BACKGROUND OF THE INVENTION Fertilizers are commonly used for the purpose of improving plant growth and development by providing chemicals, mineras, vitamins, microbes and other nutrients advantageous to plants.

Fertilizers may be used on a small scale, such as in home vegetable and ornamental gardens, or on a large scale in farms, vineyards, urban parks and gardens, plant nurseries, herbariums and the like.

Fertilizers suitable for plants may be in solid form (e. g. pellets, granules or powders) or in liquid form (e. g. suitable for agricultural spraying equipment).

Traditionally, it has been common to use waste by-products of human activity as fertilizers. This serves the dual purposes of creating a relatively economical fertilizer and returning waste nutrients to the soil for utilization by plants. Well known examples include the utilization of dehydrated abattoir waste in the form of"blood-and-bone", dehydrated animal manure (e. g."dynamic lifter"), and the by-products of plant harvesting such as sugar cane and lucerne mulches.

Usually, waste which is useful for the production of fertilizer contains substantial amounts of organic matter. A useful measure of the amount of organic matter present in waste is Biochemical Oxygen Demand (BOD).

A definition of BOD applicable to this specification is provided in Tortora et a/., 1982, Microbiology: An Introduction (Benjamin/Cummings Publishing Co. Inc) at p681, as"the amount of biologically-degradable organic matter determined according to the

amount of oxygen required by bacteria to metabolize the organic matter".

A BOD5, for example, refers to the decrease in oxygen concentration of a waste sample after five (5) days incubation at 20°C in the presence of bacteria and an initial supply of oxygen. BOD values are usually expressed as mg/L oxygen (02) used.

Typical BODs values for certain types of waste are as follows:- Domestic sewage. 100-400 mg/L; Brewery effluent 6000-18000 mg/L; Food processing 100-15000 mg/L; Meat processing 700-2300 mg/L; Palm-oil effluent 10000-45000 mg/L.

As used hereinafter, biological waste is any waste which has a BODY in excess of 100 mg/L.

It has long been known that worms are capable of converting a variety of waste materials into castings which may be used as an excellent solid fertilizer.

"Castings"as used herein is particulate material which includes soil, nutrients and bacteria, deposited through the anus. It is considered that the main value of worm castings as fertilizer resides in their microbial activity and nutrients.

Worms from which castings may be obtained include, for example, Lumbricus rubellus, Eisenia fetida, Eudrilus eugeniae and Perionyx excavatus.

The ability of worms to consume a variety of substances, including waste, and convert such substances to castings, together with the value of castings as fertilizer and the"ecologically friendly"nature of this process, has led to a resurgence in vermiculture.

In this regard, reference may be made to Australian Patent Application No. 45647/96 which discloses the conversion of a wide variety of organic refuse materials into worm castings useful as solid fertilizer.

Further to this, French Patent No. 2587993 discloses the <BR> <BR> use of Eisenia sp. or Fetida sp. worms for the conversion of organic liquid refuse with BOD5 below 10000 mg/L into worm castings suitable for use as a solid fertilizer.

It has also become practice to add worm castings to manures and composts to provide an enhanced solid fertilizer. For example, reference is made to Website www. vermiculture. com which features a"pulverizer"for producing a ground particulate fertilizer from worm castings combined with compost and/or manure.

OBJECT OF THE INVENTION The present inventors have realized that the prior art has focussed on creating solid fertilizers from worm castings, while ignoring the benefits of producing liquid fertilizer therefrom.

It is therefore an object of the invention to provide a method of producing a liquid fertilizer.

It is another object of the invention to provide an apparatus for producing a liquid fertilizer.

It is another object of the invention to provide a liquid fertilizer.

SUMMARY OF THE INVENTION In a first aspect, the present invention resides in a method of producing a liquid fertilizer including the steps of:- (i) combining worm castings with liquid biological waste to form a fertilizer mixture; (ii) separating the fertilizer mixture obtained in step (i) into a particulate fraction and a liquid fraction; and (iii) collecting said liquid fraction for use as liquid fertilizer.

Surprisingly, the present inventors have found that the liquid fertilizer formed according to the process of the invention has superior fertilizer properties as will be hereinafter described.

As used herein, liquid biological waste is defined as biological waste (as previously defined) which comprises water, such that a fertilizer mixture formed therefrom is separable into a liquid fraction and a particulate fraction under the influence of gravity.

Although not restricted to any of the following, said liquid biological waste may be in the form of domestic wastewater or sewage, grease-trap waste, brewery waste, dairy waste, food processing and manufacturing waste such as starch waste, and piggery or abattoir waste.

Preferably, the liquid biological waste has a BODY in the range 100-50000 mg/L.

Preferably, the worm castings are combined with an excess of liquid biological waste.

Preferably, the ratio of liquid waste to castings is greater than 2: 1 (v/w) but less than 60: 1 (v/w). Advantageously, the ratio is 5: 2 (v/w).

Preferably, additional materials may be included to form said fertilizer mixture, said additional materials including solid paper mill waste, tallow, chicken manure, pozzolanic ash, charcoal, sawdust, clays such as bentonite, zeolite and kaolinite, magnesium scrap or dross, gums and pentosans.

Advantageously, the additional materials are selected from the group consisting of tallow and chicken manure.

Preferably, the additional materials constitute up to one fifth (20%) of the materials used to form said fertilizer mixture.

Inclusion of said additional materials may have any one of the following effects:- (i) improving fertilizer shelf life; (ii) improving fertilizer nutrient content; and (iii) increasing the level of suspended solids.

The worm castings can be obtained readily from a variety of vermiculture sources.

In a second aspect, the present invention resides in an apparatus for producing liquid fertilizer, said apparatus having one or more mixing containers, whereby in use, liquid biological waste and worm castings are combined in said one or more mixing containers to form a fertilizer mixture, which mixture is separable into a particulate fraction and a liquid fraction.

The liquid biological waste may be stored in a holding tank or reservoir more or less permanently associated with the apparatus of the invention. However, it is also contemplated that the apparatus of the invention could be transported to a site which provides its own source of liquid biological waste.

Preferably, one or more circulation conduits interconnect said one or more mixing containers.

Preferably, one or more valves are associated with said circulation conduits, said valves in use regulating circulation of fertilizer mixture through said conduits.

Preferably, said apparatus inclues a screening means such as a sieve or a basket, to screen clumps and debris above a desired size from said worm castings.

Preferably, the apparatus of the invention include (s) a mixing means such as a pump, stirrer or paddle, to facilitate combining the liquid biological waste and worm castings to form said fertilizer mixture. Preferably, mixing occurs over a period of four (4) hours.

Once mixing is complete, said fertilizer mixture is allowed to settle under the influence of gravity into said particulate fraction and said liquid fraction.

The liquid fraction may be decanted, pumped or otherwise collected from said mixing container (s), preferably via one or more collection conduits. Preferably, the liquid fraction is filtered, particularly if it is to be used as a liquid fertilizer in conjunction with spraying equipment.

According to one embodiment of the second aspect, the apparatus of the invention inclues a first mixing container and a second mixing container, wherein the liquid biological waste is supplie to said first mixing container via a waste supply conduit. Preferably, the worm castings are added to said first mixing container via a screening means prior to addition of said liquid waste to form said fertilizer mixture. A mixing means is provided in the form of a pump. The fertilizer mixture is pumped from the first mixing container to the second mixing container and circulated through one or more circulation conduits. The fertilizer mixture is then allowed to settle in said second mixing container under influence of gravity and the liquid fraction collecte by being pumped from said second mixing container through one or more collection conduits.

Preferably, the fertilizer mixture undergoes several cycles of mixing in the second mixing container.

Preferably, the pump-driven circulation continues for four (4) hours to facilitate adequate mixing of the fertilizer mixture.

In a third aspect, the present invention resides in a liquid fertilizer having a total bacterial count of at least 2.5 x 106 colon forming units per millilitre (cfu/ml), and a carbon to nitrogen (C/N) ratio of at least 7: 1.

Preferably, the liquid fertilizer has a total bacterial count of at least 2. 5 x 10'cfu/ml.

More preferably, the liquid fertilizer has a total bacterial count of at least 1.5 x 108 cfu/ml.

Advantageously, the liquid fertilizer has a total bacterial count of at least 4.5 x 108 cfu/ml.

Optionally, in order to enhance microbial activity, microbes may be added to said liquid fertilizer. In cases where said liquid fertilizer is prepared according to the method of the invention, microbes may be added to said fertilizer mixture, to said liquid fertilizer and/or to said worm castings in order to enhance microbial activity of the resultant liquid

fertilizer. With the foregoing in mind, it is preferable to add microbes according to the ultimate use of said liquid fertilizer. That is, with regard to factors such as the plant variety to which said fertilizer is to be applied, and environmental factors such as soil type and condition, climate, and rainfall. In this regard, the microbiology of soil is extremely complex, and there is a wide variety of microbes potentially useful as additives.

Examples of microbes potentially useful for this purpose include bacteria such as Nitrosomonas and Nitrobacter which enhance soil nitrification, and bacteria such as Rhizobium and Azotobacter which"fix"soil nitrogen in a form suitable for leguminous plants.

An example of a commercial available source of microbes is the microbial preparation SC27 distributed by Envirocorp, Mudgeeraba, Queensland, Australia.

Preferably, the liquid fertilizer has a C/N ratio of at least 10: 1.

More preferably, the liquid fertilizer has a C/N ratio of at least 13 : 1.

Advantageously, the liquid fertilizer has a C/N ratio of at least 20: 1 Preferably, the liquid fertilizer has one or more nutrients selected from the group consisting of:- (i) calcium (as Ca2+) at a concentration of at least 19 g/L; (ii) phosphorous (as phosphate) at a concentration of at teast 1.4 g/L; (iii) potassium (as K+) at a concentration of at least 0.7 g/L; (iv) nitrates at a concentration of at least 1.3 g/L; (v) ammonia at a concentration of at least 1.0 g/L; (vi) nitrogen (as protein) at a concentration of at least 4.2 g/L;

(vii) total nitrogen at a concentration of at least 6.5 g/L; (viii) iron (as Fe2+ and/or Fe3+) at a concentration of at least 1. 7 g/L; (ix) zinc (as Zon") at a concentration of at least 0.6 g/L; (x) magnesium (as Mg2+) at a concentration of at least 0.5 g/L; and (xi) sulphur (as sulphate) at a concentration of at least 6.8 g/L.

Optionally, in order to enhance or supplement the nutrients in said liquid fertilizer, inorganic nutrients may be added to said liquid fertilizer, to said fertilizer mixture, to said castings and/or said liquid waste.

Said inorganic nutrients include, for example, nitrogen, phosphorus, potassium, iron, sulphur, calcium, magnesium, copper, zinc, manganese and boron.

In use, the liquid fertilizer of the invention has advantages over solid fertilizers which include:- (i) it can be applied by a wider variety of means: spraying, irrigation and the like; (ii) it provides nutrients and microbes which are quickly released into the soil and hence readily available to plants; and (iii) it is readily miscible with water to achieve a desired concentration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1: Elevation view of an apparatus for treating liquid waste; and FIG. 2: Plan view of a modified version of the apparatus in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, apparatus 1 includes first mixing

container 2 and second mixing container 3.

Worm castings 6 are added to first mixing container 2.

Usually, a screening means for excluding clumps and debris is provided.

In this case, screening means is sieve 4 located above mixing container 2 to prevent clumps and debris above a desired size being added to mixing container 2. In this case, sieve 4 is shaken, as shown by hatched lines and double-headed arrow. Debris and clumps are discarded into bin 5.

An alternative screening means is a basket into which are placed worm castings 6, the basket being located within mixing container 2.

With valve 8 (and all other valves) closed, liquid biological waste is pumped along waste supply conduit 9 and enters first mixing container 2. In this case, liquid biological waste enters via spray bar 10 and thereby combines with castings 6 to form a fertilizer mixture (not shown). Should worm castings 6 be placed in a basket, the spray bar is not necessary, and conduit 9 may enter mixing container 2 directly.

Spray bar 10 comprises a series of spray jets or nozzles, best seen in FIG. 2 to flush worm castings 6 into the lower portion of first mixing container 2.

With valves 8 and 11 open, pump 7 draws the fertilizer mixture from first mixing container 2 via circulation conduits 13,14 and 15 into second mixing container 3.

At this stage, more liquid waste may be added to first mixing container 2 to achieve the desired ratio of waste to castings. Again, the fertilizer mixture once formed is pumped into second mixing container 3.

Once the desired ratio of liquid waste to worm castings has been achieved, valve 8 is closed and valves 11 and 16 opened. Pump 12 then circulates fertilizer mixture from mixing container 3 through circulation conduits 17,18 and 13 and then back into container 3 via conduits 13,14 and 15.

This circulation which assists mixing of the fertilizer mixture proceeds for a desired period of time, preferably 4 hours.

At the expiration of this time, pump-driven circulation is stopped and the fertilizer mixture is left to settle under gravity into a more dense particulate fraction and a less dense liquid fertilizer fraction (not shown) in second mixing container 3.

By opening valve 19, the particulate fraction is selectively discharged via conduits 17 and 20.

By opening valve 21, the liquid fraction can be directed along collection conduit 22 into a drum or other small collection vessel.

By opening valve 23 the liquid fraction can be directed along collection conduit 24 into a tanker or other large collection vessel (not shown).

As shown in FIG. 2, collection conduit 24 may be bifurcated into segments 24A and 24B, which segments include filters 25A and 25B to remove particulate material of at least approximately 130 pm from the liquid fertilizer. Collection conduit 22 may also include such filters.

The presence of filters renders the liquid fraction suitable for use as a liquid fertilizer in conjunction with agricultural spraying equipment.

It will be appreciated by a person skilled in the art that the present invention is not limited to the particular embodiments presented in detail herein. Various modifications and combinations of features are contemplated which nevertheless fall within the broad scope and spirit of the invention.

EXPERIMENTAL The liquid fertilizer of the present invention was assessed in terms of it's relative efficacy compared to two commercially available fertilizers.

For the purposes of this study, the fertilizers will be referred to hereinafter as:- FERTILIZER A: inorganic fertilizer (standard NPK type); FERTILIZER B: an organic product containing twenty-seven (27)

different microbes intended to assist root development and plant growth (marketed by Envirocorp in Australia as SC27); FERTILIZER C: the liquid fertilizer of the invention.

Fertilizer efficacy was measured in terms of wheat plant growth, crop yield and soil characteristics following fertilizer treatment.

1. RESULTS With reference to Table 1, it is clear that wheat plants treated with the fertilizer of the invention are taller than those treated with the other fertilizers (by an average of 8%). However, it should be noted that FERTILIZER B encouraged growth of a longer roots than did FERTILIZER C.

As a measure of the health of the plant itself, the nitrogen content of the root was ascertained in relation to carbon (C/N ratio), the results being shown in Table 2. Both organic FERTILIZERS B and C appeared to be more beneficial to the plant than FERTILIZER A, that is by virtue of a significantly lower C/N ratio. However, on closer inspection, thee measures do not necessarily translate to crop yield.

In this regard, and referring to Table 3, it can be seen that although FERTILIZER B preferentially influenced root mass, the fertilizer of the invention significantly outperformed the other fertilizers with respect to head mass through greatly-increased kernel mass. It should also be noted that the composition of wheat kernels in these experiments did not vary according to the fertilizer used (data not shown). For example, the C/N ratio of the kernels was in the order of 13 irrespective of fertilizer.

Thus, the superior crop yield attributable to the fertilizer of the invention was attributable to kernel mass (more than 2-fold of at least for FERTILIZER B) and the number of kernels per wheat plant.

Although an extensive set of chemical and physical indicators of the health of trial plants were measured, the purpose of this trial was to assess the improvement of crop yield through addressing soil

health as well as plant health and nutrition. Therefore, the nutrients within the soil were measured as extractable NPK, rather than total NPK. As seen from Table 4, the fertilizer of the invention was significantly more effective than the other fertilizers in terms of"unlocking"nitrogen from the soil. This efficacy is probably related to two factors:- (i) microbial activity in the fertilizer of the invention; and (ii) inorganic nutrients present in the fertilizer of the invention.

Clearly, FERTILIZERS A and B respectively provide (ii) and (i) individually, but this is not as effective as the dual role played by these factors present in combination in the fertilizer of the invention. In this regard, it is clear from other data (not shown) that the fertilizer of the invention acts as a"microbial soil conditioner", enhancing soil healthiness by encouraging the growth of useful microbes while suppressing the growth of pathogenic microorganisms. Electron micrograph studies have shown that this soil conditioning function is also attributable to the fertilizer of the invention acting as a dispersant to break down densely- packed particle layers in the soil, such as found in clays. Lower density soil improves air and moisture availability and also promotes root penetration.

2. CONCLUSIONS This study has shown the benefits provided by the liquid fertilizer of the present invention, particularly with regard to crop yield.

The fertilizer of the present invention increases the crop yield without changing grain quality, and without significantly altering overall plant biomass or root growth. The increase in wheat kernel yield provided by the fertilizer of the invention was approximately 31% compared to the inorganic fertilizer (FERTILIZER A). Significantly, this increased yield was achieved without the risk of soil damage usually associated with the harsh effects of inorganic fertilizers.

TABLES TABLE 1 Stalk (cm) 62 62 67 Root (cm) 14 16 13 TABLE 2 I''''"'SES Hr N(dry wt %) 0. 4 1. 3 1.3 C/N 82. 9 29. 8 25.0 TABLE 3 ................................................. Whole plant (g) |:::: ::::::::::::::: :::::::::::::::::::::::::;::::::::::::::::::;::::::::::::::: : : ::;::::::: :::::::::::::::::::::: °'.::; ;':': :::::::::::::::::: >.:::::::. .:::::::::...:::::::::::::::::::::::: : : : : :. : : : : : ; ; : ; ; :v :' : : : : : : : : : : : : : : ; : : : : : : ; : : : : : : : : : : : : : : : : : ; :. : : : : : : : : :' ; : : : : ; : : : ;,i ; : : : : Whole plant (g) 1.6 2.2 2.1 Roots (g) 0.2 0. 2 0.1 Heads (g) 0.2 0. 3 0.4 Kernel (mg) 7.4 4. 1 9.7 TABLE 4 , f................. =E w. >grm. a Extractable N 41 29 136 (mg/kg) Extractable P 19.5 10.4 32.2 (mg/kg) Extractable K 258 180 234 (mg/kg)

TABLE LEGENDS TABLE 1 Average height of wheat plants grown under three different fertilizer regimes.

TABLE 2 Average carbon (C) and nitrogen (N) content and C/N ratios of wheat plants grown under three different fertilizer regimes.

TABLE 3 Average weight of wheat plant components grown under three different fertilizer regimes.

TABLE 4 Soil nutrient characteristics resulting from three different fertilizer treatment regimes.