NZ606227B2

NZ606227B2 - Agricultural additives, compositions and methods

Info

Publication number: NZ606227B2
Application number: NZ606227A
Authority: NZ
Inventors: Peter Andrew Bishop; Bertram Francis Charles Quin
Original assignee: Advanced Agricultural Additives () Limited
Filing date: 2013-01-24
Publication date: 2014-12-02

Abstract

Disclosed herein is an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers, and the use thereof for the treatment of soil to reduce soil metal toxicity thereby reducing or eliminating the quantity of liming material required. Specifically wherein the poly-carboxylic acid(s) is/are selected from the group comprising poly maleic acid (PMA), copoly acrylic maleic acid (PAMA), co-poly vinyl alcohol maleic acid (PVaMA), hydrolised co-poly vinyl acetate maleic acid (HPVAMA), poly fumaric acid (PFA), co-poly fumaric maleic acid (PFMA), poly itaconic acid (PIA), co-poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, co poly vinyl alcohol fumaric acid (PVaFA), co-poly vinyl actetate fumaric acid (PVAF), hydrolyzed PVAF (HPVAF), co-poly vinyl alcohol itaconic acid (PVaIA), co-poly vinyl actetate itaconic acid (PVAIA), hydrolyzed PVAIA (HPVAIA), combinations of poly and co-poly vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof. Specifically wherein the silicate polymer(s) is/are selected from the group comprising potassium silicates, sodium silicates and mixtures thereof, more specifically wherein the ratio of SiO2:M2O is between 2:1 and 3.75:1 where M is sodium or potassium. material required. Specifically wherein the poly-carboxylic acid(s) is/are selected from the group comprising poly maleic acid (PMA), copoly acrylic maleic acid (PAMA), co-poly vinyl alcohol maleic acid (PVaMA), hydrolised co-poly vinyl acetate maleic acid (HPVAMA), poly fumaric acid (PFA), co-poly fumaric maleic acid (PFMA), poly itaconic acid (PIA), co-poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, co poly vinyl alcohol fumaric acid (PVaFA), co-poly vinyl actetate fumaric acid (PVAF), hydrolyzed PVAF (HPVAF), co-poly vinyl alcohol itaconic acid (PVaIA), co-poly vinyl actetate itaconic acid (PVAIA), hydrolyzed PVAIA (HPVAIA), combinations of poly and co-poly vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof. Specifically wherein the silicate polymer(s) is/are selected from the group comprising potassium silicates, sodium silicates and mixtures thereof, more specifically wherein the ratio of SiO2:M2O is between 2:1 and 3.75:1 where M is sodium or potassium.

Description

Patents Form # 5 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION AFTER PROVISIONAL NO: 597821 DATED: 25 January 2012 TITLE: AGRICULTURAL ADDITIVES, COMPOSITIONS AND METHODS We, Advanced Agricultural Additives (NZ) Limited, a New Zealand company of 13 Kowhai Street, Tokomaru, Horowhenua, 4864, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: FIELD OF INVENTION This invention relates generally to agricultural additives, compositions and methods having an intended effect of enhancing plant growth by reducing soil metal toxicity. It has particular application to agricultural additives, compositions and methods which can be used to reduce the quantity of liming materials required to achieve soil detoxification and yield increases, or to replace the use of liming materials.

BACKGROUND OF INVENTION In many countries of the world, agricultural production is limited by toxicity from metals such as aluminium, manganese and iron. The occurrence of metal toxicity in many cases can be overcome by the addition of lime (calcium carbonate), or slaked lime (calcium hydroxide) or other alkaline/liming materials to increase the soil pH and precipitate the toxic metal and thus increase plant growth. This phenomenon is commonly termed the “lime response”.

Wheeler (1998) demonstrated that the addition of limestone to a soil at rates of 5000 kg/ha and 10000 kg/ha increased the soil pH (water) from an initial pH 5.26 to pH 5.97 and pH 6.25 respectively in the first year following application. The increase in soil pH resulted in reduced surface and subsoil extractable (1M KCl) aluminium from 65mg Al/kg at 0-5 cm and 260 mg Al/kg at 5-10 cm soil depths to <5mg Al/kg. This resulted in increases in pasture production of 7% and 13% over the following four years at the two application rates. The required application rates of liming material are large relative to the toxic metal concentration, which for aluminium can be toxic at soil solution levels as low as 0.13 mg Al /l for clovers (Edmeades et al. 1991), which is equivalent to about 130 g Al /ha in the top 10 cm of soil.

The manipulation of soil pH to resolve metal toxicity is however an expensive practice, due to the large amounts of limestone required (the amount of limestone needed to lift a soil’s pH is approximately 1 tonne for every 0.1 pH unit, depending on the soil type and amount of calcium carbonate present in the limestone). Application of liming materials can therefore become very expensive by the time the cost of the liming material per tonne, and its cartage and spreading is taken into account, especially in hill country where aerial application is required.

Other methods of reducing metal toxicity to plants have been contemplated. For example, it is known that many aluminium tolerant plants excrete organic acids such as citric, malonic and oxalic acids which assist in nutrient solubilisation, and which have been shown to complex with Al (Hikaru et al. 2009) and reduce aluminium toxicity in plants.

Hikaru et al (2009) have also shown that higher weight polymers such as oxidized Kraft lignin (KL) (at levels of > 25mg/l) were capable of reducing aluminium toxicity (at a level of 0.91 mg Al/l) in radishes without dramatically lowering the total soluble aluminium.

This is a similar result to earlier work on Kraft lignin by Kyoko et al (2001), who found 140 mg/l of oxidised KL was required to reduce the toxicity produced by 5 mg Al/l thus resulting in a mass ratio of 28 oxidized KL:1Al. The detoxifying effects of polymeric compounds have also been shown in a review by Haynes and Mokolobate (2001) in which the natural polymer of fulvic acid at a 40 mg C/l relieved the toxic effects of 0.78 mg Al/l on the growth of maize roots. However there is currently no commercially available product which is specifically designed and used to ameliorate soil metal toxicity.

The use of anionic polymers (such as poly carboxylic acid compounds) in agriculture has a long history. In the 1950’s polymers such as poly vinyl acetate maleic acid (PVAMA) were used as soil conditioners (Martin W.P 1953). More recently poly maleic acid (PMA) is used as a soil wetting agent for irrigated agriculture. Anionic polymers made up of vinyl and dicarboxylic moieties for use with fertilisers (for example as a fertilizer coating) are commercially available under the trade name AVAIL by Specialty Fertilizer Products, LLC. These products are designed to enhance plant growth by enhancing the uptake of phosphate from high-analysis NP fertilizers such as diammonium phosphate (DAP).

Although expensive, these products have been shown to increase yields and increase fertilizer efficiency on less acid soils.

There remains a need for an improved product and/or method which will reduce or ameliorate soil metal toxicity (particularly on acid soils) efficiently and cost-effectively.

In this specification unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

Throughout this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

OBJECT OF INVENTION It is therefore an object of the present invention to provide an improved agricultural additive and/or agricultural composition and/or method which will at least go some way towards overcoming one or more of the above mentioned problems, or at least provide the public with a useful choice.

STATEMENTS OF THE INVENTION In a first aspect, the invention may broadly be said to consist in an agricultural additive for use with or in place of an agricultural liming material, wherein said additive comprises one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers, and wherein use or application of said additive has the effect of reducing or eliminating the quantity of liming material required in order to achieve substantially the same or greater soil detoxification benefits as would be achieved from application of liming material alone.

Preferably, the invention relates to an agricultural additive when used for reducing the phyto-toxicity of one or more metal cations present in soil, wherein said additive comprises one or more polymers selected from the group consisting of synthetic poly- carboxylic acids and salts thereof, having the following general formula: where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups.

Preferred poly-carboxylic acids for use in the invention include poly maleic acid (PMA), co-poly acrylic maleic acid (PAMA), co-poly vinyl alcohol maleic acid (PVaMA), hydrolised co-poly vinyl acetate maleic acid (HPVAMA), poly fumaric acid (PFA), co- poly fumaric maleic acid (PFMA), poly itaconic acid (PIA), co-poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, co-poly vinyl alcohol fumaric acid (PVaFA), co- poly vinyl actetate fumaric acid (PVAF), hydrolyzed PVAF (HPVAF), co-poly vinyl alcohol itaconic acid (PVaIA), co-poly vinyl actetate itaconic acid (PVAIA), hydrolyzed PVAIA (HPVAIA), combinations of poly and co-poly vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof.

Preferred silicate polymers for use in the invention include potassium silicates, sodium silicates and mixtures thereof.

Preferably the ratio of SiO :M O is between 2:1 and 3.75:1 where M is sodium or potassium.

Combinations of poly-carboxylic acids and silicate polymers are also useable in the invention.

Preferably said agricultural additive is a liquid composition comprising said polymer(s) in liquid dispersion.

Alternatively the agricultural additive is a solid composition, for example in powdered or granular form, wherein the liquid dispersion has been dried or applied to a solid carrier.

Preferably said agricultural additive comprises from about 1 – 80% w/w of said polymer(s). More preferably said agricultural additive comprises from about 40 – 50% w/w of said polymer(s).

The agricultural additive may further comprise other components such as micro-nutrients, plant growth hormones, herbicides, and/or ammonium.

If the additive is used with an agricultural liming material, the preferred agricultural liming material is limestone. Preferably the limestone is fluidized limestone.

Alternatively, the limestone may be in finely ground form, or granulated.

Preferably the additive is mixed with or coated on to the agricultural liming material prior to application.

Alternatively the additive may be applied separately, before, during, or after the liming material is applied.

Preferably the additive is applied in an amount in the range of about 1 to 10% by weight, based on the weight of the liming material.

For example the application rate of the additive may be between about 0.1 to 25 litres of undiluted additive per hectare, which may be applied with between about 1 – 250 kg of liming material per hectare.

If the additive is used alone (without liming material) the benefits may be seen with applications in the range of about 0.1 to 25 litres of undiluted additive per hectare.

The additive may be diluted with water prior to use. In terms of spreading practicalities, a minimum of about 20 litres per hectare of total liquid is desirable.

In terms of spreading practicalities the additive may be mixed with or coated on to another agricultural product such as a fertilizer or a pesticide to enable spreading of more than one agricultural product at a time to reduce spreading costs for the user.

Application of the agricultural additive of the invention has the effect of either reducing the quantity of liming material required, or eliminating the need to apply liming material, in order to reduce or ameliorate soil metal toxicity. Thus the agricultural additive of the invention can be used as a lime replacement in some circumstances, for example, particularly where the response to lime is low due to high plant tolerance to metals, and/or in the subcritical soil pH 5.0 to 5.6, and/or when seasonal water logging may occur forming reducing conditions solubilising Fe and Mn.

The agricultural additive works by complexing toxic soil metals such as aluminium, manganese and iron, thereby reducing the phyto-toxicity of the metal ion without the requirement to raise the soil pH, thus reducing the quantity of liming material needed to achieve detoxification of the soil and its inhibition of plant root vigor, as well as other desired soil characteristics such as nutrient availability, adequate calcium nutrition, improved soil biological activity etc.

In a further aspect, the invention may broadly be said to consist in an agricultural composition comprising an agricultural liming material and an agricultural additive, said additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

Preferably the agricultural additive comprises one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups.

Preferably the particles of the agricultural liming material are in intimate contact with the particles of the agricultural additive.

Preferably the agricultural additive comprises one or more polymers selected from the group comprising poly maleic acid (PMA), co-poly acrylic maleic acid (PAMA), co-poly vinyl alcohol maleic acid (PVaMA), hydrolised co-poly vinyl acetate maleic acid (HPVAMA), poly fumaric acid (PFA), co-poly fumaric maleic acid (PFMA), poly itaconic acid (PIA), co-poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, co-poly vinyl alcohol fumaric acid (PVaFA), co-poly vinyl actetate fumaric acid (PVAF), hydrolyzed PVAF (HPVAF), co-poly vinyl alcohol itaconic acid (PVaIA), co-poly vinyl actetate itaconic acid (PVAIA), hydrolyzed PVAIA (HPVAIA), combinations of poly and co-poly vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid, potassium silicates, sodium silicates, and combinations thereof.

Preferably the agricultural liming material is limestone.

Preferably the limestone is fluidized limestone.

Alternatively, the limestone may be in finely ground form, or granulated.

Preferably the liming material and additive are co-ground, or mixed together, or the additive is surface coated on to the liming material. The agricultural composition is preferably in fluidised form, liquid suspension form, fine particle form, or granulated form.

Most preferably the agricultural composition is applied in fluidized form or liquid suspension form. Water may be added to a solid composition during application (spreading) of the composition in order to achieve a liquid or fluidized form of the composition.

If the composition is pre-mixed in fluidized or suspension form, preferably the composition comprises from about 50 – 85% by weight of liming material, from about 10 – 50% by weight of water, and from about 1 – 10% by weight of additive.

For compositions in fine particle or granular form, preferably the composition comprises from about 90 – 99% by weight of liming material, and from about 1 – 10% by weight of additive.

If the agricultural composition is applied in fluidized form or liquid suspension form, preferred application rates are in the range of 20 to 500 litres per hectare If the agricultural composition is applied in solid form, such as fine particle or granular form, preferred application rates are in the range of 1 to 250 kg per hectare.

Trials have shown that the agricultural composition of the invention works synergistically to enhance plant growth. The combination of the agricultural additive and the agricultural liming material has a synergistic effect because plant growth is enhanced beyond that which would be achieved by use of the agricultural additive or agricultural liming material alone.

In a further aspect, the invention may broadly be said to consist in a method of reducing the quantity of liming material needed to be applied to soil and/or plants to reduce soil metal toxicity, or eliminating the need to apply liming material to soil and/or plants to reduce soil metal toxicity, said method comprising the step of applying to the soil and/or plants an effective amount of an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

If the method is to eliminate the use of liming material, an effective amount of the agricultural additive refers to the lime equivalence value, i.e. the amount required in order to achieve substantially the same or greater soil detoxification benefits as would be achieved by application of liming material alone.

The effective amount would generally be between about 0.1 to 25 litres of undiluted additive per hectare.

If the method is to reduce the quantity of liming material needed, preferably the agricultural additive is applied in conjunction with a reduced quantity of agricultural liming material. A reduced quantity refers to the balance of liming material required (in conjunction with the additive) to achieve the same or greater soil detoxification benefits as would be achieved with application of liming material alone (i.e. without addition of the additive).

If the additive is used with an agricultural liming material, preferably the additive is co- ground with, mixed with or coated on to the agricultural liming material prior to application. Alternatively the additive may be applied separately, before, during or after the liming material is applied.

Preferably the quantity of liming material applied is reduced by between about 10 – 90%.

In a further aspect, the invention may broadly be said to consist in a method for reducing the quantity of agricultural liming material required to be applied to an area, said method comprising the step of applying to the area an agricultural composition comprising an agricultural liming material and an agricultural additive, said additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

In a further aspect, the invention may broadly be said to consist in a method of reducing the phyto-toxicity of toxic metals in soil, said method comprising the step of applying to the soil and/or plants growing therein, an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

In a further aspect, the invention may broadly be said to consist in a soil treatment method including an application of an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers to the soil and/or plants growing therein, to reduce the phyto-toxicity of toxic metals present in the soil.

Preferably, the agricultural additive comprises one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: C C C where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups.

In a further aspect, the invention may broadly be said to consist in a method of improving plant growth by applying an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers to the plants and/or soil surrounding said plants, to thereby reduce the phyto- toxicity of toxic metals present in the soil which are suppressing plant growth.

In a further aspect, the invention may broadly be said to consist in a method of reducing and/or ameliorating soil metal toxicity in an area comprising the step of applying to the area an agricultural composition comprising an agricultural liming material and an agricultural additive, said additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

In each of the above methods, preferred poly-carboxylic acids for use in the invention include poly maleic acid (PMA), co-poly acrylic maleic acid (PAMA), co-poly vinyl alcohol maleic acid (PVaMA), hydrolised co-poly vinyl acetate maleic acid (HPVAMA), poly fumaric acid (PFA), co-poly fumaric maleic acid (PFMA), poly itaconic acid (PIA), co-poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, co-poly vinyl alcohol fumaric acid (PVaFA), co-poly vinyl actetate fumaric acid (PVAF), hydrolyzed PVAF (HPVAF), co-poly vinyl alcohol itaconic acid (PVaIA), co-poly vinyl actetate itaconic acid (PVAIA), hydrolyzed PVAIA (HPVAIA), combinations of poly and co-poly vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof.

The agricultural additive may be applied with or without an agricultural liming material.

Alternatively, the limestone may be in finely ground form, or granulated.

In a further aspect, the invention may broadly be said to consist in a method of farming comprising the steps of: determining the quantity of agricultural liming material required to achieve desired soil detoxification benefits on a selected area of a farm, and applying to said area 10 - 50% of said quantity of agricultural liming material in conjunction with an effective amount of an agricultural additive, said additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

Preferably the additive is pre-mixed or mixed with the agricultural liming material prior to or during application.

In a further aspect, the invention may broadly be said to consist in a method of farming comprising the steps of: determining the quantity of agricultural liming material required to achieve desired soil detoxification benefits on a selected area of a farm, and applying to said area an effective amount of an agricultural additive in place of the liming material, said additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and silicate polymers.

An effective amount is the lime equivalence value, i.e. the amount required in order to achieve substantially the same or greater soil detoxification benefits and consequent yield increases as would be achieved by application of the determined quantity of agricultural liming material.

The effective amount would generally be between about 0.1 to 25 litres per hectare of undiluted additive.

DETAILED DESCRIPTION Further aspects of the present invention will become apparent from the following description which is given by way of example only.

The invention broadly relates to agricultural additives, compositions and/or methods for reducing or eliminating the amount of lime required to reduce or ameliorate soil metal toxicity in order to enhance plant growth.

Soil metal toxicity in plants or a crop occurs when there is a reduction in yield from its maximum due to the presence of a metal in the soil. The toxic effect of the metal may be below the critical levels in which the crop becomes visually symptomatic, i.e. exhibiting symptoms such as leaf bronzing, brown spots and yellowing.

In its broadest sense the invention relates to an agricultural additive which can either be used with an agricultural liming material, to reduce the quantity of liming material required to treat the soil, or can be used as a replacement for the liming material (i.e. where no liming material is required as application of the additive alone is able to achieve substantially the same or greater soil detoxification benefits as the application of liming material would achieve).

Agricultural liming materials include any materials comprising limestone or calcium carbonate intended for application to soil, pasture or crops for the purposes of increasing soil pH, supplying calcium as a nutrient, correcting nutrient imbalances, enhancing soil biological activity etc.

The agricultural additive of the invention comprises one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, and silicate polymers.

The poly-carboxylic acids useable in the invention have the following general formula: C C C where R can be any combination of the following groups H, COOH, OH, CH COOH and OOCCH , and (a+b) ranges from about 2 – 1500. It is preferred that most of the R groups have terminal acid (COOH), or that at least three out of the four structural carbons of the polymer subunit depicted above have COOH or COO¯ functional groups.

They are generally soluble at low pH’s (pH 1 – 4) and they can be mixed with or complexed with metal ions such as Fe, Mn, Mg, Zn, Cu, Ni.

Preferred poly-carboxylic acids for use in the invention include (but are not limited to) poly maleic acid (PMA), co-poly acrylic maleic acid (PAMA), co-poly vinyl alcohol maleic acid (PVaMA), hydrolised co-poly vinyl acetate maleic acid(HPVAMA), poly fumaric acid (PFA), co-poly fumaric maleic acid (PFMA), poly itaconic acid (PIA), co- poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, co-poly vinyl alcohol fumaric acid (PVaFA), co-poly vinyl actetate fumaric acid (PVAF), hydrolyzed PVAF (HPVAF), co-poly vinyl alcohol itaconic acid (PVaIA), co-poly vinyl actetate itaconic acid (PVAIA), hydrolised PVAIA (HPVAIA), combinations of poly and co-poly vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid.

In general, these polymers can be made by free radical polymerisation methods which convert selected monomers into the desired polymers with recurring polymeric subunits.

Such methods are well known in the art. The polymers are generally recovered as liquid dispersions, which may be used in liquid form either as is, or diluted with water, or they may be added to liquids used to fluidize fertilisers or liming materials, or added to fluid suspensions of other agricultural products such as fertilizers, liming materials and sprays.

Alternatively the polymers may be dried to a solid form, or the liquid polymer dispersion may be applied to a solid carrier (for example by spray drying onto the carrier), and further processed by methods known in the art into a powdered form or granular form (for example the polymer solution may be added into binder solutions used in the granulation of liming materials or fertilisers, or the polymer solution may be coated onto granular or course crystalline materials).

The silicate polymers (also known as “water glass”) useable in the invention have the following general formula: M SiO where M is sodium and/or potassium and x can range from 0.5 to 2.

Preferably the ratio of SiO :M O is between 2:1 and 3.75:1 where M is sodium or potassium. More preferably the silicate polymer has a SiO :M O ratio of less than 3.22:1 and preferably about 2:1 to allow for stable mixing with neutralized PMA.

An example of a suitable sodium silicate is that available under the trade name SSD from Orica NZ and having a SiO :Na O ratio of 2:1.

An example of a suitable potassium silicate is that available under the trade name KASIL#6 from Orica NZ and having a SiO :K O ratio of 2.1:1.

The silicate polymers useable in the invention can be prepared by preparing a soluble silicate solution by heating sodium carbonate or potassium carbonate and silica sand to between 1100 and 1200 C to form glass. On cooling, the glass is heated with water under pressure to form a solution.

It is further contemplated that the agricultural additive of the invention may comprise a combination of one or more poly-carboxylic acids and one or more silicate polymers. For example, a combination of PMA and sodium silicate is described in Example 2 below.

In preferred embodiments of the invention, the agricultural additive is a liquid composition comprising the polymer(s) in liquid dispersion. However, the agricultural additive may be a solid composition, for example in powdered or granular form, formed by drying of the liquid dispersion or by application of the liquid dispersion to a solid carrier, as described above.

Preferably said agricultural additive comprises from about 1 – 80% w/w of said polymer(s). More preferably said agricultural additive comprises from about 40 – 50% w/w of said polymer(s). The remainder of the composition is generally water unless other components have been added to the composition.

The agricultural additive may further comprise other components such as micro-nutrients (including the major plant nutrients such as N, P, K, S, Mg, Ca, Si and minor nutrients such as Co, Se, Fe, Mo, B, Zn, Cu), and/or plant growth hormones (for example gibberellic acid, tricontanol), and/or selective herbicides (for example, 2-methyl chlorophenoxyacetic acid (MCPA), or 4-(4-chloromethylphenoxy)butanoic acid (MCPB)), and/or ammonium.

The agricultural additive of the invention can either be used with an agricultural liming material, having the effect of reducing but not entirely eliminating the amount of liming material required to achieve the desired soil detoxification benefits and yield increase, or the agricultural additive of the invention can be used as a replacement for liming material, thereby eliminating the need for liming material to achieve the desired soil detoxification benefits and yield increase.

The agricultural additive of the invention works by complexing toxic soil metals such as aluminium, manganese or iron thereby reducing the phyto-toxicity of the metal ion without the requirement to raise the soil pH, thus reducing or eliminating the quantity of liming material needed to achieve detoxification of the soil and its inhibition of plant root vigor, as well as other desired soil characteristics such as nutrient availability, adequate calcium nutrition, improved soil biological activity etc.

If the additive of the invention is applied with a liming material, preferably the agricultural liming material is limestone, and more preferably, fluidized limestone.

Alternatively, the limestone may be in finely ground form, or granulated.

If the additive is applied with a liming material the additive may be applied separately from the liming material before, during, or after the liming material is applied to the area to be treated. The additive would generally be applied in an amount in the range of about 1 to 10% by weight, based on the weight of the liming material. For example the application rate of the additive may be between about 0.1 to 25 litres of (undiluted) additive per hectare, which may be applied with between about 1 – 250 kg of liming material per hectare. If the additive is used alone (without liming material) the benefits may be seen with applications in the range of about 0.1 to 25 litres per hectare (of undiluted additive). The additive may be diluted with water prior to use. In terms of spreading practicalities, a minimum of about 20 litres per hectare of total liquid is desirable.

If the additive is to be applied with an agricultural liming material, the additive is preferably mixed with the liming material prior to application to form a composite pre- mixed agricultural composition comprising the liming material and the additive, wherein the particles of the liming material are in intimate contact with the particles of the additive. Several methods of combining the liming material and the additive can be used.

For example, the additive may be co-ground with the liming material, applied as a surface coating to the liming material, or otherwise thoroughly mixed with the liming material by methods known in the art.

The resulting agricultural composition can either be in fluidized form, liquid suspension form or solid form, such as fine particle or granular form. Water may be added to a solid composition during application (spreading) of the composition in order to achieve a liquid or fluidized form of the composition.

Alternatively, the additive can be applied with an agricultural liming material by applying the additive at the same time as the liming material (for example by mixing them during application from a suitable spreading vehicle). For example, a liquid dispersion of the additive with or without water could be mixed and applied with a solid form of the liming material during spreading so that a liquid or fluidized form of the composition is spread.

The agricultural additive or agricultural composition of the invention can be applied to soil, pasture, crops or other plants by any known means, such as from ground spreading vehicles, fixed-wing aircraft or helicopters.

For economic reasons, the agricultural additive or the agricultural composition could be applied at the same time as a fertilizer or other agricultural product (such as a pesticide) in order to reduce application costs for the farmer. For example the additive could be mixed with a liquid pesticide/spray or mixed with or coated on to a liquid or solid fertilizer before application. The form of the additive or composition (i.e. solid or liquid form) would be selected depending on the form of the fertilizer or other agricultural product to be applied and the compatibility of the respective products.

It has been found that use of the agricultural additive or agricultural composition of the invention significantly reduces or potentially eliminates the quantity of agricultural liming material required to achieve substantially the same or greater soil detoxification benefits and consequent yield increases as would be achieved with the application of liming material alone.

The quantity of liming material needed can be reduced by at least 10% and as much as 100% (where no lime is required as the additive is able to be used as a complete lime replacement). This represents a significant economic advantage, and makes the application of lime a more efficient and cost-effective option, as less lime is required to achieve the same or greater soil detoxification benefits and consequent yield increases.

For example, in the case where a farmer previously needed to apply lime at a rate of 5000 kg/ha in order to maintain soil pH, if lime is applied in conjunction with an agricultural additive of the invention, it is likely that less than 2500 kg/ha of lime would be required to achieve the same results, or possibly no lime would be required at all. Lime is more likely to be required in conjunction with the additive in situations where there are extreme levels of metal toxicity present in the soil and/or where a sensitive crop is grown.

EXAMPLE 1 An agricultural additive comprising the polymer, poly maleic acid (PMA) was prepared by mixing five kilograms of maleic anhydride with five litres of water in a stainless steel reactor with a mechanical stirrer. The mixture was heated to 95-100°C and 25 grams of iron sulphate catalyst was added. 1.8 litres of hydrogen peroxide 50% was slowly added while stirring over 3.5 – 4.5 hours. The mixture was then left to cool and finish polymerising (for approximately 12 hours). The mixture was then reheated and 1 – 3 kg of urea was added over 3 hours to hydrolyse and neutralise the acid polymer (the amount of urea depends on the degree of neutralisation required). The pH can be adjusted if required (preferably to a minimum of pH 3.5).

The polymer solution was neutralised by the addition of sodium hydroxide (caustic soda).

The resulting polymer is a liquid dispersion which can be used as is, or mixed with a solid or liquid agricultural liming material, or other agricultural material such as a fertiliser.

The application of non-neutralized PMA polymer solution was tested on a low pH Dannevirke silt loam (pH 4.2, with toxic Al levels in the range of 4.5 to 9.1 mg Al per litre of soil solution) in conjunction with DAP to determine the effect on radish growth.

The polymer solution was applied at 2 and 4 litres per hectare to the soil at sowing as a dilute solution (1:1000) in water. One granule of DAP per 5cm pot was then added.

The plants were harvested at 5 weeks and dry matter yields compared between treatments.

Results are shown in the graph in Figure 1.

The results show an increase in radish dry matter above that of DAP alone and the Zero DAP control.

This shows the growth enhancing effect of the agricultural additive in aluminium toxic soils, in this case without the addition of any liming material.

EXAMPLE 2 In this example, an agricultural additive of the invention was prepared by combining equal amounts of sodium neutralised PMA with liquid sodium silicate solution (available under the trade name SSD from Orica NZ and having a SiO :Na O ratio of 2:1) to produce a stable solution.

A field trial was carried out on poorly drained pasture, Tokomaru silt loam (pH 5.8) which is subject to frequent water logging and manganese/iron phyto-toxicity as evidenced by iron/manganese oxide accumulation on and around the grass roots (2.1 to 3.7 % Fe and 0.21 to 0.35 % Mn of washed root weight on a dry basis). The application of 4 litres per hectare of the agricultural additive produced an additional 94 kg (P = 0.18) of dry matter (DM) production over a 30 day period compared to the control. This result was most significant in one set (strip 6-5) of paired treatments producing an additional 241 kg DM per hectare (P = 0.08), while paired strips 4-3 and 2-1 were not by themselves significantly different due to the high spatial variability of the metal toxicity (root samples from paired strip 2-1 contained the lowest Fe and Mn at 0.65 and 0.19% respectively, while root samples from paired strips 4-3 contained 2.1% Fe and 0.21% Mn, and root samples from paired strip 6-5 contained 3.7% Fe and 0.35% Mn).

EXAMPLE 3 On an acid Dannevirke silt loam (pH 4.2) comparison of the surface application of finely ground limestone (Lime Flour), an agricultural additive of the invention comprising sodium silicate (SSD), an agricultural additive of the invention comprising sodium neutralised PMA (PMA Na) were assessed in ryegrass pot trials, with application rates of Lime Flour at 0, 50, 100, 200, 500, 1000 kg per hectare and application rates of each of the agricultural additives at 2 litres per hectare. Results are presented in the graph in Figure 2.

The results show that the application of PMA Na at a rate of 2 l/ha produced 25% more dry matter than the application of 1000 kg/ha of Lime Flour after six weeks, while the application of SSD at 2 l/ha produced equivalent results to application of 1000 kg/ha Lime Flour. These results show that the agricultural additive of the invention can be used as an alternative to the application of liming material for the amelioration of soil metal toxicity in acid soils.

EXAMPLE 4 Two agricultural additives were prepared as follows: Additive A – comprising a neutralized PMA containing 50% w/v solids in water.

Additive B – comprising a sodium neutralized PMA containing 50% w/v of sodium PMA in water.

Pot trials were conducted to determine plant growth (measured in herbage dry matter yield) after surface application of one of each of the above additive formulations, and finely ground limestone flour (LF) to annual ryegrass and white clover grown on acidified Dannevirke silt loam with pH 4.2. Pots where no additive or LF was added were used as the controls.

The additive formulations of the invention were applied at a rate of 21 l/ha, while the LF was applied at rates of 100, 500, 1000, 1470 (wheat only) and 2660 (wheat only) kg/ha.

Results are discussed below.

Table 1 – Ryegrass pot trials 4/08/2012 24/08/2012 15/09/2012 7/10/2012 Dry Dry Dry Dry Matter Matter Matter Matter (g) P value (g) P value (g) P value (g) P value Control 0.037 0.153 0.182 0.283 100 kg LF/ha 0.046 0.294 0.179 0.239 0.310 0.009 0.308 0.657 500 kg LF/ha 0.046 0.240 0.187 0.153 0.365 0.002 0.410 0.089 1000 kg LF/ha 0.041 0.557 0.195 0.128 0.312 0.009 0.389 0.130 Additive A 0.036 0.819 0.191 0.158 0.290 0.050 0.333 0.410 Additive B 0.045 0.301 0.187 0.160 0.313 0.008 0.414 0.082 Table 1 shows that the application of the additive formulations of the invention, and the lime flour (at all rates of application) produced significant increases in herbage dry matter yields compared to the control. This was observed following the second harvest when the pots were leached on a weekly basis to reduce excess salinity (up to 2mS) produced by the acidification with elemental S which suppressed plant growth.

Table 2 - Clover pot trials Herbage Roots Dry Matter Matter (g) P value (g) P value Control 0.021 0.106 100 kg LF/ha 0.358 0.017 0.412 0.016 500 kg LF/ha 0.633 0.003 0.729 0.000 1000 kg LF/ha 0.647 0.006 0.835 0.007 Additive A 0.268 0.022 0.305 0.041 Additive B 0.191 0.000 0.303 0.000 Table 2 shows that the application of the additive formulations of the invention, and the lime flour (at all rates of application) produced significant increases in herbage dry matter yields and root dry matter production compared to the control. However because clover is known to have a low tolerance to low soil pH’s and metal toxicity, a higher response to LF occurred which was not able to be fully matched by the additive formulations of the invention. These results indicate that application of the agricultural additive of the invention for increased clover yields will be optimised at the subcritical pH level 5.0 to .5 where the lime response is low but metal toxicity may be present but not diagnosed.

Calculation of Lime Equivalence Following the above trials, an equivalence value of the additive formulations of the invention to finely ground limestone (LF) was calculated based on the modelled LF response curves for each plant species in the pot trials. The lime equivalence value was obtained using a plant response model (see equation below) based on an exponential response decrease constant (c) in yield response with increasing LF additions, with response limited to between the yield without lime flour addition (Y ) and the maximum trial yield (Y ).

The herbage response to LF was then modelled using the above equation by plotting Ln(Ymax-Y) against LF to obtain response constant c. The equation was then rearranged to give LF as a function of dry matter yield and thus allow the conversion of the dry matter yield of the additive formulations (Y ) to be converted into equivalent LF additive application rates – see Tables 3 and 4 below.

Therefore, the lime equivalence value (kg LF per litre of additive) = (ln(Y -Y )- max additive ln(Y -Y ))/(c*additive rate(l/ha)). max o Table 3 – Lime Equivalence Values for Ryegrass Pot Trials /09/2012 7/10/2012 Kg LF/l Kg LF/l Additive A 411 296 Additive B 542 2116 This table shows that application of 1 litre of additive produced an equivalent growth response to application of between 296 – 2116 kg of lime flour. Both of the additive formulations of Example 4 thus have high lime equivalence values in respect of the growth enhancement of annual ryegrass in Dannevirke silt loam. This shows that application of an additive of the invention can reduce the amount of liming material required by 38 to 100%.

Table 4 – Lime Equivalence Values for Clover Pot Trials Herbage Roots Kg LF/l Kg LF/l Additive A 20 33 Additive B 33 34 This table shows that application of 1 litre of additive produced an equivalent growth response to application of between 20 – 34 kg of lime flour. These results were not as high as those of the annual ryegrass because of the known sensitivity of white clover to both aluminium and soil pH, but the results still show that use of an additive of the invention can reduce the amount of liming material required by 7 to 10% in these circumstances.

EXAMPLE 5 An agricultural composition of the invention in the form of a dry powder was prepared, comprising a mixture of an additive of the invention with lime flour. The additive comprised of 500 g/l of sodium PMA in water. The mixture was prepared by blending 2 ml of the additive into 50 g of lime flour and allowing it to air dry, thereby providing a dry formulation comprising 4% v/w of additive.

Pot trials were conducted to determine the growth response of ryegrass in an acid Dannevirke silt loam (pH 4.2) to application of the agricultural composition of the invention, in comparison to the growth response achieved by application of lime flour alone and additive alone.

The growth response lime equivalence values of both the mixed agricultural composition and the additive alone were calculated based on the growth response curve as calculated in the previous example.

The three separate treatments were applied at the following rates: the mixed agricultural composition was applied at a rate of 576 kg/ha; the additive alone was applied at a rate of 23 l/ha and the lime flour was applied at rates of 0, 576, 1153, 2605, and 3632 kg/ha. The control did not receive any treatment.

All treatments were applied to the surface of the soil in the pots with four ryegrass seedlings having been transplanted into the pots in March 2012 and clipped on a monthly basis. The pots contained 500 g of air dried Dannevirke silt loam (pH 4.2) which was maintained at about 80% of its water holding capacity throughout the trial period of two months. Results are shown in Table 5 below.

Table 5 Cumulative dry matter weights mean gram per LF application rates kg/ha 24/08/2012 7/10/2012 0 0.329 0.786 576 0.386 0.774 1153 0.359 0.767 2605 0.382 0.823 3632 0.366 0.841 Additive at 23 l/ha 0.387 0.838 Agricultural composition (additive + LF) 576 kg/ha 0.391 0.872 Table 5 shows that following the application of the treatments, little increase in ryegrass yield was observed until the second harvest, in which significant growth response was observed with treatment with the mixed agricultural composition, the additive alone, and lime flour at a rate of above 1153 kg/ha. The combined composition comprising the additive and lime flour shows an increase in dry matter production above that shown by treatment with the additive alone and lime flour alone. This indicates that the agricultural composition of the invention works synergistically or has a synergistic effect in terms of enhancing plant growth.

The lime response equivalence values based on a linear response to lime flour showed that application of the additive alone had a lime equivalence value of 145 kg LF/l, and that application of the agricultural composition had a lime equivalence value of 195 kg LF/l.

EXAMPLE 6 A solution culture study was carried out to investigate the effect that application of an agricultural additive of the invention has on the phyto-toxicity of Al, Mn and Fe in the soil of crops of annual ryegrass, wheat and paddy rice.

Methodology A glasshouse trial was conducted using paddy rice, wheat and annual ryegrass plants in solution culture media containing various levels of Al, Mn, Fe and an agricultural additive according to the invention. The solution culture media was a mixture of ‘Solution A’ (KNO3 – 530 mg/L, (NH4)2SO4 – 100 mg/L, MgSO4 – 370 mg/L, CaSO4 – 1290 mg/L, Na2SO4 – 480 mg/L, Na2SiO3 – 60 mg/L and NH4NO3 – 400 mg/L), ‘Solution B’ (KH2PO3 – 200 mg/L, H3PO3 – 270 mg/L, ZnSO4 – 220 mg/L, MnCl2 – 70 mg/L, CuSO4 – 40 mg/L, NaMoO – 4 mg/L and CoSO4 – 20 mg/L) and Iron solution (FeSO4.7H2O – 8340 mg/L) at the rate of 100A:1B:1Iron solution respectively per litre of purified water.

The paddy rice seedlings were initially raised in 5 ml vials containing nutrient solution for the first week prior to the application of the metal and/or additive treatments. Following the application of the treatments the paddy rice seedlings remained in the 5 ml vials with treatment solutions being changed every three days. By 14 days the rice plant growth required the plants to be transferred to 50ml containers with weekly solution changes.

The wheat seedlings were prepared in the same manner as the rice seedlings however they remained in the 5ml vials for the full period of the experiment to avoid full submersion of the wheat roots in the treatment solution and increased aeration.

The annual ryegrass seedlings were initially raised in solution for the first seven days and then transferred to perforated PVEA foam support sheets allowing five plants to be grown floating with an air gap between the treatment solution surface in a 250ml reservoir. The treatment solutions were changed on a weekly basis.

Total metal concentrations (mg/L solution) in the treatments were as follows: Al – 0, 0.1, 0.2, 0.4, 0.8 and 1.6; Mn – 0.5, 1, 10, 20 and 40; Fe – 1, 10, 20, 40, and 80.

Each metal treatment was again treated with an agricultural additive of the invention comprising of 50% w/v sodium PMA in water, at the rate of 0.0, 0.2, 2.0 and 20 ul/ml.

Therefore, for each metal concentration there were four levels of agricultural additive (one was the control without any additive). The treatments were replicated five times.

The containers were arranged in a Randomized Complete Block Design (RCBD) in a glasshouse. The glasshouse temperature was maintained at 11±5 C minimum (night) and 30±6 C maximum (day). After 42 days of plant growth the experiment was concluded, and plant shoots and roots from each container were progressively collected.

The pH and EC of each of the treatment solutions were measured periodically, with the following results: The pH values of the Al and Mn treatments for all three plants did not change significantly (4.5±0.3). However, the pH values of the treatments of rice plants with Fe reduced significantly from pH 4.42±0.08 to pH 2.1±0.04 in between solution changes, while the pH changes for the treatments of wheat and ryegrass with Fe were not significant (at 4.4±0.4 and 4.5±0.2 for wheat and annual ryegrass, respectively). The significant reduction in solution pH associated with the rice plants in the iron containing solutions > 1 mg/l during the experimental period is most likely due to oxygen exudations ++ +++ via the rice roots, which would have resulted in oxidation of the iron Fe to Fe , which would have precipitated in a hydroxide/oxide form, releasing H ions and lowering the solution pH.

Results The growth of the plants was measured after exposure for six weeks to the treatments. In summary, the results showed that the agricultural additive of the invention reduced the phyto-toxicity of: • Al in annual ryegrass and rice, increasing both herbage and root growth.

• Mn in annual ryegrass, wheat and paddy rice with increases in herbage and root growth.

• Fe in annual ryegrass and wheat with increases in herbage and root growth.

However no effect was seen in rice due to the rapid drop in pH, which occurred ++ +++ only in the paddy rice plant solutions as a result of oxidation of the Fe to Fe and its precipitation.

The reduction in metal toxicity due to the addition of the agricultural additive of the invention shows that the additive of the invention has the ability to reduce the quantity of liming material required to ameliorate metal phyto-toxicity, or to replace the use of lime or liming materials.

Detailed results are presented below.

Growth Response of Annual Ryegrass to Aluminium and Additive Table 6 – Annual ryegrass response to Aluminium and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgAl/l No additive 0.2 ul/l 2 ul/l 20 ul/l 0 33 55.4 168% 74.2 225% 83.4 253% 0.1 26.6 65.8 247% 69.8 262% 75 282% 0.2 24.8 69 278% 74.6 301% 68.4 276% 0.4 27.2 63.6 234% 69 254% 69.2 254% 0.8 36.8 77 209% 72 196% 67.8 184% 1.6 35.8 73.6 206% 80.4 225% 66.6 186% Roots Additive mgAl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l l 0 92 89.6 97% 104.2 113% 109.8 119% 0.1 60.2 68.2 113% 73 121% 79 131% 0.2 50.2 56 112% 65.6 131% 74.8 149% 0.4 46.8 55.6 119% 59.2 126% 67 143% 0.8 31.2 40.6 130% 50 160% 61.2 196% 1.6 20.2 21 104% 24.8 123% 53 262% Table 6 shows that the addition of an agricultural additive of the invention at levels from 0.2 ul/ml to 20 ul/ml to nutrient solutions containing Al over the range of 0 to 1.6 mg Al/l resulted in increases in both herbage (up to 301%) and root (up to 262%) dry matter in annual ryegrass grown in the treatment solutions. The toxic effect of Al was most strongly seen in the suppression of root growth in the annual ryegrass while herbage showed little growth suppression due to Al. The addition of the agricultural additive of the invention produced only a minor increase in root growth in the control with no Al, and significantly reduced the toxic effects of Al on root growth. In terms of the herbage production of the annul ryegrass, application of the agricultural additive produced high levels of growth above the nil-Al control which were not dramatically affected by Al concentrations up to 1.6 mg Al/l.

Growth Response of Wheat to Aluminium and Additive Table 7 – Wheat response to Aluminium and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgAl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 0 126.2 90.4 72% 127.2 101% 97.8 77% 0.1 65.8 69 105% 83.4 127% 85 129% 0.2 88.8 74 83% 76.2 86% 102.4 115% 0.4 71.6 70.4 98% 77 108% 73.2 102% 0.8 43.4 65.8 152% 66.4 153% 74.4 171% 1.6 46 43.4 94% 41.4 90% 31.6 69% Roots Additive mgAl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 0 57.8 58.2 101% 51.4 89% 54.2 94% 0.1 45.2 48 106% 44.2 98% 61.8 137% 0.2 45 44 98% 44.2 98% 48.6 108% 0.4 42.2 39.2 93% 39.4 93% 45.6 108% 0.8 40.4 40.4 100% 38 94% 42.4 105% 1.6 32.8 31.4 96% 40.8 124% 31.2 95% Table 7 shows that in the wheat plants, strong growth inhibition occurred in herbage and root growth as Al concentration increased. The addition of the agricultural additive showed inconsistent responses until the level reached 20 mg/l at which point small increases in both herbage and root growth were observed up to 1.6 mg Al/l.

Growth Response of Paddy Rice to Aluminium and Additive Table 8 – Paddy Rice response to Aluminium and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgAl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 0 52.4 55.8 106% 52.4 100% 57.6 110% 0.1 45.4 52.4 115% 43 95% 50.2 111% 0.2 48 45.2 94% 55 115% 53.2 111% 0.4 41.4 49.4 119% 53.4 129% 49.4 119% 0.8 44.8 49.6 111% 41.2 92% 52.8 118% 1.6 41.2 48.6 118% 42.8 104% 38.2 93% Roots Additive mgAl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 0 35.8 39.8 111% 36.2 101% 38 106% 0.1 37.4 42.2 113% 31.8 85% 41 110% 0.2 30.4 30.6 101% 34.8 114% 34.8 114% 0.4 27 30.6 113% 31.8 118% 34.6 128% 0.8 23.8 29.4 124% 24 101% 33.2 139% 1.6 19.6 22.4 114% 20.8 106% 27.6 141% The effect of Al on paddy rice was to suppress root growth with herbage growth being less affected. The addition of the agricultural additive showed increases in both herbage and root growth from 0.2 to 20 ul/l up to 1.6 mg Al/l.

Growth Response of Annual Ryegrass to Manganese and Additive Table 9 – Annual ryegrass response to manganese and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgMn/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 50.2 61.4 122% 62 124% 61.6 123% 52.8 56.85 108% 63.2 120% 63.6 120% 57.6 50 87% 69.6 121% 70 122% 18.8 21.4 114% 65.6 349% 70.4 374% 22.2 25.8 116% 30.6 138% 58 261% Roots Additive mgMnl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 57.2 77.6 136% 107.2 187% 112 196% 61.6 71.4 116% 107 174% 109 177% 52.2 49 94% 55.2 106% 60.2 115% .4 20 130% 51 331% 54.2 352% 16.2 15.2 94% 20 123% 28 173% Table 9 shows the effect of Manganese on the growth on annual ryegrass is the suppression of both herbage and root growth. The addition of the agricultural additive of the invention produced significant increases in annual ryegrass growth of both herbage and roots of 22 to 24% and 36 to 96%, respectively, at 0.5 mg Mn/l. The herbage growth response of annual ryegrass was dependent on the concentration of the additive with 0.2, 2.0 and 20 ul/l maintaining initial growth levels up to 1, 20 and 20 mg Mn/l respectively and up to 1 mg Mn/l in roots. At levels of Mn above these critical levels the additive reduced the adverse effects of Mn.

Growth Response of Wheat to Manganese and Additive Table 10 – Wheat response to manganese and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgMnl/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 93 99.8 107% 112.2 121% 107.4 115% 76.2 113.2 149% 117.2 154% 117.8 155% 64.8 79.8 123% 74.8 115% 72.2 111% 50.6 46 91% 58.6 116% 61.2 121% 71 81.8 115% 80.8 114% 82.6 116% Roots Additive mgMn/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 29.4 30.4 103% 32.2 110% 46 156% .4 29.8 84% 30.8 87% 36.2 102% 44.4 42.2 95% 56 126% 59 133% 33.2 38.2 115% 38.4 116% 39 117% 11.4 14.2 125% 19.8 174% 18.8 165% Table 10 shows that the effect of manganese on wheat plants is the suppression of both herbage and root growth. The addition of the agricultural additive above 2 ul/l showed consistent increases in herbage growth over the range of 0.5 to 40 mg Mn/l, while root growth required 20 ul/l of additive for consistent increases in growth.

Growth Response of Paddy Rice to Manganese and Additive Table 11 – Paddy Rice response to manganese and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgMn/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 57.4 55.4 97% 64.2 112% 58 101% 56.2 57.8 103% 61.6 110% 58 103% 57 50 88% 63.8 112% 59.4 104% 52.4 51.2 98% 60.2 115% 58.2 111% 55.2 60.6 110% 63 114% 62.2 113% Roots Additive mgMn/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 36.6 40.4 110% 45.8 125% 48.2 132% 36 43.8 122% 44 122% 47.6 132% 34.4 32.2 94% 38.6 112% 48.2 140% 31.4 33 105% 36.8 117% 42 134% 27.2 35.4 130% 37.6 138% 39.2 144% Table 11 shows the response of paddy rice to increasing levels of manganese was minor with only a minor reduction in growth of herbage and roots. Root growth being most affected. The effect of the agricultural additive was to increase both herbage and root growth over the range from 0.5 to 40 mg Mn/l for concentrations above 2.0 ul/l of additive.

Growth Response of Annual Ryegrass to Iron and Additive Table 12 – Annual ryegrass response to iron and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgFe/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 1 90.8 54 59% 53.2 59% 51.2 56% 37.6 49.4 131% 48.6 129% 73.4 195% 35.6 27.4 77% 40.2 113% 45.2 127% 40 34.2 33.2 97% 41 120% 39.8 116% 80 35.8 31.4 88% 45.8 128% 48.6 136% Roots Additive mgFe/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 1 49.8 74.2 149% 90.2 181% 92.4 186% 40.6 70.8 174% 75.8 187% 85.8 211% 41 50.2 122% 59.8 146% 74.6 182% 40 35 46.8 134% 58 166% 66.6 190% 80 31.6 45 142% 48.8 154% 50.4 159% Table 12 shows that the herbage and root growth of annual ryegrass was suppressed by Fe levels greater than 10 mgFe/l. The toxicity to herbage and root growth was reduced by the addition of 2 ul/l and 0.2 ul/l of agricultural additive, respectively. The addition of the additive showed an initial drop in annual ryegrass herbage growth of 56 to 59% of the control value at 1 mgFe/l, this drop in herbage was however compensated by increases in root growth of 142 to 159%.

Growth Response of Wheat to Iron and Additive Table 13 – Wheat response to iron and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgFe/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 1 92.8 95.8 103% 100.8 109% 103.8 112% 58.4 72.2 124% 78 134% 74.4 127% 47.8 42.4 89% 40.2 84% 53.6 112% 40 28.2 28.4 101% 33.8 120% 19.4 69% 80 24.2 27.4 113% 26.6 110% 26 107% Roots Additive mgFe/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 1 49.8 46.8 94% 46 92% 51.8 104% 36.2 43.6 120% 31.2 86% 40.6 112% 30.6 28.4 93% 31.8 104% 33.2 108% 40 26.2 26 99% 25.6 98% 29.6 113% 80 22.6 20.6 91% 23 102% 32.6 144% The growth of wheat was suppressed by levels of Fe++ greater than 1 mgFe/l. The toxic effect of iron was reduced by additions of the agricultural additive with increases in plant herbage and root growth up to 20 mgFe/l being observed at all concentrations of additive, but the most consistent effect being gained by the addition of 20 ul/l of additive. .

Growth Response of Paddy Rice to Iron and Additive Table 14 – Paddy Rice response to iron and Additive in terms of herbage and root dry weight and % of control without Additive Herbage Additive mgFe/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 1 70.6 66.6 94% 69.8 99% 74.4 105% 36.8 36.8 100% 36.6 99% 39.4 107% 41.2 39.2 95% 36.4 88% 41 100% 40 40.6 51.6 127% 41.8 103% 49 121% 80 36.4 36 99% 34.8 96% 39.6 109% Roots Additive mgFe/l No Additive 0.2 ul/l 2 ul/l 20 ul/l 1 52.6 50.4 96% 49.8 95% 50.2 95% 52 54 104% 53.8 103% 57.8 111% 46.6 45.4 97% 46.8 100% 50.4 108% 40 34.6 33 95% 33.8 98% 35.6 103% 80 32.8 28.4 87% 32 98% 29.4 90% Table 14 shows that paddy rice was badly affected by Fe levels above 1 mgFe/l, however application of the agricultural additive had little effect on the reduction of phyto- toxicity as the nutrient solutions with Fe showed rapid reductions also in pH decreasing to 2.1 within four days. Thus both Fe and pH played major parts in growth suppression which could not be remedied by addition of the additive.

ADVANTAGES Thus it can be seen that the invention provides an agricultural additive which can be used in conjunction with or in place of an agricultural liming material to reduce or eliminate the quantity of liming material required to achieve substantially the same or greater soil detoxification benefits and yield increases. The additive reduces metal (particularly aluminium, iron and manganese) toxicity in soils, and thereby reduces the phyto-toxicity of the metal ion without having to raise the soil pH, thus reducing or eliminating the quantity of liming material needed to achieve detoxification of the soil and its inhibition of plant root vigor, as well as other desired soil characteristics such as nutrient availability, adequate calcium nutrition, improved soil biological activity etc. This provides significant economic advantages as it reduces costs not only of the liming material itself, but also transport and application/spreading costs, making the application of liming materials a much more viable option for maintaining and preserving soil health, particularly in hill country where transport and application costs are very high. In some cases application of liming material can be avoided altogether, with only small amounts of the additive being required to achieve the same results, application of which is a lot less expensive, and can be done in conjunction with applications of other agricultural products such as fertilizers or pesticides to further reduce spreading costs. The additives, compositions and methods of the invention are particularly useful in soils with low pH (acid soils), wet or water logged soils, and in steep terrain.

VARIATIONS Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof. For example, while the examples involve use of the poly-carboxylic acid PMA, the scope of the invention clearly extends to the other poly- carboxylic acids as claimed as they possess similar chemical properties and characteristics. ___________________________________ PIPERS Attorneys for Advanced Agricultural Additives (NZ) Limited

Claims

1. An agricultural additive when used for reducing the phyto-toxicity of one or more metal cations present in soil, wherein said additive comprises one or more polymers selected from the group consisting of synthetic poly-carboxylic 5 acids and salts thereof, having the following general formula: C C C where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups. 10

2. An agricultural additive as claimed in claim 1, wherein said additive reduces or replaces the use of agricultural liming material to achieve said reduction in phyto-toxicity of the metal cations in the soil.

3. An agricultural additive as claimed in claim 1 or 2, wherein the poly- carboxylic acid(s) is/are selected from the group comprising poly maleic acid 15 (PMA), co-poly acrylic maleic acid (PAMA), poly fumaric acid (PFA), co- poly fumaric maleic acid (PFMA), co-poly itaconic maleic acid (PIMA), co- poly itaconic fumaric acid, combinations of poly and co-poly acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof.

4. An agricultural additive as claimed in any one of the previous claims, wherein 20 the metal cation(s) is/are selected from the group comprising iron, aluminium and manganese.

5. An agricultural additive as claimed in any one of the previous claims wherein said additive comprises from about 1 – 80% w/w of said polymer(s) in liquid dispersion.

6. An agricultural additive as claimed in claim 5 wherein said agricultural additive comprises from about 40 – 50% w/w of said polymer(s) in liquid dispersion.

7. An agricultural additive as claimed in claim 5 or 6, wherein the liquid 5 dispersion has been dried or applied to a solid carrier to form a solid composition.

8. An agricultural additive as claimed in claim 2, wherein said additive reduces the use of liming material to about 1 – 50% of the amount that would normally be required to reduce the phyto-toxicity of the metal cations in the soil. 10

9. An agricultural additive as claimed in any one of the previous claims, wherein said additive is mixed with an agricultural liming material prior to or during use.

10. An agricultural additive as claimed in claim 9, wherein the mixture is in fluidised form or liquid suspension form, and comprises from about 50 – 85% 15 by weight of liming material, from about 10 – 50% by weight of water, and from about 1 – 10% by weight of additive.

11. An agricultural additive as claimed in claim 9, wherein the mixture is in fine particle form, or granulated form, and comprises from about 90 – 99% by weight of liming material, and from about 1 – 10% by weight of additive. 20

12. Use of one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups, for reducing the phyto-toxicity of one or more metal cations present in soil.

13. Use of one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: 5 where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups, for reducing or replacing the use of agricultural liming material to reduce the phyto-toxicity 10 of one or more metal cations present in soil.

14. Use as claimed in claim 12 or 13, wherein the poly-carboxylic acid(s) is/are selected from the group comprising poly maleic acid (PMA), co-poly acrylic maleic acid (PAMA), poly fumaric acid (PFA), co-poly fumaric maleic acid (PFMA), co-poly itaconic maleic acid (PIMA), co-poly itaconic fumaric acid, 15 combinations of poly and co-poly acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof.

15. Use as claimed in claim 12 or 13, wherein the metal cation(s) is/are selected from the group comprising iron, aluminium and manganese.

16. Use as claimed in claim 13, wherein use of the agricultural liming material is 20 reduced to about 1 – 50% of the amount that would have been used to treat the phyto-toxicity of the metal cations in the soil.

17. Use as claimed in any one of claims 12 – 16, wherein said polymer(s) is/are mixed with an agricultural liming material prior to or during use.

18. Use as claimed in claim 17, wherein the mixture is in fluidised form or liquid 25 suspension form, and comprises from about 50 – 85% by weight of liming material, from about 10 – 50% by weight of water, and from about 1 – 10% by weight of polymer(s).

19. Use as claimed in claim 17, wherein the mixture is in fine particle form, or granulated form, and comprises from about 90 – 99% by weight of liming 5 material, and from about 1 – 10% by weight of polymer(s).

20. Use of one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) 10 ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups, as a lime reducing or lime replacing agent in an agricultural composition.

21. An agricultural composition comprising a mixture of an agricultural additive and an agricultural liming material; wherein said additive comprises one or 15 more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons 20 of the polymer subunit have COOH or COO¯ functional groups.

22. An agricultural composition as claimed in claim 21, wherein the poly- carboxylic acid(s) is/are selected from the group comprising poly maleic acid (PMA), co-poly acrylic maleic acid (PAMA), poly fumaric acid (PFA), co- poly fumaric maleic acid (PFMA), co-poly itaconic maleic acid (PIMA), co- poly itaconic fumaric acid, combinations of poly and co-poly acrylic acid, maleic acid, fumaric acid, itaconic acid, and combinations thereof.

23. An agricultural composition as claimed in claims 21 or 22, wherein the 5 agricultural liming material is limestone.

24. An agricultural composition as claimed in any one of claims 21 to 23, wherein the composition is in fluidised form or liquid suspension form and comprises from about 50 – 85% by weight of liming material, from about 10 – 50% by weight of water, and from about 1 – 10% by weight of additive. 10

25. An agricultural composition as claimed in any one of claims 21 to 23, wherein the composition is in fine particle form or granulated form and comprises from about 90 – 99% by weight of liming material and from about 1 – 10% by weight of additive.

26. A method of reducing the phyto-toxicity of one or more metal cations present 15 in soil, said method comprising applying to the soil and/or plants growing therein, an agricultural additive as claimed in any one of claims 1 – 11.

27. The method as claimed in claim 26, wherein the agricultural additive is applied in an amount in the range of about 0.1 to 25 litres of undiluted additive per hectare. 20

28. The method as claimed in claim 26, wherein the agricultural additive is applied in conjunction with an agricultural liming material.

29. The method as claimed in claim 28, wherein the additive is applied in an amount in the range of about 1 to 10% by weight, based on the weight of the liming material. 25

30. A method of reducing or replacing the use of an agricultural liming material for treating phyto-toxicity of one or more metal cations present in soil, said method comprising applying to the soil and/or plants growing therein, an agricultural additive as claimed in any one of claims 1 – 11.

31. The method as claimed in claim 30, wherein the agricultural additive is applied in an amount in the range of about 0.1 to 25 litres of undiluted additive per hectare.

32. The method as claimed in claim 30 for reducing the use of an agricultural 5 liming material, wherein the agricultural additive is applied in conjunction with about 1 – 50% of the amount of agricultural liming material that would normally be required to reduce the phyto-toxicity of the metal cations in the soil.

33. The method as claimed in claim 30, wherein the additive is applied in an 10 amount in the range of about 1 to 10% by weight, based on the weight of the liming material.

34. A soil treatment method comprising an application of an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general 15 formula: C C C where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups, to the soil 20 and/or the plants growing therein, to reduce phyto-toxicity of one or more metal cations present in the soil.

35. A method of enhancing plant and/or root growth comprising an application of an agricultural additive comprising one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having 25 the following general formula: C C C where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups, to the soil 5 and/or the plants growing therein, to thereby reduce phyto-toxicity of one or more metal cations present in the soil.

36. Use of one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: where R can be any combination of 10 the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons of the polymer subunit have COOH or COO¯ functional groups, in the manufacture of an agricultural composition to be used for reducing the phyto- toxicity of one or more metal cations present in soil. 15

37. Use of one or more polymers selected from the group consisting of synthetic poly-carboxylic acids and salts thereof, having the following general formula: where R can be any combination of the following groups H, COOH, OH, CH2COOH and OOCCH3, and (a+b) ranges from about 2 – 1500, and wherein at least three of the structural carbons 20 of the polymer subunit have COOH or COO¯ functional groups, in the manufacture of an agricultural composition to be used for reducing or replacing the use of liming material to treat phyto-toxicity of one or more metal cations present in soil.

38. An agricultural additive as claimed in claim 1, substantially as herein described with reference to the examples and/or any appropriate selection or 5 combination of the accompanying drawings.

39. Use as claimed in any one of claims 12, 13, 20, 36 or 37, substantially as herein described with reference to the examples and/or any appropriate selection or combination of the accompanying drawings.

40. An agricultural composition as claimed in claim 21, substantially as herein 10 described with reference to the examples and/or any appropriate selection or combination of the accompanying drawings.

41. A method as claimed in any one of claims 26, 30, 34 or 35, substantially as herein described with reference to the examples and/or any appropriate selection or combination of the accompanying drawings.