Abstract:
A method is described for cutting sub-surface cavities into a region of soil and for delivering liquid fertilizer directly to each cavity while minimizing overflow or spillage of liquid fertilizer onto the surrounding surface soil. A cutting apparatus is described for creating sub-surface cavities the soil, each cavity is associated with an opening at the soil surface through which liquid fertilizer can be delivered to the cavity. A system for delivery of liquid fertilizer to the cavities is described, which includes a fertilizer dispenser including a metering valve assembly for delivery of liquid fertilizer to each cavity. A synchronization system may be incorporated into the system for locating each cavity and directing the dispensing of liquid fertilizer.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/561,916 filed 14 Apr. 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to injecting liquid fertilizer, such as liquid manure, into the ground, and specifically to a method and metering equipment for doing so while causing: low disturbance to the surface, low contamination of and damage to vegetation, and high absorption by the soil.  
       BACKGROUND  
       [0003]     Land application of liquid manure has been recognised as a cost-effective and sustainable practice for using manure. Comparable crop yields can be achieved when using liquid manure to replace chemical fertilisers. However, all stakeholders recognise that some adverse environmental impacts are associated with manure application, such as nutrient loss through volatilization, nuisance odour emissions, and runoff of phosphorus to surface water. Known techniques for manure application include:  
         [0000]     1) Broadcasting  
         [0004]     When broadcasting, a tank wagon, sprayer boom, or irrigation gun discharges manure slurry under pressure in a fan spreading or high-trajectory pattern, such that 100% of the ground surface is covered with manure, maximizing volatilization loss and odour emissions. In grassland (e.g. hay or other forage) applications, the “painting” of existing crops with liquid manure provides additional area having exposed manure, which aggravates the problem of volatilization loss and odour, in addition to contaminating the forage leading to potentially pathogenic activities not desirable for animal grazing.  
         [0000]     2) Surface Banding  
         [0005]     In an attempt to alleviate the problems associated with broadcasting, surface banding has been tried on both grassland and cropland. Using a dribble bar, manure is delivered near and above the surface of the ground by pouring it out at low pressure leaving less than 100% of the surface covered with bands of manure, but still suffering from substantial evaporation, volatilization, odour, and contamination of feed or crops.  
         [0000]     3) Surface Incorporation  
         [0006]     After manure has been delivered by broadcasting or surface banding, it may be better incorporated into the soil by a tillage operation (e.g. using discs, cultivator tines, sweeps, or harrows) to mix the manure with soil. Since manure is mixed with soil, less manure is exposed such that less volatilization and odour occurs, but the manure is often only partially covered with soil. Surface incorporation usually is not an option for cropland where the tillage action would damage the crop stands.  
         [0000]     4) Injection  
         [0007]     Manure has also been delivered below the surface of the soil to minimise volatilization losses, odour, and runoff pollution—simultaneously providing more nutrients to plants. Conventional manure injection has been performed using high soil disturbance tillage tools, such as: discs, knives, openers, chisels, shovels, or sweeps. Disadvantageously, plant damage reducing yield, limits the applicability of such operations. Further, the high power requirement associated with soil cutting consumes large amounts of fuel, which adversely affects the economics of the farming operation that it supports.  
         [0000]     5) Aeration  
         [0008]     Aerators (e.g. AerWay™) have also been used to incorporate liquid manure into grassland, during which operations aerators perforate the top 50 to 150 mm of soil (without significantly damaging the crop), into which perforations manure is conventionally delivered by broadcast or banding. Disadvantageously, although part of the manure eventually runs into the perforations, the delivery of the fertilizing fluids above the surface still results in significant volatilization loss, odour, and contamination, such that this method is not classified as “injection” by regulatory bodies.  
         [0009]     Examples of known technology include that taught in European patent application 94200180.1, which describes a device for injecting liquid manure into the ground using a “tillage means” having teeth or “protrusions” of a pointed, pyramidal, or conical design that create a plurality of aligned “depressions” much like the indentations of an aerator. A “manure feed means” including an outlet then pours or drizzles liquid manure in proximity above the resulting line of indentations in the ground. Disadvantageously, the indiscriminate delivery of manure slurry continuously along the line formed by the depressions results in significant contamination since the manure is not just deposited within the openings, but rather spills over onto both the forage and the surface of the ground between adjacent depressions. Further, the depressions are created by compressing rather than cutting an opening in the soil such that the compressed soil of the surface area inside each depression is less permeable to absorb liquids, resulting in the manure soaking into the surrounding soil at a slower rate.  
         [0010]     U.S. Pat. No. 6,142,084 issued to Hatlo on 7 Nov. 2000, describes equipment for periodically injecting a concentrated jet of manure slurry under pressure sufficient that the jet bores its own “groove” or elongate cavity in the soil. A shoe including a breaker element is used to interrupt the jet in order to avoid creating a continuous opening in the soil. According to an alternate embodiment, the shoe also serves to close the groove after each injection cycle is complete. Disadvantageously, the system of Hatlo relies on significant and stable pump pressure in order to bore down to a consistent penetration depth, which choice of a complex sub-assembly leads to the need for substantial maintenance of the system. Further, the shoe element dragged along the ground tends to disturb forage by flattening anything along each of a series of continuous paths.  
         [0011]     Environmental regulations increasingly require that producers apply manure on agricultural land as fertilizer in an environmentally friendly fashion, and in some cases it has been specifically regulated that liquid manure be injected, such that it is desirable to identify a technique and equipment useful to efficiently deliver liquid fertilizers, in properly metered amounts, below the surface of low compaction soil permitting with a high rate of absorption, but without erosion-promoting soil-disturbance or either severely damaging planted crops or contaminating forage present on the surface.  
       SUMMARY OF THE INVENTION  
       [0012]     In a first aspect of the invention, there is provided a method for dispensing liquid fertilizer directly into one or more sub-surface cavities in a region of crop or forage ground having a soil surface, the one or more cavities each having an opening at the soil surface, the method comprising the steps: locating a cavity; estimating the fluid capacity of the cavity; calculating dispensing parameters for delivery of liquid fertilizer into the cavity; and delivering to the cavity a volume of liquid fertilizer approximately equal to the fluid capacity of the cavity in accordance with said dispensing parameters.  
         [0013]     The method may further comprise the step of cutting at least one sub-surface cavity into the ground prior to or in lieu of the step of locating a cavity.  
         [0014]     In a further embodiment, the step of estimating the fluid capacity of the cavity comprises estimating the volume of the cavity and estimating the hydraulic conductivity of the soil surrounding the cavity.  
         [0015]     In a further embodiment, the liquid fertilizer is dispensed from a moving platform, and the dispensing parameters may be preset or may be continuously adjusted, the parameters may include fertilizer flow rate, fertilizer viscosity, dispensing temperature, dispensing pressure, and height of dispensation above the soil surface.  
         [0016]     In a second aspect of the invention, there is provided a soil-cutting apparatus for creating a sub-surface cavity while minimizing compaction of soil surrounding the cavity, wherein the cutting apparatus includes at least one cutting blade for slicing into the soil surface to create an opening at the soil surface and a cavity below the level of the soil surface.  
         [0017]     In an embodiment, each cutting blade comprises a plate member anchored to the cutting apparatus, the plate member having a free cutting edge for slicing through soil, and the cutting edge may be profiled, having a curved or parabolic profile.  
         [0018]     In a further embodiment, the cutting apparatus includes a plurality of cutting blades mounted on at least one cutting wheel coupled to at least one axle for rotation thereabout. The cutting apparatus may be raised or lowered based on the desired volume and depth of each cavity to be created.  
         [0019]     In a further embodiment, the apparatus is coupled to a liquid fertilizer dispensing system such that each cavity may be filled with liquid fertilizer as it is created.  
         [0020]     In a third aspect, there is provided a dispensing system for delivering liquid fertilizer to at least one soil sub-surface cavity having an opening at the soil surface, the system including at least one metering valve assembly for controlling the dispensing of fertilizer through any suitable injection device such that the fluid volume of liquid fertilizer dispensed corresponds to the fluid capacity of the cavity so as to avoid or minimize overflow onto the soil surface surrounding each opening.  
         [0021]     In an embodiment, the fluid capacity of the cavity is determined by estimating the volume of the cavity and estimating the hydraulic conductivity of soil surrounding the cavity.  
         [0022]     In a further embodiment, liquid fertilizer is delivered to a plurality of cavities in a region of crop or forage ground using a mobile platform comprising a liquid fertilizer tank having at least one dispensing nozzle.  
         [0023]     In a further embodiment, the dispensing system may be associated with the above-described cutting system for cutting sub-surface cavities. If so associated, the metering valve assembly may be synchronized with the soil-cutting apparatus in order to dispense fertilizer into the cavities shortly after they are created. The synchronization may be accomplished using interacting mechanical gears or sprocket and chain assemblies; or any suitable location sensor and position control technology to locate cavities and direct the dispensing of liquid fertilizer. The location sensing may be accomplished by depth sonar, EMF proximity, laser, or light reflection technology.  
         [0024]     In an embodiment, the metering valve assembly is adjustable in accordance with the effective momentary fluid capacity of the cavities, and may include a programmable control system to automatically adjust each metering valve assembly.  
         [0025]     In a further embodiment, the injection device of the dispensing system is coupled to and integrated with the soil-cutting apparatus such that liquid fertilizer is simultaneously delivered to a cavity through the cutting blade creating the cavity while the cavity is created.  
         [0026]     In a fourth aspect of the invention, there is provided an apparatus for applying liquid fertilizer to a region of crop or forage ground having a soil surface, the apparatus including a mobile platform for travelling over a region of crop or forage ground; a soil-cutting apparatus operably attached to the mobile platform, the soil-cutting apparatus including at least one cutting blade for slicing into the soil surface to create an opening at the soil surface and a cavity under the soil surface, while minimizing compaction of soil surrounding the cavity; a liquid fertilizer dispenser associated with the soil-cutting apparatus, the dispenser including at least one metering valve assembly for controlling the dispensation of fertilizer through at least one associated injection device; and a synchronization system for associating the metered fluid volume of liquid fertilizer dispensed with the location and size of each cavity; wherein as the mobile platform travels over the soil surface of the ground, cavities are created by the soil-cutting apparatus, and liquid fertilizer is delivered directly to each cavity by the dispensing system as determined by the synchronization system, in an amount less than or equal to the fluid capacity of each cavity so as to minimize overflow onto the soil surface surrounding each opening.  
         [0027]     The accompanying drawings, which are incorporated and which constitute a part of this specification, illustrate preferred embodiments of the method, system, and apparatus according to the invention and, together with the description, serve to explain the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     The present invention, in order to be easily understood and practised, is set out in the following non-limiting examples shown in the accompanying drawings, in which:  
         [0029]      FIG. 1  is a schematic side view of a liquid fertilizer injection system in use;  
         [0030]      FIG. 2  is a perspective view of a soil cutting apparatus connected to a metering valve assembly;  
         [0031]      FIG. 3  is a side view of a soil cutting apparatus with a drive sub-assembly;  
         [0032]      FIG. 4  is a perspective view of a soil cutting apparatus having 6 cutting wheels;  
         [0033]      FIG. 5  is an exploded perspective view of a metering valve assembly;  
         [0034]      FIG. 6  includes left and right perspective views of a metering valve connected to 2 injector tubes;  
         [0035]      FIG. 7  is a perspective view of a drive sprocket sub-assembly; and,  
         [0036]      FIG. 8  is a rendering in perspective view of the liquid fertilizer dispensing system of the invention in towed position behind a liquid manure tank.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]     Referring to  FIGS. 1 through 8  there is depicted one embodiment, denoted generally as  10 , of the system of the invention for the controlled flow injection of liquid fertilizer into ground  12  (any appropriate crop or forage land). A source  14  (e.g. a tank) of liquid fertilizer supplies manifold  40  through at least one flow metering valve  42  (details seen in  FIG. 6 ), sometimes referred to as a “pulsing valve assembly”, for periodically dispensing a definable volume of liquid. System  10  is typically located behind a source  14  (on any suitable moving platform) and supported for rolling movement along ground  12  behind a towing vehicle (not shown). Draw bar  16  as shown provides for height adjustment of system  10  in relation to ground  12 . System  10  uses frame  18  to support soil cutting assembly  110  (wheels  30  on shaft  28  as defined in more detail below) that when towed across ground  12  cuts a plurality of low-compaction, spaced openings that may subsequently be filled with metered amounts of liquid manure.  
         [0038]     According to one embodiment of system  10 , frame  18  includes beams  20  oriented substantially parallel and spaced from one another above the ground, and substantially perpendicular to a forward working direction  22  of system  10 . Cross bars  24  are connected at each end of frame  18  between beams  20 . Side members  26  are mounted at each end of frame  18  forming plates extending downwardly therefrom parallel to working direction  22  for carrying a wheel shaft  28  spanning therebetween. Shaft  28  is rotatably supported in relation to frame  18  by any suitable bearings and other hardware. A plurality of wheels  30  are mounted at spaced intervals along shaft  28  (forming soil cutting assembly  110  as seen in  FIG. 4 ) in fixed orientation relative to shaft  28  for rotation therewith as shaft  28  rolls above ground  12 . Each wheel  30  comprises an annular collar  32  fixed on shaft  28  using any suitable means for fastening a plurality of radially extending blades  34  protruding from each collar  32 . Each protruding blade  34  comprises a plate member that narrows as it extends radially outward from shaft  28 . Blades  34  are typically evenly spaced around the circumference of shaft  28  and each plate member is angled at an inclination of approximately 20° in relation to a vertical plane perpendicular to the axis of shaft  28 . The outer end of each blade  34  is curved in profile so as to be substantially parabolic adjacent its apex  36 . The purpose of combining these features is to cause soil cutting assembly  110  to slice (rather than compressing as would a blunt object) into ground  12  in order to create somewhat oblong openings—without excessively compacting the soil forming the walls (not shown) of each cavity through which liquid fertilizer must pass as it is absorbed by ground  12 . Rails  38  are supported on frame  18  to extend rearwardly from inside members  26  generally horizontally spaced above ground  12 . Rails  38  are spaced below the beams of frame  18  near shaft  28  for supporting manifold  40  spanning the rear free ends of rails  38 . Manifold  40  comprises a hollow tube oriented perpendicular to working direction  22 . Conduits (e.g. hoses, not shown) communicate with source  14  for connection to at least one position along manifold  40  supplying liquid fertilizer evenly to metering valves  42 .  
         [0039]     Advantageously, soil cutting assembly  110  includes a plurality of sharp edged blades  34  (having a curved or somewhat arched top view while also being substantially parabolic from a side view) designed to cut soil rather than dig into or rip up the surface of ground  12 . In that respect soil cutting assembly  110  acts more like an aerator than a conventional tillage tool. The purpose of slicing open the surface (rather than compressing a small area to create a hole) is to relatively gently part the soil sideways without compacting the bottom of the resulting cavity in order that the porosity (permeability) of the soil at the bottom of the cavity is relatively undisturbed and the hydraulic conductivity of the region being fertilized is not reduced by the creation of the openings. Further, it is the objective of soil cutting assembly  110  to create a plurality of openings each leading to a low-compaction cavity having a proportionately large internal surface area through which to absorb liquids dispensed therein. By removing a small divot of soil in the course of opening the surface and separating the soil to sides that form a cavity, the exposed sub-surface soil of the internal walls of the cavity provide a larger porous surface through which liquids may be absorbed to feed adjacent roots. The slicing action of blades  34  also limits disturbance to plants adjacent the opening.  
         [0040]     According to one embodiment of system  10 , each wheel  30  includes three blades  34 , such that each wheel  30  creates three openings per rotation, which may optionally be offset relative to openings created by the two wheels immediately adjacent along shaft  28 . Sets of wheels may be oriented at even angular offsets about their axis of rotation so that only one set of blades penetrates the ground at any given time.  
         [0041]     At least one metering valve  42  is associated with each wheel  30  at evenly spaced positions along manifold  40 , however one metering valve  42  may also supply more than one wheel  30 . Each metering valve  42  includes a cylindrical body having an inlet  45  to fluidly communicate with supply manifold  40  and an outlet  44  to fluidly communicate with dispensing injector tubes  46 . According to one embodiment of system  10 , each metering valve  42  includes a pair of injection tubes  46  such that one tube is provided for each wheel  30  of the set being supplied. Tubes  46  extend downward to near ground  12 . A bottom open end  48  (to which any suitable flow controlling nozzle—not shown—may be attached) of each tube is positioned adjacent ground  12  when in use.  
         [0042]     According to a preferred embodiment of system  10 , soil conditions (e.g. measurements of current local hydraulic conductivity or permeability) are taken into account prior to fertilizing the region of land in question, and the fluid capacity of the cavities is estimated. Estimating the total fluid capacity of the cavities permits setting each metering valve  42  to release more or less liquid fertilizer into cavities that have been created by the soil cutting assembly  10 . For example, if it is determined that the soil surrounding the cavity, based on the hydraulic conductivity of the soil in the region, is able to quickly absorb additional volumes of liquid fertilizer, then an amount of liquid fertilizer may be dispensed into the cavity which is greater than the actual volume of the cavity, while minimizing overflow onto the surrounding soil. A person of skill in soil fertilization would understand that by raising or lowering soil cutting assembly  110  relative to ground  12 , both opening size and cavity depth will be smaller or larger respectively, which will (like soil conditions) influence the effective momentary fluid capacity of the resulting cavities for a given fluidity of the manure slurry comprising the liquid fertilizer. Other factors such as platform velocity and dispensation rate will affect the volume of the liquid that may be discharged by metering valve  42  into a cavity of known dimensions, without overflow onto the surface and plants surrounding the opening to the cavity being injected.  
         [0043]     Various dispensing parameters, such as fertilizer flow rate, fertilizer viscosity, dispensing temperature, dispensing pressure, and height of dispensation above the soil surface, may be determined and preset or controlled during dispensation of fertilizer into the cavities. These parameters may be calculated and controlled during delivery by an automated system, or may simply be preset based on estimated optimal parameters.  
         [0044]     According to one embodiment of system  10 , each metering valve  42  includes a rotating valve member within its cylindrical body. Each valve member  50  comprises any suitable sealing components supported for rotation about the axis of the cylindrical body and aligned along a common axis extending between metering valves  42  for supporting all rotating valve members  50  on a common valve shaft  52  that is formed in sections with couplings connecting adjacent sections. The openings at the inlet and outlet of each metering valve  42  are spaced by approximately 120°, while the openings between the free ends of the curved plate forming rotating valve member are approximately 230° apart so that both are open to the hollow interior of metering valve  42  over a small range of rotation of valve member, each of which are offset circumferentially by 120° from adjacent valve members when used with wheels  30  having three blades  34 . Valve members are fixed on valve shaft  52  to synchronize rotation with wheel shaft  28  so that the timing of injection matches the openings being formed by wheels  30 . As also seen in  FIG. 7 , a driven sprocket  56  is supported at one end of valve shaft  52  while a drive sprocket  58  is supported at the same end of wheel shaft  28  in which said sprockets are coupled to rotate together by any suitable drive chain  60 . An idler sprocket  62  is provided for meshing engagement with chain  60  and supported on any suitable tightening mechanism for reducing slack in chain  60 .  
         [0045]     As described above, according to one of its embodiments, the system of the invention comprises cutting wheels (driven by contact with the ground) and synchronized metering valves, which together cut spaced openings in the ground and dispense controllable amounts of liquid fertilizer directly into associated sub-surface cavities through those openings. “Spoked” cutting wheels are mounted on a central shaft and each time a spoke reaches the ground it slices a substantially parabolic shaped opening in the ground. The wheel spacing along the central shaft and the spoke spacing on each wheel are designed in such a way that the openings in the ground are approximately 1 foot away from any other openings. If each pair of spoke wheels slice the ground at the same time, a single metering valve can reliably supply liquid manure for two wheels. The time that fertilizer is dispensed by the valve compared to when the cutter contacts the ground may be controlled by the chain drive, and it can be modified by simply changing the orientation of the sprockets in relation to each other prior to the chain being attached. On a system having  3  cutters per wheel, to produce one rotation of the metering valve per impact of the cutters with the ground, the valve is geared to rotate  3  times faster than the cutting wheel shaft  28 .  
         [0046]     Using any form of valve to meter doses of liquid manure into cavities created by the cutting wheels is novel, but a person of skill in soil fertilization machines would understand that a wide range of valves may be applied to this new use. As seen in  FIG. 5 , one layout of such metering valves is a simple row of rotary valves mounted on a suitably sized (e.g. 89 mm diameter on the prototype) horizontal tube substantially perpendicular to the direction of travel of the system. Advantageously, this horizontal tube acts as both a support for the valves and a manifold supplying manure to those same valves. Mounting the tube behind the wheels allows the valves to be closer to the ground and spaced from the cutting wheels. Each valve can supply the required volume of liquid manure to two adjacent openings simultaneously. The injectors connected to the metering valve outlet are typically mounted so as to either avoid or allow them to absorb any impacts from surface obstacles such as clumps of soil, sticks, or stone on the ground. The bodies of the metering valves may be any suitable size (e.g. 125 mm diameter) and inside the valve body, an interior tube is attached to a drive shaft that extends out through both sides of the body. The interior tube is designed to cover the opening in the valve body through 230 degrees of its rotation and allow fluid to flow into the valve during the other 130 degrees of its rotation. In this way the valve can control the time that liquid manure is allowed past it in order to place the liquid manure into the cavities as the injectors pass over the openings in the ground.  
         [0047]     Alternatively, the metered flow of liquid fertilizer may be delivered directly through each cutting head while creating a cavity, rather than by a separate dispensing sub-assembly trailing the soil cutting assembly.  
         [0048]     Various additional methods of synchronizing cavity cutting with liquid manure injection are suitable for use in accordance with the invention. In the embodiment described above, the synchronization of the metering valve assembly with the soil cutting assembly is be achieved by interacting mechanical gears or sprocket &amp; chain assemblies. However, the targeting of the delivery of the required volume of fluid may instead be accomplished using any suitable location sensor and position control technologies (e.g. depth sonar, EMF proximity, laser or light reflection) to locate cavities and direct streams of liquid fertilizer thereto.  
         [0049]     The major application of the system of the invention is to inject liquid manure in forage fields. Another application is injecting manure in no-tillage systems that require low disturbance field equipment to maintain most of the residue cover on the soil surface. The system of the invention is suitable for liquid manure injection in spring. The ideal time for land application of liquid manure is after fall harvest. However, many producers need to apply manure in both spring and fall, due to the limited capacity of their manure storage facilities. Spring injection of liquid manure has proven very problematic to crop producers to the point of neighbours refusing “free” manure if it is to be injected in the spring. First, breaking the ground when injecting causes losses of soil moisture, which is quite detrimental in dry areas. Second, seedbeds are destroyed when injecting, as the conventional injectors break the ground and leave a very rough seedbed. The system of the invention may also be used with annual crop systems and the low power requirement of the system will be attractive to producers using those systems.  
         [0050]     In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.  
         [0051]     Although the disclosure describes and illustrates various embodiments of the invention, it is to be understood that the invention is not limited to these particular embodiments. Many variations and modifications will now occur to those skilled in the art of liquid fertilizer application. For full definition of the scope of the invention, reference is to be made to the appended claims.