GB1603106A

GB1603106A - Agricultural implement

Info

Publication number: GB1603106A
Application number: GB3697877A
Authority: GB
Original assignee: National Research Development Corp UK; National Research Development Corp of India
Current assignee: National Research Development Corp UK; National Research Development Corp of India
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-11-18

Description

(54) AGRICULTURAL IMPLEMENT (71) We, NATIONAL RESEARCH DEVELOPMENT CORPORATION, of Wings gate House, 66-74 Victoria Street, London, SW1, a British Corporation established by Statute, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to coulters and has particular, but not exclusive, application to coulters for use in direct seed drilling of soil.

Coulters are tools which are moved translationally through the soil in order to form grooves in the soil. Traditionally, a plough comprises a coulter to make a vertical cut in the soil, a plough share to form a subsequent horizontal cut at or towards the base of said vertical cut, and a mouldboard which turns over the furrow slice formed by said cuts. It is conventional to till soil for seed sowing by turning the soil up with a plough. However, this procedure requires considerable energy expenditure by a draught animal or vehicle especially when, as is usual, it is subsequently necessary to draw a harrow over the soil to break up clods of earth. Moreover, the procedure buries the fertile top layer of the soil.

It has been known since at least 1958 that, under some circumstances, it is advantageous to directly place the seed into untilled soils (see for example Blackmore L.W. Overdrilling of pastures and crops", N.Z. Jl. Agric., 1958 96 (2) 121). In this procedure, which has become known as "direct drilling", seeds are placed in the groove finned by a coulter and thereby massive disturbance of the topsoil is avoided.

The most commonly used type of coulter in direct drilling is the so-called "triple disc" in which a leading rotatable disc cuts a slit in the soil which is subsequently opened into a "V" shape groove by an opposed pair of mutually inclined rotatable discs. In an alternative commonly used type coulter, known as a "hoe" or "suffolk" coulter, the opposed blades are replaced by a "V" shaped tine. For certain applications, such as in loosely packed soil with little surface trash, the leading disc can be omitted from these coulters. Both of said coulters suffer from a number of disadvantages. In particular, they often require the application of considerable pressure in order to penetrate the untilled soil thereby requiring the presence of substantial springs or the like in order to obtain the required depth penetration. A main disadvantage of such a machine is the weight that is required to achieve penetration, the spring being used in such machines as a transfer mechanism.

Moreover, they often smear the sides of the groove thereby encouraging attacks by predators and impeding root growth. These problems are particularly noticeable with triple disc coulters. A particular problem with "hoe" coulters is that they create an amount of loose rubble on the surface and are prone to clogging with surface trash. Moreover, the "V" shape of the groove provides a relatively large catchment area directing water to the base of the groove and thereby promoting rotting of the seeds. The shape of the groove also promotes substantial moisture variation in the environment of the seed. Another disadvantage is that the prepared groove is merely a target for the seed or other material, and the lack of precision in the discharge means that not all seed reaches the target area.

In an attempt to overcome some of the problems encountered with the said commonly used coulters, it has been proposed to use coulters having lateral wings to transversely extend the groove in sub-surface cavities. In particular, Baker C.J. (J. Agriv. Engng. Res.

(1976) 21, 133-144) describes a so-called chisel coulter. In this coulter the tine of a hoe coulter was replaced by a blade having lateral sub-surface wings inclined downwardly in the direction of travel and upwardly in the respective lateral direction and the seed is dropped through the slit formed by the blade into the transversely extending channel thus formed. In a so-called "SATRA TUME" wing coulter (available commercially from Satra Balarus Limited) lateral sub-surface wings are inclined downwardly in both of said directions from a hollow blade to form an inverted "V" shaped cavity into which seeds are dropped through the blade. Seeds are deflected by a deflector member immediately below the slit formed by the blade. The intention of the wing coulter is to place the seeds in a band instead of a row as in the case of the other coulters discussed above.

Said chisel and wing coulters have a number of advantages over the disc and hoe coulters.

In particular, the sub-surface wings tend to urge the coulter into the ground thereby reducing the amount of downward force required to achieve a given degree of penetration of the soil. Further, the slit formed in the soil is narrow and thereby results in less surface disturbance than that caused in the formation of the "V"-shaped groove of the disc and hoe coulters, the soil disturbance caused by chisel and wing coulters being substantially confined to the sub-surface area. The narrow slit also reduces water ingress into and moisture loss from the seed environment compared with the "V"-shaped groove of the commonly used coulters. However, even in the case of the wing coulter, seed is still located in the immediate vicinity of the base of the slit and is therefore still subject to substantial moisture variation and smear effects which militate against germination and emergence of seedlings.

U.K. Patent No. 1307019 (ceased) relates to coulters having a separate slanting surface associated with each of one or more feeding channels and leading seed or other material to be sown under a sowing blade, the said surface(s) being adapted to attempt to direct material to be sown away from the direction of travel of the coulter. In a preferred embodiment, slanting surfaces are associated with two vertical feeding channels so as to attempt to direct the material laterally with respect to the said direction of travel. The coulter particularly described in the patent specification has lateral sub-surface wings, inclined downwardly both in the direction of travel and the respective lateral direction from the hollow blade, and deflector plates below the wings to direct material falling through respective feed channels in the blade.

The coulter of patent No. 1307019 attempts to overcome many of the disadvantages of the other known coulters referred to above in that it attempts to locate seeds at a distance from the slit formed by the blade and hence in a position protected from excessive moisture variation and predators. Further, the spacing between the outer extremities of the sub-surface cavities and the slit are sufficient to cause or allow the cavity roof to collapse to bury the seed and thereby promote germination. However the coulter is not entirely satisfactory in operation and therefore has not been adopted commercially at least in the United Kingdom. In particular, the coulter cannot operate at shallow depth because of the lateral inclination of the wings, which disadvantage it shares with the aforementioned chisel and wing coulters, and does not satisfactorily locate the seeds at the outer extremities of the sub-surface cavity.

It is an object of the present invention to provide an improved coulter which delivers seed to the extemities of a sub-surface cavity, and in its preferred embodiment can be used for shallow drilling.

According to the present invention there is provided a coulter comprising a shank adapted to extend through the surface of the soil, sub-surface wing means projecting laterally relative to the shank to form a transversely extending sub-surface cavity in the soil on translational movement of the shank, and conduit means for conveying material from above the soil surface into the sub-surface cavity, the conduit means being arranged to extend to positions at or near the lateral extremities of the cavity, and to constrain the material to debouch laterally through openings of the conduit means positioned at or near the lateral extremities of the said cavity, so as to convey the material substantially to the lateral extremities of the sub-surface cavity.

Preferably the conduit means extends, at least immediately prior to debouching through the said openings, substantially horizontally.

Also preferably the conduit means extends, at least immediately prior to debouching through the said openings, substantially at right angles to the intended direction of travel of the coulter.

Usually but not necessarily, the material conveyed to the cavity by the conduit will be seeds, particularly but not exclusively cereals and brassicas. However, the coulter can be adapted to convey other particulate or fluid materials, such as fertilizer or pesticides, instead of or in addition to seeds.

Usually, the said wing means will comprise two sub-surface wings projecting from respective sides of the shank and the conduit means will comprise two conduits each wing having a respective conduit debouching laterally at or near the outer extremity of the respective wing, preferably substantially at the outer extremity of the respective wing. In this manner material can be introduced on each side of the slit formed by or receiving the shank.

Conveniently detachable wings may be bolted to a cast shank and base. Thus the wings may be either integral with the shank or detachable therefrom.

Each wing preferably comprises a rigid top plate which is inclined downwardly in the direction of travel of the coulter to lift the soil to form the cavity and also to urge the coulter into the soil. Suitably, the angle of which said plate is thus raked is between 5 to 30 degrees especially about 11 degrees. The leading edge of said plate suitably is chamfered to aid transverse cutting of the soil. It is also preferred that the plate extends substantially perpendicularly in the lateral direction from the shank to minimise the depth at which the coulter can drill. If desired, at least the leading section of the base of the top plate can be closed by a bottom plate to protect the material-delivering conduits against abrasion on passage through the soil. However, a conduit usually will be protected by mounting behind, and conveniently on, a rearwardly inclined shroud plate depending from the top plate and spaced from the leading edge thereof.

The extent to which each wing projects from the shank will be determined by the spacing required between placement of the material supplied by the conduit and the soil slit formed by or receiving the shank. The distance usually will be in the range 4 to 25 em especially 9 to 20 cm measured from the centre line of the shank. It is important ie note that this distance is greater than the corresponding distance of the previously known chisel and Satra Tume wing coulters referred to above.

The top plate conveniently is formed of metal sheet of 2 to 15 mm especially about 5 mm thickness. The top plate usually will be of generally triangular shape whereby the leading edge is inclined rearwardly. However, other perimeteral shapes can be adopted if desired.

The length of the wing adjacent to the shank suitably will be 4 to 14 cm especially about 11 cm.

The shank preferably has a substantially vertical leading edge which is chamfered on both sides to minimise the resistance to movement through the soil. Suitah;ly, said leading edge is inclined forwardly at the foot of the shank to form a point (the "sock") which is intended to penetrate the soil at a depth of between 3 and 20 em, especially about 6 cm below the soil surface. This depth is usually between 1 and 5 elm especially about 2 cm below the base of the lateral wings). Part of the shank can be hollow to receive or fefine a portion of the conduit fordeivery material to the transverse cavity. It is preferred however, that the major part of the shank is solid being formed of. for exampie, steel. Suitably the shank has a width of 8 to 25 mm especially about 12 mm and a length from it leading edge to its trailing edge of 50 to 150 mm especially about 75 mm. When th&commat; te shank is solid, it is preferred that one or more shroud plates extend rearwardly from the shank n order to protect the material-containing conduit against abrasion.

The material-containing conduit means preferably comprises a passage formed in the shank and/or wing, for example case therein. Alternatively the conduits may be pipes, especially flexible pipes, which pass through or are mounted on the shank and/or wing.

Where there is more than one conduit, the conduits can share a common conduit portion although it is much preferred that the conduits should be separate in order to facilitate accurate metering of material to the cavity. When the conduit is intended for direct seed drilling, the or each conduit usually will have a diameter of 8 to 40 mm especially about 20 mm.

The or each conduit has an inlet above soil level to receive material and an outlet in or behind the respective wing in order to deliver the material in the lateral direction to a position substantially at the extremity of the cavity formed by the wing. Usually, the outlet will be spaced at least 40 mm from the centre line of the shank and will usually be between 50 and 125 mm especially about 75 mm from said centre line. When particulate material such as seeds are being placed in the cavity, the outlet orifice of the conduit is preferably just slightly larger than the maximum particulate size in order to facilitate accurate placing of the material in the cavity.

If required, material such as fertiliser also can be debouched into the cavity at additional position in the or each wing. Preferably, each material outlet will be supplied by its own conduit to facilitate accurate metering of the material.

It will be appreciated that in some respects the direction in which the material outlets debouch into the cavities distinguishes the coulter of the present invention from prior art coulters. As previously mentioned, the Satra Tume wing coulter distributes a single band of material which is interrupted immediately below the centre of the soil slit by a deflector plate. However, it does not have a conduit which debouches material at or near the extremity of the lateral cavity, and so is not capable of placing two or more distinct rows of material into the soil. Moreover, the band of material distributed by a wing coulter only extends to about 35 mm from the centre line of the shank.

In order to accurately meter particulate material through a conduit into the cavity and to carry the material to the extremity of the cavity, it is preferred that the material is pneumatically conveyed along the conduit. The use of compressed air in this manner will at least reduce hindrance of material flow by sharp bends in the conduit which are likely to be required in order for the conduit to conform within the profile of the shank and wing. The compressed air aids the horizontal transfer of material towards the extremity of the wing.

Material can be metered into the inlet of the or each conduit using conventional means, such as a fluted roller in the case of particulate material or a metering pump in the case of liquid or slurry.

It is preferred that the shank of the coulter is attached to an arm pivoted for movement in a vertical plane, especially at a pivot point spaced forwardly of the coulter. The arm, which conveniently is constructed of hollow box-sectioned steel, can be straight or, if required to accommodate the coulter or other soil working devices, can be fabricated with bends, especially in the vertical plane. Conveniently, the pivot point is located between 10 and 60 cm especially about 50 cm in front of the point of attachment of the shank to the arm. The pivot is typically a horizontal steel pin acting through a brass bush.

The arm preferably extends rearwardly of the point of attachment to the coulter shank.

Conveniently the total length of the arm is between 40 and 140 cm, typically about 95 cm.

The arm can be supported rearwardly of said point of attachment by a stabiliser connecting the arm to a point fixedly located relative to the pivot point of the arm. Suitably, the stabiliser is a rod pivoted to and extending upwardly from the arm to a bracket mounted on the trailer to which the arm is pivoted.

It is also preferred that resilient means are provided to urge the arm downwardly to assist penetration of the coulter into the soil. The resilient means can comprise a compression spring acting between the arm and the vehicle to which it is attached. It is particularly convenient when a stabilising rod is present to arrange for the resilient means to act on the rod. In particular, the resilient means can consist of a compression spring acting between the bracket receiving the rod and a seat carried by the rod. The position of the seat along the length of the rod can be adjustable in order to vary the spring pressure acting on the arm and hence the force with which the coulter penetrates the soil.

In order to prevent excessive penetration of the soil by the coulter, it is preferred that means are provided to limit the depth of penetration. Said means can comprise a ground-engaging member, such as a roller or skid, depending from the arm. Usually, such a ground engaging member will be provided rearwardly of the coulter in order to assist or cause closure of the slit and/or collapse of the cavity after the introduction of material by the coulter.

Except in the case of light soils with little surface trash, it is preferred that the coulter should be preceded by a preliminary coulter, such as a tine or, especially, a disc to cut through any surface trash and form a slit to facilitate passage of the coulter of the invention through the soil. Usually, the preliminary slit thus formed will be narrower than the shank of the coulter of the invention whereby the shank will widen the slit upon passage therethrough. The preliminary coulter can be mounted on the arm between the pivot point and the coulter of the invention and conveniently will penetrate 15 to 60 mm especially 30 mm into the ground. If desired, the edges of the preliminary coulter can be fluted and/or the coulter slightly angled.

The coulter will usually be mounted on a frame which is adapted to be moved translationally on the soil surface. Conveniently, the frame will be a wheeled vehicle having a hopper for containing material to be dispensed and means for metering the material into the mouth of the or each conduit of the coulter. In particular, such a wheeled frame can be a conventional seed drill.

The arrangement of the arm, stabiliser, roller and disc can be regarded as a unit and several such complete units will normally be used on each machine, the number and spacing depending on the width of the machine and the desired spacing between seed rows. The arms of the units can either be the same length, or staggered to minimise the possibility of interference between adjacent coulters.

As has been mentioned, a main disadvantage of existing machines for direct drilling is the weight that is required to achieve penetration using a spring as a transfer mechanism.

Although a drill embodying the present invention may use a spring, the weight required may be made much less.

The following is a description by way of example only and with reference to the accompanying drawings of a preferred embodiment of the present invention. In the drawings.

Figure 1 is a side view of a coulter in accordance with a preferred embodiment of the invention; Figure 2 is a view in the direction of arrow A of Figure 1; Figure 3 is a view in the direction of arrow B of Figure 1; Figure l(a) is a side view of a modified coulter embodying the invention; Figure 2(a) is a view in the direction of arrow A in Figure 1(a); Figure 3(a) is a view in the direction of arrow B in Figure 1(a); Figure 4 is a side view of a soil working assembly including the coulter of Figures 1 to 3; Figure 5 is an underneath plan view of the assembly of Figure 4; and Figure 6 is a perspective view of the assembly of Figures 4 & 5 attached to a seed drill but with the roller omitted for clarity.

Referring to Figures 1, 2 and 3, a coulter generally indicated at 1 comprises a shank 2 having a pair of lateral wings 3, 4 protruding from the respective sides thereof. The shank is a substantially rectangular solid steel blade in which the foot is angled forwardly and downwardly to form a sock 5. Shroud plates 6, 7 project rearwardly from each side of the shank towards the base thereof to define a conduit-receiving groove. The wings 3, 4 each comprising a generally triangular plate 8, 9 respectively attached to the respective side of the shank so that the leading edge is inclined rearwardly from a point behind the sock 5.

Said plates 8, 9 are raked upwardly along the base of the respective shroud plate 6, 7 and extend perpendicularly therefrom in the transverse direction The leading edge of each plate 8, 9 is chamfered to aid transverse cutting of the soil. Rearwardly inclined shroud plates 10, 11 depend from the respective plates 8, 9 towards the rear thereof to support an outlet end portion of the respective pipe 12, 13 and protect that end against abrasion on passage through the soil. The pipes 12, 13 are located between shroud plates 6, 7 and between the respective pairs of plates 3, 10 and 4, 11 by pads 14 welded into position after insertion of the pipers. The pipes extend above the shank 2 and at their lower ends debouch laterally of said shank in outlets 12a, 13a.

In use, the coulter 1 is located vertically in the soil with the sock 5 and wings 3, 4 below the surface thereof and the shank 2 protruding upwardly through the surface. The shank is moved, usually drawn, translationally through the soil, usually along a narrow vertical slit previously cut by a disc or tine. The coulter forms, or enlarges, the vertical slit by passage of the shank through the soil whilst the wings lift sub-surface soil to form lateral cavities extending on each of the slit. Seeds or other particulate material, liquids or slurries are metered into the upper inlets of the pipes 12, 13 and pass through the pipes to debouch laterally from the outlets 12a, 13a below the plates 3,4. Usually, the flovi of particulate material is assisted by a supply of compressed air to blow the material through the pipes and thence to the extremities of the cavities.

Referring now to Figures 1(a), 2(a) and 3(a) there is shown a modification of the coulter shown in Figures 1, 2 and 3. The modification lies in the fact that the flexible pipes 12 and 13 of Figures 1, 2 and 3 are replaced by shorter pipes 12' and 13' in Figures 1(a), 2(a) and 3(a), which are coupled to internal passageways 12" and 13" cast in a solid coulter formed by a shank 2' and wings 8' and 9'. Otherwise the remaining elements of the modified coulter are similar or identical to those shown in Figures 1, 2 and 3 and are indicated by like reference numerals. In the following description with reference to the remaining Figures, it is to be understood that the coulter shown (being the arrangement of Figures 1, 2 and 3) may equally well be replaced by the modified coulter of Figures 1(a), 2(a) or 2(b).

In the assembly shown in Figures 4 and 5, the shank 2 of the coulter 1 is bolted at its upper end to an intermediate portion of an arm 15 of hollow box-section steel. The arms has at its forward end a transversely extending brass bush 16 adapted to fit about a horizontal steel pivot pin 17 secured to the body of a seed drill (see Figure 6).

A preliminary coulter 18 is carried by the arm 15 at a point between the coulter 1 and the bush 16. This preliminary coulter comprises a single disc 19 rotatably mounted on a spindle 20 extending between lugs 21 depending from the arm 15.

The arm 15 extends rearwardly of the coulter 1 in a short straight section 15a and is then bent upwardly to terminate in a rear portion 15b parallel to the forward portion of the arm.

A clevis 22 is pivotally attached to arm 15 behind the coulter 1. A stabilising rod 23 extends from the clevis 22 to a bracket 24 fixed to a hopper 25 of a seed drill 40 (see Figure 6). The rod is slidably received through a hole in the bracket 24 and a bush 26 is provided on the rod 23 above the bracket to limit downward movement of the rod and hence of the arm, about the pivot pin 17. A compression spring 27 acts between the bracket 24 and a seat 28 carried by the rod 23. The position of the seat 28 along the rod is adjustable by, for example, having the relevant portion of the rod screw threaded.

The terminal part 15b of the arm 15 has a pair of upstanding lugs 29 to which are bolted respective brackets 30 constituting a yoke carrying a roller 31 rotatably mounted on a spindle 32 extending between the free ends of the brackets 30. The upper ends of the brackets 30 are provided with a plurality of vertically aligned holes 33 to permit adjustment of the distance between the arm 15 and the axis of rotation of the roller 31.

When the soil working assembly of Figures 4 and 5 is connection to the seed drill 40 as shown in Figure 6, the pipes 12, 13 of the coulter 1 are each connected via "Y" joints 34 to respective hopper outlets via a metering unit 35 to which compressed gas is supplied via a line 36. Other more sophisticated arrangements for metering seeds through the pipe into the cavity will usually be adopted in seed drills specifically built for use with coulters of the invention. Although Figure 6 shows only one soil working assembly attached to the seed drill, a plurality of such assemblies will be attached to the same drill. For reasons explained below, the number of assemblies attached to the drill will be half the number of assemblies embodying conventional direct drilling coulters. Thus, the drill can have, for example, 8 to 12 of the assemblies of Figures 4 and 5 attached thereto.

In a typical assembly, the arm 15 is 950 mm long and 50 x 37 mm cross section. The pivot pin 17 is 300 mm above ground level and 25 mm in diameter and the bus 16 spaced 25 mm rearwardly of the front of the arm 15. The disc 19 of the preliminary coulter 18 is mounted 217 mm behind the pivot pin 17 and is 300 mm in diameter and arranged to penetrate 30 mm into the soil. The coulter 1 is mounted with its leading edge 480 mm behind the pivot pin 17.

The sock 5 is 330 mm below the arm 15 and will penetrate the soil to a depth of about 60 mm. The width of the shank is 12 mm with the shroud plates 6, 7 extending a further 40 mm for the lowest 130 mm of the shank 1. The length of the shank 1 to its trailing edge is 75 mm.

The plates 3, 4 project to a distance of 90 mm from the centre line and are raked at an angle of 11 degrees upwardly from a point 20 mm above the sock 5. The maximum length of the plates 3, 4 adjacently shank 1 is 110 mm and the plates themselves are formed from 5 mm thick metal sheet. The conduits 12, 13 are of 20 mm diameter and their outlets 12a, 13a are located 75 mm from the center line. The stabiliser rod 23 is pivoted to the arm 600 mm behind the pivot pin 17 and is 700 mm long. The bracket 24 to which the stabiliser rod 23 is attached is 650 mm above the arm 15. The spring 27 mounted on the stabiliser arm has a diameter of 45 mm with a free length of 340 mm and a spring constant of 10 kN/M. The roller 31 is a metal, plastic or wooden cylinder with a diameter of 300 mm and a width of 250 mm. It is mounted 800 mm behind the pivot pin 17 and the medium distance of the centre of the roller below the arm is 200 mm.

In use the seed drill 40 is drawn by a tractor (not shown) across land to be directly drilled with seed. The preliminary coulter 18 cuts a slit which is subsequently widened by the coulter 1 in the manner described above. The roller 31 following the coulter 1 tends to close the slit and to collapse the sub-surface cavity into which the seeds have been directed. The extent of penetration of the coulter into the soil can be adjusted by varying the height of the arm 15 above the roller 31. The downward force on the arm 15 can be varied by adjusting the distance between the seat 28 and the bracket 24 between which the spring 27 acts.

The direct drilling of seed using the coulter 1 of the invention has the advantage of placing the seed substantially at the extremity of the cavity in a position where it is not affected by the adverse conditions in the region of the slit formed by the shaft. Further the width of the coulter 1 and the depth of the drill slit and cavities and hence the energy required to drill, can be minimized. In the usual construction in which the coulter has wings on each side of the shank, two or more rows of seed can be planted from one coulter thereby reducing the number of coulters required by at least half compared with conventional coulters. The coulter can be used

Claims

**WARNING** start of CLMS field may overlap end of DESC **. shown in Figure 6, the pipes 12, 13 of the coulter 1 are each connected via "Y" joints 34 to respective hopper outlets via a metering unit 35 to which compressed gas is supplied via a line 36. Other more sophisticated arrangements for metering seeds through the pipe into the cavity will usually be adopted in seed drills specifically built for use with coulters of the invention. Although Figure 6 shows only one soil working assembly attached to the seed drill, a plurality of such assemblies will be attached to the same drill. For reasons explained below, the number of assemblies attached to the drill will be half the number of assemblies embodying conventional direct drilling coulters. Thus, the drill can have, for example, 8 to 12 of the assemblies of Figures 4 and 5 attached thereto. In a typical assembly, the arm 15 is 950 mm long and 50 x 37 mm cross section. The pivot pin 17 is 300 mm above ground level and 25 mm in diameter and the bus 16 spaced 25 mm rearwardly of the front of the arm 15. The disc 19 of the preliminary coulter 18 is mounted 217 mm behind the pivot pin 17 and is 300 mm in diameter and arranged to penetrate 30 mm into the soil. The coulter 1 is mounted with its leading edge 480 mm behind the pivot pin 17. The sock 5 is 330 mm below the arm 15 and will penetrate the soil to a depth of about 60 mm. The width of the shank is 12 mm with the shroud plates 6, 7 extending a further 40 mm for the lowest 130 mm of the shank 1. The length of the shank 1 to its trailing edge is 75 mm. The plates 3, 4 project to a distance of 90 mm from the centre line and are raked at an angle of 11 degrees upwardly from a point 20 mm above the sock 5. The maximum length of the plates 3, 4 adjacently shank 1 is 110 mm and the plates themselves are formed from 5 mm thick metal sheet. The conduits 12, 13 are of 20 mm diameter and their outlets 12a, 13a are located 75 mm from the center line. The stabiliser rod 23 is pivoted to the arm 600 mm behind the pivot pin 17 and is 700 mm long. The bracket 24 to which the stabiliser rod 23 is attached is 650 mm above the arm 15. The spring 27 mounted on the stabiliser arm has a diameter of 45 mm with a free length of 340 mm and a spring constant of 10 kN/M. The roller 31 is a metal, plastic or wooden cylinder with a diameter of 300 mm and a width of 250 mm. It is mounted 800 mm behind the pivot pin 17 and the medium distance of the centre of the roller below the arm is 200 mm. In use the seed drill 40 is drawn by a tractor (not shown) across land to be directly drilled with seed. The preliminary coulter 18 cuts a slit which is subsequently widened by the coulter 1 in the manner described above. The roller 31 following the coulter 1 tends to close the slit and to collapse the sub-surface cavity into which the seeds have been directed. The extent of penetration of the coulter into the soil can be adjusted by varying the height of the arm 15 above the roller 31. The downward force on the arm 15 can be varied by adjusting the distance between the seat 28 and the bracket 24 between which the spring 27 acts. The direct drilling of seed using the coulter 1 of the invention has the advantage of placing the seed substantially at the extremity of the cavity in a position where it is not affected by the adverse conditions in the region of the slit formed by the shaft. Further the width of the coulter 1 and the depth of the drill slit and cavities and hence the energy required to drill, can be minimized. In the usual construction in which the coulter has wings on each side of the shank, two or more rows of seed can be planted from one coulter thereby reducing the number of coulters required by at least half compared with conventional coulters. The coulter can be used for a wide variety of purposes, including conventional drilling of brassicas and cereals into cultivated land, direct drilling of brassicas and cereals into uncultivated land, direct sowing of grass or clover for pasture improvement, introduction of fertiliser into the soil, injection of slurry below the soil surface, and introduction of pesticides below the soil surface. It will be appreciated that the invention is not restricted to the particular details described above but that numerous modifications and variations can be made without departing from the scope of the invention. In particular, the preliminary coulter 18 could be replaced by a tine, or, in light soils, omitted. Further the roller 31 could be replaced by a ground-engaging skid. Moreover, a centrally located additional conduit could be provided to deposit fertiliser centrally at the foot of the slit. In a particularly preferred modification, the seed conduits may take the form of channels cast into the body of the shank and/or wing of the coulter. WHAT WE CLAIM IS:

1. A coulter comprising a shank adapted to extend through the surface of the soil, sub-surface wing means projecting laterally relative to the shank to form a transversely extending sub-surface cavity in the soil on translational movement of the shank, and conduit means for conveying material from above the soil surface into the sub-surface cavity, the conduit means being arranged to extend to positions at or near the lateral extremities of the cavity and to constrain the material to debouch laterally through openings of the conduit means positioned at or near the lateral extremities of the said cavity, so as to convey the material substantially to the lateral extremities of the said cavity.

2. A coulter according to Claim 1 in which the conduit means extends, at least

immediately prior to debouching through the said openings, substantially horizontally.

3. A coulter according to Claim 1 or 2 in which the conduit means extends, at least immediately prior to debouching through the said openings, substantially at right angles to the intended direction of travel of the coulter.

4. A coulter according to Claim 1, 2 or 3 in which the said conduit means is adapted to convey seeds.

5. A coulter accordng to any of Claims 1 to 4 in which the said wing means comprises two sub-surface wings projecting from respective sides of the shank and the conduit means comprises two conduits, each wing having a respective conduit debouching laterally at or near the outer extremity of the respective wing.

6. A coulter according to Claim 5 in which each wing comprises a rigid top plate which is inclined downwardly in the direction of travel of the coulter to lift the soil to form the cavity and also to urge the coulter into the soil.

7. A coulter according to Claim 6 in which the angle at which said plate is thus raked is in the range 5 to 300.

8. A coulter according to Claim 7 in which said angle is about 11 degrees.

9. A coulter according to Claim 6, 7, or 8 in which the plate extends substantially perpendicularly in the lateral direction from the shank to minimize the depth at which the coulter can drill.

10. A coulter according to any of Claims 6 to 9 in which the or each material-delivering conduit is mounted behind a rearwardly inclined shroud plate depending from the top plate and spaced from the leading edge thereof to protect the conduit or conduits against abrasion on passage through the soil.

11. A coulter according to any of Claims 6 to 9 in which the or each top plate is of generally triangular shape with the leading edge inclined rearwardly.

12. A coulter according to any preceding claim in which the distance to which the or each wing projects from the shank is in the range 4 to 25 cm measured from the centre line of the shank,

13. A coulter according to Claim 12 in which the said distance is in the range 9 to 20 em measured from the centre line of the shank.

14. A coulter according to any preceding claim in which the shank has a substantially vertical leading edge which is chamfered on ooth sides to minimise the resistance to movement through the soil, said leading edge being inclined forwardly at the foot of the shank to form a point which is intended to penetrate the soil.

15. A coulter according to Claim 5 or any of Claims 6 to 14 insofar as dependent upon Claim 5 in which each of said conduits comprises a separate conduit leading from an inlet above soil level to an opening below soil level.

16. A coulter according to Claim 15 in which each conduit comprises a flexible pipe.

17. A coulter according to Claim 15 in which each conduit comprises a passageway formed in the shank and/or wing.

18. A coulter according to Claim 15, 16, 17 or 18 in which each opening is spaced at least 40 mm from the centre line of the shank and is spaced between 50 and 125 mm from said centre line.

19. A coulter according to any preceding claim in combination with means for conveying, or assisting the conveying of material along the or each conduit by air under pressure.

20. A coulter according to any preceding claim in combination with means for metering material into the or each conduit.

21. A coulter according to any preceding claim in combination with a preliminary disc coulter positioned ahead of the first mentioned coulter to cut through any surface trash to form a slit to facilitate passage of the first mentioned coulter through the soil.

22. A coulter according to any preceding claim in combination with a following roller or skid to press down soil closing the sub-surface cavity and to limit the depth of penetration of the coulter.

23. An agricultural implement including a coulter according to any preceding claim, in which the shank of the coulter is attached to an arm pivoted for movement in a vertical plane about a pivot point spaced forwardly of the coulter.

24. An agricultural implement according to Claim 23 in which the arm extends rearwardly of the point of attachment to the coulter shank and the arm is supported rearwardly of said point of attachment by a stabiliser connecting the arm to a point fixedly located relative to the pivot point of the arm.

25. An agricultural implement according to Claim 24 in which the stabiliser is a rod pivoted to and extending upwardly from the arm to a bracket mounted on a trailer to which the arm is pivoted, and resilient means are provided to urge the arm downwardly to assist penetration of the coulter into the soil, the resilient means comprising a compression spring acting between the bracket receiving the rod and a seat carried by the rod, the position of the seat along the length of the ro being adjustable in order to vary the spring pressure acting on the arm and hence the force with which the coulter penetrates the soil.

26. An agricultural implement according to Claim 23, 24 or 25 including a groundengaging member depending from the arm to limit the depth of penetration of the coulter.

27. An agricultural implement according to any of Claims 23 to 26 including a plurality of coulters as set out in preceding claims together with mounting means for mounting the coulters in an array generally transverse to the intended direction of travel of the implement.

28. A coulter substantially as hereinbefore described with reference to the accompanying drawings.

29. An agricultural implement substantially as hereinbefore described with reference to the accompanying drawings.