BACKGROUND ART It is becoming more common to not remove crop residue from a field, but instead to mulch the crop residue to improve soil properties. Thus, post-harvested top residue (also called trash), are mulched back into the field, and after a period of time, a new crop is planted in the usual way by forming furrows and planting seed in the furrows.

Fields with trash on them presents certain problems with cultivation. For instance, cultivation is typically done using a number of tynes behind a tractor. The tynes rip through the trash layer (or trash blanket), and into the soil and functions to force some of the trash blanket into the soil.

However, the tynes quickly become clogged with trash accumulating immediately in front of the tynes and the tynes periodically need to be cleaned which slows down the time taken to cultivate a field.

Another problem with field cultivation is to ensure that the upper layer of soil is finely separated and does not include large clods of dirt. Clods disrupt the seeding process, and if not broken, up have a deleterious effect.

Currently, tynes alone do not effectively break up clods but instead bring the clods to the surface.

It is known to provide a towed apparatus having a forward coulter disc, a tyne behind the coulter disc and a crumble roller behind the tyne, the function of which is to break up any clods of dirt which are raised to the surface by the counter or the tyne. The crumble roller can become clogged when the soil is wet.

SUMMARY OF THE INVENTION The present invention is directed to an agricultural implement

which may overcome the abovementioned disadvantages or provide the public with a useful or commercial choice.

In one form, the invention resides in an agricultural implement comprising a rotatable body adapted to roll over a field and at least one soil penetration means which penetrates the soil and which passes compacted soil underneath the body to be broken up thereby.

The soil penetration means can comprise a prong, spike, tyne, knife, rib, helical flight, disc, or any other type of soil penetration means which as, well as penetrating the soil is configured or functions to push or otherwise pass any clods or compacted soil towards and underneath the rotatable body which then breaks or crushes the clods or compacted soil.

The soil penetration means may be attached to the rotatable body and typically at or adjacent one side of the body. To improve efficiency, a number of soil penetration means may be attached to the rotatable body, for instance three or four prongs or tines, and the like, may be spaced about the rotatable body.

In one form, the rotatable body may have an axis of rotation which is between eighty to less than ninety degrees relative to the direction of travel. This slight inclination can provide the mechanism whereby the soil penetration means passes compacted soil to underneath the body. In another form, a helical screw, or the like, can be provided adjacent the rotatable body to pass clods or other compacted soil underneath the body.

The rotatable body is preferably driven by engagement with the ground as opposed to being separately driven by a drive motor, or the like.

The rotatable body may be sufficiently wide to appreciably break up or crush any clods or compacted earth under it. The rotatable body can comprise a drum, cylinder, or a polygonal type elongate body which can roll over the ground. The length of the rotatable body can vary to suit and can be between one centimeter up to one metre, with a preferred range being between ten to forty centimetres. The rotatable body is typically mounted to an axle which is itself supporte by a frame or tool bar, the frame or tool bar- being known in the art.

To increase the crushing action of the rotatable body and/or to provide extra traction, ground enhancing means may be provided and these can include cleats, projections, knobs, and the like.

In another form, the invention resides in a method of cultivating a field containing a crop residue, the method comprising an agricultural tyne adapted to pass through the crop residue and the soil and an adjacent rotatable body adapted to roll over the field and which temporarily holds the crop residue against the ground as the tyne passes through.

The adjacent ratable body may be identical or similar to the one described as above and may have soil penetration means.

By having the combination of the agricultural tyne which rips through the trash blanket and soil (but which has a tendency to become clogged), and the rotatable body being positioned adjacent the tyne (which functions to hold down or temporarily clamp the trash blanket against the ground). It is found that this combination provides improved ripping of the trash blanket and reduces the amount of trash which remains on the tyne as the trash blanket is temporarily held down or clamped as the tyne passes through it.

In another form, the invention resides in an agricultural implement for covering a furrow with adjacent soil, the implement comprising a rotatable body adapted to roll over a field, at least one soil penetration means on the body, the body and/or the soil penetration means being constructed that rotation of the body adjacent the furrow causes the at least one soil penetration means to pass soil adjacent the furrow into the furrow.

In this arrangement the field may or may not include a trash blanket and the rotatable body and its soil penetration means can flick or pass soil from the walls of the furrow back into the furrow in an efficient manner. As well, the rotatable body can function to break up any clods or compacted soil.

Typically, a furrow is formed with a tyne and immediately behind the tyne is a tube through which seeds pass such that the seeds pass into the furrow formed by the tyne. The rotatable body can be positioned adjacent a

tyne such that the system can be used for a field having a trash blanket or residual trash. In this manner, the tyne functions to provide the furrow, the ratable body can function inter alia to minimise clogging of the tyne and also to fill in the furrow after the seeds have been placed in it.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be described with reference to the following drawings in which Figure 1 shows an agricultural implement having a rotatable body and a number of soil penetration means; Figure 2 is a side view of an agricultural implement of Figure 1; Figure 3 shows a pair of agricultural implements attached to a common tool bar; Figure 4 illustrates the agricultural implement of Figures 1 and 2 adjacent an agricultural tyne; Figure 5 illustrates a scraper to keep the rotatable body clean; Figure 6 shows (in slightly exaggerated format) the incline angle of the rotatable bodies relative to the direction of travel ; Figures 7A-7C are side views of the agricultural implement of Figure 1 breaking up a soil clod; Figures 8A-8C are plan views of the agricultural implement corresponding to Figures 7A-7C; Figure 9 illustrates the use of an agricultural implement for covering a furrow with soil.

BEST MODE Referring to the drawings, and initially to Figures 1 and 2, there is shown an agricultural implement 10 which includes a rotatable body 11 which is adapted to roll over a field and a number of soil penetration means in the form of prongs 12 which penetrate the soil.

Implement 10 is mounted to an axle (not shown), one end of which is fixed to a support bracket 13 which is itself fixed to a steel member 14, steel member 14 being fixed to a tool bar 15 (see Figure 3), tool bar 15 being known in the art.

Member 14 is adjusted in length such that body 11 contacts the ground or is adjacent the ground and rolls along the ground as the tool bar 15 is pulled forwardly by a tractor or other type of vehicle.

Body 11 in the embodiment is a cylindrical steel hollow drum having a continuous outer surface to prevent clogging. The drum has opposed ends 16,17 and the length of the drum (that is, the distance between end 16,17) can vary to suit but in the embodiment is between twenty to fifty centimetres.

Arranged adjacent each end 16,17 are a number of prongs 12 which function as the soil penetration means. In the embodiment, four prongs are spaced equi-distant about each end 16,17 such that body 11 supports eight prongs. Of course, the number and size and configuration of the prongs can vary to suit. Prongs are typically formed from steel and are knife- shaped to facilitate penetration into and through the soil. In the embodiment, each prong has length of between ten to thirty centimetres. The prongs on one end of body 11 are non-aligned with the prongs on the other end of body 11, this providing a smoother action.

It is possible for body 11 to accumulate debris as it rolls across a field and therefore there is an option to provide a scraper 18 (see Figure 5) between the prongs on end 16 and end 17 to keep the body fairly clean.

Referring to Figure 6, a pair of implements 10A, 10B are illustrated showing that the implements are slightly inclined relative to the direction of the travel (indicated by arrow 19). This slight inclination is an embodiment of how the prongs 12 function to push compacted soil or clods to beneath body 11 to be crushed thereby.

This mechanism is better illustrated with reference to sequential Figures 7A-7C (which are side views of a particular implement) and Figures 8A-8C which are sequential top views of the implement.

Referring initially to Figure 7A, body 11 rolls over ground surface 20 and leading prong 12A is above the ground surface. Figure 7A also shows a below ground clod of earth 21. In Figure 7B, leading prong 12A has penetrated ground surface 20 and has contacted clod 21. Because of

the incline angle of body 11 (see Figure 8A), continued rotation of leading prong 12A will provide a sideways push indicated by arrow 22 in Figure 8B which pushes clod 21 to the side. As clod 21 is below the ground, such a sideways push will force clod 21 more towards the surface as is illustrated between Figure 7B and Figure 7C. Prong 12A also pushed clod 21 in front of the path of body 11 and body 11 rolls over clod 21 (see Figures 7C and 8C) which crushes or breaks up the clod. This series of steps is continually repeated by each of the prongs as body 11 rolls over the ground surface.

In the sequential steps illustrated in Figures 7 and 8, the prongs 23 on the other side of roller 11 (see Figure 8A) do not function to push any clods underneath roller 11 but function to further cultivate and aerate the soil.

Referring to Figure 4, there is shown another use of implement 10. In this embodiment, implement 10 is positioned adjacent a conventional other type of tyne 24. Tyne 24 in the embodiment is a conventional tyne that rips through the trash blanket and into the soil. These tynes accumulate or get fouled with trash in front of the tyne and need to be periodically cleaned.

However, by positioning implement 10 adjacent tyne 24, rotatable body 11 functions to press down the trash blanket (or in another manner of speaking clamp the trash blanket to the ground surface) just long enough for tyne 24 to rip therethrough. It is found that this reduces or eliminates fouling of tyne 24 by the trash blanket. Implement 10 can still function to crush any clods which are loosened by prongs 12.

Figure 9 shows another use for the agricultural implement 10.

Figure 9 shows a top view of implement 10 next to a tyne 24 which moves in the direction of arrow 25. Behind tyne 24 is a hollow tube 26 which functions as a seeder to drop seeds into the furrow 27 created by tyne 24. The prongs of implement 10 push soil in the direction of arrow 28 into furrow 27 thereby providing an effective means to cover the furrow without unduly affecting the seeds.

It can be seen that the invention includes the function of piercing a trash blanket on the soil surface, engaging the soil beneath it and exerting forces to loosen compaction caused by the passage of time and

machinery. By positioning implement 10 adjacent a tyne, the implement pins or traps the trash blanket to the soil thereby causing the trash blanket to be drawn from the leading edge of the tyne allowing it to pass without or with reduced clogging. The implement has an effect on the crop residue which allows inputs of crop nutrients and soil conditioners to percolate through the residue to the soil surface and places the residue in a position that is desirable for crop husbandry.

By staggering the prongs, clogging is reduced and staggered soil contact points are made. Body 11 in the embodiment is fully sheeted to prevent clogging, provide good contact with disturbed soil and to protect the internal parts (typically the bearings). Typically a pair of implements are provided as a left-hand and a right-hand set and the set of the unit is manufactured into the mounting angles and the prongs.

When rotating in a forward direction, the off-set angle of implement 10 to the direction of travel causes the prong as it contacts the ground to travel in a transverse direction creating sideways thrust on the soil which loosens and raises clods of compacted soil which are in turn crushed or broken up by body 11. As the prong leaves the soil it continues to travel sideways which further loosens the soil and moves the trash blanket in that direction and fluffs it up. The prongs also mix some residue with the soil during this action.

When implement 10 is used in conjunction with a separate tyne 24 (see Figure 4) the lumps of soil dug up by tyne 24 are crushed by body 11 and it is found that prongs 12 are able to incorporated substantial amounts of residue into the disturbed soil.

The prongs on body 11 allow for a more positive pressure over the trash blanket than is noted with a conventional coulter, because the prongs action is to press down with no forward tendency, this causing residue to build up in front of the coulters. The staggered and spaced soil contact points illustrated in the embodiment do not provide a complete passageway for runoff water thereby reducing erosion and slowing the movement of water to allow more time for absorption of the water.

Prongs 12 generally have a sideways movement of less than ten centimetres while in contact with the soil. This allows the implement to be used much closer to the stool of the crop which is being ratooned than is possible with conventional systems which are much more aggressive and can destroy the root system of the crop.

It is found that any clods of soil on the base of the crop stalks are a major cause of wear to harvesters. Also, harvesters often lift the clods of soil into the harvested material causing further problems and expenses to the mill. The implements can be used close to the stool of the crop and can reduce or eliminate many of the clods of soil, thereby reducing harvester wear and problems and expenses to the mill.

Conventional soil aerators roll over the soil in a totally forward direction and rely solely on pressure exerted by weights to pierce the soil.

There is little or no loosening effect as the prongs in the known aerators have no sideways or transverse movement. By having a paired set of implements (see Figures 3 and Figure 6) the sideways action on the tool bar from one implement is counteracted by the opposite sideways movement of the other implement.

When the paired units are set so the prongs move further apart when operating, the volume of the crop residue is lessened in the area between the units. This aids tillering of the stool by allowing some light to reach the stool.

If the units are used without accompanying tynes a complete trash blanket is maintained while the soil beneath has been disturbed. This benefit is used to restrict weed emergence and prevents evaporation from the soil surface.

When fertilisers are applied to the residue surface, the nitrogen component can be lost into the atmosphere through volatilisation. By following the band of fertiliser with one of these units, the fertiliser will move down through the trash blanket because of the action of the unit. Under the trash blanket, it will be protected from the effects of fog, dew and light rain until sufficient rain or irrigation occurs to penetrate the trash blanket and

dissolve the fertiliser for the plants to access.

The unit's dimension can be matched to suit particular circumstances because ripping tynes can be of varying lengths or, if used in conjunction with a machine such as a seed drill, the area between the drill boots and below the frame and mechanisms dictates the maximum measurements.

It should be appreciated that various other changes or modifications can be made to the embodiment described without departing from the spirit and scope of the invention.