EP4366496A2

EP4366496A2 - Agricultural implement and method of working stubble field

Info

Publication number: EP4366496A2
Application number: EP22769411.4A
Authority: EP
Inventors: Crister Stark; Urban HAMMARSTRÖM
Original assignee: Vaderstad Holding AB
Current assignee: Vaderstad Holding AB
Priority date: 2021-07-07
Filing date: 2022-07-05
Publication date: 2024-05-15
Also published as: SE2150901A1; WO2023282831A3; WO2023282831A2

Abstract

An agricultural implement (1) for working soil, over which the agricultural implement travels in a working direction (F), comprises a tool frame (10, 10a, 10b, 10c, 11), a plurality of ground-breaking tools (14a, 14b) of a first tool type which are carried by the tool frame (10a, 10b, 10c, 11) and distributed over a width of the agricultural implement (1), and a pretool (2, 2a, 2b, 2c) which is arranged in front of said ground-breaking tool (14a, 14b) viewed in the working direction. A pretool frame (20) is height-adjustable via a substantially vertical displacement of the pretool frame (20) relative to the tool frame (10, 10a, 10b, 10c, 11).

Description

AGRICULTURAL IMPLEMENT AND METHOD OF WORKING STUBBLE

FIELD

Technical Field

This document concerns an agricultural implement for working the soil, and in particular an agricultural implement for very shallow working of the soil on fields with a large amount of straw, and in particular for working stubble fields with a large amount of straw.

Background

When harvesting using combine harvesters, straw is ejected onto the field. This straw may be collected fully or partly to be used for example for animal rearing, but often at least some of the straw remains on the field, whereby it is desirable to break this down before the next crop.

A particular problem is that such remaining straw is often unevenly distributed on the field, either as a direct consequence of the combine harvester’s function, such as a consequence of how the combine harvester is operated, for example with stoppages, or as a consequence of external factors such as wind.

It is known to use a particular implement in the form of a straw harrow for distributing the straw on the field. Such a straw harrow is shown for example in US2018139883A1.

A trend within modern agriculture is to work the ground less deeply and to allow the root system of the crop to remain during most of the loosening of the soil, instead of using a conventional harrow or cultivator. This however means that it is desirable to avoid, as far as possible, compacting the ground by driving a tractor over it. It is therefore important to minimise the number of runs.

A undulating disc tool which has been proved particularly suitable for very shallow working and for breaking down the straw is shown in WO201 7213575A1. This tool too however is less efficient if the layer of straw on the soil surface is too thick. It is known to use a simpler form of a single- or double-row straw harrow as a pretool on a cultivator, with the aim of creating a more favourable distribution of the straw before the action of the disc tool.

There is however need for a more effective agricultural implement for shallow working of the soil in the field with a large amount of straw.

Summary

One object is therefore to achieve a more effective agricultural tool for shallow working of the soil in the field with a large amount of straw.

The invention is defined by the appended independent claim. Embodiments arise from the dependent claims, from the description which follows and from the appended drawings.

According to a first aspect, an agricultural implement is provided for working soil over which the agricultural implement travels in a working direction. The agricultural implement comprises a tool frame, a plurality of ground-breaking tools of a first tool type, which are carried by the tool frame and are distributed over a width of the agricultural implement, and a pretool which is arranged in front of said ground-breaking tool, viewed in the working direction. The pretool comprises a pretool frame which carries a plurality of straw harrow tines distributed over a width of the pretool frame. The pretool has a frame fixing device which is located at a rear part of the pretool frame viewed in the working direction. The pretool has a free end which is located at a front part of the pretool frame viewed in the working direction. The tool frame has a pretool fixing device which is configured for releasable fixing of the pretool relative to the tool frame. The straw harrow tines are distributed over at least three separate transverse shafts in the working direction, so that the straw harrow tines are arranged rotatably relative to the pretool frame, and are connected by a synchronising device so that the straw harrow tines are rotatable in common and in synchrony relative to the pretool frame. The pretool frame is height-adjustable via a substantially vertical displacement of the pretool frame relative to the tool frame.

It is evident that a pretool may comprise a single pretool frame which is mounted on a tool frame. Alternatively, the pretool may be divided into a number of pretool parts which can be mounted against the respective adjacent frame part of the agricultural implement.

Straw harrow tines are known in themselves and are designed such that their tips drag over the soil and have an acute angle to the ground surface when viewed in a vertical plane containing the working direction. In contrast to cultivator tines and harrow tines, they are not “soil-following”.

When the straw harrow tines do not rest on the ground, the pretool fixing device transfers the entire weight of the pretool to the tool frame.

The term “vertical displacement” means a displacement of the pretool frame with substantially retained orientation.

By making the pretool frame height-adjustable and the straw harrow tines rotatable, it is possible to set the pretool with sufficient precision to be able to penetrate the ground sufficiently but not too deeply. This is particularly important for a pretool with a plurality of shafts which are attached to the tool frame at the rear edge, since penetrating the ground too deeply may lead to an overload of the pretool fixing, or to undesirable oscillations of the pretool.

The load-bearing connection between the frame fixing device and/or the pretool fixing device on one side and the tool frame on the other may comprise a parallel linkage.

The parallel linkage may comprise a first pair of rotary shafts which are associated with the pretool frame and a second pair of rotary shafts which are associated with the tool frame, wherein the rotary shafts associated with the tool frame are arranged behind the rotary shafts associated with the pretool frame when viewed in the working direction.

The agricultural implement may furthermore comprise a first adjustment device for adjusting the rotary position of the straw harrow tines relative to the pretool frame, wherein said first adjustment device comprises at least one first actuator.

The first actuator may be supported by the pretool frame.

The agricultural implement may furthermore comprise a second adjustment device for adjusting the height position of the pretool relative to the tool frame, wherein said second adjustment device comprises at least one second actuator. The second actuator may be supported by the pretool frame.

The agricultural implement may furthermore comprise a control unit which is configured to control said first and/or second actuator.

The agricultural implement may furthermore comprise a straw detector which is configured to detect a quantity of straw carried along by the pretool, wherein the control unit is configured to give an indication corresponding to said quantity of carried straw.

Said first tool type may be selected from a group comprising cultivator tines, disc tools, levelling tools and cross-cutting disc tools.

Said first tool type may be formed by cross-cutting undulating disc tools which each have a plurality of cutting edges which work a width amounting to around 5-18 cm, preferably around 8-15 cm or 10-15 cm, projected onto a plane containing the respective disc rotation axis.

The straw harrow tines may be distributed over 4-6 separate transverse shafts in the working direction.

The straw harrow tines may be configured to create an effective tine spacing of around 6 +/- 3 cm, preferably 6 +/- 1 cm.

The agricultural implement may furthermore comprise at least one second set of ground-breaking tools of another tool type, which is arranged behind said ground-breaking tool of the first tool type.

The agricultural implement may furthermore comprise a recompacting tool, such as a roller, arranged behind said ground-breaking tool of the first tool type.

According to another aspect, a method is provided for working stubble fields, comprising: within 1 month, preferably within 2 weeks, within 1 week, within 3 days or within 24 hours from threshing, carrying out at least one run with an agricultural implement according to any of the preceding claims, wherein said straw harrow tines are set to a working depth of less than around 5 cm, preferably around 2-3 cm, and wherein said ground-breaking tool of the first tool type is set to a working depth of less than around 5 cm, preferably around 2-3 cm.

The method may furthermore comprise resetting the rotary position of the straw harrow tines and/or the height position of the pretool frame while the agricultural implement advances over the stubble field and the straw harrow tines penetrate the ground.

The method may also comprise detection of a quantity of straw carried along with the pretool, and preferably resetting the rotary position of the straw harrow tines and/or the height position of the pretool frame based on said detection.

According to a third aspect, a method is provided for handling an agricultural implement comprising a straw harrow which has a plurality of straw harrow tines. The method comprises moving the agricultural implement over ground on which a plurality of substantially mutually parallel rows of straw are left after threshing, wherein the agricultural implement advances in a working direction which has an angle of around 20-90 degrees relative to the rows, and at a plurality of times, by means of a straw detector, registering a measurement value which indicates a quantity of straw present on the straw harrow, so as to create a data series which indicates the straw quantity, and based on said data series, determining a state of the straw harrow.

The duration between the times at which registration takes place may be very short, for example so short as to achieve one measurement value per 5 cm or per 10 cm. A higher frequency may also be suitable in order to increase the number of reliable measurement values at each point. Suitable frequencies may be 10 - 50 Hz, preferably 10 - 30 Hz.

The method may furthermore comprise resetting a ground height and/or working angle for the straw harrow tines based on the state.

While some combine harvesters discharge straw in a row directly behind the combine harvester, other combine harvesters have different types of spreading devices which are designed to distribute the straw evenly behind the combine harvester. Even with combine harvesters with such spreading devices, however, there is a tendency to form rows in the form of ridges of thicker straw layers.

The agricultural implement described herein also in this case advances at an angle of around 20 - 90° relative to the working direction of the combine harvester. Brief Description of the Drawings

Fig 1 shows an agricultural implement 1 viewed from above.

Fig 2 shows the agricultural implement with the pretool in non-mounted position. Fig 3 shows an enlargement of a part of figure 2.

Fig 4a-4b show a pretool fixing device.

Fig 5a-5b show the agricultural implement with the pretool installed in various positions.

Fig 6a-6b show an agricultural implement with a first design of a straw detection device.

Fig 7a-7b show an agricultural implement with a second design of a straw detection device.

Fig 8a-8c show filling diagrams for a straw harrow. Detailed Description

Figure 1 shows an agricultural implement 1 viewed from above. Figure 2 shows the agricultural implement 1 viewed from the side, with the ground support 15 in the up and down positions.

As figure 2 shows, straw harrow tines are formed from relatively long and slender rods of metal which are arranged at an acute working angle Va at the front, viewed in a vertical plane containing the working direction F.

In the example shown, the agricultural implement 1 is divided into three frame sections 1a, 1b, 1c which are arranged next to one another and are rotatable relative to one another about horizontal axes H 1 , H2 which run parallel to a working direction F of the agricultural implement 1. By dividing the agricultural implement into two or more frame sections which are arranged rotatably relative to one another, the agricultural implement can be folded up into a transport position and the ground pressure and/or contour following of the respective frame section can be controlled, i.e. the agricultural implement can follow the height variations of the ground being worked.

It is evident that a number of different configurations are possible with the agricultural implement 1 divided into two, three, four or five adjacent sections, depending on what is desirable in order to achieve the desired working width and transport width/transport height.

The agricultural implement 1 comprises a tool frame 10, 10a, 10b, 10c which carries a first tool set comprising a plurality of ground-breaking tools 14a, 14b of a first tool type. The tools 14a, 14b may be spring-mounted relative to the tool frame 10, 10a, 10b, 10c.

A towbar 11 may be connected to the tool frame 10 and has a tow coupling 12 at a front end, viewed in the working direction F.

The tool 14a, 14b of the first tool type may be any type of soil-working tool, such as cultivator tines, harrow tines, a disc tool or levelling tool. As a further alternative, the tool of the first tool type may comprise discharge units for discharging seed, fertiliser and/or herbicides/pesticides. Such discharge units may take the form of seed drills, disc drills or row seeders for precision sowing.

In the example shown, the tool 14a, 14b of the first type is a cross cutting undulating disc tool, i.e. a disc tool which is arranged rotatably relative to the tool frame 10, and the periphery of which has a undulating form with a plurality of cutting edges which extend non-perpendicularly to the respective rotation axis of the disc. Specifically, the cutting edges may extend at an angle of around 10 to 80° relative to the rotation axis, preferably around 20 to 70°, or around 30 to 60°. The cutting edges may be substantially straight and extend over a width amounting to 5 - 18 cm, preferably 8 - 15 or 10 - 13 cm, projected onto a plane containing the respective rotation axis of the disc.

Such cross-cutting disc tools are known for example from SE536761C1, WO2014137281 A1 and WO20127213575A1.

One or more ground supports 15, such as wheels or rollers, may be arranged at a rear part of the tool frame 10. Such ground supports 15 may be connected to the tool frame 10 via a ground support frame 13, which may be adjustable relative to the tool frame 10, for example by being rotatable relative to the tool frame 10. By adjusting the height position of the ground support 15 relative to the tool frame 10, for example by using an actuator 16 (figure 2), the working depth of the tool 14a, 14b can be controlled. It is possible to arrange further tools of a second tool type after the tool of the first tool type, viewed in the working direction F. For example, some form of recompacting tool may be provided, such as a roller with a plurality of rings with a outwardly rounded or pointed circumference and made of steel or rubber, or a so-called soil-to-soil roller, i.e. a roller with U-shaped profiles. Alternatively, a ribbed roller may be used.

The tool of the second type, in the form of a roller, may be combined with or provided instead of the ground support 15.

A pretool 2 is arranged at a front part of the tool frame 10. The pretool 2 may comprise a pretool frame 20 which carries a plurality of tools 21 in the form of straw harrow tines, i.e. relatively slender metal tines.

It is evident that the pretool 2 may be divided into a number of pretool sections, the number of which corresponds to the number of frame sections 1a, 1b, 1 c of the agricultural implement 1.

A plurality of such straw harrow tines 21 are distributed over the width of the pretool 2, and over at least three, preferably 4 - 6 shafts 22 distributed in the working direction F. The straw harrow tines 21 may be arranged so as to give an effective tine spacing of around 6 cm +/- 1 cm. An “effective tine spacing” refers to the track pattern created by the tool. The tines may thus, in a manner known in itself, being mutually offset along the working direction.

Each of the straw harrow tines 21 may, in a manner known in itself, be spring-mounted on the shaft 22.

The spring mounting may be achieved by one or more straw harrow tines being mounted on a carrier which in turn is spring-mounted on the shaft 22.

Alternatively, the spring mounting may be achieved by the straw harrow tines being provided with an integral torsion spring, such as a spiral spring. The shafts 22 are rotatably mounted relative to the pretool frame 20, for example so that all straw harrow tines 21 mounted on a shaft 22 are rotatable together with the shaft 22.

A synchronising device may be provided for carrying all shafts 22 associated with a pretool frame 20. The synchronising device may comprise at least one lever 23 which is fixedly connected to the respective shaft 22. The lever arms 23 may be connected to one another via a linkage 24, so that the positions of all levers 23 and hence all shafts 22 are synchronised with one another. An actuator 25 for adjusting the straw harrow tines 21 may be arranged so as to work between the pretool frame 20 and one of the lever arms, alternatively with a separate lever. Thus the rotary position of all shafts 22, and hence the straw harrow tines 21 connected to the shafts 22, may be synchronised by means of a first actuator 25.

The height position of the pretool 2, 2a, 2b, 2c is adjustable relative to the tool frame 10, 10a, 10b, 10c by means of a parallel linkage 27.

With reference to figure 3, the parallel linkage 27 may comprise a pair of rotary shafts 271 , 272 which are fixed relative to the pretool frame 20, and a pair of rotary shafts 273, 274 which are fixed relative to the tool frame 10, 10a, 10b, 10c, together with parallel links 275, 276 extending between the rotary shafts 271, 272; 273, 274. The parallel linkage 27 thus constitutes the load-bearing connection between the tool frame 10, 10a, 10b, 10c and the pretool 2, 2a, 2b, 2c.

A second actuator 26 may be provided for adjusting the position of the pretool 2, 2a, 2b, 2c relative to the tool frame 10, 10a, 10b, 10c.

At least one and preferably both of the first and second actuators 25I 26 may be supported by the pretool frame 20.

With reference to figures 4a - 4b, a fast coupling device 14 may be provided for simple and releasable coupling of the pretool 2, 2a, 2b, 2c to the tool frame 10, 10a, 10b, 10c. The fast coupling device 14 may comprise a pair of cradles 141, 142 which are designed to receive horizontally extending parts of the pretool 2, 2a, 2b, 2c.

In the example shown, the rotary shafts 273, 274, which are fixed relative to the tool frame 10, 10a, 10b, 10c, may be received in the respective cradles 141, 142.

A locking part 143, 143' may be arranged on at least one of the cradles 141, 142, and be designed and configured to prevent the horizontally extending parts of the pretool 2, 2a, 2b, 2c from leaving the respective cradle.

In the example shown, an upper one of the cradles 141 , 142 is provided with a locking part 143, 143', which is mounted so as to be rotatable about a locking part axis 144 and which can be pretensioned in a locking position, for example by means of a spring 145, 145'.

The locking part 143, 143' may have a guide surface 1431 and a locking surface 1432. The guide surface 1431 may face outward from the cradle 141, 142 and be designed so that a load on the guide surface brings the locking part 143, 143' to rotate around the locking part axis 144, while the spring 145, 145' acts in the opposite direction against a locking part lever 1433.

The locking part 143, 143' may also have a locking surface 1432 which is designed to prevent a horizontally extending part of the pretool 2, 2a, 2b,

2c, which is received in the cradle 141, 142, from leaving the cradle 141, 142.

The pretool 2, 2a, 2b, 2c may be released by rotation of the locking part around the locking part axis 144, such that the engagement of the locking surface 1432 with the horizontally extending part of the pretool 2, 2a, 2b, 2c is released.

The pretool 2, 2a, 2b, 2c is releasably coupled to the tool frame 10,

10a, 10b, 10c by means of a fast coupling 14.

Figure 5a shows the agricultural implement 1 in a first working position, in which the pretool frame 20 is set to an upper height position relative to the tool frame 10, and the straw harrow tines 21 are set to a position with a large angle relative to the pretool frame 20.

Figure 5b shows the agricultural implement 1 in a second working position, in which the pretool frame 20 is set to a lower height position relative to the tool frame 10, and the straw harrow tines 21 are set to a position with a small angle relative to the pretool frame 20.

When the agricultural implement 1 advances over a field strewn with straw, and in particular over a stubble field strewn with straw, the height position of the pretool relative to the tool frame can be set from the working depth to which the tool is set, for example by means of the ground support device 15.

It is possible to provide the agricultural implement, and in particular the pretool 2, 2a, 2b, 2c, with a ground distance sensor and to continuously or intermittently determine the distance of the pretool from the ground surface, and based on such a determined distance, correct the height position of the pretool frame 20 relative to the tool frame 10, 10a, 10b, 10c, and/or the rotary position of the straw harrow tines 21 relative to the pretool frame 20.

An agricultural implement as described above has proved particularly suitable for working stubble fields shortly after harvest. It is desirable to have as high a moisture content as possible in the field during working, since this promotes the break-down of the straw. Depending on the weather conditions, periods of varying length may be left between threshing and working. Depending on different methods, working may be carried out within 1 month from threshing if the weather conditions are sufficiently damp. Preferably, working should take place within 2 weeks from threshing, within 1 week from threshing, within 3 days from threshing or preferably within 24 hours from threshing. Such working may be carried out with an agricultural implement provided with a pretool in the form of a straw harrow, with straw harrow tines 21 which have a tine spacing of 6+/- 3 cm, with tines distributed over 4 - 6, preferably 5 shafts, followed by two successively arranged rows of cross cutting undulating discs, wherein the straw harrow tines 21 work to a depth of less than 5 cm, preferably 2 to 3 cm, and wherein the undulating discs work to a depth of less than 5 cm, preferably 2 to 3 cm. The undulating discs may be followed by a roller tool for recompacting.

Figures 6a - 6b show an agricultural implement 1 with a first design of a straw detector 40, i.e. a detector intended to detect the accumulation of straw 30 on the pretool 2.

The detector may be connected to a control unit 60 which may also be configured for example to control actuators 25, 26 via a force converter. The control unit 60 may be common to the entire agricultural implement. Alternatively, the control unit 60 may be implemented as a part in a control unit arranged in the tractor, for example as an application therein.

The straw detector 40, 40' illustrated in figures 6a - 6b comprises an elongate part which is configured to trail over the ground with the pretool so that the part is pressed upward when straw 30 has accumulated under the pretool. By detecting the curvature of the elongate part, e.g. by means of a strain sensor, or the torque by means of a rotation sensor, it is possible to estimate the quantity of straw 30 which has accumulated under the pretool and adjust the pretool in the case where too much or too little straw 30 is present.

Figures 7a - 7b show an agricultural implement 1 with a second design of a straw detector 50, 51 , i.e. a detector intended to detect the accumulation of straw 30 at the pretool 2.

The straw detector 50, 51 illustrated in figures 7a - 7b comprises one or more cameras which can take images of the area in front of and/or below the pretool 2, and based on the images, estimate the quantity of straw 30 which has accumulated under the pretool, so as to allow adjustment of the pretool for the case where too much or too little straw 30 is present.

For example, an Al-based image processing may be applied, whereby an assessment algorithm such as a classification algorithm is trained on the basis of images with different quantities of accumulated straw.

Camera-based straw detectors may use visible light, IR light or near IR light. Alternatively or additionally, a straw detector may use radar or ultrasound.

A straw harrow is often used after threshing has taken place, and often with a run pattern which crosses the run pattern of the threshing, usually at an angle of around 20 to 90°, preferably around 30 to 60°. The thresher usually leaves a row of straw behind it. Thus an uneven distribution over the field occurs, with straw distributed in a number of parallel straw rows.

With a correctly set straw harrow, it is possible to achieve a significantly improved distribution of straw over the field when the straw harrow is advanced across the straw rows.

Figure 8a shows a filling diagram (F= full, E = empty) for a correctly set straw harrow, wherein the straw harrow is regularly filled to almost full, and regularly loses straw to almost empty, which means that the straw is very well levelled out. Thus the correct balance is maintained between the pretool frame height and the angle of the straw harrow tines or their pressure against the ground.

Figure 8b shows a filling diagram for a straw harrow which is filled easily and may be overfull, but which has poor capacity for losing/discharging straw. The reason - or possible reason - may be that the frame height is too high, and possibly also the pressure of the straw harrow tines against the ground is too great. The straw harrow functions as a rake. With such a position, it may be suitable to reduce the frame height and reduce the pressure of the straw harrow tines and the angle against the ground. This may be done in stages, whereby an adjustment is made and the result monitored and thereafter another adjustment made.

Figure 8c shows a filling diagram for a straw harrow which is not able to be fully filled and from which material is easily lost. This may be because the straw harrow frame lies too close to the ground, and the angle of the straw harrow tines against the ground is relatively flat. Thus the straw harrow is not able to pick up and collect a sufficient quantity of straw. The straw quantity which is nonetheless captured is easily lost, as the tines have a poor capacity for retaining straw because of the small angle between the ground and the straw harrow tine.

It is thus possible not only to measure how much straw is present in the straw harrow at any time, but also - when used as described above - to measure how the straw quantity fluctuates over time, and based on this fluctuation, to draw conclusions about how the implement is set and how it should be adjusted.

Measurement data concerning the straw quantity may be used so as to indicate, for example via the control unit 60, the state of the agricultural implement 1 to the operator, such as a driver, whereby the latter can make adjustments to the settings of the pretool 2.

Alternatively, the control unit may be provided so as to make such adjustments of the pretool settings directly, i.e. autonomously, or after request/proposal to the operator.

It is furthermore possible to store measurement data in the control unit and associate the measurement data with different settings of the pretool. Thus measurement data may be used for monitoring the movement over the field and for training the Al software for future settings.

It is evident that control and storage may take place remotely from such an agricultural implement 1, such as in a central control unit, which may be configured to remotely control a plurality of agricultural implements which are active on a farm or within an area.

Claims

1. Agricultural implement (1 ) for working soil over which the agricultural implement travels in a working direction (F), wherein the agricultural implement comprises: a tool frame (10, 10a, 10b, 10c, 11 ), a plurality of ground-breaking tools (14a, 14b) of a first tool type which are carried by the tool frame (10a, 10b, 10c, 11) and are distributed over a width of the agricultural implement (1), and a pretool (2, 2a, 2b, 2c) which is arranged in front of said ground breaking tool (14a, 14b), viewed in the working direction, wherein the pretool (2, 2a, 2b, 2c) comprises a pretool frame (20) which carries a plurality of straw harrow tines (21 ) distributed over a width of the pretool frame (20), wherein the pretool (2, 2a, 2b, 2c) has a frame fixing device (27) which is located at a rear part of the pretool frame (20), viewed in the working direction (F), wherein the pretool (2, 2a, 2b, 2c) has a free end which is located at a front part of the pretool frame (20), viewed in the working direction (F), and wherein the tool frame (10, 10a, 10b, 10c, 11) has a pretool fixing device (14) which is configured for releasable fixing of the pretool (2, 2a, 2b, 2c) relative to the tool frame (10, 10a, 10b, 10c, 11 ), characterized in that the straw harrow tines (21 ) are distributed over at least three separate transverse shafts in the working direction (22), so that the straw harrow tines are arranged rotatably relative to the pretool frame (20) and connected by a synchronising device (23, 24) so that the straw harrow tines (21) are rotatable in common and in synchrony relative to the pretool frame (20), and the pretool frame (20) is height-adjustable via a substantially vertical displacement of the pretool frame (20) relative to the tool frame (10, 10a, 10b, 10c, 11).

2. Agricultural implement according to Claim 1 , wherein the load- bearing connection between the frame fixing device (27) and/or the pretool fixing device on one side and the tool frame (10, 10a, 10b, 10c, 11 ) on the other comprises a parallel linkage (271 , 272, 273, 274, 275, 276).

3. Agricultural implement according to Claim 2, wherein the parallel linkage (271, 272, 273, 274, 275, 276) comprises a first pair of rotary shafts (271 , 272) which are associated with the pretool frame (20), and a second pair of rotary shafts (273, 274) which are associated with the tool frame (10), wherein the rotary shafts (273, 274) associated with the tool frame (10) are arranged behind the rotary shafts (271, 272) associated with the pretool frame (20) when viewed in the working direction (F).

4. Agricultural implement according to any of the preceding claims, furthermore comprising a first adjustment device (23, 24, 25) for adjusting the rotary position of the straw harrow tines (21) relative to the pretool frame (20), wherein said first adjustment device comprises at least one first actuator (25).

5. Agricultural implement according to Claim 4, wherein the first actuator (25) is supported by the pretool frame (2, 2a, 2b, 2c).

6. Agricultural implement according to any of the preceding claims, furthermore comprising a second adjustment device (26, 271, 272, 273, 274, 275, 276) for adjusting the height position of the pretool (2, 2a, 2b, 2c) relative to the tool frame (10), wherein said second adjustment device comprises at least one second actuator (26).

7. Agricultural implement according to Claim 6, wherein the second actuator (26) is supported by the pretool frame (20).

8. Agricultural implement according to any of Claims 4-7, furthermore comprising a control unit which is configured to control said first and/or second actuator (25, 26).

9. Agricultural implement according to Claim 8, furthermore comprising a straw detector (40, 40’, 50, 51 ) which is configured to detect a quantity of straw carried along by the pretool (2), wherein the control unit is configured to give an indication corresponding to said quantity of carried straw.

10. Agricultural implement according to any of the preceding claims, wherein said first tool type is selected from a group comprising cultivator tines, disc tools, levelling tools and cross-cutting disc tools.

11. Agricultural implement according to Claim 10, wherein said first tool type is formed by cross-cutting undulating disc tools, which each have a plurality of cutting edges which work a width amounting to around 5-18 cm, preferably around 8-15 cm or 10-15 cm, projected onto a plane containing the respective disc rotation axis.

12. Agricultural implement according to any of the preceding claims, wherein said straw harrow tines (21) are distributed over 4-6 separate transverse shafts (22) in the working direction.

13. Agricultural implement according to any of the preceding claims, wherein said straw harrow tines (21) are configured so as to achieve an effective tine spacing of around 6 +/- 3 cm, preferably 6 +/- 1 cm.

14. Agricultural implement according to any of the preceding claims, furthermore comprising at least one second set of ground-breaking tools of another tool type, which is arranged behind said ground-breaking tool (14a, 14b) of the first tool type.

15. Agricultural implement according to any of the preceding claims, furthermore comprising a recompacting tool (15), such as a roller, arranged behind said ground-breaking tool of the first tool type.

16. Method of working stubble fields, comprising: within 1 month, preferably within 2 weeks, within 1 week, within 3 days or within 24 hours from threshing, carrying out at least one run with an agricultural implement according to any of the preceding claims, wherein said straw harrow tines (21 ) are set to a working depth of less than around 5 cm, preferably around 2-3 cm, and wherein said ground-breaking tool (14a, 14b) of the first tool type is set to a working depth of less than around 5 cm, preferably around 2-3 cm.

17. Method according to Claim 16, furthermore comprising resetting the rotary position of the straw harrow tines (21 ) and/or the height position of the pretool frame (20) while the agricultural implement advances over the stubble field and the straw harrow tines penetrate the ground.

18. Method according to Claim 16 or 17, furthermore comprising detection of a quantity of straw carried along with the pretool, and preferably resetting the rotary position of the straw harrow tines (21) and/or the height position of the pretool frame (20) based on said detection.

19. Method for handling an agricultural implement (1 ) comprising a pretool in the form of a straw harrow (2) which has a plurality of straw harrow tines (21), comprising: moving the agricultural implement (1 ) over ground on which a plurality of substantially mutually parallel rows of straw are left after threshing, wherein the agricultural implement (1) advances in a working direction (F) which has an angle of around 20-90 degrees relative to the rows, at a plurality of times, by means of a straw detector (40, 40’, 50, 51 ), registering a measurement value which indicates a quantity of straw present on the straw harrow, so as to create a data series which indicates the straw quantity, and based on said data series, determining a state of the straw harrow.

20. Method according to claim 19, wherein the agricultural implement comprises a plurality of ground-breaking tools (14a, 14b) of a first tool type which are carried by the tool frame (10a, 10b, 10c, 11) and are distributed over a width of the agricultural implement (1), and said pretool (2, 2a, 2b, 2c), which is arranged in front of said ground breaking tool (14a, 14b), viewed in the working direction, wherein straw harrow tines (21) are distributed over at least three separate transverse shafts (22) in the working direction, so that the straw harrow tines are arranged rotatably relative to the pretool frame (20), and are connected by a synchronising device (23, 24) so that the straw harrow tines (21) are rotatable in common and in synchrony relative to the pretool frame (20), and the pretool frame (20) is height-adjustable via a substantially vertical displacement of the pretool frame (20) relative to the tool frame (10, 10a, 10b, 10c, 11).

21. Method according to claim 19 or 20, furthermore comprising, based on the state, resetting a ground height and/or working angle for the straw harrow tines.