Abstract:
A horticulture growing medium mixture or so-called “potting soil” provides a generally soil-less medium that does not rely on the use of peat moss, soil or compost. A unique combination of anaerobically digested solids, perlite, vermiculite, and various additives and amendments provides a growing medium with a surprisingly high acid-buffering coefficient. Although the growing medium is particularly suited for orchids, the medium can be tailor-mixed for various other plants as well.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of provisional patent application Ser. No. 60/711,725 filed on Aug. 26, 2005 by present inventors. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention generally pertains to potting soils and more specifically an alternative growing medium. 
   2. Description of Related Art 
   A wide variety of potting soils and other growing media have been developed for supporting the growth of potted plants. Perhaps the most common are mixtures having a base of sphagnum moss peat, soil, ground coconut coir, composted hardwood bark, or composted manure (aerobically reduced manure or crop byproducts). Current potting soils, however, have various drawbacks. 
   Harvesting peat from wetland bogs is becoming expensive and is raising environmental concerns. Compost and other base materials often have one or more disadvantages such as high shipping costs, poor nutrient holding capacity, unpleasant odor, or unsuitable water retention. Moreover, some potting mixes have a pH that is unsuitable for certain plants. 
   Thus, there is a need for a better plant growing medium that overcomes the drawbacks of existing potting mixes. 
   SUMMARY OF THE INVENTION 
   An object of the invention is to provide a growing medium for plants that uses anaerobically digested solids instead of peat or compost. 
   Another object of some embodiments is to provide a growing medium that avoids the environmental problems and high cost of alternatives that rely on composted materials or peat moss. 
   Another object of some embodiments is to provide a growing medium that has a relatively high acid-buffering capacity. 
   Another object of some embodiments is to provide a horticulture growing medium that is preferably a substantially dry mixture whose sulfur content is controlled so as to provide a growing medium that is nearly odorless, lightweight, easy to package in an airtight bag, easy to handle, and easy to ship. 
   Another object of some embodiments is to provide a growing medium having a base of anaerobically digested solids so as to provide a mixture whose pH can be lowered by aluminum sulfate, iron sulfate, or some other pH amendment to a level that is suitable for plant growth. 
   Another object of some embodiments is to provide a growing medium that is suitable for growing orchids without having to rely on peat moss, coconut coir or other alternatives. 
   Another object of some embodiments is to create a growing medium with anaerobically digested solids yet still have desirable amount of humic acid. 
   Another object of some embodiments is to provide a growing medium whose pH can be adjusted with a reasonable amount of a pH amendment. 
   Another object of some embodiments is to provide a growing medium for orchids by adding coconut coir and excluding peat moss. 
   Another object of some embodiments is to provide a growing medium for bedding plants, cut flowers, nursery plants and other plant species grown in containers by adding coconut coir or other suitable organic constituent and excluding peat moss. 
   Another object of some embodiments is to provide a mixture of soluble components each of a particular concentration to create a growing medium that is suitable for geraniums, wherein the components include, but are not limited to, nitrate, phosphorous, potassium, calcium, magnesium, sulfur, zinc, boron, manganese, and copper. 
   Another object of some embodiments is to provide a mixture of soluble components each of a particular concentration to create a growing medium that is suitable for container-grown plants, wherein the components include, but are not limited to, nitrate, phosphorous, potassium, calcium, magnesium, sulfur, zinc, boron, manganese, and copper. 
   Another object of some embodiments is to provide a mixture of soluble components each of a particular concentration to create a growing medium that is suitable for orchids, wherein the components include, but are not limited to, nitrate, potassium, calcium, magnesium, and sulfur. 
   One or more of these and/or other objects of the invention are provided by a submixture of digester solids, vermiculite and perlite, plus amendments to make the submixture particularly suitable for certain plants. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a schematic diagram illustrating a horticulture growing medium according to the subject invention. 
       FIG. 2  is chart showing recipes of various horticulture growing media mixes. 
       FIG. 3  is a block diagram showing how growing media can be produced and used. 
       FIG. 4  is a graph illustrating the acid-buffering characteristic of various materials. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a horticulture growing medium  10  comprises a submixture  12  that may include a pH amendment  14  and various other components  16 . Submixture  12  comprises an organic component  18 , perlite  20  and vermiculite  22  in various concentrations. In currently preferred embodiments, organic component  18  is primarily comprised of substantially anaerobically digested manure (as opposed to conventional aerobically decomposed compost or peat moss), however, it is conceivable that organic component  18  could include coconut coir  24 , peat moss, composted bark, and other organic substances. 
   A pH amendment  14  can be added to submixture  12  to provide medium  10  with a pH (reference numeral  26  of  FIG. 2 ) that is appropriate for certain plants. Medium  10  may include various soluble components  28  in various concentrations to provide medium  10  with qualities that are beneficial to plants. Soluble components  28  may be added to submixture  12  and/or they may exist as natural or pre-existing ingredients of organic components  18 , perlite  20  and/or vermiculite  22 . Moreover, pH amendment  14  may actually be one of the soluble components  28 . Aluminum sulfate or iron sulfate, for instance, may be part of the soluble components  28  and may also serve as pH amendment  14 . Flowers of sulfur (sulfur) may be substituted for aluminum or iron sulfate but would be considered insoluble without suitable micro-organisms to promote its decomposition. In all, growing medium  10  can provide a generally soil-free mixture without having to rely on a significant amount of peat moss, compost or soil and preferably no peat moss, no compost and no soil whatsoever. 
   Various examples of growing medium  10  are illustrated in  FIG. 2 , and the examples are labeled Mix-A  10   a , Mix-B  10   b , Mix-C  10   c , and Mix-D  10   d . Mix-A  10   a  was originally intended for growing geraniums  30  ( FIG. 3 ) and other bedding plants; and Mix-B  10   b , Mix-C  10   c , and Mix-D  10   d  were designed for Cypripedium and other basophilic orchids  32  ( FIG. 3 ). It should be noted, however, that the various mixes A-D are exemplary embodiments and that their specified mixtures and uses may vary. Moreover, the tabulated values of  FIG. 2  are target values, and the actual values could deviate from those listed and still provide beneficial results. For the soluble components  28  (those measured in ppm), their values could vary by plus or minus 20% and still provide beneficial results. The listed values in ppm (parts per million) for the soluble components are measured by an appropriate conventional method using standard greenhouse filters and standard potting media tests that are well known to those of ordinary skill in the art. Although  FIG. 2  suggest specific proportions of organic component  18 , vermiculite  22 , perlite  20  and coir  24 , the actual range of those proportions could vary greatly and still remain well within the scope of the invention. Organic component  18  (in the form of anaerobically digested solids with or without coir  24 ) could actually make up 5% to 75% of the volume of growing medium  10 , vermiculite  22  could make up 0% to 50% of the volume of medium  10 , and perlite  20  could make up 0% to 50% of the volume of medium  10  and still provide beneficial results. 
   Perlite  20  provides medium  10  with water drainage and aeration. Vermiculite  22  may do this also; however, vermiculite  22  also has a slightly negative charge and some porosity, which can help hold moisture and positively charged nutrients. In some embodiments, it is conceivable to replace the perlite or vermiculite with alternatives such as polystyrene or sand. Moreover, a mixture of perlite and vermiculite could conceivably be replaced with perlite alone or vermiculite alone. 
   The soluble components  28  have been chosen to provide various benefits of which some have been identified as follows: nitrate  34  for chlorophyll and organic plant molecules containing nitrogen; phosphorous  36  for energy reactions and DNA bonding; potassium  38  for water regulation and movement; calcium  40  for cell membrane cell wall biosynthesis and associated electric charges, and cell division; magnesium  42  for enzyme regulation, respiratory passageway, and chlorophyll biosynthesis; salts  44  include soluble salts such as those containing sulfur, magnesium or other inorganic macro- or micro-nutrients; sulfur  46  for amino acids containing sulfur; zinc  48  for auxin production; boron  50  helps develop shoot tip growing point; manganese  52  regulates enzymes in respiration and moves electrons in photosynthesis; iron  54  regulates enzymes in respiration, moves electrons in photosynthesis, and activates enzymes for producing chlorophyll; and copper  56  moves electrons in photosynthesis. 
   In addition to the components shown in  FIG. 2 , organic component  18  is preferably comprised of anaerobically digested solids with 0.4% to 6% by weight of humic acid for positive results, and it is notably beneficial to have between 4% and 6% by weight of humic acid. When organic component  18  includes some coconut coir, as is the case with Mix-C  10   c , such a mix may be particularly suitable for growing orchids  32 . 
   A unique and valuable quality of growing medium  10  is its organic component&#39;s acid-buffering capacity or its ability to resist a decrease in its pH level as an acidic solution is added to organic component  10 . An organic component&#39;s acid-buffering capacity can be quantified as an acid-buffering coefficient (see  FIG. 4 ), which can be determined by performing a Zauche test on a sample of organic component  18 . 
   A Zauche test involves taking a 500-mg. dry weight sample of organic component  18 , and soaking it in 20 mL of 0.0993 M acidic acid for one hour. While the solution or suspension is soaking, it is stirred with a magnetic stir-bar. Upon completion of the one-hour soaking period, the suspension is vacuum filtered through a Whatman #1 filter paper. The remaining solids collected by the filter are rinsed with 160 mL of de-ionized water. The rinse water is combined with the filtrate and is then titrated with 0.133 M sodium hydroxide while measuring the rinse water&#39;s pH. The pH is plotted as a function of the quantity of the sodium hydroxide, as shown in  FIG. 4 . Curve  58  represents a Zauche test performed on a sample of anaerobically digested solids, which comprise the organic component of Mix-A  10   a , Mix-B  10   b , and Mix D  10   d . The greatest slope of curve  58  is identified as point  60 , which corresponds to 8 mL or an acid-buffering coefficient of 8 on an X-axis  62  of  FIG. 4 . Thus, organic component  18  (e.g., anaerobically digested manure) has an acid-buffering coefficient of 8. Curve  64  represents a Zauche test performed on conventional compost (e.g., aerobically decomposed manure). The steepest point of curve  64  is at point  66 , which indicates that the compost sample has an acid-buffering coefficient of 13. Curve  68  represents a Zauche test performed on a sample of peat moss. The steepest point of curve  68  is at point  70 , which indicates that the peat sample has an acid-buffering coefficient of 14. This means that the digester solids were able to neutralize 0.922 millimoles of acid compared to 0.196 millimoles for composted manure and 0.124 millimoles for peat moss. Or the composted manure and peat moss can neutralize approximately 15 to 20% of the acid that the digester solids can on a per gram basis of material. That is, the Zauche test will show that the growing medium can neutralize at least 0.400 millimoles of acid per gram of organic component which is twice the amount neutralized by composted manure or peat moss. 
   The acid-buffering effect of organic component  18  can be observed in growing medium  10 . It has been found, for instance, that upon adding 200 grams of aluminum sulfate to a 2.5 cubic-foot sample of a growing medium, similar to Mix-A  10   a  but with 60% by volume of organic component instead of 50% (and 20% vermiculite and 20% perlite), the pH of the 2.5 cubic-foot sample would decrease less than 1.7 pH units. And the 1.7 pH figure would decrease proportionately more with a corresponding decrease of the volume percentage of the organic component. A mix with 30% organic component, for example, would decrease more than 1.7 pH units as it would have less buffering capacity and would change more. 
   When organic component  18  consists of anaerobically digested manure, it has been found that the pH of submixture  12  is approximately 8 pH units or at least greater than 7 pH units. Since this is too basic for many plants, a small quantity (e.g., less than 5% by weight) of a pH amendment such as aluminum sulfate, iron sulfate, or other inorganic or organic acidification agent can be added to submixture  12  to reduce the pH of growing medium  10  to a more desirable level such as 5.5 to 8.5 pH units, or perhaps 5 to 7.5. For orchids  32 , a target pH may be approximately 7 or 7.5. For geraniums and other plants, a more appropriate target pH may be around 7 to 7.3 or perhaps even less than that, such as 5 to 6.5. In currently preferred embodiments, submixture  12  has an initial soluble sulfur content of less than 150 ppm, and after adding pH amendment  14  and/or soluble components  28 , growing medium  10  has a final soluble sulfur content of around 100 to 800 ppm. In certain cases, pH amendment  14  may be a soluble lime to increase the mixture&#39;s pH level. 
   A method of creating and using growing medium  10  is illustrated in  FIG. 3 . A block  72  represents the step of anaerobically digesting manure  74  to create organic component  18 . Anaerobically digesting manure has been practiced for years for the purpose of disposing of farm animal and crop waste and for creating useful byproducts such as fertilizer and methane gas. The actual method of anaerobically digesting animal manure  74  can take many forms, all of which are well known by those of ordinary skill in the art. Block  76  represents the creation of submixture  12  by mixing vermiculite  22 , perlite  20 , and organic components  18  (e.g., digester solids) generated in block  72 . Submixture  12  may already inherently include some or all of soluble components  28 . 
   Submixture  12  from block  76  represents a basic mix or foundation that can be later modified for specific uses, such as, for example, growing orchids  32 , geraniums  30 , geraniums, begonia, petunia, impatiens, phlox paniculata, etc. Blocks  78  and  80  represent the steps of modifying submixture  12  to create, for example, medium Mix-C  10   c  for orchids  32  or medium Mix-A  10   a  for geraniums  30 . The amendments of blocks  78  and  80  may include, but are not limited to, aluminum sulfate, iron sulfate, hydrated lime, fertilizer, OSMOCOTE-PLUS, coconut coir, peat moss, magnesium sulfate, MICROMAX, phosphates, potassium nitrate, calcium nitrate, etc. 
   Growing medium  10  is preferably a substantially dry mixture whose sulfur content is controlled so as to provide a growing medium that is nearly odorless, lightweight, easy to package in an airtight bag (low vapor pressure), easy to handle, and easy to ship. 
   Although the invention is described with reference to a preferred embodiment, it should be appreciated by those of ordinary skill in the art that various modifications are well within the scope of the invention. The scope of the invention, therefore, is to be determined by reference to the following claims.