Abstract:
A fertilizer spike, in an exemplary embodiment, includes particulate fertilizer source material compacted together under pressure in a die to form a substantially wedged shaped spike body. The spike is configured to be hammered into a terrain such that the spike remains substantially intact. At least a portion of the fertilizer source materials are releasable into the terrain through microbial action. The fertilizer spike is substantially free of a thermoset binder material.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to fertilizers, and more particularly to time-release fertilizer.  
         [0002]     At least some known slow-release fertilizer spikes include a plurality of water-soluble particles, that may include some urea formaldehyde polymers, at least some of which may include fractions of water insoluble, sparingly soluble, and/or water-soluble polymers. The release of the fertilizer source materials, and more specifically, the timing of when the nutrients contained within the source materials are released from the spikes to the surroundings, is at least partially dependent on the porosity of such spikes. Known spikes include a plurality of fibrous particles, such as sawdust particles, in addition to the fertilizer source materials. Although such non-nutrient particulate matter facilitates increasing the porosity of known spikes, the fibrous particles also increase the frangibility of the spike such that the spikes may shatter if driven into compacted soil.  
         [0003]     To facilitate enhancing the structural strength and the controlled release of the fertilizer source materials, at least some other known fertilizer spikes bind fertilizer source materials and fibrous materials together with a hardened material binder. The binder facilitates increasing the resistance of the spike to shattering. For example, at least some known spikes are bound together by a hardened material such as asbestos fibers and/or thermosetting resins. However, because spikes may require substantial amounts of binding material, the binding materials may inhibit the release of the fertilizer source materials from the spike, and thus decrease the effectiveness of the fertilizer spike. Moreover, the manufacturing costs of such spikes are generally increased in comparison to other known spikes due to the cost of the binder materials and/or the thermosetting process.  
         [0004]     Other known fertilizer spikes require the use of tooling for insertion into compacted soil. For example, U.S. Pat. No. 3,892,552 describes a fertilizer spike that includes compressed granulated fertilizer particles bound together by an amount of urea-formaldehyde resin that is reduced in comparison to at least some other spikes that are bound by resins. Although the cured thermoset resin generally facilitates increasing the overall strength of the spike, the spike is described in a preferred embodiment as requiring a plastic cap to be placed on top of it, to facilitate reduced shattering when the spike is hammered into the ground.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     In one aspect, a fertilizer spike that includes particulate fertilizer source material compacted together under pressure in a die to form a substantially wedged shaped spike body is provided. At least a portion of the fertilizer source material is releasable into the terrain through microbial action. The fertilizer source material includes about 1 to about 30 parts by weight diammonium phosphate, about 1 to about 30 parts by weight muriate of potash, about 1 to about 30 parts by weight of a material comprising 38 weight percent CH(NO 2 ) 3 , about 1 to about 50 parts by weight of ammonium sulfate, and about 1 to about 20 parts by weight gypsum.  
         [0006]     In another aspect, a fertilizer spike that includes particulate fertilizer source material compacted together under pressure in a die to form a substantially wedged shaped spike body is provided. The spike is formed without thermosetting the materials. At least a portion of the fertilizer source material is releasable into the terrain through microbial action, the fertilizer source materials are substantially free of a thermoset binder material.  
         [0007]     In another aspect, a method for delivering a fertilizer to a plant over an extended period of time is provided. The method includes providing a fertilizer spike including particulate fertilizer source material compacted together under pressure in a die to form a substantially wedged shaped spike body, at least a portion of the fertilizer source material is releasable into the terrain through microbial action. The method also includes positioning an end of the spike against the terrain, and hammering directly against the opposite end of the spike such that the spike remains substantially intact and is forced into the terrain.  
         [0008]     In a further aspect, a method for fabricating a fertilizer spike is provided. The method includes mixing a plurality of fertilizer source materials together, such that at least a portion of the fertilizer source materials is releasable into the terrain through microbial action. The fertilizer source materials are substantially free of a thermoset binder material. The method also includes injecting the mixture of fertilizer source materials into a spike-shaped die, using a tableting press to compress the mixture of fertilizer source materials into a wedge-shaped spike that has a structural strength that enables the spike to be hammered into a terrain such that said spike remains substantially intact.  
         [0009]     In yet another aspect, a time-release fertilizer spike including a plurality of fertilizer source materials compacted together via a tableting process is provided. The spike includes a first end, a second end, and a body extending integrally therebetween. The body has a substantially rectangular cross-sectional profile. At least a portion of the fertilizer source materials are releasable into the terrain through microbial action. The fertilizer spike substantially free of a thermoset binder material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a plan view of an exemplary time-release fertilizer spike;  
         [0011]      FIG. 2  is a side view of the fertilizer spike shown in  FIG. 1 ; and  
         [0012]      FIG. 3  is a flowchart illustrating an exemplary method of fabricating a time-release fertilizer spike, such as the spike shown in  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  is a plan view of an exemplary time-release fertilizer spike  10 .  FIG. 2  is a side view of fertilizer spike  10 . Referring to  FIGS. 1 and 2 , spike  10  is a unitarily-formed, wedge-shaped spike that includes an impact end surface  12 , an insertion end portion  14 , and an elongated body  16  extending between end portion  14  and end surface  12 . In the exemplary embodiment, body  16  has a substantially rectangular cross-sectional profile that is defined by a pair of identical opposing sidewall surfaces  20  and  22 , and by an upper surface  24  and a lower surface  26  that extend between sidewall surfaces  20  and  22 . In the exemplary embodiment, upper surface  24  is substantially parallel to, and identical to, lower surface  26 . Moreover, in the exemplary embodiment, sidewall surfaces  20  and  22  are substantially parallel to each other, and each extends substantially perpendicularly between lower surface  26  and upper surface  24 . In alternative embodiments, body  16  has a non-rectangular cross-sectional profile.  
         [0014]     Body  16  has a thickness T measured between sidewall surfaces  20  and  22 , and a height H measured between lower surface  26  and upper surface  24 . In the exemplary embodiment, thickness T and height H are substantially constant throughout body  16 . Accordingly, in the exemplary embodiment, sidewall surfaces  20  and  22 , upper surface  24 , and lower surface  26  are each generally planar.  
         [0015]     Impact end surface  12  extends integrally from body  16  and has a substantially rectangular cross-sectional profile. Impact end surface is substantially planar and extends generally perpendicularly across body  16  with respect to sidewall surfaces  20  and  22 , and with respect to upper surface  24  and lower surface  26 . In the exemplary embodiment, a peripheral edge  30  of impact end surface  12  is formed with a radius of curvature to facilitate inadvertent shattering of spike  10  by a mis-directed blow while spike  10  is driven into the terrain during use.  
         [0016]     Insertion end portion  14  extends integrally from body  16  and tapers to an insertion tip  32 . More specifically, in the exemplary embodiment, the lower surface and upper surface  24  are substantially planar within insertion end portion  14 , and sidewall surfaces  20  and  22  taper inwardly towards an axis of symmetry  34  extending through spike  10 . In the exemplary embodiment, each surface  20  and  22  tapers approximately 24° inwardly to insertion tip  32 . Tip  32  is formed with a radius of curvature that extends between sidewall surfaces  20  and  22 . In the exemplary embodiment, tip  32  is substantially hemi-ellipsoidal shaped.  
         [0017]     Alternatively, spike  10  may be formed to have any shape that, as described in more detail below, enables spike  10  to be hammered, unsupported, into the soil without shattering and such that spike  10  remains substantially undamaged while being driven into the ground. As used herein, the terms “undamaged” and/or “intact” means that the spike remains substantially unbroken when driven into the terrain, and may receive only minor splintering, cracking, dusting, powdering, and/or fracturing. In alternative embodiments, a plastic cap is inserted over impact end surface  12  prior to spike  10  being hammered into the soil. The plastic cap facilitates increasing the structural strength of spike  10  to further facilitate the spike remaining substantially undamaged while driven into the ground. As used herein, the term “hammered into the soil” means driving the fertilizer spike  10  into the soil by hitting spike  10  with a device, such as, but not limited to, a hammer, mallet, or similar device normally used to drive stakes, pegs, or similar objects. More specifically, spike  10  typically is fabricated to enable hammering directly against impact end surface  12  to force insertion end portion  14  into the soil.  
         [0018]      FIG. 3  is a flowchart illustrating an exemplary method of fabricating a time-release fertilizer spike, such as spike  10  shown in  FIG. 1 . In the exemplary embodiment, raw fertilizer source materials, as described in more detail below, are supplied  100  from a plurality of different containers. The fertilizer source materials are weighed and mixed  102  together such that a pre-determined amount of each source material is introduced to the mixture. In the exemplary embodiment, a conventional ribbon blender is used to mix  102  the materials together. Alternatively, other known means are used to mix  102  the materials together.  
         [0019]     The resulting mixture is a substantially homogeneous granular mixture. As used herein, the term “homogeneous” means that the fertilizer source materials are mixed with substantially the same ratio of ingredients throughout spike  10 . The blended mixture of fertilizer source materials is then sized  106  to ensure that generally only mixture particles of a pre-determined size limitation are used in the formation of the fertilizer spike. In the exemplary embodiment, a conventional roller mill is used to size the particles of the mixture. The sized particles are then channeled  108  to a press assembly to be formed into a fertilizer spike. In the exemplary embodiment, a conventional tablet press with uniquely-shaped die members, punches or molds is used to form the fertilizer spike. In one exemplary embodiment, a modified Stokes 210 Ton Tablet Press is used in forming the fertilizer spikes. In another exemplary embodiment, a modified Ballwin 45 Ton Tablet Press is used to form the fertilizer spikes. Pressure is applied to the dies to compress  110  the fertilizer source materials together such that the spike is bound together via the compression process. In an alternative embodiment, other compaction equipment such as, but not limited to, roll compaction presses or briquetting presses, is used rather than the tablet press, to form the fertilizer spike. More specifically, the mechanical bonding is sufficient to enable handling and/or packaging without awaiting a cure time, or without requiring heating/cooling cycles, thermosetting processes, thermoset resins, or adhesives. Accordingly, the fertilizer spikes are ejected from the dies and are packaged  112 .  
         [0020]     The spike is fabricated from a substantially homogenous granular mixture of fertilizer source materials which are comprised of water soluble, water insoluble, and sparingly soluble fertilizer sources. More specifically, the compaction of the fertilizer materials enables the nutrients to be gradually released due to reduced solubility from occlusion and through microbial activity into the surrounding soil solution for a continued delivery of nutrients which can be over a period of up to twelve months. As a result, nutrients are released from the fertilizer spike at a slower rate than with other known fertilizers, and fertilizer burn and nutrient loss through leaching is facilitated to be reduced in comparison to other known fertilizer spikes.  
         [0021]     Generally, the fertilizer spike composition of any fertilizer source materials approved by the American Association of American Plant Food Control Officials, Inc. (AAPFCO). Moreover in one embodiment, the fertilizer spike composition includes nitrogen, phosphorus, and potassium source materials such as, but not limited to, magnesium ammonium phosphate or other metal ammonium phosphates, slag, ammonium metaphosphate, ammonium sulfate, Muritate of Potash, gypsum, calcium carbonate, dolomite, bone products, brucite, calcined phosphate, calcium metaphosphate, calcium phosphate, calcium polyphosphate, cement flue dust, chats, cottonseed extract, crotonylidene diurea, diamido phosphate, dicyandiamide, dolomite, fused calcium magnesium phosphate, fused tricalcium phosphate, fused phosphate, phosphate rock, gradually efficacious potassium phosphate, potassium silicate, guanylurea, greensand, magnesium oxide, magnesium phosphate, monocalcium diammonium pyrophosphate, methylene urea, ureaform, organiform, oxamidine phosphate, phosphatetraurea, phosphate sand, phosphoryltriamide, polyhalite, potassium polyphosphate, tankage, sludge, sulfate of potash magnesium, triuret, urea formaldehyde, uric acid, and/or sulfur. In addition, the fertilizer spike composition may also include calcium sulfate, sulfate of potash magnesia, potassium nitrate, Nutralene®, Nitroform®, monoammonium phosphate, and/or calcium nitrate.  
         [0022]     The amounts of the components used in the fertilizer spike may vary based on the particular application of the spike and based on the plants desired to receive the nutrients from the spikes. However, generally the above fertilizer source materials are combined to provide a composition having pre-determined amounts of nitrogen, phosphorus, and potassium (NPK). The amounts of available nitrogen, phosphorus, and potassium are varied based on the requirements of the plants to be fertilized. However, the composition is typically selected to provide a spike that has a mechanical strength which enables it to be inserted into the terrain or compacted soil, without shattering, and such that the spike remains substantially undamaged while being driven into the soil.  
         [0023]     In one embodiment, the fertilizer spike is formed with an NPK fertilizer weight percentage of 12-5-7, et al, i.e., 12 parts nitrogen to 5 parts phosphorus to 7 parts potassium. Other nutrient ratios may be varied according to specific plant requirements. More specifically, in such an embodiment, the fertilizer spike is formed with a fertilizer composition which contains about 9.0 parts Diammonium Phosphate, DAP 18-46-0, about 13.75 parts Muriate of Potash, MOP 0-0-60, 12.65 parts Nitroform® 38-0-0 (CH(NO2) 3 ), about 46.25 parts Ammonium Sulfate 21-0-0, and about 18.35 parts granular gypsum, where the parts are parts by weight. In alternate embodiments, the fertilizer spike contains from about 1 to about 30 parts of diammonium phosphate, from about 1 to about 30 parts of muriate of potash, from about 1 to about 30 parts of Nitroform® 38-0-0 (CH(NO2) 3 ), from about 1 to about 50 parts of ammonium sulfate, and from about 1 to about 20 parts gypsum, where the parts are parts by weight.  
         [0024]     In an alternative embodiment, the spike may also include an active component which has a particular desired effect on plant growth or health when released to the plant over an extended period of time. For example, such desired effects may include, but are not limited to, control of pests or diseases, such as would be available from a pesticide. As used herein, the term “pesticide” includes any substance or mixture of substances, including fungicides, intended for preventing, destroying, repelling, or mitigating any insect, rodents, nematodes, fungi, or weeds, or any other forms of life declared to be pests, and any substance or mixture of substances intended for use as a plant growth regulator, rooting hormone, defoliant, or desiccant. Moreover, the term pesticide includes, but is not limited to including, systemic and non-systemic herbicides, algaecides, fungicides, insecticidal toxicants, nitrification inhibitors, acaricides, and nematocides.  
         [0025]     The above-described fertilizer spike provides a cost-effective and reliable means for delivering nutrients to a plant over an extended period of time. More specifically, the wedge-shaped fertilizer spike is fabricated through a tableting process that produces a spike having a shape and a mechanical strength that enables the spike to be hammered into the soil without shattering, such that the spike remains substantially undamaged while being driven into the ground. In other embodiments, a cap is inserted over the spike to facilitate increasing the structural strength of the spike and to further facilitate the spike remaining substantially undamaged while driven into the ground. Furthermore, following fabrication through the tableting process, the mechanical bonding properties of the spike enable the spike to be immediately handled and/or packaged following ejection from the tablet press dies. Accordingly, manufacturing costs are reduced in comparison to other known spikes because no cure times or heating/cooling cycles are required. Moreover, manufacturing costs are also reduced because the fertilizer spike is fabricated without thermoset materials or adhesives. As a result, a fertilizer spike is provided which facilitates the delivery of nutrients through hydrolysis and microbial activity in a cost-effective and reliable manner.  
         [0026]     An exemplary embodiment of a fertilizer spike and an associated method of fabrication are described above in detail. The fertilizer spike illustrated is not limited to the specific embodiments described herein, but rather, as will be appreciated by one skilled in the art, other embodiments of fertilizer spikes and other methods of fabrication are available.  
         [0027]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.