SOIL TREATMENT WITH METAM SALTS AND ONE OR MORE OF CALCIUM THIOSULFATE, CALCIUM CHLORIDE AND CALCIUM NITRATE

Abstract

A stable concentrated solution of a metam salt and one or more of calcium thiosulfate, calcium chloride and calcium nitrate, can be used to treat for soil pathogens, including the pathogen responsible for potato early die. It is believed that the high concentrations of the compounds, that is, the high concentration of calcium thiosulfate, calcium chloride and/or calcium nitrate admixed with a metam, results in lower rates of degradation that result from calcareous soil, increased soil adsorption or retention, and improved distribution of metam or methyl isothiocyanate (MITC) in the soil.

Claims

1. A stable concentrated liquid solution, said stable concentrated liquid solution comprising: a. between about 4% and about 30% total by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate; b. at least about 2% by weight of a soil fungicide, insecticide or fumigant; and c. water.

2. The stable concentrated liquid solution of claim 1, wherein said stable concentrated liquid solution comprises between about 4% and about 30% total by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate, and between about 4% and about 54% by weight of a soil fumigant, said fumigant comprising a dithiocarbamate.

3. The stable concentrated liquid solution of claim 2, wherein the dithiocarbamate comprises N-methyldithiocarbamate, and wherein the weight ratio of the fumigant to the calcium thiosulfate, calcium chloride and/or calcium nitrate is between about 10:1 to about 1:10.

4. The stable concentrated liquid solution of claim 1, wherein the soil fungicide, insecticide or fumigant comprises a salt of dithiocarbamate.

5. The stable concentrated liquid solution of claim 4, wherein the dithiocarbamate comprises an alkali salt of N-methyldithiocarbamate, and wherein the weight ratio of the salt of the methyldithiocarbamate to the calcium thiosulfate, calcium chloride and/or calcium nitrate is between about 10:1 to about 1:10.

6. The stable concentrated liquid solution of claim 1, wherein the fumigant comprises a salt of metam, and wherein the concentration of the salt of metam and the concentration of the calcium thiosulfate, calcium chloride and/or calcium nitrate in the concentrated solution are each greater than about 5% by weight.

7. A method of treating soil pathogens, preferably in arable soil, said method comprising the step of treating a soil with the stable concentrated solution of claim 1.

8. The method of claim 7, wherein at least a portion of the concentrated liquid solution is placed at a depth about 4 inches subsurface or below.

9. A stable concentrated liquid solution, said stable concentrated liquid solution comprising: a. between 4% and about 50% total by weight of calcium thiosulfate, calcium chloride, and/or calcium nitrate; b. between 4% and about 56% by weight of a fumigant, said fumigant comprising a salt of methydithiocarbamate or other MITC generator; and c. water.

10. A method of treating disease in arable soil prior to crop planting, comprising: applying to the surface or subsurface of the arable soil a stable aqueous solution comprising an MITC-generating fumigant and one or more of calcium thiosulfate, calcium chloride and/or calcium nitrate prior to planting, wherein the amount of calcium thiosulfate, calcium chloride and/or calcium nitrate added is at least about 137 kg/ha.

11. The method of claim 10 wherein at least a portion of the aqueous solution is applied below the soil surface.

12. The stable concentrated liquid solution of claim 4 wherein the salt of dithiocarbamate is selected from the group consisting of alkali salts of dithiocarbamate, a sodium salt of N-methyldithiocarbamate, a potassium salt of N-methyldithiocarbamate and mixtures thereof.

13. The stable concentrated liquid solution of claim 1 wherein said stable concentrated liquid solution comprises between about 4% and about 30% total by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate, and between about 4% and about 54% by weight of a soil fumigant, said fumigant comprising a N-methyldithiocarbamate or a salt of dithiocarbamate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0034] In one embodiment the invention is a stable concentrated solution of a dithiocarbamate fumigant and an inorganic compound, said inorganic compound comprising, consisting essentially of, or alternatively consisting of at least one of calcium thiosulfate, calcium chloride, calcium nitrate, or any mixtures thereof By stable is meant that there is no phase separation under standard conditions and that the ingredients mix well. Stability over time and shelf life are further documented herein. Said fumigant preferably is a dithiocarbamate fumigant, preferably a metam salt. The concentrated solution used in the invention in general comprises at least about 2% by weight calcium thiosulfate, calcium chloride, calcium nitrate, or any mixture thereof, and at least about 0.5% by weight of fumigant, which may be an alkali salt of a fumigant, more preferably greater than about 5% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate and greater than about 2% by weight of the fumigant, for example wherein each of the dithiocarbamate fumigant and the (total of) calcium thiosulfate, calcium chloride and/or calcium nitrate is present in the concentrated solution in an amount 3% by weight or greater, 4% by weight or greater, 6% by weight or greater, or 10% by weight or greater. In one embodiment, the solution can additionally comprise calcium polysulfide in an amount up to about 60% of the weight of the calcium thiosulfate, calcium chloride, calcium nitrate or any mixture thereof. In one embodiment the solution is free of or is substantially free of calcium polysulfide, for example containing calcium polysulfide in an amount less than about 20% of the weight of the calcium thiosulfate, calcium chloride, calcium nitrate or any mixture thereof The dithiocarbamate is preferably a salt of methyldithiocarbamate, for example an alkali salt. Examples thereof are metam sodium (sodium N-methyldithiocarbamate), metam potassium (potassium N-methyldithiocarbamate) and/or metam ammonium (ammonium N-methyldithiocarbamate). In particular metam sodium and/or metam potassium are preferred. In concentrated solutions, as described herein, metam is not reactive to calcium thiosulfate, calcium chloride and/or calcium nitrate, such that less than 5% of the dithiocarbamate, and less than 5% of the calcium thiosulfate, calcium chloride, calcium nitrate or any mixture thereof is lost to reaction or precipitation during normal storage, that is, over about 8 months' time period at warehouse conditions, preferably in a closed container. Further, the combination of fumigant and calcium thiosulfate, calcium chloride and/or calcium nitrate aids both penetration of the fumigant into soil and suppresses adverse reactions between certain soil types and the fumigants. The invention also relates to treating soil pathogens (fungi, bacteria, and nematodes) with the concentrated solution, advantageously comprising or consisting essentially of a fumigant and an inorganic compound being calcium thiosulfate, calcium chloride and/or calcium nitrate, and said dithiocarbamate preferably comprising or consisting essentially of an alkali salt of methyldithiocarbamate. It is believed that the high concentration of said inorganic compounds, results in lower rates of degradation, increased soil adsorption or retention, and improved distribution of metam or methyl isothiocyanate (MITC) in the soil. In one embodiment of the invention the soil pathogen is a fungus. In another embodiment of the invention the soil pathogens are bacteria. In yet another embodiment of the invention the soil pathogen treated is a nematode. In yet another embodiment of the invention the soil pathogen is an insect. The method of the invention is in particular useful for the treatment of fungi.

[0035] The invention is believed to be useful with a number of other fumigants and soil insecticides/pesticides, including those fumigants disclosed in WO 1997000857, allyl isothiocyanate, Oxamyl [Methyl NN-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate], penthiopyrad, fluopyram N-[2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl]-2-(trifluoromethyl)benzamide with or without imidacloprid, methyl bromide (when used with the soluble calcium chlorides and/or nitrates), ethanedinitrile, fluensulfone: 5-chloro-2 (3,4,4-trifluoro-but-3-ene-1-sulfonyl)-thiazole, dimethyl disulfide, and calcium phosphide. These can be used together with the concentrate of the invention (e.g. be provided as a separate solution) and/or they can be added to the concentrate of the invention. The invention may further be useful with 1,3-dichloropropene and chloropicrin if the fumigant is stabilized. Advantageously, and preferably, the soil has not been treated, at least within the past month or preferably within the last two months, with a sterilant such as sodium azide.

[0036] The invention also relates to treating soil for soil pathogens, including fungi, bacteria, and nematodes, for example the lists of diseases that can be found on the label for metam, said soil to be used to grow vegetables, especially root, tuber and bulb vegetables, but also including leafy vegetables, cucurbits, and fruiting vegetables, and small fruit such as strawberries, or tomatoes, that are susceptible to Verticillium wilt and other listed diseases, including for example Pythium on carrots. Other examples of susceptible crops include cabbage, celery, cucumber, eggplant, lettuce, melons, pepper, potato, pumpkin, radish, rhubarb, peanut, and tomato. Treating is accomplished by applying to the subsurface of the soil the concentrated solutions described above and herein, and/or by applying a slightly diluted solution of this invention. By slightly diluted we mean for example diluting the concentrate by a factor of for example 10:1 with water, or for example diluting but keeping calcium thiosulfate, calcium chloride and/or calcium nitrate concentrations above about 1%. The treatment is most beneficial when the concentration of the calcium thiosulfate, calcium chloride and/or calcium nitrate solution contacting pests is high, for example greater than 1%, more typically greater than 2%, for example greater than 3%, 4% or 5% by weight. These values include dilution by moisture in soil. Said treatment is especially beneficial for treating soil used for growing root and bulb vegetables and especially potatoes, as well as tomatoes, berries and small fruit as well as fruiting vegetables, wherein the treatment is applied before the vegetables or fruits are planted, or simultaneous with planting if seeds are not subject to phytotoxic effect from the treatment of the fumigant calcium thiosulfate, calcium chloride and/or calcium nitrate. Preferred treatment time is pre-planting, before crops or seeds are put into the soil.

[0037] In another embodiment of the invention, a stable concentrated pre-mix solution as described in the paragraphs above is used to treat arable soil, wherein the solution is added to irrigation water or in a holding vessel with water at low dosage, that is, less than about 1% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate in the treatment water. The alkalinity in the metam, typically present as alkali hydroxides, will typically buffer the irrigation water solution and prevent precipitation (blooming) provided the carbonate concentration in the water is low. Advantageously and preferably, the solution thus prepared is free from added alkali sulfides, which are an immediate health concern.

[0038] As used herein, when an application rate of metam sodium is expressed as gallons per acre, it is understood that a gallon contains 4.25 pounds of sodium methyldithiocarbamate per gallon, and one gal./acre sodium metam solution such as Sectagon-42 is equivalent to 4.76 kg/ha of metam sodium. As used herein, when an application rate of potassium metam is expressed as gallons per acre, it is understood that a gallon contains 5.63 pounds of potassium methyldithiocarbamate per gallon, and one gal./acre potassium metam solution such as Sectagon-54 is equivalent to 6.3 kg/ha of potassium methyldithiocarbamate. Various fumigants are used at different rates and have different molecular weights, but it is well within the skill of the practitioner to adjust weights of the fumigant to account for these issues.

[0039] In preferred embodiments of the invention, the calcium thiosulfate, calcium chloride and/or calcium nitrate and the salt of metam are applied as a single mixed solution, to ensure that the benefits of the mixture are achieved. Applying as two separate mixtures runs a risk of having insufficient mixing and distribution, resulting in volumes of soil that are deficient is one ingredient or the other, which would suppress several advantages of the invention. Advantageously the calcium thiosulfate, calcium chloride and/or calcium nitrate is preferably primarily calcium thiosulfate, for example wherein the amount by weight of calcium thiosulfate is greater than or equal to the total amount of any calcium chloride and/or calcium nitrate present. In a particular embodiment of the invention, the inorganic calcium-containing compounds used comprise at least one calcium thiosulfate. In another particular embodiment of the invention, the inorganic calcium-containing compound is selected from thiosulfates.

[0040] Another aspect of the invention is a stable concentrated pre-mix solution of calcium thiosulfate, calcium chloride and/or calcium nitrate, optionally but preferably additionally comprising minor amounts of liquid lime sulfur (aqueous calcium polysulfide, CAS No 1344-81-6), and a polysulfide-stable fumigant or fumigants, including for example methyl isothiocyanate (MITC) generating fumigants, preferably a metam, wherein said solution is shelf stable and can be applied to the subsurface of soil using existing equipment used in the art. By shelf stable we mean the solution is stable over a season, that is, less than about 5%, preferably less than about 3%, more preferably less than about 0.5% by weight of the fumigant and each of the calcium thiosulfate, calcium chloride and/or calcium nitrate present is lost when stored at ambient conditions in a closed container over an 8 month period of time. Advantageously the weight ratio of the salt of metam to the inorganic calcium compounds range from 20:1 to 1:20, for example between 10:1 and 1:10, or 4:1 and 1:4, or between 2:1 and 1:2, or between 3:1 and 1:3, or other ranges using the above range endpoints, such as for example 2:1 to 1:10. Preferred weight ratios are about 1 part calcium thiosulfate to between about 0.3 to 5 parts fumigant. Advantageously the polysulfides, if present, are primarily calcium polysulfides. Advantageously the methyl isothiocyanate (MITC) generating fumigants comprises, consists essentially, or alternatively consists of metam sodium, potassium metam, or a mixture thereof.The solution can optionally contain added stabilizers, antifreeze agents, wetting agents, and penetrating agents.

[0041] The invention relates to a stable concentrated solution of a dithiocarbamate fumigant, preferably comprising or consisting essentially of an MITC generator, and calcium thiosulfate, calcium chloride and/or calcium nitrate, wherein the concentrated solution comprises at least 2% by weight calcium thiosulfate, calcium chloride and/or calcium nitrate and at least 0.5% of an alkali salt or salts of a dithiocarbamate fumigant, more preferably greater than 5% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate and greater than 2% by weight of the dithiocarbamate, for example wherein each of the dithiocarbamate fumigant and calcium thiosulfate, calcium chloride and/or calcium nitrate is present in the concentrated solution in an amount 4% by weight or greater. The preferred concentration of the solution of calcium thiosulfate, calcium chloride and/or calcium nitrate and salts of metam (sodium or potassium), called collectively active ingredients here, are at least 2 pounds of active ingredients per gallon (240 g/L), more preferably at least 2.5 pounds of active ingredients per gallon (300 g/L), more preferably at least 2.75 pounds of active ingredients per gallon (330 g/L). A practical maximum is about 5 pounds of active ingredients per gallon (less than 600 g/L).

[0042] The dithiocarbamate is preferably an alkaline salt of methyldithiocarbamate. Alkaline earth or ammonium methyldithiocarbamate, for example calcium salt, can also be used, though it is not preferred. Advantageously in one embodiment the treating solution comprises or consists essentially of at least 2% by weight calcium thiosulfate, calcium chloride and/or calcium nitrate, and at least 0.5% of a salt of a dithiocarbamate fumigant. More preferably the treating solution comprises greater than 5% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate or any mixture thereof and greater than 2% by weight of the fumigant. In one aspect the fumigant is a salt of metam, and the concentration of the salt of metam and the concentration of the calcium thiosulfate, calcium chloride and/or calcium nitrate, in the concentrated solution are each greater than about 5% by weight, for example greater than 8% by weight, or alternatively greater than 12% by weight. The concentrated solution is used to treat arable soil to inhibit soil pathogens. It is believed that the high concentrations of the compounds, that is, the high concentration of lime sulfur admixed with a metam, results in lower rates of degradation, increased soil penetration and retention, and improved distribution of metam or methyl isothiocyanate (MITC) in the soil.

[0043] Another aspect of the invention is a stable concentrated pre-mix solution of calcium thiosulfate, calcium chloride and/or calcium nitrate, and a metam, wherein said solution is shelf stable and can be applied to the subsurface of soil using existing equipment used in the art. Advantageously the concentration of the salt of metam and the concentration of at least one of calcium thiosulfate, calcium chloride and/or calcium nitrate, or any mixture thereof, are each greater than 3% by weight or greater than 5% by weight, for example greater than 8% by weight, and in most preferred cases greater than 12% by weight. Advantageously the weight ratio of the salt of metam to the calcium thiosulfate, calcium chloride and/or calcium nitrate range from 20:1 to 1:20, for example between 10:1 and 1:10, or 4:1 and 1:4, or between 2:1 and 1:2, or other ranges using the above range endpoints, such as for example 2:1 to 1:10. The amount of calcium thiosulfate, calcium chloride and/or calcium nitrate in a concentrated solution of fumigant can vary, with less calcium thiosulfate, calcium chloride and/or calcium nitrate needed when treating soils not containing large amounts of alkaline deposits and clays. A useful concentration can be as little as 4% by weight calcium thiosulfate, calcium chloride and/or calcium nitrate in a solution of 30% or more of a salt of metam can improve the performance of the metam.

[0044] The invention also relates to stable concentrated solutions of calcium thiosulfate, calcium chloride and/or calcium nitrate and MITC-generating fumigants. The invention also relates to treating soil for soil pathogens, including fungi, bacteria, and nematodes, by applying to the subsurface of the soil the concentrated or diluted premixed formulations of this invention.

[0045] In another embodiment of the invention, a stable concentrated pre-mix solution as described in the paragraphs above is used to treat arable soil, wherein the solution is added to irrigation water or in a holding vessel with water at low dosage, that is, less than about 2% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate in the treatment water. The alkalinity in the metam, typically present as alkali hydroxides, will buffer the irrigation water solution and prevent precipitation. Advantageously the solution is free from added alkali sulfides, which are an immediate health concern.

[0046] Advantageously the concentration of the (total of) calcium thiosulfate, calcium chloride and/or calcium nitrate is greater than 2% by weight, alternatively greater than 5% by weight, for example greater than 8% by weight, and in most preferred cases greater than 12% by weight. Said stable calcium thiosulfate, calcium chloride and/or calcium nitrate is added to the subsurface of the soil, and applying includes mechanically disturbing the soil so as to assist movement of the calcium thiosulfate, calcium chloride and/or calcium nitrate solution through the soil, where the treatment rate is at least 100 pounds per acre (121 Kg/ha), preferably at least 127 Kg/ha, more advantageously at least 150 pounds per acre (181 Kg/ha), for example between 200 pounds per acre (242 Kg/ha) and 400 pounds (484 Kg/ha) or to 600 pounds (726 Kg/ha) or 800 pounds per acre (987 Kg/ha). Alternatively the treatment rates are for the calcium thiosulfate, calcium chloride and/or calcium nitrate per acre a rate of at least 138 pounds per acre, more preferably at least 153 pounds per acre, for example at least 184 pounds per acre, or at least 246 pounds per acre, for example at least 307 pounds per acre.

[0047] A exemplary formulation is a stable concentrated solution that comprises water, about 10% by weight or greater of a salt of metam, about 10% by weight or greater of calcium thiosulfate, calcium chloride, calcium nitrate, or any mixture of two or more of the above, optionally up to about 10% by weight calcium polysulfide, and optionally between 0.01 and 5% auxiliaries such as pH buffers, surfactants, antioxidants, antimicrobials, antifreeze, and other common adjuvants, with the balance being water.

[0048] An example is a stable concentrated liquid solution, said stable concentrated liquid solution comprising between 2% and about 30% of calcium thiosulfate, calcium chloride and/or calcium nitrate; between 2% and about 54% of a soil fumigant, said fumigant comprising a salt of a dithiocarbamate; and water. Concentrated solutions are preferred, so another example comprises between 4% and about 30% of calcium thiosulfate, calcium chloride and/or calcium nitrate; between 4% and about 54% of a soil fumigant, said fumigant comprising a salt of a dithiocarbamate; and water. Percentages are herein percentages by weight, relative to the total weight of the composition. Generally, when we state dithiocarbamate we include alkyl-substituted versions thereof including N-methyldithiocarbamate, which is the preferred fumigant. The stable concentrated liquid solution contains both the fumigant and the calcium thiosulfate, calcium chloride and/or calcium nitrate. For the exemplary solution where the dithiocarbamate is methyldithiocarbamate, and the inorganic calcium compound is calcium thiosulfate, the weight ratio of the salt of the methyldithiocarbamate to the calcium thiosulfate is generally between about 10:1 to about 1:10, for example between 1:9 to 9:1, or alternatively between about 5:1 to 1:5. The commercial blends may have a weight ratio of inorganic thiosulfate (preferably comprising or consisting essentially of calcium thiosulfate) to fumigant (preferably an MITC-generating fumigant) of between 4:1 to about 1:15.

[0049] All weights are percent by weight of the solution unless otherwise stated. Calcium salts means soluble calcium salts, that is, calcium nitrate or calcium chloride. Weight percent of salts of metam includes the alkali metal counter ion.

[0050] A stable concentrated liquid solution can be formulated, said stable concentrated liquid solution comprising between 4% and about 30% of calcium thiosulfate, calcium chloride and/or calcium nitrate, between 4% and about 56% of a soil fumigant, said fumigant comprising a salt of a metam. Percentages are herein percentages by weight, relative to the total weight of the composition. In certain conditions, the preferred concentrated solution contains between 10% and 50% by weight, for example between 15% and 40% by weight, of the total of the dithiocarbamate salts and calcium thiosulfate, calcium chloride and/or calcium nitrate. The solution is preferably free of alkali sulfides. The weight ratio of calcium thiosulfate, calcium chloride and/or calcium nitrate to alkali metam is between about 15:1 to about 1:15, or between about 10 to 1 to about 1:10, for example between about 4:1 to 1:4, or between 2:1 to 1:2, or any ratio using the above listed boundaries in any combination.

[0051] The invention also relates to treating soil pathogens with the concentrated solution, advantageously comprising or consisting essentially of a dithiocarbamate fumigant and calcium thiosulfate, calcium chloride and/or calcium nitrate, and a fumigant that is stable in a concentrated solution of the calcium thiosulfate, calcium chloride and/or calcium nitrate, preferably the fumigant comprising a dithiocarbamate, more preferably comprising or consisting essentially of an alkali salt of methyldithiocarbamate. Advantageously, the treatment is applied below the surface of the soil, particularly at a depth of about 2 inches or more below the surface of the soil, for example below 4 inches below the surface of the soil. Often treatment is applied at more than one depth, for example at 4 inches depth and at 8 inches depth. Advantageously in one embodiment the treating solution comprises or consists essentially of at least 2% by weight calcium thiosulfate, calcium chloride and/or calcium nitrate, and at least 0.5% of a salt of a dithiocarbamate fumigant. In another embodiment the treating solution comprises greater than 5% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate and greater than 2% by weight of the dithiocarbamate. In one aspect the fumigant is a salt of metam, and the concentration of the salt of metam and the concentration of the calcium thiosulfate, calcium chloride and/or calcium nitrate, in the concentrated solution are each greater than about 5% by weight, for example greater than 8% by weight, or alternatively greater than 12% by weight. It is believed that the high concentrations of the compounds, that is, the high concentration of calcium thiosulfate, calcium chloride and/or calcium nitrate admixed with a dithiocarbamate fumigant, preferably calcium thiosulfate, calcium chloride and/or calcium nitrate admixed with a metam, results in more uniform effectiveness of metam, possibly due to lower rates of degradation by adverse soil conditions, increased soil retention, or improved distribution of the metam or methyl isothiocyanate (MITC) in soil.

[0052] While treating with a pre-mix is desired, the invention in a different embodiment also includes treating soil with tank mix or in a flowing pipe mix, where said mix includes both the MITC-generating fumigant, for example a salt of metam, and calcium thiosulfate, calcium chloride and/or calcium nitrate, wherein the mix comprises more than 1%, for example more than 2% by weight of the calcium thiosulfate, calcium chloride and/or calcium nitrate, or wherein the applied amount is sufficient to add more than about 100 pounds per acre of the calcium thiosulfate, calcium chloride and/or calcium nitrate, along with the MITC-generating fumigant.

[0053] In another embodiment a stable concentrated liquid solution can be formulated, said stable concentrated liquid solution comprising between 4% and about 50% of calcium thiosulfate, calcium chloride and/or calcium nitrate, between 4% and about 56% of a soil fumigant, said fumigant comprising or consisting essentially of an MITC-generating compound, or a salt of a dithiocarbamate, preferably methyldithiocarbamate or salt thereof; and water. In most preferred conditions, the concentrated solution contains between 10% and 50% by weight total of the dithiocarbamate salts and calcium thiosulfate, calcium chloride and/or calcium nitrate. Percentages are herein percentages by weight, relative to the total weight of the composition. The solution is preferably free of alkali sulfides. However, the solution can contain alkali hydroxides, surfactants, and other adjuvants. The weight ratio of calcium thiosulfate, calcium chloride and/or calcium nitrate to fumigant depends on the atomic weight of the calcium thiosulfate, calcium chloride and/or calcium nitrate and the salt of fumigant selected.

[0054] In another embodiment the mole ratio of calcium thiosulfate, calcium chloride and/or calcium nitrate to fumigant, said fumigant being selected from one or more of a sodium metam, potassium metam, other MITC generator, or combinations thereof, is between about 15:1 to about 1:15, or about 10:1 to about 1:10, or alternatively about 8:1 to 1:8, for example between about 4:1 to 1:4, or between 2:1 to 1:2, or any ratio using the above listed boundaries in any combination.

[0055] In another embodiment of the invention, a concentrated solution as described above is used to treat soil. It can be important to use concentrated liquids for application subsurface using a shank or other such mechanical device. The growers do not have the capacity to haul large tanks of diluted compositions in these operations. Metam as either sodium or potassium salts are typically sold in concentrations greater than 20% by weight, for example between 25% and 45% by weight for sodium metam (also called metam sodium), or between 35% and 42% by weight for potassium metam. For potassium metam, the concentration is even greater, say between 20% and 70%, for example between 35% and 65%, often nearer 60% by weight for some commercial products. As some of the mixtures of the present invention can be made by simply admixing commercially available metam and calcium thiosulfate, calcium chloride and/or calcium nitrate compositions, say in a ratio between 1:20 to 20:1, the resulting compositions will typically have less of both the fumigant and of the calcium thiosulfate, calcium chloride and/or calcium nitrate than the formulations from which it was made. This is not always the case, however, as more concentrated products than are routinely marketed can be used to formulate the pre-mix of fumigant and calcium thiosulfate, calcium chloride and/or calcium nitrate.

[0056] In a preferred embodiment of the invention, a highly concentrated stable solution of an alkali salt of metam and of calcium thiosulfate, calcium chloride and/or calcium nitrate are injected into the soil in ground that will be used for planting tomatoes, vegetables and small fruit including tomatoes, strawberries, or other crops. In most preferred embodiments, the solution contains more than 2%, preferably more than 4%, and typically more than 6% or more than 8% total of the fumigant(s), for example a sodium and/or potassium salt of a dithiocarbamate fumigant such as metam, and of the calcium thiosulfate, calcium chloride and/or calcium nitrate.

[0057] In another embodiment of the invention, a concentrated solution as described in the paragraphs above is used to treat soil, wherein the above solution is added to irrigation water at low dosage, that is, less than about 2% by weight or less than about 1% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate in the treatment water, said solution further comprising a salt of metam and an alkali hydroxide.

[0058] Dilute liquid lime sulfur or calcium polysulfide (CPS) going through the sprinklers may eventually result in precipitation and nozzle clogging. Similar problems exist with calcium nitrate and calcium chloride forming precipitates if added water has alkalinity (carbonates). Calcium thiosulfate may also bloom. The solutions of the invention are therefore advantageously slightly basic, typically the result of added alkali hydroxides, to buffer the irrigation water solution and prevent precipitation during injection. Potassium hydroxide is preferred. Based on laboratory testing, we determined that KOH at less than 1%, for example between about 0.1% to 1%, or between 0.2% to 0.5%, by weight, will prevent precipitation of diluted calcium thiosulfate, calcium chloride and/or calcium nitrate solutions in water. Advantageously the alkali hydroxide is added to the dilution water before or at the same time as the calcium thiosulfate, calcium chloride and/or calcium nitrate. During chemigation, a typical dilution would be the number of gallons of treatment, say for example 80 gallons of a 1:1 mixture of a metam solution (40% or 42% for metam sodium, or 52% to 54% for potassium metam), and a liquid calcium thiosulfate, calcium chloride and/or calcium nitrate solution (29%). For chemigation, this solution may be diluted in 14000 gallons of water, providing about 0.5 inches of treated water.

[0059] Without being bound by theory, we believe that when concentrated solutions of calcium thiosulfate, calcium chloride and/or calcium nitrate and dithiocarbamate are used to treat the subsurface of the soil, especially those comprising or consisting essentially of concentrated calcium thiosulfate, calcium chloride and/or calcium nitrate and an alkali salt of metam, the reactions between the calcium thiosulfate, calcium chloride and/or calcium nitrate and the soil slow the degradation of metam from calcareous deposits and clays in the soil. Without being bound by theory, the cause may also be salt displacement resulting in better MITC movement in the soil profile, or a sulfur effect, that is, calcium thiosulfate, calcium chloride and/or calcium nitrate effects the pH.

[0060] In general, sodium has a negative effect on soil structure. When present in high enough quantity, sodium causes soil particles (clay particles) to deflocculate (disperse) resulting in slow water infiltration and hydraulic conductivity (water movement through the soil). Like potassium, sodium is a monovalent cation with only one positive charge with a large shell of hydration. It is this combination of factors that causes the clay particles to disperse and plug up soil pores to the extent that prevents or greatly slows down water movement. Calcium on the other hand has a slightly larger shell of hydration but two positive charges resulting in a stronger attraction for the clay particles. Calcium has 43 times the flocculating power of sodium. Clay particles stack up like little sandwiches called tactoids in the soil allowing water to infiltrate.

[0061] Gypsum can be used to as source for calcium to the soil (especially calcareous soils) but a disadvantage is its low solubility, it hence is used primarily in solid form. The claimed inorganic compounds: calcium thiosulfate (CaS.sub.2O.sub.3), calcium nitrate Ca(NO.sub.3).sub.2 and/or calcium chloride (CaCl.sub.2) have the right solubility and proved surprisingly stable in a concentrated solution together with soil fungicides, insecticides or fumigants, more in particular dithiocarbamate based fumigants like metam salts.

[0062] All of these productscalcium thiosulfate (CaS.sub.2O.sub.3), calcium nitrate (Ca(NO.sub.3).sub.2) and/or calcium chloride (CaCl.sub.2)can be blended easily with metam sodium or metam potassium to add soluble calcium. By adding soluble calcium, sodium is displaced off of the soil exchange sites and flushed down below the root zone allowing better water penetration into the soil and more even application of the fumigant.

[0063] Of the claimed compounds, calcium thiosulfate is the most preferred as it does not contain nitrogen or chloride and is 125 times more soluble than gypsum. Another advantage of calcium thiosulfate is it contains a form of reduced sulfur that can acidify the soil releasing even more calcium.

[0064] When applied together to the subsurface of soil, the calcium thiosulfate, calcium chloride and/or calcium nitrate is believed to keep the metam from reacting with and binding to soil, being absorbed, or being converted into non-efficacious compounds. Therefore, in many soil types the applied metam may have increased efficacy.

[0065] We believe the concentrated calcium thiosulfate, calcium chloride and/or calcium nitrate combination with the dithiocarbamate has a pesticidal effect against certain soil-borne diseases, including efficacy against Verticillium and potentially against other diseases.

[0066] In another embodiment the formulations of this invention, exemplified by a concentrated calcium thiosulfate, calcium chloride and/or calcium nitrate/metam pre-mix, can be added to irrigation water. Therefore treating solution need not be concentrated but rather can be added to irrigation water. Treatment rates of greater than 30 gallons of concentrated 29% liquid calcium thiosulfate, calcium chloride and/or calcium nitrate per acre, are needed to show commercially acceptable effect on the target.

[0067] One potential issue is that dilute solutions of liquid calcium thiosulfate, calcium chloride and/or calcium nitrate, especially when the dilution water contains substantial carbonic acid and/or dissolved oxygen, can over time result in calcium thiosulfate, calcium chloride and/or calcium nitrate degradation and solid precipitation, thereby potentially plugging lines. Therefore, in one embodiment a dilute yet strong solution is desired, for example between 2% and 6% by weight of calcium thiosulfate, calcium chloride and/or calcium nitrate (and optionally metam or salt thereof) and the treatment can advantageously be followed by overwatering to flush nozzles.

[0068] In all embodiments, performance can be enhanced by addition of adjuvants, including for example additives to enhance a calcium thiosulfate, calcium chloride and/or calcium nitrate plus metam combination product, including e.g. stability/storability enhancer, odor mitigation, surfactants, and the like. Calcium thiosulfate, calcium chloride and/or calcium nitrate stability can be enhanced by addition of minor amounts of caustic, e.g., 3% or less, more typically 1.5% or less, for example 0.5% by weight or less of alkali hydroxides. In any of the above embodiments, the stability of the solution can be promoted by the addition of alkali sulfites, typically present in amounts of 1% or less, for example between 0.01 and 0.5% by weight. Various other additives, including hygroscopic gels, penetrators, and the like can also be included as adjuvants. Generally, the entire adjuvant formulation added will be less than 5% by weight of the composition, with active ingredients (fumigant and calcium thiosulfate, calcium chloride and/or calcium nitrate) and water comprising the remaining ingredients.

[0069] Of course, the calcium thiosulfate, calcium chloride and/or calcium nitrate will rapidly react in the soil despite treatments to retard degradation in water or chemical distribution lines. This is beneficial for the soil.

[0070] In a broad embodiment, one aspect of the invention is using calcium thiosulfate, calcium chloride and/or calcium nitrate, to provide a stable alkaline environment when admixed with certain fumigants. One class of fumigants particularly useful in the invention are those that are 1) degraded by direct contact with acids, but 2) are also degraded by or not effective in calcareous soils. This broad aspect of the invention may be applicable to other fumigants, especially those fumigants that do not degrade when exposed to calcium thiosulfate, calcium chloride and/or calcium nitrate.

[0071] In another embodiment of the invention the liquid calcium thiosulfate, calcium chloride and/or calcium nitrate and the fumigant can be added independently. This will require separate nozzles on the shanks, however, and multiple tanks. Such systems, where calcium thiosulfate, calcium chloride and/or calcium nitrate and fumigant are admixed on location, are less preferred as it requires multiple tanks and equipment not normally used in the industry. Such a system of multiple injection ports at different depth may be useful when treating soil at various depths, where the ratio of metam to calcium thiosulfate, calcium chloride and/or calcium nitrate in the solution may be different for solutions injected at 2 to 8 inches or at 2 to 4 inches depth as compared to a solutions injected at more than 8 inches depth.

[0072] The concentrated pre-mix of calcium thiosulfate, calcium chloride and/or calcium nitrate and Metam solution was shown to be effective to treat for late blight and Verticillium. The concentrated calcium thiosulfate, calcium chloride and/or calcium nitrate and Metam formulation is also expected to be effective in the treatment of Strawberry diseases including Charcoal rot (Macrophomina phaseolina) and Phytophthora crown rot (Phytophthora cactorum), and for Potato diseases including Fusarium Dry Rot (Fusarium solanum), Tuber Rot (Phytophthora infestans), and Black Dot (Colletotrichum coccodes). While the pesticidal effects may be additive, the presence of calcium thiosulfate, calcium chloride and/or calcium nitrate appears to reduces metam or MITC degradation by certain elements in certain soils, allowing the applied metam to be effective in soil types where it would otherwise be neutralized or less ineffective.

[0073] The invention is illustrated by the examples but is not limited to the examples.

EXAMPLES

Example 1: Stability of the Concentrates

[0074] Metam & calcium thiosulfate: Compatibility of calcium thiosulfate (CaTs) and metam sodium or metam potassium were examined as follows: Stock solutions of metam sodium (42%) or metam potassium (54%) were mixed with stock solutions of calcium thiosulfate (CaTs, 25%) in 1:1 ratios first. 50 grams of the metam samples were mixed separately with 50 grams of calcium thiosulfate and mixed well. The blends were observed for chemical changes (i.e., reactions, hydrogen sulfide generation, heat formation, or precipitation) as well as physical changes (i.e., color change, phase separation). The samples were monitored over six months period. No changes were observed. 1/9 ratios of the metam sample and CaTs as well as 9/1 ratios were found to be stable as well.

[0075] Metam & calcium chloride: Compatibility of calcium chloride (CaCl.sub.2, 50% solution in water) and metam sodium or metam potassium were examined as follows: Stock solutions of metam sodium (42%) or metam potassium (54%) were mixed with stock solution of calcium chloride (CaCl.sub.2, 50%) in 1:1 ratios first. 50 grams of the metam samples were mixed separately with 50 grams of calcium chloride solution and mixed well. The blends were observed for chemical changes (i.e., reactions, hydrogen sulfide generation, heat formation, or precipitation) as well as physical changes (i.e., color change, phase separation). The samples were monitored over six months period. No changes were observed. 1/9 ratios of the metam sample and CaCl.sub.2 as well as 9/1 ratios were found to be stable as well.

[0076] Metam & calcium Nitrate: Compatibility of calcium nitrate [Ca(NO.sub.3).sub.2, 50% solution in water] and metam sodium or metam potassium were examined as follows: Stock solutions of metam sodium (42%) or metam potassium (54%) were mixed with stock solution of calcium nitrate [Ca(NO.sub.3).sub.2, 50%] in 1:1 ratios first. 50 grams of the metam samples were mixed separately with 50 grams of calcium nitrate solution and mixed well. The blends were observed for chemical changes (i.e., reactions, hydrogen sulfide generation, heat formation, or precipitation) as well as physical changes (i.e., color change, phase separation). The samples were monitored over six months period. No changes were observed. 1/9 ratios of the metam sample and Ca(NO.sub.3).sub.2 as well as 9/1 ratios were found to be stable as well.

[0077] The above stable concentrated liquid solutions prove very useful in the treatment of soil-borne pathogens. No precipitation was noticed so that there is little to no risk of clogging of nozzles. The compounds were found to be compatible, the liquid solutions proved to be stable and have a long shelf life. The me tam salts did not precipitate nor decompose.

[0078] The claimed stable concentrated liquid solutions of the invention will hence be useful for treating all agricultural and horticultural plants for which metam alone is useful. The claimed stable concentrated liquid solutions of the invention will hence also be useful for treating all agricultural and horticultural plants for which the particular fumigant alone is useful. The claimed stable concentrated liquid solutions of the invention allow the use of metam salts in calcareous soils too, as the inorganic calcium-containing compounds allow the metam salt to penetrate into the soil better and deeper. In particular the use of a calcium thiosulfate is beneficial, as explained supra, either alone or in combination with the calcium chloride and/or the calcium nitrate.

[0079] For the amounts of metam and of calcium thiosulfate, calcium nitrate and/or calcium chloride to use, see the preferred amounts to use as given heretofore. Preferably the stable concentrated liquid solutions of the invention are applied at a depth of 4 inches subsurface or below, the rate of application being varied in accordance with the pest to control and its severity. A person skilled in the art will be a able to adapt to the circumstances.