WO 2008/084428 PCT/IB2008/050030 1 PLANTING OF SEEDLINGS 5 This invention relates to the planting of seedlings. More particularly the invention relates to a pitting device for removing slash from a soil surface and creating a planting pit in the soil, and to a seedling planter vehicle. According to one aspect of the invention there is provided a pitting device 10 for removing slash from a soil surface and creating a planting pit in the soil, the device including a vertically displaceable, rotatable pitting head operable to drill a planting pit in the soil; a slash arm anchor guide extending upwardly from the pitting head; 15 at least one slash arm anchor mounted for floating displacement relative to the pitting head along the slash arm anchor guide, between a position proximal to the pitting head and a position distal from the pitting head; and a plurality of slash arms for clearing slash from below the pitting head, the slash arms being pivotally anchored to at least one slash arm anchor and being guided for 20 outward displacement of lower ends of the slash arms away from the pitting head when the slash arm anchor is displaced away from the pitting head along the slash arm anchor guide. The pitting head may depend from said at least one slash arm anchor 25 guide and may be relatively rotatably mounted to said at least one slash arm anchor guide. The pitting head may include a rotatable digging member carrier and a plurality of digging members depending from said rotatable digging member carrier. In one embodiment of the invention at least one of the digging members may be an auger which is located centrally on the rotatable digging member carrier. 30 The at least one slash arm anchor may be in the form of a collar which is fitted around the slash arm anchor guide, said collar being slidingly displaceable relative to the pitting head along said slash arm anchor guide between said proximal position and said distal position.
WO 2008/084428 PCT/IB2008/050030 2 The at least one slash arm guide may be a member of a telescopic arm. Typically, the telescopic arm includes an inner member and an outer member, with the inner member being slidably received within the outer member. The members may be 5 square in transverse cross section. The at least one slash arm guide in one embodiment of the invention is in the form of the inner member of the telescopic arm. Preferably, one of the inner member and the outer member of the telescopic arm is provided with friction reducers, e.g. in the form of strips of low friction material, to reduce friction between the members of the telescopic arm. 10 At least some of the slash arms may be curved and the pitting device may include at least one slash arm guide in contact with at least one of said curved slash arms, the slash arm guide being arranged guidingly to force said at least one curved slash arm outwardly away from the pitting head when said at least one curved slash 15 arm is in use pushed past the slash arm guide by contact with the soil surface, or pulled by said at least one slash arm anchor past the slash arm guide. The pitting device may include a base or support, e.g. in the form of a flange, at a lower end of the slash arm anchor guide, with the pitting head thus also 20 being rotatable relative to the base. The at least one slash arm guide may be mounted to the base. Typically, each slash arm is associated with a slash arm guide mounted to the base. The slash arms may be pivotally suspended from a single slash arm 25 anchor and may be shaped to extend downwardly past the pitting head and to curve inwardly below the pitting head when the slash arms are in a rest position and the slash arm anchor is in said position proximal to the pitting head. Typically, each slash arm extends through an elongate guide slot defined by its associated slash arm guide. 30 The pitting device may include a slash hook at the lower ends of at least some slash arms, the slash hook being pivotally connected to the slash arm. Preferably, the slash hooks are biased downwardly, e.g. by means of a spring.
WO 2008/084428 PCT/IB2008/050030 3 The pitting device may further include a wheel at the lower ends of at least some slash arms. The wheel may be mounted ahead of the slash hook to lead the slash hook when the slash arm is displaced outwardly away from the pitting head. In one embodiment of the invention, a pair of side by side wheels is provided at the lower end 5 of each slash arm. The pitting head may also include a fertilizer reservoir. A fertilizer feed path may lead from the fertilizer reservoir to a discharge location underneath the pitting head. The fertilizer reservoir is typically located below the base so that in use it rotates 10 as part of the pitting head. A filler opening leading into the fertilizer reservoir may be provided in the base. The pitting device may further include a seedling depositor assembly mounted for displacement with the pitting head and configured in use to deposit a 15 seedling in the planting pit which has been created by the pitting head. The seedling depositor assembly may include a swing arm which may be pivotally mounted to a support, e.g. the base, above the pitting head and an elongate seedling depositor at an end of the swing arm remote from the support, the swing arm 20 being pivotally displaceable between a raised position in which the seedling depositor is in a vertical plane adjacent the pitting head, and a lowered, i.e. planting, position in which the seedling depositor is located underneath the pitting head. The seedling depositor may further be pivotally mounted to the swing arm 25 and may be restrained so that a longitudinal axis of the seedling depositor remains upwardly extending during pivoting of the swing arm. The seedling depositor may also include an elongate seedling housing with a lower seedling deposit outlet and an upper seedling receiving inlet. The seedling 30 depositor may further include at least two jaws hingedly mounted at the seedling deposit outlet, the jaws being hingedly displaceable between a closed position in which the seedling deposit outlet is closed by the jaws with the jaws defining a pointed soil penetrator, a first open condition in which the jaws project downwardly and open the seedling deposit outlet for depositing of a seedling, and a second open condition in WO 2008/084428 PCT/IB2008/050030 4 which the jaws project substantially horizontally away from the seedling housing defining soil compacters. The pitting device may include a drive arrangement for drivingly rotating 5 the pitting head. In one embodiment of the invention the drive arrangement is in the form of a drive train arrangement which includes a motor drive, e.g. a hydraulic motor drive; at least one motor drive sprocket connected to the motor drive; at least one pitting head sprocket on the pitting head; and 10 at least one chain drive operatively linking the at least one pitting head sprocket and the at least one motor drive sprocket. The pitting device may further include a control system which is configured to control at least some operations of the pitting device. 15 According to another aspect of the invention there is provided a seedling planter vehicle which includes at least one automated pitting device comprising a vertically displaceable, rotatable pitting head operable to drill a planting pit in the soil, and a plurality of slash arms for clearing slash from below the pitting head. 20 The automated pitting device may be a pitting device as hereinbefore described. The seedling planter vehicle may include slash reducing components in 25 addition to the slash arms of the pitting device. The slash reducing components may include, arranged in front of at least one pitting device in the direction of normal forward travel of the vehicle, a slash reducer comprising an elongate upwardly extending spinner blade rotatable about an upwardly extending axis. 30 The additional slash reducing components may further include a stationary cutting blade associated with the slash reducer, the cutting blade having an upwardly extending cutting edge and being arranged immediately behind the slash reducer in the direction of normal forward travel of the vehicle to break or deflect any slash thrown against it by the spinner blade.
WO 2008/084428 PCT/IB2008/050030 5 The additional slash reducing components may further include a slash deflector blade arranged behind the sash reducer to deflect slash sideways away from the seedling planter vehicle as the seedling planter vehicle moves forward in use. 5 The seedling planter vehicle may include a base vehicle, typically a self propelled vehicle, carrying the at least one automated pitting device and a wheeled carrier which is attached to the base vehicle, the wheeled carrier carrying the additional slash reducing components and being pivotally attached to the base vehicle to pivot 10 about an axis transverse to the normal direction of forward travel of the seedling planter vehicle, and horizontal when the vehicle is horizontally disposed. Typically, the wheeled carrier is located in front of the base vehicle and supports a tank, e.g. a weedicide tank. The wheeled carrier may comprise a centre portion and two transversely 15 spaced chassis portions with each transversely spaced chassis portion carrying at least some of the additional slash reducing components and being supported on wheels. The transversely spaced chassis portions may be pivotally attached to the centre portion so that they can be pivoted upwardly and inwardly to narrow the wheeled carrier. The transversely spaced portions may also be pivotal about an axis to allow leading ends of 20 the transversely spaced portions to be higher or lower than trailing ends of the transversely spaced portions. The invention will now be described by way of example only with reference to the following diagrammatic drawings. 25 In the drawings: Figure 1 shows a three-dimensional view of a pitting device in accordance with the invention, with a slash arm anchor in a position proximal to a pitting head and a swing arm of a seedling depositor assembly in a raised position; 30 Figure 2 shows a side view of the pitting device of Figure 1 in use, with the slash arm anchor in a position distal from the pitting head; Figure 3 shows a side view of the pitting device of Figures 1 and 2 in use with the swing arm of the seedling depositor in a lowered, planting position; WO 2008/084428 PCT/IB2008/050030 6 Figure 4 shows a side view of a seedling planter vehicle in accordance with the invention; and Figure 5 shows a schematic top plan view of a wheeled carrier forming part of the seedling planter vehicle of Figure 4. 5 Referring to the drawings and in particular to Figure 1, reference numeral 10 generally indicates a pitting device in accordance with the invention, the pitting device 10 being shown in a rest or raised condition. The pitting device 10 is typically mounted to a vehicle by means of a frame or other carrier (not shown in Figures 1 to 3). 10 The pitting device 10 includes a pitting head 12 which is rotatably connected to a lower end of a slash arm anchor guide 14, via a flange-like base or support 32 of 600 mm diameter and 25mm thickness bolted by eight bolts (not shown) to a flange 45 (see Figures 2 and 3) welded to the lower end of the slash arm anchor 15 guide 14. A drive train cover (not shown) is also bolted to the base or support 32. The pitting head 12, comprising a double flange 42, is mounted (by means of inner and outer bearing seals, inner and outer taper roller bearings, a washer, a nut, a split pin and a grease cap, all of which are not shown), on a downwardly extending 20 axle stub 20 (see Figures 2 and 3) of 60mm diameter welded centrally to the base or support 32. The slash arm anchor guide 14 is constructed from square tubing (150mm x 150mm OD) and forms part of a telescopic arm 23, the slash arm anchor guide 14 thus being vertically or upwardly and downwardly displaceable in telescopic fashion relative to a square tubular member 22 (200mm x 200mm OD with a wall thickness of 6 mm and 25 a length between 1200mm and 1800mm) in which it is slidably received. A rack with 7 teeth per 25 mm length (not shown) bolted to one side of the slash arm anchor guide 14 and a rotary encoder (not shown) at a bottom inner side of the tubular member 22 are used to measure and control travel of the slash arm anchor guide 14 in and out of the tubular member 22. 30 The pitting head 12 further comprises four digging members 40 extending downwardly from the double flange 42. The four digging members 40 are arranged so that two digging members 40 are radially inner digging members and two digging members 40 are radially outer digging members. Each digging member 40 has a WO 2008/084428 PCT/IB2008/050030 7 welded on tip (not show) arranged at a downward angle of 30 degrees to the horizontal. The tips of the outer digging members 40 also slope inwardly at an angle of about 10 degrees. 5 The double flange 42 comprises two 12mm thick steel flanges (570mm diameter top flange and 550mm diameter bottom flange), spaced by spacers 47. Slots are provided in the top and bottom flanges of the double flange 42 for the digging members 40 to be inserted from below. A slot in an upper end of each digging member 40 and a cooperating lock pin (not shown) pushed in between two spacers 47 flanking 10 the slots in the top and bottom flanges of the double flange 42 are used to lock each digging member 40 in position. The lock pins have a T end that is bolted onto the double flange 42 to keep them in place. A downwardly extending auger 44 is bolted centrally onto a lower surface 15 of the bottom flange of the double flange 42. In use the auger 44 centres the pitting head 12 and facilitates easy digging into the soil. A truncated 280mm OD flange of the auger 44 bolted to the bottom flange of the double flange 42 has two parallel side edges, thus avoiding blocking a fertilizer outlet (see below) in the bottom flange of the double flange 42 and is 16mm thick. On opposed upper sides of the auger 44 two 20 downwardly angled tine tips (not shown) are provided to break up the soil structure in use. The auger 44 is mounted on a 60mm shaft (not shown) depending downwardly from the truncated auger flange and is secured with a bolt. The auger 44 tapers towards a tip of hardened steel, has a length of about 260mm and an upper diameter over tine tips of about 160mm. 25 A slash arm anchor in the form of a square floating collar 16 of 6mm steel and a width of about 150mm is fitted around the slash arm anchor guide 14, the collar 16 being slidingly displaceable relative to the pitting head 12 along the slash arm anchor guide 14. Three slash arms 18 are pivotally connected to the collar 16, two to one side 30 and one on an opposed side of the collar 16. The slash arms 18 are connected using two pivot connections 49 with bearings, the pivot connections 49 being in a shoulder and elbow arrangement. The slash arms 18 extend downwardly past the pitting head 12 and are curved inwardly below the pitting head 12. The three slash arms 18 pass through slash arm guides 24 which are welded to the support or base 32, and in- WO 2008/084428 PCT/IB2008/050030 8 between two spaced guide rollers (not visible) which are provided in the slash arm guides 24 and which are respectively rotatable about axes 46. The outer guide rollers are spring loaded. The inner guide rollers of the slash arm guides 24 in use force the slash arms 18 outwardly, away from the pitting head 12, when the pitting head 12 and 5 the slash arm anchor guide 14 are displaced downwardly and the slash arms 18 are pushed upwardly past the slash arm guides 24 by contact with a soil surface (see Figures 2 and 3). A fertilizer ring 19 is provided on top of the double flange 42, for rotation 10 with the double flange 42. A fertilizer reservoir (not shown) with a capacity of 15 kg and a tapered bottom and a volume adjustable feeding dispenser (not shown) activated by the upwards movement of the collar 16, are also provided. When the collar 16 is in a position distal from the base or support 32, the dispenser is charged with fertilizer from the fertilizer reservoir. During downward travel of the collar 16 relative to the slash arm 15 anchor guide 14, charging of the dispenser is stopped and the dispenser feeds fertilizer into an annular zone defined between the fertilizer ring 19 and a sprocket arrangement 38 and from there through a fertilizer feed path which extends downwardly through the double flange 42 to open out in the bottom flange of the double flange 42, radially spaced from the axle stub. In use, as a result of the rotation of the pitting head 12, a 20 fairly even distribution of about 150 g fertilizer around a planted seedling is obtained whilst direct contact of the fertilizer with the seedling roots is avoided. The pitting device 10 includes, on each slash arm 18, a slash hook 26 which is pivotally connected to a lower end of its associated slash arm 18. The slash 25 hooks 26 are each preferably biased downwardly by a spring (not shown) and in use prevent digging of the slash arms 18 into the soil whilst simultaneously clearing remaining slash. The pitting device 10 further includes a pair of 125mm diameter nylon wheels 28 which is mounted ahead of the slash hook 26 at the lower ends of the slash arms 18. The pair of wheels 28 leads their associated slash hook 26 over the soil 30 surface when their associated slash arm 18 is displaced outwardly away from the pitting head 12. The pitting device 10 further includes a seedling depositor assembly 30 which includes a swing arm 34, which is pivotally mounted to the support or base 32 WO 2008/084428 PCT/IB2008/050030 9 above the pitting head 12, and a seedling depositor 36 provided at an end of the swing arm 34 remote from the support or base 32. The swing arm 34 is pivotally displaceable by means of a hydraulic cylinder 33 and a cam (not shown) between a raised position (as shown in Figure 1 and Figure 2) wherein the seedling depositor 36 is located in a 5 vertical plane adjacent the pitting head 12 and a lowered, planting position (see Figure 3) wherein the seedling depositor 36 is located underneath the pitting head 12. The seedling depositor 36 includes an elongate seedling housing 36.1 of 60mm square tubing with a length of about 250mm with a lower seedling deposit outlet 36.2 and an upper seedling receiving inlet 36.3. The seedling depositor 36 further includes two jaws 10 36.4 which are hingedly mounted at the seedling deposit outlet 36.2 and which taper together at an angle of about 202. The jaws 36.4 are hingedly displaceable between a closed position wherein the seedling deposit outlet 36.2 is closed by the jaws 36 (as shown in the drawings), a first open condition (not shown) wherein the jaws 36 are spaced about 60mm and project downwardly and open the seedling deposit outlet 36.2 15 for depositing a seedling, and a second open condition (not shown) wherein the jaws 36.4 project substantially horizontally away from the seedling housing 36.1 defining soil compacters which act to compress loose soil around the deposited seedling, thereby to secure the seedling in the planting pit. The seedling depositor 36 is pivotally mounted to the swing arm 34 so that a longitudinal axis of the seedling depositor 36 remains 20 upwardly extending during pivoting of the swing arm 34. The sprocket arrangement 38 comprises a stacked arrangement of three sprockets 38.1 with a diameter of about 544mm, bolted to the upper flange of the double flange 42. The sprocket arrangement 38 forms part of a drive train arrangement 25 (not shown) making use of drive chains and a hydraulic motor (not shown) drivingly to rotate the pitting head 12 at a low speed and a high torque relative to the base or support 32 and the slash arm anchor guide 14. The slash arm anchor guide 14 also has friction reduction strips 50 30 provided on each side thereof and fastened by means of twenty grub screws (not shown), the friction reduction strips 50 reducing friction between the slash arm anchor guide 14 and the tubular member 22 when said slash arm anchor guide 14 is being displaced relative to the tubular member 22.
WO 2008/084428 PCT/IB2008/050030 10 In Figure 2, the pitting device 10 is shown with the slash arm anchor guide 14 being partially pushed out of the tubular member 22 (by means of hydraulics which are not shown) towards an extended condition for the telescopic arm 23, displacing the pitting head 12 downwardly towards a soil surface 35 and with the slash arms 18 having 5 been pushed upwardly together with the collar 16 relative to the dropping pitting head 12 as a result of contact between the slash arms 18 and the soil surface 35. The slash arms 18 are shown guided or pushed outwardly, away from the pitting head 12, as a result of the downwards movement of the slash arm guides 24 along the curved slash arms 18.. 10 In use, the pitting device 10 is initially in a retracted or rest position (Figure 1) and is completely raised above the soil surface 35 with the slash arm anchor or collar 16 in a rest position in abutment with the support or base 32. As the pitting head 12 is displaced downwardly, the slash arm anchor or collar 16 remains in abutment with the 15 support or base 32 and the slash arms 18 are consequently also displaced downwardly with the pitting head 12 towards the soil surface 35 in which a planting pit is to be created. The slash arms 18 subsequently contact the soil surface 35 prior to the pitting head 12 and are then guided outwardly by the slash arm guides 24 and guide rollers (not visible) whilst the collar 16 is displaced upwardly along the slash arm anchor guide 20 14 and the pitting head 12 continues downwardly towards the soil surface 35. The outward movement of the slash arms 18 is facilitated by the pairs of wheels 28 which are mounted at lower ends of the slash arms 18. The wheels 28 lead the outward motion of the slash arms 18 and the slash hooks 26 over the soil surface 35, thereby enabling the slash arms 18 and the slash hooks 26 to collect and displace at least some 25 slash which may be located on the soil surface 35, below the pitting head 12. Referring now to Figure 3, the pitting device 10 is shown with the seedling depositor assembly 30 having been pivotally displaced into the lowered, planting position wherein the seedling depositor 36 is located beneath the pitting head 12. As in 30 Figure 2, the pitting head 12 has been displaced downwardly by the vertically displaceable slash arm anchor guide 14 and the slash arms 18 have been forced and guided radially outwardly, away from the pitting head 12 with the seedling depositor 36 being located beneath the pitting head 12.
WO 2008/084428 PCT/IB2008/050030 11 In use, after a planting pit has been created with the rotating pitting head 12 and the pitting head 12 has been raised again away from the soil surface 35, the seedling depositor 36, loaded with a seedling, is swung into the lowered, planting position . In order to deposit the seedling in the planting pit the seedling depositor 36 is 5 displaced downwardly into the planting pit by downward displacement of the pitting head 12 and the slash arm anchor guide 14 until the seedling depositor 36 is at a desired distance from a bottom of the planting pit. The jaws 36.4 (Figure 1) are subsequently displaced into the first open condition using an actuation mechanism of which a lever 37 forms part and which includes a dual hydraulic cylinder (not shown) 10 pushing and pulling a slot and pins (not shown) on the jaws 36.4 and the seedling is deposited by gravity in the planting pit at a depth of about 120mm. The pitting head 12, and thus the seedling depositor assembly 30, is subsequently raised slightly to just above ground level while water is released (discussed in more detail hereinafter), the jaws 36.4 are displaced into the second open condition and the pitting head 12 and the 15 seedling depositor assembly 30 are displaced downwardly for a predetermined distance, bringing the horizontal jaws 36.4 into contact with the soil surrounding the deposited seedling, thereby to compact loose soil around the deposited seedling to eliminate air pockets at a root plug of the seedling and to secure the seedling in the soil. 20 Referring now to Figure 4, reference numeral 400 generally indicates in schematic fashion a seedling planter vehicle in accordance with the invention. The planter vehicle 400 includes a self-propelled base vehicle 402, e.g. a Bell SJ315 TLB, which carries a frame 404 to which six pitting assemblies 406 are operatively attached. Three assemblies 406 are provided on either side of the vehicle 402. Each pitting 25 assembly 406 includes a pitting device 10 in accordance with the invention (shown schematically only). Each pitting device 10 is attached to the frame 404 by means of its sleeve 22, and a seedling cassette 408 (shown schematically only) is provided adjacent each pitting device 10. The seedling cassettes 408 are also mounted to the frame 404. In use, each seedling cassette 408 contains a plurality of seedlings and gravity feeds 30 the seedlings contained therein directly, by means of a chute 409 or the like, to the seedling depositor 36 of its associated seedling depositor assembly 30, with the seedling depositor assembly 30 in the raised position shown in Figures 1 and 2. Each seedling cassette 408 can contain up to 100 seedlings in a continuous chain of PVC seedling tubes (not shown) of 60mm diameter and 1 00mm length embedded in a tube WO 2008/084428 PCT/IB2008/050030 12 guide. A feed arrangement (not shown) feeds the chain of seedling tubes forward one tube diameter at a time in discrete steps to feed seedlings to the seedling depositor 36, via a bottom hole in a housing of the seedling cassette 408. The feed arrangement comprises a chain pusher which uses a lever action to push the chain of seedling tubes 5 in one direction in ratchet fashion for the required distance. The lever of the lever action is activated by the upward movement of the swing arm 34 to bring the seedling depositor 36 to right underneath the bottom hole in the housing of the seedling cassette 408 to receive a seedling via the chute 409. 10 The seedling planter vehicle 400 further includes a wheeled carrier 432 (see Figure 5) in front of the base vehicle 402, the wheeled carrier 432 supporting slash reducing components in addition to the slash arms 18 of the pitting devices 10. The wheeled carrier 432 is shown in Figure 4 separated from the base vehicle 402 for clarity. The wheeled carrier 432 includes two transversely spaced chassis portions 434 15 which are hingedly attached to a roughly triangular centre portion 436 about hinge axes 41. This allows the chassis portions 434 to be hinged upwardly and inwardly (e.g. hydraulically) to narrow the wheeled carrier 432 and to lift the slash reducing components away from the soil surface 35. In addition, the chassis portions 434 are pivotal about pivot axes 43. The centre portion 436 is configured to be pivotally or 20 hingedly mounted to the base vehicle 402 about a hinge axis 70. The pivotal attachment of the chassis portions 434 to the centre portion 436 and of the centre portion 436 to the base vehicle 402 enables the wheeled carrier 432, and the chassis portions 434 to follow a profile of a surface across which the seedling planter vehicle 400 is moving, limiting digging or grading by the slash reducing components 25 The wheeled carrier 432 supports two slash defector blades 414 which are respectively attached to the two chassis portions 434 and which are slash reducing components. The slash deflector blades 414 have a concave cross sectional profile and are slanted rearwardly outwardly relative to a direction of normal forward motion of the 30 vehicle 400. Each slash deflector blade 414 is located behind an associated slash reducer comprising an upwardly extending spinner blade 418 mounted for rotation about an upwardly extending axis at an inner end of the associated slash deflector blade 414.
WO 2008/084428 PCT/IB2008/050030 13 A stationary cutting blade 438 is further provided on each of the slash deflector blades 414 adjacent the spinner blades 418. The cutting blades 438 each defines an upwardly extending cutting edge and act to break or deflect any slash thrown against it by the spinner blades 418, in use. 5 The wheeled carrier 432 also supports a weedicide reservoir or tank 416 and a weedicide applicator (not shown) behind the slash deflector blades 414. The weedicide reservoir 416 and applicator are used to apply weedicide to the soil surface over which the seedling planter vehicle 400 is moving and in which seedlings are being 10 planted. The seedling planter vehicle 400 further includes a glass fibre water supply tank 420 with a capacity of 1000 litres at a rear end of the base vehicle 402. The tank 420 in use provides water to outlet nozzles (not shown) which are provided at the 15 pitting assemblies 406 to supply water or gel to a planted seedling, as hereinbefore mentioned. The volume of water per seedling is regulated by solenoid valves. The water is discharged at a tangent to the pitting hole created by the pitting device 10 to swirl into the pitting hole. 20 A programmable controller (not shown), e.g. a PC104 controller, is used to automate the planting and associated activities and functions of the seedling planter vehicle 400 in a closed loop. The invention, as illustrated, provides an automated pitting device and a 25 seedling planter vehicle which will greatly speed up the mechanical planting of seedlings, particularly where the planting operation will require the removal of slash from the soil surface prior to planting, as is often the case in forestry operations. 30