions of the piercing assembly shown with respect to  FIGS. 7 b    and  7   c,    
         FIG. 10  shows a side schematic view of a soil planting and covering apparatus provided in accordance with an alternative embodiment to that shown with respect to  FIGS. 1 to 9 , 
         FIG. 11  shows an end view of the piercing assembly illustrated with respect to  FIG. 10 , 
         FIG. 12  shows a side view of the piercing assembly illustrated with respect to  FIGS. 10 and 11 , 
         FIG. 13  shows perspective and side views of the drive structure which moves the piercing assembly illustrated with respect to  FIGS. 11 and 12 , 
         FIGS. 14 a  through 14 g    illustrate the sequence of operational of movements performed by the piercing assembly of  FIGS. 11-13  relative to the rotation of a ground following wheel trigger mechanism, 
         FIGS. 15 a , 15 b  and 15 c    show front, side and top views of one of the spike hammers shown with respect to  FIG. 10 , 
         FIG. 16  shows components of a spike magazine drive system incorporated into the spike hammer shown with respect to  FIGS. 15 a   - 15   c,    
         FIG. 17  show an exploded schematic view of parts of the spike hammer illustrated in  FIGS. 15 a - c   , and 
         FIGS. 18 a  through 18 e    illustrate the sequence of operational movements performed by the spike hammer of  FIGS. 15 through 17  relative to the rotation of a ground following wheel trigger mechanism. 
     
    
    
     Further aspects of the invention will become apparent from the following description of the invention which is given by way of example only of particular embodiments. 
     BEST MODES FOR CARRYING OUT THE INVENTION 
       FIG. 1  shows a side view of a soil covering and planting apparatus  1  as provided in accordance with a preferred embodiment of the invention. 
     In the embodiment shown the invention defines a main support frame  2  used to locate a ridging structure  3 , irrigation conduit reel  4 , cover material reel  5 , a pair of spike hammers  6  and compaction roller  7 , piercing assembly  8  and pneumatic accumulator tank  9 . These components are mounted on the support frame  2  which is lifted and moved along the length of a soil bed by a conveyer vehicle tractor  10 . The tractor is also used to lift and support an air pump  11  which supplies compressed air to the accumulator tank  9 . 
     In the embodiment shown the apparatus  1  is configured to move along a flat area of soil. As it moves over the soil bed it forms a raised ridge through the action of the ridging structure, applies a length of irrigation conduit supplied by the irrigation conduit reel, and then covers the raised ridged bed with a sheet of weed deterrent cover material supplied by the cover material reel and pressed and pinned into place by the spike hammers and compaction roller. The piercing assembly mounted to the rear of the support frame then operates to cut a series of holes in the cover material at the top of the ridged soil bed and to deposit a plant into the hole formed under each cut. 
       FIG. 2  shows a detailed view of the ridging structure  3  integrated in the apparatus of  FIG. 1 . As can be seen from  FIG. 2  this structure incorporates two sets of paired angled blades  12  which project upwards from the soil towards an open apex region  13  at the rear of the structure. The front of the structure defines an open leading throat which is used to collect soil from a wide span to be mounted into the ridged soil bed. 
       FIGS. 3 a , 3 b , 3 c , 3 d  and 3 e    show a number of perspective views of the cover reel  5 , compaction roller  6  and irrigation conduit reel  4  provided in the apparatus shown with respect  FIG. 1 . In the views shown the progress of the conveying tractor is moving in the direction of left to right. This collection of components is arranged so that the irrigation conduit reel  4  firstly deploys its conduit  14  directly onto the soil bed. The cover reel  5  then supplies a loose sheet of material  15  down to the compaction roller  6  by way of a series of intermediate spreading and tensioning rollers  16 , as shown in  FIG. 3 d   . The compaction roller  6  then compresses the irrigation conduit and cover material onto the soil bed, with a following of spike hammers (not shown) being used to turn to pin the edges of the cover material in place. 
       FIG. 3 e    also shows a perspective view of the compaction roller  6 , and illustrates how in this embodiment defines a ground contact profile which is complementary to the profile or shape of the soil bed to be prepared. The compaction roller has a cylindrical form with a tapered central waist which complements the shape of the ridged soil bed. 
       FIG. 4  shows a view of one of the two spike hammers  7  integrated into the apparatus of  FIG. 1 . As can be seen from  FIG. 5  an array of staple shaped spikes  17  are arranged on a track leading to the spike hammer  7 . An operator urges the staples  17  towards and underneath the spike hammer as it is reciprocated up and down by a pneumatic ram based actuation system  18 . 
       FIG. 5  shows components of the trigger mechanism which operates one of the spike hammers  7  integrated provided the apparatus of  FIG. 1 . 
     Preferably each actuation structure  18  engaged with a spike hammer includes a trigger mechanism  19  which controls the placement distance between spikes used to secure one edge of the cover material to the soil bed. These trigger mechanisms can be used to trigger the application of a driving force by the actuation structure to a spike hammer at particular times or when the conveyor vehicle has traveled a certain distance. 
     In this embodiment the trigger mechanism  19  incorporates a ground travelling wheel  20  which is rotated by the progress of the tractor. This ground travelling wheel rotates a gear  21  connected via a drive chain  22  through to a cam mechanism (not shown) which repetitively trips a trigger switch (not shown) operating the associated spike hammer. The delay time between hammer triggers—and hence the distance between adjacent pins or staples—can be adjusted by changing the size of the gear mounted to the ground travelling wheel. 
       FIG. 6  shows a view of the piercing assembly provided in the apparatus of  FIG. 1 .  FIGS. 7 a , 7 b  and 7 c    show the range of motion and configuration of the piercing assembly integrated into the apparatus of  FIG. 1  during various stages of operation. 
     In the embodiment shown the piercing assembly incorporates an elongate shaft  23  which defines a hollow interior bore. The top of this shaft is open and defines an inlet port  24  which can receive plants into the hollow interior bore of the shaft. The opposite end of the assembly defines a pair of jaws  25 , shown in a closed configuration in  FIGS. 7 a  and 7 b   , and in an open configuration in  FIG. 7 c   . As can be seen from  FIGS. 7 a  and 7 b    the leading edges of these jaws are the first surfaces to contact the sheet of cover material and together define a piercing blade  26 . As can be seen from  FIG. 7 c    the same jaws placed in an open configuration define a delivery port  27  giving access to the hollow interior of the bore and allowing a plant to drop down into the soil bed exposed by the action of the piercing assembly. 
       FIG. 6  shows in more detail components of the piercing assembly  8  which are used to move the shaft  23  up and down and to open and close the pair of jaws  25 . 
     The shaft is connected to the end of a hydraulic ram system  28  which operates to reciprocate the shaft up and down, piercing the cover material and positioning the delivery port  27  adjacent to the underlying soil. 
     A series of lever arms  29  are connected to each jaw  25  located at the lower end of the shaft. An additional side mounted pneumatic ram  30  is provided for each jaw and linked to these lever arms, with the side rams being actuated in a timed manner to synchronise with the vertical reciprocal motion applied by hydraulic ram system  28 . 
       FIGS. 8 a , 8 b  and 8 c    show the motion of the side mounted pneumatic rams and lever arms as the jaws moved from their close to open positions. As can be seen from these figures each side mounted ram can push the topmost lever arm towards the shaft to open the jaws and expose the delivery port. Motion of the side hydraulic ram in the opposite direction will act to close the jaws. 
       FIG. 9  shows components of the trigger mechanism  31  which triggers the actions of the piercing assembly shown with respect to  FIGS. 7 b  and 7 c   . This component therefore controls the distance between each plant deposited by the piercing assembly. This trigger mechanism incorporates a ground travelling wheel  32  which is rotated by the progress of the tractor. 
     A series of magnets  33  are mounted on the side of the wheel  32  at the same distance from the centre of the wheel to align with a magnetic sensor  34  and associated trigger electronics. As the ground wheel rotates each of the sensors shown will move past the magnetic sensor to induce a trigger pulse in the associated electronic which is used to actuate the operation of the piercing mechanism  8 . 
     In the embodiment shown the piercing mechanism is actuated every time a magnet passes the sensor. However the behaviour of this component can be modified in other embodiments by the addition of further magnets to the wheel and/or triggering of the piercing mechanism only after the passage of a set number of magnets has been detected. 
       FIG. 10  shows a side schematic view of a soil covering and planting apparatus  101  as provided in accordance with an alternative embodiment to that shown with respect to  FIGS. 1 to 9   
     Similarly with the embodiment shown with respect to  FIGS. 1 to 9  the apparatus  101  of  FIG. 10  also incorporates a support frame  102  which is used to mount and support the various other components of the apparatus. A ridging structure  103  is mounted to the front or forward end of the support frame and forms the leading component of the apparatus when moved along a soil bed. This ridging structure  103  shapes a loose mound of soil which is then pressed together by a set of compaction rollers  107 . The end insert view  107   a  shown illustrates how each compaction roller  107  defines a ground contact profile which is complimentary to the profile of the soil bed being prepared. In the embodiment shown each compaction roller has a cylindrical form with a tapered central waist which complements the shape of the ridged soil bed. 
     An irrigation conduit reel  104  is provided to deploy a length of irrigation conduit on to the soil bed with the assistance of a series of translation rollers  110 . This conduit is sandwiched between the soil bed and a layer of weed deterrent cover material supplied by a cover material reel  105 . Cover material supplied by the cover material reel  105  is pressed into the soil bed by one of the compaction rollers  107  with the irrigation conduit located underneath the cover material. 
     The apparatus  101  also includes a pair of spike hammers  106  with one shown by the side view provided as  FIG. 10 . The construction and operation of these components of the invention are shown and discussed in more detail respect to  FIGS. 15 to 18 . 
     The final component of the apparatus mounted to the support frame  102  is a piercing assembly  108 . The piercing assembly  108  and spike hammers  106  are connected to and powered by a pneumatic drive system which includes a series of accumulator tanks  109 . The construction and operation of the piercing assembly  108  is shown and discussed in more detail with respect to  FIGS. 11 to 14 . 
     In particular,  FIG. 11  shows an end view of the piercing assembly illustrated with respect to  FIG. 10 , while  FIG. 12  shows a side view of the same piercing assembly. When used the piercing assembly  108  is arranged to form a series of holes in the sheet of cover material. These piercing operations are completed using a drive structure  135  configured to reciprocate the piercing assembly to drive one end of the piercing assembly through the sheet of cover material. 
     The piercing assembly defines a hollow bore  123  configured to receive at least one plant to be planted in the soil bed. Plants are fed into this hollow bore through an entry port  124 . 
     The end of the piercing assembly driven through the cover material defines a pair of jaws  125  which are movable between an open configuration and a closed configuration, as shown in further detail with respect to  FIGS. 14 a  through 14 g   . In the closed configuration shown in  FIG. 11  the jaws define a piercing blade  126  which is driven through the sheet of cover material by the drive structure to form a planting hole in the underlying soil bed. 
     The drive structure  135  includes a pneumatic ram  128  assembly linked to the hollow bore  123  and terminating jaws  125 . This ram is used to reciprocate the hollow bore and jaws up and down as shown with respect to  FIGS. 14 a  through 14 g   . The ram is used to rapidly force the bore downwards and the closed jaws through the cover material so that the action of gravity and the impact with the cover material and soil causes a plant within the hollow bore to move down the bore. The jaws are then moved into the open configuration to define a delivery port (not shown) which allows a plant located in the hollow bore to be delivered to the planting hole formed in soil bed through the hole formed in the cover material.  FIG. 14 e    shows the formation of this delivery port  127  when the jaws are opened. 
       FIGS. 11 and 12  also illustrate the provision of a lateral adjustment mechanism  136  which provides an intermediary component used to engage the piercing assembly  108  with the support frame  102 . In the embodiment shown the piercing assembly and its associated drive structure  135  are suspended from a threaded shaft  137  linked to an electric drive motor  138 . 
     Forward and backwards operation of this motor rotates the driveshaft to produce a lateral translation in the suspended piercing assembly. This feature therefore allows for precise adjustment of the relative position of the piercing assembly to the left and right on the support frame to adjust for deviations in the soil bed being traversed by the apparatus. 
       FIG. 12  also shows the provision of a resilient tilt mounting  139  and a height adjustment mechanism  143  used as intermediary components to engage the piercing assembly  108  with the support frame  102 . In the embodiment shown the resilient tilt mounting is engaged with and suspends the lateral adjustment mechanism discussed above. This component is in turn suspending by a pivot connection  140  from the height adjustment mechanism which is engaged directly with the support frame. 
     The height adjustment mechanism incorporates a further pneumatic ram assembly  144  which lifts or lowers the pivot connection  140  relative to the support frame. This feature therefore allows for precise adjustment of the relative height of the piercing assembly  108  on the support frame  102  to adjust for deviations in height of the soil bed being traversed by the apparatus. This feature can also be used to control the depth of the planting hole formed by the operation of the piercing assembly. 
     The resilient tilt mounting  139  utilises the pivot connection  140  to the height adjustment mechanism  143  in combination with spring returns  141  to minimize the length of a cut formed in the surface of the cover material as the apparatus moves forward along the length of a soil bed. A deformable braking and steading element is also provided, as implemented in this embodiment by rubber tipped stop  142 . 
     As a piercing and planting operation is taking place the support frame is still moving forward along the length of the soil bed and will therefore drag the jaw of the hollow bore along the length of the cover material in front of where a plant has been deposited. This can inadvertently rip or cut a longer hole in the cover material than is desirable if the piercing assembly is rigidly mounted to the support frame. However the resilient tilt mounting allows the resistance experienced by the jaw as the apparatus moves forward to be translated into a backward tilting motion in the piercing assembly. Once the jaws are clear of the soil bed and cover material the return springs will draw the piercing assembly back into a substantially vertical orientation and ready for the next piercing operation. The rubber tipped stop  142  brakes the motion of the piercing assembly as it moves back to a vertical orientation, as well as steadying and damping down vibrations in the piercing assembly when used. 
       FIG. 13  shows additional shuttle components  130  of the drive structure  135  which are used to open and close the jaws of the piercing assembly as the pneumatic ram assembly  128  reciprocates the hollow bore. This pair of shuttle components are each formed by a guide head  145  linked by a drive shaft  146  to a pneumatic ram drive assembly  147 . Each guide head is linked to one of two lever arms  129  which are linked by a sequence of pivot connections to either side of the jaws. The ram  147  associated with each shuttle assembly is operated by control signals supplied by a trigger mechanism  131 , formed in this embodiment by a magnetic sensor  134  mounted on the support frame  102  adjacent to a ground following wheel  132 . This wheel has a magnet  133  mounted to its side in a position where the magnet will rotate past the sensor with every revolution of the wheel. 
       FIGS. 14 a  through 14 g    illustrate the sequence of operational movements performed by the piercing assembly of  FIGS. 11-13  under the action of the drive mechanism and relative to the rotation of this ground following wheel based trigger mechanism  131 . 
       FIG. 14 a    (1) shows the initial positioning of the piercing assembly as a plant is dropped through the entry port of the hollow bore and as the trigger mechanism&#39;s wheel mounted magnet rotates into alignment with the sensor. 
       FIG. 14 b    (2) shows the plant falling through the hollow bore under the action of gravity towards the jaws. At this stage of a piercing operation the rotating magnet is aligned with the sensor and a trigger signal is sent to each of the shuttle mechanisms to pull the guide heads away from the hollow bore and to activate the pneumatic ram to drive the hollow bore downwards. The guide heads of the shuttles are engaged with shoulder regions B of the lever arms as illustrated by  FIG. 13 . 
       FIG. 14 c    (3) shows the pneumatic ram having driven the hollow bore and jaw downwards through a cover material to form a planting hole in the underlying soil bed. The guide heads of the shuttles are engaged with shoulder regions A of the lever arms as illustrated by  FIG. 13 . 
       FIG. 14 d    (4) shows the guide heads beginning to be driven inwards towards the hollow bore and acting against shoulder regions A of the lever arms. 
       FIG. 14 e    (5) shows the piercing assembly after the guide heads have moved inwards and pulled the lever arms inwards towards the hollow bore, forcing the jaws to move from their closed to open configurations. This allows the plant inside the hollow bore to drop out through the exit port defined by the open jaws through the pierced cover material and into the planting hole formed by the jaws. 
       FIG. 14 f    (6) shows the operation of the pneumatic ram to lift the hollow bore upwards while the jaws remain in the open configuration. The upper sections of the tilt arms move past the guide heads of the shuttle mechanisms As discussed with reference to  FIG. 12 , the resilient tilt mounting provided with the piercing assembly allows it to tilt at this stage of the piercing operation to minimise the size of the hole formed in the cover material as the jaws are drawn upwards and away from the soil bed. 
       FIG. 14 g    (7) shows a return to the starting configuration of the piercing assembly prior to the supply of a plant into the interior of the hollow bore. As can be seen from this figure the wheel mounted magnet is again about to rotate into alignment with the sensor to trigger another cycle of the piercing and planting operation completed by the apparatus. 
       FIGS. 15 a , 15 b  and 15 c    show front, side and top views of one of the spike hammers  106  of the apparatus  101  shown with respect to  FIG. 10 . These figures show a number of views of one of the two spike hammers positioned on opposite sides of the support frame  102  and used to drive spikes through the cover material and into the soil bed. 
     The spike hammer incorporates an actuation structure, which is formed in this embodiment by a hydraulic ram  118 . This ram is configured to apply a driving force to a hammer element  148  which contacts the spike  117  to be driven through a sheet of cover material. The operation of the actuation structure is controlled by the components of a trigger mechanism  119 , shown in further detail with respect to  FIGS. 17 and 18   a  through  18   e.    
     The spike hammer also includes a spike magazine drive system  149 , as shown in further detail in  FIG. 16 . A magazine  151  of staple based spikes  117  is provided for use with the spike hammer, with a hydraulically driven pusher head  150  being provided to urge these spikes towards the end of the magazine and towards the hammer element. 
       FIG. 17  show an exploded schematic view of parts of the spike hammer illustrated in  FIGS. 15 a - c   . These figures show the location of the hammer element  148  within a guide channel  152  which positions the top of the hammer element underneath the hydraulic ram  118 . The hammer element is shown in perspective view  148   a  and top view  148   b , while the guide channel is shown in perspective view  152   a , front view  152   b  and top view  152   c . The guide channel positions the bottom end of the hammer element adjacent to the spike magazine, allowing spikes to be introduced under the hammer element for subsequent driving through the cover material. Also shown is operator pedal  153  which allows for control of the spike magazine drive system shown with respect to  FIG. 16 . 
     These figures also show the provision of elements of the spike hammer trigger mechanism  119  which includes a magnetic sensor  154  mounted to the guide adjacent to a magnet  155  mounted to the front face of the hammer element. As illustrated by  FIGS. 18 c , 18 d  and 18 e   , this trigger mechanism also includes a second magnetic sensor  157  mounted to the support frame adjacent to a ground following wheel  156  with a further magnet  158  mounted to the side of this wheel. 
       FIGS. 18 a  through 18 e    illustrate the sequence of operational movements performed by the spike hammer  106  of  FIGS. 15 through 17  relative to the rotation of a ground following wheel trigger mechanism  119 . 
       FIG. 18 a    shows the initial state of the spike magazine prior to the use of the apparatus.  FIG. 18 b    shows the loading of the spike magazine to ready the apparatus for use, with a user engaging the pedal to urge the loaded spikes towards the guide and hammer element. 
       FIG. 18 c    shows the spike hammer ready for use with the ground following wheel  156  rotating the magnet  158  into proximity with the sensor  157 . Magnetic sensor  154  mounted to the guide does not detect the presence of magnet  155  mounted to the hammer element, indicating that the hammer element is located in the raised position shown in  FIGS. 18 a - c    and  18   e.    
       FIG. 18 d    shows the activation of the pneumatic ram  118  by a control signal issued from the magnet sensor  157  determining the magnet  158  is rotating past it. The bottom end of the hammer element is rapidly moved into contact with the adjacent spike and drives it through a sheet of weed mat. Magnetic sensor  154  detects the presence of magnet  155  mounted near the top of the hammer element and indicates that the hammer element is in the lowered position shown with respect to  FIG. 18   d.    
       FIG. 18 e    shows the spike hammer being reset for another operational cycle after the magnet has rotated past the sensor. The spike has been driven into the cover material and is falling behind the apparatus as it moves forward. The spike magazine drive system urges the next adjacent spike into the guide while the hammer element is drawn upwards by the pneumatic ram, with the system arriving back at the same configuration shown with respect to  FIG. 18   c.    
     In the preceding description and the following claims the word “comprise” or equivalent variations thereof is used in an inclusive sense to specify the presence of the stated feature or features. This term does not preclude the presence or addition of further features in various embodiments. 
     It is to be understood that the present invention is not limited to the embodiments described herein and further and additional embodiments within the spirit and scope of the invention will be apparent to the skilled reader from the examples illustrated with reference to the drawings. In particular, the invention may reside in any combination of features described herein, or may reside in alternative embodiments or combinations of these features with known equivalents to given features. Modifications and variations of the example embodiments of the invention discussed above will be apparent to those skilled in the art and may be made without departure of the scope of the invention as defined in the appended claims.