AU6501490A

AU6501490A - A seed-containing water imbibing unit and methods utilising same

Info

Publication number: AU6501490A
Application number: AU65014/90A
Authority: AU
Inventors: Kenneth A. Turpin
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-10-13
Filing date: 1990-10-04
Publication date: 1991-05-16
Anticipated expiration: 2010-10-04
Also published as: GB9206931D0; FI921566A; CA2000620C; GB2255269A; EP0495809A1; CA2000620A1; FI921566A0; WO1991005459A1; GB2255269B; AU647753B2

Description

A Seed-Containing Water Imbibing unit and Methods Utilising Same

This invention relates to the planting of seeds and particularly provides both methods and means for facilitating same.

There has been a desire to improve methods of planting and propagating plants for agricultural and forestry purposes for generations. This need has been addressed largely by ever increasingly sophisticated technology and expensive scientific research. The necessity to provide simple inexpensive solutions has become all the more acute recently with intensifying difficulties in maintaining crops in certain regions of the world to provide adequate food supplies and. now widespread concerns over the ecological damage arising from deforestation. The current demand is not only to solve the problems or alleviate the difficulties of the present situation but also to do so in an environmentally acceptable manner.

It is widely recognised that plants in general, once established in a suitable environment, are for the most part self-sufficient and relatively easily cultivated. The most significant difficulties and highest losses of potential crops arise in establishing the plant in the first instance.

Therefore attention is currently directed at ways of ensuring that the plant seeds become established as plantlets.

Research is being vigorously pursued into genetic engineering of plants to improve their probability of survival to mature plants which can be harvested. Other lines of research being followed include tissue culture cloning methods, e.g. the callus culture method which involves extensive preliminary laboratory preparation work and expensive controlled culture environment before it is even possible to consider planting the young plant. Variou other culture techniques exist but they too suffer from the drawbacks of expense and labour intensive preparation procedures. Despite these obvious disadvantages workers in the field have not been discouraged from developing still further laboratory initiated methods. Thus Lion K.K. of E SHEET Japan have developed a technique for coating somatic embryos with gelling agents combined with nutrients, which technique is described in JP-A-61-40 708. Of course the use of gelling agents for seed coatings is known. Clarence c. Dannelly discloses in US-A-4 249 343 various compositions of water-insoluble but water-sensitive polymeric microgel. This gel when used as a coating for seeds provides protection for the seeds, and may be used to carry various materials such as fertilizers and pesticides. However, the polymer used does not dissolve when contacted with water.

The binding forces at the interface between the particles o the coating having a greater sensitivity to water than the binding forces which maintain the particles intact. Whereb contact with water destroys the continuity of the coating, causing it to disintegrate. In that patent, the seed coating is applied in a liquid form and allowed to dry before planting. Therefore any carried materials must be incorporated into the gel and seed at the same time. The presence of liquid in this media produces initial seed damage at time of coating. Also there is no available dissolved material once the seed is planted, due to the gel "falling" off upon water contact. Basically, the problem i that the polymer absorbs the active nutrients but does not release them to promote controlled release, over time. Onc planted, the seed nutrients carried in the gel are leached away after the first rainfall.

An object of the present invention is to obviate or mitigate the aforesaid disadvantages and provide improved methods for planting seed. A further object of the invention is to provide means for delivering with the seed to be planted nutrients remaining in an available assimilable form over a prolonged period of time. It is a still further object of the invention to provide means of delivering with the seed during planting means for enhancin the environment in the locus of the seed after planting which means develops a protective zone around the seed and roots system of the subsequent seedling which tends toward optimum conditions for the particular plant concerned. Thus according to the present invention there is provided a seed growth enhancement unit, preferably in the form of a capsule or tablet, weighing at least one-half gram, for slowly feeding germinating seeds over a period of one year. Preferably the unit comprises an intimate mixtur of dry solid particles including seed condition and growth enhancement agents of variable water solubility but which are at least capable of being broken down into water-solubl substances by the continued action of soil bacteria; a combination of various water-retentive polymers that are slowly biodegradable over a period of up to five years by soil bacteria, and a seed selected from forestry or agriculturalor horticulture etc., said combination being selected so as to provide that said unit on contact with rainfall or moisture, starts to slowly hydrate and form a controlled release gel, enveloping the seed.

The unit may be a gelatin capsule filled with the dry mixture of particulate material and seed. Gelatin is obtained by hydrolysis of collagen by boiling skin, ligaments, tendons etc. usually from bovine or porcine carcasses. Acid hydrolysis yields Type;A gelatin and alkal hydrolysis yields Type B gelatin and either can be used for the purposes of the invention. Gelatin is strongly hydrophilic absorbing up to ten times its weight of water. Consequently both "hard", and "soft" capsules are sensitive to environmental moisture and water content of the product confined within the capsule which tends to cause capsule disintegration. This means that the dry contents of the capsule are readily released upon hydration of the capsule by rainfall or other irrigation.

Although encapsulation is convenient, it is preferred to form the unit as a tablet, in which case a tableting lubricant which does not interfere with water penetration and disintegration of the tablet, e.g. talc an magnesium stearate in the amount of 3% to 6% by weight of the tablet is utilised.

Thus the invention provides a seed growth enhancement unit for nurturing a germinating seed over a period of at least about a year made up of essentially dry components comprising at least one water-insoluble hydratable polymer constituting from 20.5 to 85% dry weight of the mixture with the balance being made up of water-soluble and water- insoluble materials and a seed.

In this invention, the insoluble water-retentive polymer(s) preferably constitute from 30 - 60% of the dry composition, more preferably about 40% of the dry mixture. Advantageously the plantable unit is based on a seed growth media made from a mixture of cross-linked polyacrylamides and hydroxypropylmethyl-celluloses that can be readily added into the tablet matrix by dry mixing before compression.

As mentioned above the delivery form of the unit is variable and may be a gelatin capsule, paper cartridge, a compressed pellet, tablet or prill. It may be desirable in some instances to provide the components in discrete parts for example if it is considered that, despite the dry formulation, there is a remote possibility that under prolonged storage there could be a degradation of the complete formulation arising from an unfavourable interaction between certain components. A further possibility is to have essential polymers, fertilisers, chemical nutrients, etc. in one part which would be storage stable for lengthy periods and provide a further part for use in conjunction with the first but freshly inoculated with essential microorganisms. Thus the plantable unit could be supplied in a kit of parts to be sown together. I this instance, to facilitate this objective, the unit could be made of shaped components with engaging portions for convenience and accuracy in sowing. A possible form would be to provide one part in an annular shape with a further part of a circular shape and of a size enabling it to be simply pressed into the central aperture of the annular par thus completing the unit for sowing. Alternatively, one part could be generally cup-shaped, the seed could be included within the cup aperture and a third part of different composition could provide a plug to close the cup The possibilities for variation in delivery shape and form are numerous and the person skilled in the art will be able to select the most convenient delivery form taking into account such factors as intended manner of sowing i.e. mechanically or manually, ingredient interactions and compatibilities, size of seed, intended storage period prior to sowing etc. For the purposes of further discussion of the invention, references hereinafter, unless otherwise stated, will be to tablet or pellet forms of the plantable unit including the seed.

In summary the invention provides a tableted seed growth media that contains a specific agricultural or forestry application seed, fertilizers, micro-nutrients and a water-retentive polymer complex. Upon the.application of an aqueous medium, a gel composition is obtained. This mixture forms a gel of water, containing the water soluble fertilizers, held in a homogeneous network of swollen, hydrophilic, cross-linked polyacrylamide/hydroxypropyl- ethylcellulose, complexes. Eventually, the water is slowly released in a controlled fashion, leaving a polyacrylamide mass that can be rehydrated completely in less than an hour. The rate of water released during dry periods is slow enough to eliminate the risk of seed rot. A large quantity of the water is evaporated before the seed can absorb excessive amounts. Thus the seed is provided with a controlled zone around it which changes slowly despite whatever radical environmental conditions in the surrounding soil may occur.

In the present invention, the leach resistant properties of the tablet, combined with the direct compression of the dry mixture produce advantages in both production and controlled release of the planted tablet seed. It is not necessarily an objective to have all possible compositions exhibit a large degree of swelling, since under some circumstances the swelling could inhibit seed development, e.g. where the plantable unit is sown into a shaped container for nursery or greenhouse use (such as the popular cellular polystyrene seed trays) . A particular advantage of the plantable unit of the invention is that it is based on a seed growth media including a polymer complex that will retain water, dissolve the encapsulated nutrients and fertilizers and sustain controlled release over time.

Thus the tableted composition of the invention incorporates various agricultural seeds, fertilizers, micronutrients and water-retentive polymers in a non- leaching, controlled-release package. The above mentioned seed, fertilizers and water- retentive polymers, when dry mixed with the proper binders, lubricants, disintegrants and compressed into a tablet form, can be either applied directly into the ground using various planting machinery or spread by various aerial application methods. This allows the seeding and fertilization of areas that would otherwise be inaccessible.

The invention provides methods of seeding which are not only applicable for agricultural, horticultural and forestry purposes but also is applicable to the serious problem of soil erosion enabling rapid sowing of plants for the purposes of soil retention, e.g. grasses for regions such as Ethiopia. The seed-containing units of this invention may be distributed over deforested areas quickly to restore the lost timber or provide rapidly growing ground covering vegetation as a temporary measure to prevent loss of top soil.

The soil tablet, upon water addition, is formed into a body of elastomeric cross-linked polymer that binds a certain quantity of water, resulting in a cohesive gelled mass. The amount of bound water can range from 300-400% by weight of the polyacrylamide copolymer/hydroxypropyl- ethylcellulose complex.

One advantage of this tablet is the ability to give up the major portion of its water to seed germination, thereby aiding and abetting their growth. Additionally, the polymer gel can optionally contain plant growth additives such as agricultural modified minerals, buffers and fertilizers. These will released in a controlled release fashion with minimum chemical "dumping" and assimilated as required by the seed. Fertilizers operable herein can be water insoluble, producing a longer release curve, or soluble such as ammonium and diammonium phosphate, KN0₃, K2S, P2O5 and potash. The preferred polymer to form the tablet is a synthetic organic material such as cross-linked polyacrylamide or hydroxypropylmethyl-cellulose. However, other polymers can also be used alone or mixed and selection may be made from crosslinkable polymers capable of forming a rehydratable water retentive matrix such as poly(ethylene oxide) , poly(vinyl pyrrolidone) , sulphonated polyethylene, hydrolysed starch/methacrylo-nitrile graft copolymer, hydrolysed polyacrylamide, poly(acrylic acid salts) , starch/methacrylic acid salt copolymers, poly(vinyl alcohol) , hydrolysed vinyl ester/unsaturated carboxylic aci ester copolymers or copolymers thereof with ethylene, and hydrolysed hydroxyalkyl acrylate/acrylamide copolymers. Upon reaction with water, these polymers provide a gel body that extends around the root zone where it is placed. Such a gel structure securely holds the seed nutrients and fertilizers, while providing a reservoir of water to feed the growing seed, and eliminating the majority of leaching normally present. Of course the presence of the water- insoluble polymers does not exclude the possibility of including certain water-soluble polymers as listed, and for the purposes to be described, hereinbelow.

The seed contained in the tablet, can become encapsulated in the said gel matrix upon moisture or rainfall contact with the polymeric media originally presen as dry components of the tablet which thereafter provide an appropriate encapsulation matrix, hereafter termed "gel". In general, upon hydratiσn a gel should allow embryo respiration by permitting diffusion of gases. The gel should also be strong enough to resist external abrasion an adverse forces, yet be pliable enough to allow the growth o the embryo and its germination at the appropriate time. It may be desirable to use various gels in combination, eithe as a mixture or in layers, to achieve the desired results. The gel selected must be able to retain and hold a considerable amount of "free water" which is able to participate in the physiological process of germination. Any gel to be used in the dry tablet matrix would usually include the following characteristics upon hydration with moisture:

1. A compliance adequate to protect and cushion the seed.

2. An outer surface to provide a protective barrier to mechanical stress, facilitate handling and maintain seed viability.

3. Sufficient gel strength to maintain capsule integrity, but still allow the radicles arid roots to break out during germination and for the additives to be contained and released. 4. Once hydrated, the interior material would have solubility or emulsion forming characteristics such that it can accept or contain additives.

Under certain circumstances a shortcoming in any one of these areas can be overlooked if the proposed gel material is otherwise favourable. For example in some instances the zone boundary may not be clearly defined.

Some of the suitable gels include, but are not limited to those listed in the Table I hereinbelow.

TABLE l: GEL AGENTS

I. NATURAL POLYMERS

A. IONIC BONDS (Requires Complexing Agents)

Alginate with polypectate

Sodium pectate

Furcellaran

Dextran

Guar Gum

Sodium alginate with gelatin

B. HYDROPHOBIC INTERACTIONS Amylose Gelatin Gum Ghatti Agar Starch Agarose Amylopectin

Ti Gum Agar with Gelatin

Cornhull Gum Wheat Gum

Chitin Dextrin

Starch Gum Arabic

II. CHEMICALLY MODIFIED NATURAL POLYMERS

IT. IONIC BONDS (Requires Complexing Agents) Ethyl succinylated cellulose Succinylated zein Carboxymethylcellulose

B. HYDROPHOBIC INTERACTIONS Methylcellulose Hydroxyethyl cellulose Hydroxypropylmethyl cellulose

C. COVALENT BONDS Gelatin with glutaraldehyde

III. SYNTHETIC POLYMERS

A. COVALENT BONDS Polyacrylamide

B. HYDROPHOBIC INTERACTIONS Polyethylene glycol Hydrophilic urethane Polyvinylpyrrolidone Polyvinyl acetate Polyoxyethylene

Vinyl resins Hydron

C. IONIC BONDS

Sodium poly (styrene sulphonate) + poly (vinyl methyl pyridinium) chloride Sodium poly (styrene sulphonate) + poly (vinyl benzyl trimethyl ammonium) chloride ' Vinyl acetate homopolymer (Bordon poly Co) Polyvinyl alcohol resin (Gelvatol) It has been recognized that plant establishment, growth, and development may be enhanced by addition of additives to the soil, to the rhizosphere of the plant, and to the surface of the plant. It has been demonstrated that controlled release of the additives may provide enhancement to plant growth.

Nitrogen containing nutrients such as that of the formula B below may be included in the make-up of the tablet:

^C28^H34^N2°3 In the present invention additives which have been found to be useful by adding to the tablet matrix along wit the seeds, include pesticides including insecticides and acaricides, herbicides, fungicides any and all being selected with the objective of enhancing the seed germination environment, pesticide counteracting agents including inhibitors- and antidotes, water-soluble and insoluble fertilizers, vitamins, energy sources, simple sugars, carbohydrates, starches, modified starches, cellulose ethers, amino acids, adenosine triphosphate, micronutrients, magnesium, calcium and trace elements, enzymes, growth promoters, growth regulators, phytohormones, pheromones, soil and water conditioners, dispersants, denitrification inhibitors, wetting agents, pH controllers, metal chelating agents, safeners, and dry-cultured micro¬ organisms including bacteria and fungi.

Pesticides may be selected from the group consisting o copper sulphate, thiram, captan, benomyl, metalaxyl, carbofuran, acephate, malathion, pronamide and ethyl dipropyl thiocarbamate.

Fertilizers when present may be included at from 2-40% of dry tablet weight, herbicides at say, up to a maximum of 0.50%, trace elements and micronutrients at up to 0.75%, hormone concentrations at up to 0.05%. When considering fertilisers, a combination of water-soluble and water- insoluble fertilizers is preferred; specifically diammonium phosphate, potash, triple phosphate and potassium sulphide. Fertilizers, for example, can be added at a concentration of 0.01 to 1.0 gram per 1.5 gram seed tablet.

Microorganisms would be added in an amount considered sufficient to be beneficial and ideally would be at spore counts intended to achieve a maximum symbiotic population. The selected additives are added into the dry powder matrix, and therefore must be in a powder or crystal form t be used. Liquid additives cannot be used as such in this invention. The only possible exception to this is where th proposed liquid additive is first adsorbed on to an inert particulate dry porous material such as fuller's earth or vermiculite. Specific additives can be added to the tablet mixture at concentrations specific for the application rate of the particular additive. Pesticides, for example, can b added to the polymer dry mix in concentrations up to 99.4% of the total tablet seed additive content. More usually, pesticide concentrations will be from 0.002 to 0.30 grams active ingredient per gram. Microorganisms, for example, can be added at a concentration of l x 10¹² microorganisms per gram.

It is contemplated that the tablet or capsule could contain non-toxic chemicals that would deter animals or birds from ingesting the gel containing the seed. By use of such tablets the invention provides a method of increasing seed survivability, which is the main object of the present invention, yet involves a non-complex application procedure whereby a leach-resistant tablet that slowly releases water, fertilizers and micronutrients in a controlled fashion can be applied with seeding machinery or by aerial dispersal. Additionally the invention provides a tablet which is totally biodegradable, non-phytotoxic and contains ingredients that promote seed growth. With due consideration to these aspects, the invention utilises polysaccharides or derivatives thereof such as the following (Compound A) at from 20.5 to 85% by dry weight

wherein R represents hydrogen or alkyl groups, especially of long chain fatty acids to provide hydrophobic groups, which when dry mixed with the proper seed, fertilizers, micronutrients, binders, lubricants and compressed into a tablet form, can be directly or aerially dispersed; resulting in enhanced seed survivability.

Various testing with this particular gelling compound in a 1987-88 study in South Florida on the survival and growth effects on Ligustrum and Hibiscus transplants, was conducted with seed plantings made throughout the year, in both wet and dry seasons. Results showed that the survival rate of all three species was increased, when compared to controls. In addition, the average growth rate was also greater due partly to the fact that the soil conditions around the gel-seed was noticeably softer to the touch than the untreated soils.

Another study in Western Massachusetts, at the University of Massachusett's research nursery, again tried to determine survival and condition effects on various forestry seed. The following seeds were used: Eastern white pine (Pinus strobus) White spruce (Picea alba) Colorado blue spruce (P pungus)

Eastern hemlock (Tsuga canadensis) Red spirea (pirea foobelli) Yellow targ dogwood (Cornus lutea)

Results show that very few plants were lost in both test and control treatments. However, the gel-treated seedlings were consistently rated higher in condition.

The invention will now be^' illustrated further by way of the following examples. EXAMPLE 1 A water-retentive, fertilizer containing, seed growth enhancement tablet of this tablet is made from the following components (excluding selected seed) :

% BY WEIGHT

This composition is thoroughly mixed dry and then pelleted dry into tablets, which may be from ¹/₂ gram to 5.0 grams in size. The talc and magnesium stearate act as tablet lubricants during manufacture, ensuring release from the tableting cavity without acting to water proof the tablet.

The above formula is a scientifically balanced low- toxicity seed supplement with long-lasting water-retentive characteristics, which meet the problems of drought, 15

nutrient depletion, leaching and fertilizer dumping. The latter is accomplished through a controlled release of the soluble fertilizer to the seed environment, by the cross- linked polyacrylamide/hydroxy-propylmethylcellulose complex. The very nature of the tablet also decreases leaching loss of nutrients. EXAMPLE 2

A tablet oriented specifically for greenhouse seed growth that incorporates a much higher concentration of compound A. Since the majority of nursery stock is grown i expanded, cellular polystyrene shaped containers, the gelling characteristics of the cross-linked polyacrylamide copolymer would actually damage seed stock by blocking gas exchange. The compound A tablet would fom a gel only covering the surface of the tablet itself. There will be n swelling or increase in gel mass by this tablet. Composition excluding seed:

% BY WEIGHT

This composition is also thoroughly mixed dry and the pelleted dry into tablets, which are from ¹/₂ to 5.0 grams in size. This formula is a low-toxicity plant tablet with long-lasting water-retentive characteristics that meets th problems of seed nutrient stress.

Claims

1. A plantable water imbibing seed-containing unit weighing at least one-half gram, for growth enhancement of germinating seeds over a period of one year, comprising: an intimate mixture of solid particles of the followin ingredients; a combination of seed enhancement agents that are respectively of variable water solubility and are to a large extent capable of being broken down into water- soluble substances by the continued action soil bacteria, a combination of various water-retentive polymers that are slowly biodegradable over five years by soil bacterial, and said composition constituting the major ingredients of said unit, and a seed selected from any forestry or agricultural or horticulture seed stock whereby said unit on contact with rainfall or moisture starts to slowly hydrate and form a controlled release gel capsule, enveloping the seed.

2. A plantable unit according to claim 1 wherein the unit is in dry tablet form and contains tableting aids whic do not interfere with water penetration and disintegration of the tablet.

3. A plantable unit according to claim 2 wherein the tablet contains talc and magnesium stearate in an amount of 3% to 6% by weight of the tablet as a tableting lubricant.

4. A plantable unit according to claim 1 wherein the unit is in dry powder form and encapsulated in a soluble encapsulation medium.

5. A plantable unit according to claim 4 wherein the encapsulation medium is gelatin.

6. A plantable water imbibing unit for nurturing a germinating seed over a period of about a year made up of essentially dry components comprising at least one water- insoluble hydratable polymer constituting from-20.5 to 85% dry weight of the unit with the balance being made up of water-soluble and water-insoluble materials, and further containing a seed.

7. A plantable unit according to claim 6 wherein said materials are selected from the group consisting of natural polymers, synthetic soluble polymers, growth regulating agents, soil conditioning agents, nutrients, trace elements, symbiotic or protective microorganisms, enzymes, phytohormones, fertilisers, herbicides, fungicides, insecticides, acaricides, inert fillers, excipients, lubricants and non-harmful tableting aids.

8. A plantable unit according to claim 6 wherein the water-insoluble hydratable polymer absorbs up to 400 times its dry weight in water.

9. A plantable unit according to claim 6 wherein the water-insoluble hydratable polymer is biodegradable.

10. A plantable unit according to claim 6 wherein the water-insoluble hydratable polymer upon hydration forms a swollen slow-release gel capsule.

11. A plantable unit according to claim 6 wherein the water-insoluble hydratable polymer is a crosslinkable polymer selected from the group consisting of poly(ethylene oxide) , poly(vinyl pyrrolidone) , sulphonated polyethylene, hydrolysed starch/methacrylo-nitrile graft copolymer, hydrolysed polyacrylamide, poly(acrylic acid salts), starch/methacrylic acid salt copolymers, poly(vinyl alcohol) , hydrolysed vinyl ester/unsaturated carboxylic aci ester copolymers or copolymers thereof with ethylene, and hydrolysed hydroxyalkyl acrylate/acrylamide copolymers.

12. A plantable unit according to claim 1 or claim 6 containing water-soluble fertilizers selected from the grou consisting of mono/diammonium phosphate, caustic potash and KNO3, concentrations ranging from 5 to 20% by weight of the tablet.

13. A plantable unit according to claim 1 or claim 7 containing a microorganism selected from the group consisting of Pseudomonas species, Bacillus thuringieusis, Mycorrhizal fungi, Rhizobia species, Bacillus subtilis and Actinomycete species. 18

14. A plantable unit according to claim 1 or claim 6 containing a growth factor selected from the group consisting of giberellic acid, cytokinins, naphthalene acetic acid, indolebutyric acid and indole acetic acid.

15. A plantable unit according to claim 1 or claim 6 comprising water-retentive polymers selected from the group consisting of polymers having the formula A:

wherein R represents hydrogen or alkyl groups, especially of long chain fatty acids, which is present at a concentration of 20.50 to 85.0% by weight of the tablet.

16. A plantable unit according to claim 1 or claim 6 wherein the water-retentive polymers are cross-linked polyacrylamide copolymers.

17. A plantahle unit according to claim 1 or claim 6 wherein the water-retentive polymers are cross-linked polyacrylamide copolymers mixed with compounds of formula A defined hereinbefore.

18. A plantable unit according to claim 1 or claim 6 wherein the water-retentive polymers are cross-linked polyacrylamide copolymers mixed with hydroxypropylmethyl- cellulose.

19. A plantable unit according to claim 1 or claim 6 wherein the water-retentive polymers are present in an amount of from 30 - 60 % by dry .weight.

20. A plantable unit according to claim 1 or claim 6 wherein the water-retentive polymers are present in an amount of 40% by dry weight.

21. A plantable unit according to claim 1 or claim 6 comprising a nitrogen-containing agent of the formula 19

which is present in concentrations of 3.50 to 5.0% by weight of the tablet.

22. A plantable unit according to claim 1 or claim 6 containing micronutrients or agriculturally modified minerals, such as vermiculite or perlite, in concentrations ranging from 1 to 3% by weight of the unit.

23. A seed growth enhancement tablet weighing at least one-half gram, for slowly feeding germinating seeds over a period of one year, comprising: a tableted intimate mixture of solid particles of the following ingredients, a combination of water-soluble and non-soluble fertilizers, specifically mono/diammonium phosphate, potash, triple phosphate and potassium sulphide in an amount of from 5% to 20%, talc and magnesium stearate as the tableting lubricant in an amount of 3% to 6%, a combination of two water retentive polymers selected from the group consisting of cross-linked polyacrylamides and hydroxypropylmethyl cellulose constituting the major ingredient of said tablet, each polymer being present in an amount of from 5% to 85% b weight of the tablet, a nitrogen containing additive of the formula

present in concentrations of 0.50 to 5.0% by weight of the tablet, 20

various micronutrients, growth hormones and trace elements present in trace amounts of from 0.002% to 99.4% by weight of the tablet, said tablet on contact with rainfall or moisture starts to slowly hydrate and form a controlled release gel capsule, enveloping the seed.

24. A plantable seed growth enhancement unit having a composition according to claim 1 or claim 6 comprising a plurality of shaped forms each containing differing seed enhancement agents and designed to be sown together or assembled to form a complete unit containing a seed selected from any forestry or agricultural or horticultural seed stock, whereby said unit on contact with rainfall or moisture, starts to slowly hydrate and form a controlled release gel capsule, enveloping the seed.

25. A method of replanting or seeding areas comprising the sowing of a unit containing an intimate mixture of water-retentive polymers, soil enhancement additives and a seed in a dry plantable form.

26. A method according to claim 25 wherein the dry plantable form is a plantable unit according to any one of claims 1 to 24.

27. A method of germinating seeds in greenhouses, comprising placing a low expansion gel tablet, containing a selected seed, directly into expanded polystyrene foam formed containers soil, the tablets comprising an intimate mixture of solid particles of a water retentive polymer having low expansion rates, that is very slowly water soluble and to a large extend capable of being broken down into water soluble substances by the continued action of soil bacteria, said polymer composition constituting the major ingredient of said tablet, talc in the amount of 2% to 5% by weight as a tableting lubricant which does not interfere with water penetration and disintegration of the tablet, a combination of various fertilizers and soil enhancement additives, and a seed type specific to the fertilizers and additives contained in the tablet.