WO2013118085A1

WO2013118085A1 - Earth working apparatus

Info

Publication number: WO2013118085A1
Application number: PCT/IB2013/051043
Authority: WO
Inventors: Lodewyk Christoffel De Lange; Jacobus Du Toit Stofberg
Original assignee: Lodewyk Christoffel De Lange; Jacobus Du Toit Stofberg
Priority date: 2012-02-08
Filing date: 2013-02-08
Publication date: 2013-08-15
Also published as: ZA201406750B

Abstract

An earth working apparatus and method are disclosed. The apparatus includes a primary rotatable drum (30) having a number of picks (38) mounted on it, and a secondary rotatable drum (32) having a number of paddles (56) mounted on it. The drums are mounted adjacent one another with their axes substantially parallel and are rotatable both in the same direction or in opposite directions. The picks (38) of the primary drum cut the soil in use, while the paddles (56) pass between the picks (38) and help to mix the soil and clean the primary drum (30). The mixed soil is then re-deposited. The apparatus can be mounted on a traction unit (10) to drive the apparatus over land to be worked.

Description

EARTH WORKING APPARATUS

BACKGROUND OF THE INVENTION

THIS invention relates to earth working apparatus suitable for deep working of the soil, and to a method of earth working involving deep working of the soil.

The tilling or ploughing of the soil for agricultural purposes involves various techniques and equipment, many of age-old origin. These techniques and equipment have evolved in modern times to include a wide variety of driving systems, such as tractors, as well as ploughs and rippers of various design and construction. These ploughs and rippers are dragged through the soil by the driving systems. There are many possible combinations of driving systems and ploughs and rippers, each with a specific application in agriculture. Each application aims to create soil conditions suitable for the cultivation of a specific annual or perennial crop.

Traditionally the aim of using such a ploughing or tilling system was to loosen the soil to a certain depth to allow for root development and the penetration of water and nutrients, mostly applied to the surface of the soil.

As these ploughing and tilling systems became more sophisticated it was increasingly possible to penetrate the soil to greater depths while the reach of the system became wider; thus, the effectiveness of the process to loosen and turn the soil as well as introducing various materials including fertilizers into the soil was improved albeit marginally with each technological improvement. A measure of the efficacy of a ploughing or tilling system will be the draft force used per unit area tilled. This will be affected by increased compaction resulting in increased soil strength and bulk density.

Soil compaction and thus bulk density increase with increasing depth below the soil surface. This reality results in:

• An increased energy input required for tillage

• Impeding growth of plant roots particularly at low moisture levels.

• Impeding water penetration and the moisture retention capacity of the soil

• Diminished void spaces to hold enough water-air mixtures.

• Reduction of soil pore sizes due to increased soil bulk density which depraves crops of water and nutrients.

Even in conservation tillage systems, including minimum or no-till practices, the negative effects of compaction will accumulate. These negative impacts will occur even in virgin soils.

The amounts of energy needed to provide the draft forces required by conventional tillage implements increase at a rate greater than a proportionate increase in tilling depth, limiting deep tilling as a result of increased operating costs.

Conventional tilling, invariably using narrow tilling tools, relies on a three- dimensional mode of soil-zone failing in front of the tool as well as at its sides. A critical depth of 600 mm was postulated for this mode. Changing and improving soil-failure by increasing the working-depth/tool-width ratio - working below the critical depth - required increasing draft forces to the extent that the power needed increases exponentially but with a reduction in soil disturbance and an increase in soil compaction.

Deep working of the soil, as referred to in this specification, refers to processes which can take place at depths greater than those possible with conventional tilling tools, and which can be designed to achieve the following purposes:

• The preparation of new soil for agricultural, forestry or environmental purposes including the mixing of beneficial materials into the soil;

• The regeneration of soil which has been or is still being used for agricultural, forestry or environmental purposes including the mixing of beneficial materials into the soil;

• The rehabilitation of soils which have been used in the past for agricultural, forestry or other purposes, such as mining, and has to be physically rehabilitated to be put to use for agricultural, forestry or environmental purposes;

• The remediation of soils which have been used in the past for agricultural, forestry or other purposes, such as mining, and has to be physically, chemically and biologically remediated to be put to use for agricultural, forestry or environmental purposes such as constructed wetlands.

Deep working, including the homogeneous mixing of the soil, is necessary to ameliorate compacted soil profiles often present as layers resulting from past practices such as traffic induced compaction and limited water penetration. Deep working of the soil will result in the incorporation of valuable topsoil and surface residues into the subsoil which will have more advantages than disadvantages.

Increasing environmental awareness of industry and mining and the impact of their activities, including the pollution of the soil, has also raised the increasing need to rehabilitate and remediate soils thus polluted. To achieve soil conditions which will be useable for agricultural, forestry or environmental purposes as well as ecological interactions which will not tolerate any form of pollution often requires the soil be penetrated and moved to depths greater than normally required by agriculture, while soil ameliorants and amendments are introduced at the same time. Mechanical systems to achieve this objective are not readily available.

A need therefore exists for apparatus designed and built for deep working of the soil, to form or reform soil to optimal depths and with the addition of dedicated materials.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided earth working apparatus comprising: a primary rotatable member having a plurality of earth-engaging members mounted thereon and being rotatable in a first direction; and a secondary rotatable member having a plurality of earth-engaging members mounted thereon and being rotatable in the first direction or in a second direction opposed to the first direction, the primary and secondary rotatable members being mounted for rotation about respective first and second axes which are substantially parallel.

The primary and secondary rotatable members may take the form of rotatable drums.

The secondary drum is preferably smaller than the primary drum, preferably having a radius which is in the range of 20% to 30% of that of the primary drum. The earth-engaging members mounted on the primary and secondary drums are preferably picks on the primary drum and paddles on the secondary drum, which may be replaceable.

Preferably each pick and paddle comprises an upstanding pillar with a replaceable head mounted thereon.

Each pick and paddle may be mounted removably on a longitudinally extending elongate support member on the primary drum or the secondary drum, respectively.

The picks may have relatively sharp tips for cutting the soil, while the paddles may have generally planar tips and present a substantially flat surface to the soil in use.

The primary and secondary drums are preferably mounted sufficiently closely together that the picks and paddles of the respective drums intermesh as the drums rotate in use.

The secondary drum may be arranged to rotate at a speed at least twice that of the primary drum.

According to a second aspect of the invention there is provided an earth working machine comprising a traction unit and earth working apparatus as defined above mounted on the traction unit, the traction unit having at least one motor and a drive train arranged to drive the machine across land to be worked, and a drive system arranged to operate the earth working apparatus.

The machine preferably includes adjustable support means arranged to raise or lower the primary and secondary rotatable members to vary the working depth thereof. According to a third aspect of the invention there is provided an earth working method, the method including: arranging primary and secondary rotatable members for rotation about respective first and second axes which are substantially parallel, the primary rotatable member having a plurality of earth- engaging members mounted thereon and being rotatable in a first direction, the secondary rotatable member having a plurality of earth-engaging members mounted thereon and being rotatable in the first direction or in a second direction opposed to the first direction; and operating the primary and secondary rotatable members in counter rotation or, alternatively, in co-rotation while moving both rotatable members across land in a direction transverse to the first and second axes, so that the primary rotatable member engages soil to cut and lift it, the secondary rotatable member engaging the lifted soil to assist in mixing thereof, the soil then being re-deposited.

The method may include depositing a layer of material on the surface of land to be worked, so that the primary and secondary rotatable members effectively mix the deposited material into soil worked by the method.

Instead, or in addition, the method may include injecting a liquid formulation or a gas into soil worked by the method.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an isometric view of an earth working machine incorporating earth working apparatus according to the invention;

Figure 2 is an isometric view from below of the machine of Figure 1 ; is a side view of the machine; is a front view of the machine; is an exploded isometric view of the machine showing main components thereof; is a schematic side view of a pick of the primary drum of the machine; is a schematic side view of a paddle of the secondary drum of the machine; is a schematic front view illustrating the intermeshing of the picks of the primary drum and the paddles of the secondary drum in use; is a schematic diagram illustrating the operation of the machine in use; is a diagram showing the effect on soil of conventional tilling; and is a diagram similar to that of Figure 10 showing the effect on the soil of continuous deep working thereof using the machine and apparatus of the invention.

DESCRIPTION OF EMBODIMENTS

The earth working machine shown in Figures 1 to 5 comprises a traction unit 10 and earth working apparatus 12 which can be mounted on the traction unit. The traction unit has a ladder frame chassis 14 supporting a power unit 16 which houses at least one diesel engine and a generator in a diesel-electric configuration. An operator cabin 18 is mounted at the other end of the chassis from the power unit. An exhaust unit 20 including high capacity exhaust fans is provided to cool the motor unit. The motor unit 16 includes a primary drive train (not shown) which is generally conventional and is arranged to drive a pair of endless tracks 22, enabling the machine to traverse land to be worked.

It will be appreciated that the illustrated earth working machine is one of several example embodiments of the invention. Smaller machines may be provided with sets of wheels instead of tracks, and may have different power and drive configurations. Larger units may have multiple engines and different drive schemes.

The earth working apparatus 12 is mounted at an end of the chassis 14 remote from the power unit 16 on a pair of heavy duty brackets 24. The earth working apparatus is mounted on a frame comprising a pair of heavy plates 26 which are pivoted to the brackets 24 and which are also connected to heavy duty hydraulic rams 28 which can be extended or retracted to pivot the apparatus 12 on the bracket 24, thus raising or lowering the apparatus relative to the traction unit.

The earth working apparatus comprises a primary drum 30 and a secondary drum 32. The primary and secondary drums 30 and 32 are mounted for rotation about parallel axes, with the primary drum 30 being mounted on the main frame of the apparatus, while the secondary drum 32 is mounted on a pair of arms 34 fixed to the frame. The arms 34 are mounted rotatably to the frame and are fitted with eccentrics 36 at their innermost ends which are connected to the frame by hydraulic actuators 58, so that extension of the actuators 58 lifts the secondary drum out of engagement with the primary drum.

In normal operation, the primary and secondary drums lie adjacent to one another and cutting picks or teeth 38 which are mounted in rows on the primary drum intermesh with paddles 56 mounted on the secondary drum as the drums rotate in use. The picks 38 are mounted removably on support members in the form of elongate bands or grousers 40 and can be replaced as required. The grousers 40 extend parallel to the main axis of the drum 30. Similarly, the paddles 56 are mounted removably on longitudinally oriented grousers on the drum 32. The picks 38 have relatively sharp (or slightly rounded) tips for cutting the soil efficiently, while the paddles 56 have generally planar tips and present a flat surface to the soil.

Figures 6 and 7 illustrate the picks and paddles schematically. In both cases, the picks and paddles comprise a replaceable head mounted on a shaft or pillar 60 which is retained by a grouser 40 on the outer surface of the respective drum 30 or 32.

The primary drum 30 has a pair of end drum sections 42 and 44 at respective opposed ends thereof, to which grousers and picks are fitted, and a central section 46 which is adapted to engage and be driven by a cutting chain 48 which is of equivalent width to the end sections 42 and 44 and which carries its own grousers and picks. The configuration of the picks on the primary drum system could be varied in a pre-determined way to facilitate the moving of the soil in one or the other direction. For example, the picks could be configured in a screw-like configuration which will shift the soil to the left or the right of the working direction of the apparatus in the horizontal plane when the primary drum is turning. This ability will be useful when creating ridges on the land or when working on the contours of land which is inclined. Where the cutting chain 48 engages the primary drum 30, specifically about the underside of the primary drum, it forms a seamless part-cylindrical cutting surface with the end portions 42 and 44 of the drum.

The cutter chain 48 is driven by a pair of electric motors 50, which are powered by the diesel-electric power unit. The primary drum 30 has a pair of auxiliary drum members 52 and 54 which can be fixed to respective opposed ends of the primary drum 30 to extend its length. The auxiliary drum members have the same diameter and have grousers and picks with a complementary geometry to those on the primary drum itself.

The secondary drum 32 is also driven by electric motors, similarly to the primary drum, or could be driven by drive chains housed in the arms 34 and linked to the main drive for the primary drum 30, with suitable gearing. The secondary drum could also be driven hydraulically, as could the primary drum if so desired.

The dimensions of the primary and secondary drums will vary according to the intended application of the apparatus. The width of the primary drum can vary between 0.5m and 6m, while the radius of the primary drum will typically vary between 0.5m and 1 .5m from the centre of the drum to the tips of the picks mounted on the primary drum. In a typical medium duty application, a radius of 0.6m from the centre of the drum to the tips of the picks mounted on the primary drum would be appropriate. The radius of the secondary drum can vary but is preferably between 20% and 30% of the radius of the primary drum, again measured from the centre of the secondary drum to the tips of the paddles mounted on the secondary drum.

The support system comprising the brackets 24 and the hydraulic actuators 28 is designed to vary the depth of the primary drum in the soil being worked, typically between 300mm and 3m below the surface of the soil.

The primary drum is preferably designed so that approximately 60% of its mass is concentrated within the outer 10% of its diameter, to maximise its rotational inertia.

The secondary drum 32 is fitted with paddles 56 which are staggered in the direction of the axes of the primary and secondary drums so that they fit between the picks 38 of the primary drum and the cutter chain 48. The paddles 56 fit between the picks 38 as the picks and paddles intermesh in use, so that the paddles clean the picks and clear the spaces between the picks of stones, rocks and clods of earth which may otherwise clog the primary drum. This allows soil to pass through the spaces between the picks as the apparatus works.

Figure 8 shows schematically how the picks 38 and the paddles 56 intermesh in use. The picks 38 can be seen to have heads which are pointed, mounted at the upper ends of pillars 60, while the paddles 56 have an elongate shape which substantially fills the gap between two adjacent picks, to provide effective cleaning of the primary drum.

The radius (or diameter) of the secondary drum is preferably between 20% and 30% of that of the primary drum and it turns at at least twice the speed of the primary drum. In one example, the diameter of the secondary drum is 30% of the diameter of the primary drum and the primary drum turns at 10Orpm, in which case the secondary drum may turn at 200rpm. Where the turning speed of the secondary drum is three times the turning speed of the primary drum, the secondary drum will turn at 300rpm, and so on.

The design and construction of the secondary drum is such that 60% of the mass of the drum is concentrated within the outer 20% of the diameter of the secondary drum.

The paddles on the secondary drum rotate through the mass of soil moved by the primary drum and, as the secondary drum rotates counter to and at a higher speed than the primary drum, this also helps to ensure that optimum mixing of the soil is achieved. As mentioned above, in some embodiments the secondary drum may co-rotate with the primary drum (i.e. rotate in the same sense or direction). In such embodiments, the secondary drum still performs a cleaning and soil mixing function. In this regard, the higher rotational speed of the secondary drum is important. The cleaning function of the paddles on the secondary drum, whether counter- or co-rotating relative to the primary drum, is a function of the higher turning speed of the paddles as they pass through the spaces between the picks and thus the higher momentum achieved by the paddles when engaging any material stuck between the picks. This momentum will be effective when addressing these materials head-on (co-rotating mode) but will be most effective when addressing the materials from behind (counter-rotating mode).

The hydraulically controlled arms 34 holding the secondary drum enable it to move away from and towards the primary drum to accommodate rocks and stones or other debris that may be embedded between the picks on the primary drum, preventing damage to the drums and the support mechanism.

The primary and secondary drums will be in most applications be covered by a moveable and removable hood (not shown) reaching down to the level of the soil to ensure that no soil or other solid materials are ejected from the zone through which the drum system is moving.

The operation of the earth working machine and apparatus are shown in a simplified schematic form in Figure 9. The traction unit 10 moves forward (or, in some cases, in reverse) over land to be worked, with the primary drum 30 lowered to a desired depth. The primary drum engages the soil to cut and lift it, while the secondary drum engages the lifted soil to assist in mixing it, and the mixed soil is then re-deposited. The direction or sense of rotation of the primary drum can be selected so that the leading edge of the primary drum effects a down cut (as shown) or an up cut. In either case, the secondary drum counter-rotates (or in some embodiments, co-rotates) at a higher speed. The picks 38 on the primary drum and cutting chain have a length which could vary, but in most cases will be set between 150mm and 300mm. This means that the energy required for them to cut through the soil is relatively low, but the fact that the drum can be lowered up to 3m into the soil enables deep working of the soil with realistic power requirements.

Large quantities of solid materials, including biochar (as indicated in Figure 9 by way of example), as well as liquid formulations, can be worked into the soil and homogeneously mixed throughout the soil to the depth of working of the soil. The rotational movement of the primary drum and the counter- rotational movement of the secondary drum, intermeshing with the primary drum, result in both solid materials and liquid formulations being injected into and homogeneously dispersed throughout the fluidized soil.

Solid materials, including biochar, up to the extent of 1 000 t/ha i.e. 100 kg/m2 with a bed thickness of more than 12cm (depending on the density of the solid materials) could be injected, worked and thus mixed into the soil through the combination of the actions described herein.

Liquids, in suspensions or solutions, containing various nutrients such as macroelements, microelements and biological soil ameliorants or pesticides to treat various soil borne diseases such as nematodes, or beneficial microorganisms, can be applied into the soil through the same injection mechanism by using a dispensing system which could be mounted on the machine or on a separate dispensing unit which could be moved ahead of the machine. The liquids will then be mixed with and throughout the soil to the depth that the primary drum is working.

The liquid formulations will be applied in the specific mixed concentrations of its various components and in the volumes as required at predetermined locations, guided by a GPS tracking system.

The exhaust gas from the traction unit 10, as well as other gasses which could benefit the soil, could be injected into the soil at the bottom of the settled bed of worked soil. These gasses could be transported in pressurized containers mounted on the traction unit or could be dispensed from a separate mobile system which moves ahead of the machine. The forces needed for the horizontal working of the soil are provided by the forward or backward motion of the overall machine or system. The forces needed for the vertical working of the soil are provided by the rotation of the primary drum with the picks on the primary drum cutting either downward or upward depending on the direction of rotation of the primary drum, as well as the backward or forward horizontal movement of the overall machine or system.

The decision to use forward or backward movement of the earth working machine, the rate of movement and the length of the extension of the picks, inter alia, will be determined by factors such as the moisture and clay content of the soil, the hardness of the soil, the presence of stones and rocks in the soil as well as the mass of solid materials to be worked into the soil.

The extent and effectiveness of the horizontal and vertical movement of the drum system will determine the extent of the fluidization (movement, lifting, mixing and dispersion) of the soil which, in turn, will determine the extent to which solid materials, such as biochar and fertilizers, can be injected, incorporated and mixed homogeneously into the soil.

Contrary to conventional ploughing and tilling systems which rely on linear draft forces through the horizontal plane supplied by the power source driving the system and restricting it to a critical depth of about 600 mm, the present invention as embodied in the described apparatus and machine relies on rotational forces enabling it to cut continuously into the soil in the vertical plane at lengths varying from 150mm but not exceeding 300mm, while working to depths exceeding 600mm and as deep as 3m.

The effective functioning of the described embodiment of the invention will rely on:

Adequate diesel generated power [kW] to drive both the horizontal motion of the machine as well as the rotational motion of the primary and secondary drums; in effect, the power required will have to exceed the resistance experienced from the soil.

Adequate power [kW] to deliver the required torque [Nm] to drive both the horizontal motion of the machine to achieve a specified speed [m/min] of the overall system as well as the rotational motion of the primary and secondary drums while the drums are operating at the specified depth in the soil.

Adequate power [kW] to deliver the required torque [Nm] with the necessary revolutions per minute [rpm] of the primary drum for the picks to cut through the volume of soil [m3] per minute [m3/min] needed for the productive operation of the overall system.

The forward pulsation of the picks penetrating the soil in tandem and in sequence and cutting with a rotational force through the soil while the system is driven forward in the horizontal direction. For example, with the primary drum rotating at 100 rpm and a row of 16 picks and other rows of picks alongside it, cutting and rotating through the soil, 16 pulses per second, with a pulse width equal to the width of the primary drum, will be generated, transmitting longitudinal shear waves ahead of the picks through the void and water content of the soil and initiating the liquefaction of the soil.

Soil can be considered as a solid or elasto-plastic material with quasi-static conditions. In any tilling system in which a static member penetrates the soil, power is needed for straight-line forward penetration. The power needed increases exponentially as the member goes deeper and/or faster. In conventional tilling, such as using ploughs and rippers, an optimal power demand is soon reached which may exceed the available power. Furthermore, in conventional tilling the soil failure front propagation is largely dependent on forward speed. In conventional tilling soil disturbance increase with operating speed. In conventional tilling tillage is concerned with depths of at most 1000mm (1 m). In conventional tilling, in general, tool design is optimized to achieve the goal of minimum input energy as it is estimated that tillage accounts for about one half of the energy used in crop production. Figure 10 illustrates the mechanism soil failure or crack propagation in conventional tilling.

By contrast, the present invention enables crack initiation and propagation in three dimensions down to the working depth of the machine, as indicated in Figure 1 1 . The present invention makes use of a rotational (circular) driving force thereby avoiding the exponential increase of power needed, as the cutting depth of the picks on the cutting drum always remains relatively small. Furthermore, in this invention the soil failure front propagation is only partly dependant on forward speed, but also on the rotational speed of the picks on the primary drum, delivering pulsating forces into the soil as the picks cuts in tandem and in quick succession and at an optimal angle through the soil, requiring a lower critical speed.

The soil failure path thus precedes the motion of the working tool while crack development and propagation becomes more prominent at greater depths of operation. In this invention soil disturbance is less dependant on forward speed but also on rotational speed and the pulsating of the picks cutting through the soil and advancing the soil failure front in three dimensions. Thus, in this invention the deep working of the soil can be carried out at much greater depths than in the case of conventional tilling, even up to a depth of 3m. In this invention the "working tool" is in effect the complete configuration of picks on the primary drum driven, as a front, through the soil by forward and rotational forces, thereby reducing energy consumption to the lowest possible levels.

Various alternative embodiments of the described earth working apparatus and machine are possible. For example, the support means for the primary and secondary drums could be arrange to be swung or angled to either side by hydraulic power units mounted on the chassis of the machine. This will compensate for inclination of the soil surface such as when the machine has to work on contours of the land. In another embodiment, the support means can be arranged to be offset to one side or the other of the longitudinal axis of the traction unit, in either a fixed or movable support arrangement, to enable soil to be worked selectively in narrow areas such as orchard rows or the like.

The invention makes possible soil deep-working machines which can achieve a working depth of up to 3m and a working width of up to 6m.

Claims

1 . Earth working apparatus comprising: a primary rotatable member having a plurality of earth- engaging members mounted thereon and being rotatable in a first direction; and a secondary rotatable member having a plurality of earth- engaging members mounted thereon and being rotatable in the first direction or in a second direction opposed to the first direction, the primary and secondary rotatable members being mounted for rotation about respective first and second axes which are substantially parallel.

2. The earth working apparatus of claim 1 wherein the primary and secondary rotatable members are rotatable drums.

3. The earth working apparatus of claim 2 wherein the secondary drum is smaller than the primary drum, having a radius which is in the range of 20% to 30% of that of the primary drum.

4. The earth working apparatus of claim 2 or claim 3 wherein the earth-engaging members mounted on the primary and secondary drums are picks on the primary drum and paddles on the secondary drum.

5. The earth working apparatus of claim 4 wherein each pick and paddle comprises an upstanding pillar with a replaceable head mounted thereon.

6. The earth working apparatus of claim 5 wherein each pick and paddle is mounted removably on a longitudinally extending elongate support member on the primary drum or the secondary drum, respectively.

7. The earth working apparatus of any one of claims 4 to 6 wherein the picks have relatively sharp tips for cutting the soil.

8. The earth working apparatus of any one of claims 4 to 7 wherein the paddles have generally planar tips and present a substantially flat surface to the soil in use.

9. The earth working apparatus of any one of claims 4 to 8 wherein the primary and secondary drums are mounted sufficiently closely together that the picks and paddles of the respective drums intermesh as the drums rotate in use.

10. The earth working apparatus of any one of claims 2 to 9 wherein the secondary drum is arranged to rotate at a speed at least twice that of the primary drum.

1 1 . An earth working machine comprising a traction unit and the earth working apparatus of any one of claims 1 to 10 mounted on the traction unit, the traction unit having at least one motor and a drive train arranged to drive the machine across land to be worked, and a drive system arranged to operate the earth working apparatus.

12. The earth working machine of claim 1 1 including adjustable support means arranged to raise or lower the primary and secondary rotatable members to vary the working depth thereof.

13. An earth working method, the method including: arranging primary and secondary rotatable members for rotation about respective first and second axes which are substantially parallel, the primary rotatable member having a plurality of earth-engaging members mounted thereon and being rotatable in a first direction, the secondary rotatable member having a plurality of earth-engaging members mounted thereon and being rotatable in the first direction or in a second direction opposed to the first direction; and operating the primary and secondary rotatable members in counter rotation or, alternatively, in co-rotation while moving both rotatable members across land in a direction transverse to the first and second axes, so that the primary rotatable member engages soil to cut and lift it, the secondary rotatable member engaging the lifted soil to assist in mixing thereof, the soil then being re-deposited.

14. The earth working method of claim 13 including depositing a layer of material on the surface of land to be worked, so that the primary and secondary rotatable members effectively mix the deposited material into soil worked by the method.

15. The earth working method of claim 13 or claim 14 including injecting a liquid formulation or a gas into soil worked by the method.