The present invention relates to novel compositions having fertilising and anti-fungal effects, to processes for their preparation, and to methods of fertilising plants and controlling fungi using them.

Phosphorus is one of the essential major elements required by plants and it is usually supplied to plants in the form of phosphate and/or polyphosphate. Phosphates are the salts of phosphoric acid (having the formula H₃PO₄ and molecular weight of 98). In recent years, it has been shown that plants can obtain phosphorus from phosphonates (sometimes also referred to as phosphites) which are the salts (organic or inorganic) of phosphonic acid (also referred to as phosphorous acid) (having the formula H₃PO₃ and molecular weight of 82). See, for example, US Patent Nos. 5,514,200 & 5,830,255 to Lovatt; US Patent Nos. 5,707,418 & 5,865,870 to Hsu; US Patent No. 5,800,837 to Taylor; US Patent No. 5,047,078 to Gill. These describe formulations containing phosphorous acid or phosphonates suitable as fertilisers for plants. US Patent No. 5,865,870 shows that phosphorous acid and polyphosphonic acid can act synergistically to improve plant growth. US Patent No. 5,514,200 describes a buffer system comprising organic acids to stabilise phosphorous against oxidation to phosphate for use in phosphorous fertilisers. US Patent No. 5,047,078 describes the addition of scale inhibiting compounds to phosphate fertiliser to increase plant growth. DD 266755 describes the use of mono-, di- and triethanolamine for increasing water assimilation of cultivated plants and the addition of additional substances, including 2-chloroethanephosphonic acid and salicylic acid is also disclosed. It has also been shown that phosphonate compounds are useful as fungicides, especially where the fungal organisms are phycomycetes or oomycetes. See, for example, US Patent Nos. 4,075,324 & 4,119,724 to Thizy; US Patent No. 4,139,616 to Lacroix et al; US Patent Nos. 4,698,334, 4,806,445 & 5,169,646 to Horriere et al; US Patent Nos 4,935,410 & 5,070,083 to Bartlet; US Patent No. 5,736,164 to Taylor. These describe formulations, containing phosphorous acid or phosphonates, suitable as fungicides for plants. US Patent No. 5,795,847 refers to the use of phosphite as an electrolyte in a herbicidal composition.

Ammonium thiosulphate and potassium thiosulphate, either alone or mixed with other liquid fertiliser components, have been used for many years as fertilisers. See literature on "Thio-sul"® and KTS® sulphur fertilisers produced by Tessenderlo Kerley. See also UK Patent No. GB 2,259,912 to Sampson, which describes the use of ammonium thiosulphate in a plant growth stimulator.

WPI Abstract Accession No. 91-249421 discloses a cut flower preserving agent comprising a water-soluble silver salt (100 pts. wt.) and thiosulphate (300-2500 pts. wt.) to which a phosphite (30-300 pts. wt.) is added as a stabilising agent.

Some of the problems with the prior art are that the fertilising effect of phosphonate is less than might be expected from the amount of phosphorus applied, and the fungicidal effect is fairly limited in terms of the types of pathogen controlled. This is due to a complex mode of action involving a combination of some fungistatic action and natural plant defences coming into play (See Guest D I & Grant B R (1991) - The Complex action of phosphonates in plants - Biological Reviews 66, 159-187). The use of phosphonate, whilst improving the resistance of plants to infections of downy mildew (eg Plasmopora) and Phytophthora diseases, does tend to increase the risk of ascomycete (eg Erysiphe) infections. The present invention seeks to provide a solution to these problems.

According to one aspect of the present invention there is provided a fertiliser composition comprising at least one phosphonate and at least one thiosulphate.

In one embodiment, the fertiliser composition further comprises at least one salicylic acid, homologue, derivative, or salt thereof.

The present invention comprises using a mixture of a phosphonate together with a thiosulphate, and optionally at least one salicylic acid, homologue, derivative, or salt thereof. The use of this combination shows a synergistic effect, in that the combination of phosphonate with thiosulphate and optionally salicylic acid, homologues, salts or derivatives thereof produces a greater fertiliser effect and fungicidal effect than the individual components used separately. There may be an even greater effect if all three components (ie phosphonate, thiosulphate and salicylic acid, homologue, salt or derivative thereof) were used together. The combination of thiosulphate with a salicylic acid, homologue, salt or derivative thereof, in the absence of phosphonate, also produces a fertiliser effect and fungicidal effect.

Fertilisers based on the present invention provide a greater growth effective response than phosphonates or thiosulphates alone and the degree of fungicidal protection or resistance is broader than that achieved with phosphonates or thiosulphates alone. Plants treated with the present invention suffer less from phycomycete diseases (for example phytophthoras and downy mildews) than those treated with for example phosphonate alone and are also less prone to other parasitic fungi such as powdery mildews. Thus the present invention provides a means for applying a single product to plants which is an effective fungicide as well as an effective fertiliser.

Another advantage of the present invention is that the formulation is very storage stable, for example tests on mixtures of potassium phosphonate and ammonium thiosulphate stored for over one year have shown that there is no oxidation of the phosphonate to phosphate and the stored material shows no signs of cloudiness or precipitation. The use of further organic acids as buffers (as is required in US Patent Nos. 5,514,200 & 5,830,255) is also not required to achieve stable solutions.

By "phosphonate" we mean a salt of phosphonic acid (H₃PO₃). Phosphonates contain the trivalent ≡PO₃ radical. For the avoidance of doubt, phosphonic acid is sometimes referred to as phosphorous acid and its salts as phosphites. Mixtures of phosphonates may be employed.

The phosphonate may be any metal ion or other cation which forms such a salt. As phosphonic acid has a P-H bond it forms a mono and di series of salts. Both mono and di salts and mixtures thereof may be used in the present invention. Preferably the phosphonate is an ammonium phosphonate or alkali phosphonate. Amongst the alkali phosphonates, sodium or potassium phosphonate are preferred. Potassium phosphonate is particularly preferred, in the form of mono- and/or di-potassium phosphonate (KH₃PO₃, K₂HPO₃ respectively).

Phosphonates may be produced by the neutralisation of phosphonic acid by an alkali. The present invention also encompasses the use of phosphonic acid which is subsequently converted to its phosphonate; this conversion may take place in situ or ex situ. When using, for example, potassium hydroxide for the neutralisation, depending on the molar ratio of potassium hydroxide to phosphorous acid, the phosphonate solution will contain vaned amounts of di-potassium phosphonate, mono-potassium phosphonate and un-reacted phosphorous acid. We have found that an approximately 42% w/w solution, having a pH of between 6.7 and 7.3 and containing approximately equal amounts of mono- and di-potassium phosphonate is a clear, colourless and very stable starting material for our present invention.

The thiosulphate may be any suitable salt of a metal or other cation. Preferably the thiosulphate is ammonium, sodium or potassium thiosulphate or a mixture thereof. More preferably the thiosulphate is in the form of either ammonium or potassium thiosulphate ((NH₄)₂S₂O₃ or K₂S₂O₃).

The most common form of thiosulphate is ammonium thiosulphate, and this is readily available commercially as a 60% w/w solution, with a pH of about 7.5 and a specific gravity of about 1.32. If a higher proportion of potassium is required in the final foliar fertiliser, the ammonium thiosulphate can be substituted, either partly or wholly, with potassium thiosulphate.

The present invention includes functional homologues and derivatives of salicylic acid and its salts. By this we mean that the functional homologue or derivative should be capable of providing a fertiliser effect and/or antifungal effect. Examples of such derivatives of salicylic acid include salicylamide or a salt thereof, and esters.

Examples of homologues of salicylic acid include benzoic acid or a salt or derivative thereof, such as an ester. Examples of benzoic acid compounds which may be used in the present invention may be found in WO99/25191.

The salicylic acid is preferably in the form of its potassium salicylate salt or salicylamide - C₇H₅KO₃ or C₇H₇NO₂.

Salicylic acid itself has low solubility, but inorganic salts of salicylic acid, such as sodium or potassium salicylate are readily soluble. When salicylamide is used, rather than salicylic acid or a salicylate, the addition of a few drops of alkali assists in its solution, by forming for example sodium or potassium salicylamide. Salicylamide also dissolves more readily in the thiosulphate solution, the presence of small amounts of alkali or ammonia in the thiosulphate solution assisting in the solubilisation.

The preparation of the compounds used in the present invention is well known in the art. The compounds may be prepared in situ or ex situ.

In one embodiment, the composition of the present invention does not include a water-soluble silver salt. In another embodiment, if the composition contains a solution of 100 parts by weight water-soluble silver salt, and 300-2500 parts by weight thiosulphate, then the amount of phosphonate is other than 30 to 300 parts by weight

The compositions of the present invention are useful as fertiliser, particularly foliar fertilisers. More particularly the compositions of the present invention increase plant growth compared to the individual components alone, stimulate growth in plants, plant vigour and/or effect crop yield, for example by reducing tuber blight.

The compositions of the present invention also have an antifungal effect. This may be a fungicidal or fungistatic effect. The compositions of the present invention may have activity against parasitic fungi. The compositions may have activity against phycomycete diseases such as phytophthoras and downy mildews, for example, Plasmopora; and/or ascomycetes such as, for example,Erysiphe.

In one particularly preferred embodiment the composition further comprises a plant growth regulator. Preferably the plant growth regulator is chlormequat.

In order to apply the composition to the plant or environs of the plant, the composition may be used as a concentrate or more usually is formulated into a composition which includes an effective amount of the composition of the present invention together with a suitable inert diluent, carrier material and/or surface active agent. Preferably the composition is in the form of an aqueous solution which may be prepared from the concentrate. By effective amount we mean that the composition (and/or its individual components) provides a fertilising and/or antifungal effect. Preferably an effective amount of the components is a concentration of up to about 4M phosphonate, up to about 5M thiosulphate and/or up to about 0.8M salicylate. Thus, in one embodiment the concentrate may comprise up to about 10M of the components. The concentrate formulation may for example be diluted at ratios of concentrate to water of about 1:40 to 1:600, and generally is formulated to have pH of about 6.5 to 8.5. At a 1:40 dilution, a concentrate of about 10M would give rise to an application concentrate of up to about 0.25M.

The rate and timing of application will depend on a number of factors known to those skilled in the art, such as the type of species etc.

The composition is generally applied in an amount of from 0.01 to 10kg per heactare, preferably 0.1 to 6kg per hectare. Preferably the phosphonate is applied at 150 g/ha to 2 kg/ha. Preferably the thiosulphate is applied at 250 g/ha to 6 kg/ha. Preferably the salicylic acid, a homologue, derivative, or salt thereof is applied at 1 g/ha to 100 g/ha.

In one preferred embodiment, a fertiliser composition according to the present invention comprises about 150 g/l phosphonate, about 275 g/l thiosulphate and/or about 10 g/l salicylamide. Preferably the phosphonate comprises about 75 g/l mono-potassium phosphonate and about 75 g/l di-potassium phosphonate.

As well as varying amounts of each compound to be blended together, as is common with many foliar fertilisers, it is also possible to combine other fertilising elements, such as but not limited to, iron, copper, boron and molybdenum (often known as micronutrients) in the final solution. These may be added as soluble inorganic compounds (eg sodium borate or sodium molybdate) or as chelates (eg copper EDTA) or other metal complexes.

The compositions of the present invention can be applied to the soil, plant, seed, or other area to be protected. Preferably the present invention is applied to the foliage of plants. The composition may be applied in the form of dusting powders, wettable powders, granules (slow or fast release), emulsion or suspension concentrates, liquid solutions, emulsions, seed dressings, or controlled release formulations such as microencapsulated granules or suspensions, soil drench, irrigation component, or preferably a foliar spray.

Dusting powders are formulated by mixing the active ingredient with one or more finely divided solid carriers and/or diluents, for example natural clays, kaolin, pyrophyllite, bentonite, alumina, montmorillonite, kieselguhr, chalk, diatomaceous earths, calcium phospates, calcium and magnesium carbonates, sulfur, lime, flours, talc and other organic and inorganic solid carriers.

Granules are formed either by absorbing the active ingredient in a porous granular material for example pumice, attapulgite clays, fuller's earth, kieselguhr, diatomaceous earths, ground corn cobs, and the like, or on to hard core materials such as sands, silicates, mineral carbonates, sulfates, phosphates, or the like. Agents which are commonly used to aid in impregnation, binding or coating the solid carriers include aliphatic and aromatic petroleum solvents, alcohols, polyvinyl acetates, polyvinyl alcohols, ethers, ketones, esters, dextrins, sugars and vegetable oils, with the active ingredient. Other additives may also be included, such as emulsifying agents, wetting agents or dispersing agents.

Microencapsulated formulations (microcapsule suspensions CS) or other controlled release formulations may also be used, particularly for slow release over a penod of time, and for seed treatment.

Alternatively the compositions may be in the form of liquid preparations to be used as dips, irrigation additives or sprays, which are generally aqueous dispersions or emulsions of the active ingredient in the presence of one or more known wetting agents, dispersing agents or emulsifying agents (surface active agents). The compositions which are to be used in the form of aqueous dispersions or emulsions are generally supplied in the form of an emulsifiable concentrate (EC) or a suspension concentrate (SC) containing a high proportion of the active ingredient or ingredients. An EC is an homogeneous liquid composition, usually containing the active ingredient dissolved in a substantially non-volatile organic solvent. An SC is a fine particle size dispersion of solid active ingredient in water. To apply the concentrates they are diluted in water and are usually applied by means of a spray to the area to be treated.

Suitable liquid solvents for ECs include methyl ketone, methyl isobutyl ketone, cyclohexanone, xylenes, toluene, chlorobenzene, paraffins, kerosene, white oil, alcohols (for example, butanol), methylnaphthalene, tnmethylbenzene, trichloroethylene, N-methyl-2-pyrrolidone and tetrahydrofurfuryl alcohol (THFA).

These concentrates are often required to withstand storage for prolonged periods and after such storage, to be capable of dilution with water to form aqueous preparations which remain homogeneous for a sufficient time to enable them to be applied by conventional spray equipment. The concentrates may contain 1-85% by weight of the active ingredient or ingredients. When diluted to form aqueous preparations such preparations may contain varying amounts of the active ingredient depending upon the purpose for which they are to be used.

The composition may also be formulated as powders (dry seed treatment DS or water dispersible powder WS) or liquids (flowable concentrate FS, liquid seed treatment LS), or microcapsule suspensions CS for use in seed treatments. The formulations can be applied to the seed by standard techniques and through conventional seed treaters. In use the compositions are applied to the plants, to the locus of the plants, by any of the known means of applying fertiliser compositions, for example, by dusting, spraying, or incorporation of granules.

When the final solution is to be applied to plants which, because of their hairy or waxy surface, may be difficult to wet, it may also be advantageous to include other additives, commonly known in the agrochemical industry, such as surfactants, wetting agents, spreaders and stickers. (Examples of wetting agents include silicone surfactants, nonionic surfactants such as alkyl ethoxylates, anionic surfactants such as phosphate ester salts and amphoteric or cationic surfactants such as fatty acid amido alkyl betaines).

As indicated above, the compounds of the invention may be the sole active ingredient of the composition or they may be admixed with one or more additional active ingredients such as nematicides, insecticides, synergists, herbicides, additional fungicides, additional fertilisers or plant growth regulators where appropriate.

As indicated above, the fertilisers produced according to this present invention are usually applied to the foliage of plants but may also be applied to the soil or added to the irrigation water. The fertilisers may be used advantageously on many types of agricultural and horticultural crops, including but not limited to, cereals, legumes, brassicas, cucurbits, root vegetables, sugar beet, grapes, citrus & other fruit trees and soft fruits. More particularly, crops that will benefit from the fertiliser include, but are not limited to, peas, oil seed rape, carrots, spring barley, avocado, citrus, mango, coffee, deciduous tree crops, grapes, strawberries and other berry crops, soybean, broad beans and other commercial beans, corn, tomato, cucurbitis and other cucumis species, lettuce, potato, sugar beets, peppers, sugar cane, hops, tobacco, pineapple, coconut palm and other commercial and ornamental palms, rubber and other ornamental plants.

Various further preferred features and embodiments of the invention will now be described by reference to the following non-limited Examples.

An aqueous solution containing a total of 30% by weight of mono and di-potassium phosphonate in roughly equal proportions.

An aqueous solution containing 55% by weight of ammonium thiosulphate ("ATS").

An aqueous solution containing 20 grams per litre of potassium salicylamide.

An aqueous solution containing 75 g/L mono potassium phosphonate, 75 g/L di-potassium phosphonate, 275 g/L ammonium thiosulphate and 10 g/L potassium salicylamide.

These solutions were applied to lettuce plants, both alone and in combination, and the applications were repeated after a 10 day interval. There were five replicates of each treatment and the results are presented as means of the five replicates. Five plants were also left unsprayed as an untreated control to the other treatments. After eight, twelve, sixteen and twenty-one days, the plants were examined for disease. Powdery Mildew Score (0 - 9, where higher number equals greater degree of disease) Treatment (Applied initially and repeated 10 days later) Days after first spray 8 days 12 days 16 days Untreated 4.0 6.6 7.2 Solution 1 (1L/ha) 0.8 2.2 3.6 Solution 2 (1L/ha 1.0 1.2 2.4 Solution 3 (1L/ha) 1.6 3.2 4.2 Solution 1 (1L/ha) + Solution 2 (1L/ha) 0.0 0.4 1.0 Solution 1 (1L/ha) + Solution 3 (1L/ha) 0.4 0.6 1.0 Solution 1 (1L/ha) + Solution 2 (1L/ha) + Solution 3 (1L/ha) 0.8 0.6 0.6 Table 1 shows the synergistic effect on disease levels achieved by adding Solutions 1 & 2 (phosphonate + ATS) and between Solutions 1 & 3 (phosphonate + salicylamide) and the further effect of using all three solutions together. Disease levels were reduced from a mean of 7.2 to a mean of 0.6

As well as assessing disease levels, the growth of the plants was assessed by measuring the mean plant diameters after 35 days growth and by measuring the mean above ground fresh and dry weights. Plant Growth after treatment with the example solutions Treatment (Applied initially and repeated 10 days later) Amount of Rooting (0-9, 0= least rooting) - mean Plant Diameter (mm) -mean Above-Ground Fresh Weight (g) - mean Above-Ground Dry Weight (g) - mean Untreated 5.3 124 102.3 8.3 Solution 1 (1L/ha) 6.0 148 116.3 9.3 Solution 2 (1L/ha 5.3 160 109.0 8.7 Solution 3 (1L/ha) 4.7 150 104.7 8.5 Solution 1 (1L/ha) + Solution 2 (1L/ha) 6.7 144 119.0 9.5 Solution 1 (1L/ha) + Solution 3 (1L/ha) 6.7 170 120.7 9.7 Solution 1 (1L/ha) + Solution 2 (1L/ha) + Solution 3 (1L/ha) 6.7 168 131.7 10.6 Table 2 shows the synergistic effect on plant growth caused by adding Solutions 1 & 2 (phosphonate + ATS), Solutions 1 & 3 (phosphonate + salicylamide) and the further effect of using all three solutions together.

The abbreviations used in the following Examples A-E are:

• A = phosphonate + thiosulphate
• B = phosphonate + salicylate/salicylamide
• C = thiosulphate + salicylate/salicylamide
• D = thiosulphate + salicylate/salicylamide + phosphite
• E = thiosulphate + salicylate + chlormequat

• KP40 = 40% potassium phosphonate
• KT47 = 47% potassium thiosulphate (w/v)
• KS20 = 20% potassium salicylate (w/v)
• CS8 = salicylamide (20g/l)
• AT60 = 60% ammonium thiosulphate
• PF723 = 55% ammonium thiosulphate

• Solution 1 = KP40 at 0.75 l/ha every 10 days
• Solution 2 = PF723 at 1.0 l/ha every 10 days

• Solution 1 = KP40 at 0.75 l/ha
• Solution 3 = CS8 at 1.0 l/ha

Benefits of Ammonium Thiosulphate (ATS) and Potassium Salicylate (KS) with Chlormequat (CCC) on Spring Barley Treatment (Treatments applied at 3 leaves stage) Powdery Mildew (%) at + 15 days Amount of Rooting (0-9) Mean of 10 plants Above Ground Fresh Weight (g) Total of 10 plants Above Ground Dry Weight (g) Total of 10 plants Untreated 25 5.8 30.5 3.4 CCC (1.25 l/ha) 15 5.5 34.0 3.7 CCC (1.25 l/ha) + ATS (1.25 l/ha) 13 6.0 31.5 3.6 CCC (1.25 l/ha) + KS (20 g/ha) 18 6.0 31.3 3.5 CCC (1.25 l/ha) + ATS (1.25 l/ha) + KS (20 g/ha) 8 6.5 36.0 4.0 Benefits of Ammonium Thiosulphate (ATS) and Potassium Salicylate (KS) with Chlormequat (CCC) on Spring Barley Treatment (Treatments applied at 3 leaves stage (T1) and prior to start of stem extension (T2)) Powdery Mildew (%) at + 12 days Powdery Mildew (%) at + 15 days Powdery Mildew (%) at + 18 days Number of Tillers initiated per Plant (mean of 10 plants) Untreated 20 25 38 3.0 CCC (0.8 l/ha at T1 & T2) 8 8 10 3.5 CCC (0.8 l/ha at T1 & T2) + ATS (0.8 l/ha at T1 & T2) 5 5 8 3.5 CCC (0.8 l/ha at T1 & T2) + KS (20 g/ha at T1 & T2) 8 8 13 3.3 CCC (0.8 l/ha at T1 & T2) + ATS (0.8 l/ha at T1 & T2) + KS (20 g/ha at T1 & T2) 0 3 5 4.3