Herbicides used to control weeds or undesired vegetation in agriculture may be applied by postemergence spraying of a herbicide on the crop. The spray mixture for herbicide application usually contains an effective amount of known herbicide along with adjuvants and water. The adjuvants are commonly added to herbicidal spray mixtures to enhance postemergence weed control and/or to reduce spray drift during herbicide application.
Adjuvant surfactants provide increased spray retention on the leaf surface and increased herbicide absorption into the plant. However, surfactant(s) alone often are not able to increase herbicide efficacy, especially when hard or very hard water is used as a spray carrier. Ammonium sulfate overcomes the antagonistic effect of sodium, calcium and magnesium ions from hard water. Further, ammonium ions from ammonium sulfate may increase herbicide absorption. The mixture of surfactant(s) and ammonium sulfate is often a beneficial combination that increases efficacy of herbicides, mainly glyphosate and other weak acid herbicides.
Ammonium sulfate is a common solid fertilizer. The commercial fertilizer often lacks purity and causes sprayer nozzle plugging and thus non-uniform spray distribution and weed control efficacy. Spray-grade solid (dry) ammonium sulfate products are available that have reduced the sprayer nozzle plugging problems. Both a surfactant and ammonium sulfate usually are required to maximize efficacy of postemergent herbicides.
Surfactant adjuvants are sold commercially for use with herbicides and most are physically compatible with ammonium sulfate when dilute with water in a sprayer tank. However, specific surfactants are required for maximum efficacy when used in combination with ammonium sulfate and the wrong surfactant can even reduce efficacy. There are a large number of surfactant products available, so it is difficult for growers to know the most effective product for use with ammonium sulfate. A formulated adjuvant containing both surfactant and ammonium sulfate is desired by growers to assure efficacy, to reduce the number products for storage, and to minimize errors associated with mixing two or more products during herbicide spray preparation.
The combination of an effective surfactant with ammonium sulfate in a concentrated formulation would be logical. However, until now, only the alkyl polysaccharide surfactants have been compatible with ammonium sulfate in a concentrated adjuvant formulation, as described in U.S. Pat. Nos. 5,356,861 and RE 36,149. These surfactants, selected mainly because of physical compatibility with ammonium sulfate, may not maximize efficacy with herbicides.
Glyphosate (N-phosphonomethylglycine) is well known in the art and is a widely used herbicide for postemergence, nonselective weed control. Most herbicides, including glyphosate, are applied in a water carrier. To be effective, the spray mixture must be retained on a weed leaf surface; the herbicide active ingredient must be absorbed by the plant; and the herbicide must be translocated to the site of action.
Many cations present in a spray carrier, usually water, antagonize the efficacy of glyphosate and other weak acid herbicides formulated as salts, e.g., 2,4-D [(2,4-dichlorophenoxy)acetic acid], MCPA [(4-chloro-2-methylphenoxy)acetic acid], dicamba (3,6-dichloro-2-methoxybenzoic acid), and bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide]. To increase spray droplet retention on the weed surface, to enhance absorption into the plant, and to overcome the antagonistic effect of cations present in the spray carrier, glyphosate and other weak acid herbicides are often applied with an adjuvant.
Typically commercial glyphosate formulations contain an adjuvant, usually a surfactant. However, the amount of surfactant in commercial glyphosate formulations often is not sufficient to optimize efficacy and does not prevent antagonism from spray-carrier cations. Thus, additional surfactant and/or ammonium sulfate often are recommended. In practice, the additional surfactant and/or ammonium sulfate and herbicide are added separately to the sprayer tank during spray mixture preparation.
U.S. Pat. No. 6,228,807 refers to dry herbicidal compositions containing one or more herbicides plus surfactant, ammonium sulfate, and other ingredients. As described in the ""807 patent, the adjuvants are not added separately into the tank but concomitant with a defined rate of herbicide. Because the recommended rate of herbicide changes depending on crops, weed species, and environment, the rate of surfactant and ammonium sulfate adjuvants applied with such dry herbicidal composition will change directly with the herbicide rate and may not be in a proper amount to provide optimum herbicide efficacy. This is especially important when a herbicide is used at a low rate. As described in the ""807 patent, the amount of adjuvant applied is automatically reduced when the herbicide formulation is used at a low rate, so the adjuvant concentration may be too low for spray retention and to overcome antagonistic effect of minerals in the spray water. In fact, low herbicide rates typically require a comparatively high adjuvant concentration to attain acceptable herbicide efficacy.
The present invention is directed to a liquid adjuvant blend that is homogeneous and which is particularly useful for improving the efficacy of the herbicide glyphosate. The liquid adjuvant blend is used as a tank mixture, where the liquid adjuvant blend is added to a sprayer tank as a separate product along with water and herbicide. The amount of liquid adjuvant blend added to the sprayer tank may be adjusted independent of the herbicide rate to take into account water hardness, weed species, spray volume, and environmental conditions.
The liquid homogeneous adjuvant blend of the invention includes from about 10 to about 25 weight to volume percent of an iminodipropionate amphoteric surfactant. In this aspect of the invention, the iminodipropionate amphoteric surfactant is selected from the group consisting of C12-15 alkyloxypropyl-3-iminodipropionic acid, mono(sodium or potassium or ammonium) salt, decyloxypropyl-3-iminodipropionic acid, mono(sodium or potassium, or ammonium) salt {alternate name: beta.-alanine, N-(2-carboxyethyl)-N-[3-(decyloxy)propyl]-,mono(sodium or potassium or ammonium) salt}, and mixtures thereof. The liquid homogeneous adjuvant blend of the invention further includes from about 15 to about 36 weight-to-volume percent ammonium sulfate. The remaining volume of the adjuvant blend is water.
Optionally, this adjuvant composition may also include a drift retardant, dye, humectant, corrosion inhibitor, microbial inhibitor, pH adjuster, anti-foam agent, and mixture thereof. Also, the adjuvant could be mixed with glyphosate or other herbicide(s) to form a liquid complete herbicide-adjuvant formulation.
In another aspect, when needed for weed control purposes, about 1 to about 2 percent of the liquid adjuvant blend of the present invention is blended with water and an effective amount of herbicide to provide a postemergence herbicidal aqueous spray composition. In this aspect of the invention, the herbicidal spray composition typically includes about 95 to about 98 percent water, about 1 to about 4 percent herbicide, and about 1 to about 2 percent of the adjuvant of the present invention, based on weight of the total herbicidal spray composition. In an important aspect of the invention, the preferable herbicide used in the herbicidal spray composition is glyphosate.
In another aspect, the present invention provides a method for controlling weeds by applying a postemergence herbicidal spray composition to weeds and/or other undesired vegetation. The herbicidal aqueous spray composition includes iminodipropionate amphoteric surfactant, ammonium sulfate, and herbicide as described above.
In an important aspect, the present invention provides a liquid adjuvant that is homogeneous and stable. As used herein a xe2x80x9chomogeneous and stablexe2x80x9d formulation means that all components of the adjuvant composition when mixed together form a clear, continuous blend that does not separate during storage at temperatures between 0xc2x0 C. and 500xc2x0 C. for at least about 180 days.
In another important aspect of the invention, the liquid adjuvant is compatible with various qualities of water. Even where the liquid adjuvant of the invention is blended with moderate, hard or very hard water, the liquid adjuvant remains homogeneous and stable. The use of moderate, hard or very hard water with the liquid adjuvant blend and herbicide provides a herbicide efficacy that is similar to the efficacy of the same liquid adjuvant and herbicide blended with soft water. Water described as xe2x80x9chardxe2x80x9d is high in dissolved minerals, specifically calcium and magnesium. The degree of hardness becomes greater as the calcium and magnesium content increases. Hardness of water as defined by the U.S. Geological Survey is described as follows:
In a very important aspect of the invention, liquid adjuvant blended with water having up to 500 mg/L Ca and Mg remained homogeneous and stable and provided a herbicide efficacy that was similar to the efficacy of the same liquid adjuvant and herbicide blended with soft water.
Liquid amphoteric surfactants useful in the present invention are from the iminodipropionate group, e.g., products from Tomah Products Inc.: C12-15 alkyloxypropyl-3-iminodipropionic acid, monosodium salt (trade name Amphotheric N), decyloxypropyl-3-iminodipropionic acid, monosodium salt (trade name Alkali Surfactant NM) and other iminodipropionates from Tomah Product Inc. (e.g., Amphoteric NM.RTM). Salts other than the sodium salt of these surfactants also may be used, e.g., ammonium and potassium salts of these surfactants.
Thus, the surfactants used in the present invention are not amino oxides or betaines as described in U.S. Pat. No. 6,228,807 and are not nonionic surfactants, particularly alkyl polysaccharides, as described in U.S. Pat. No. 5,356,861 and RE 36,149.
Ammonium sulfate component useful in the present invention is commercially available solid or liquid product containing between 20 to 100 percent of ammonium sulfate, and preferably is spray grade.
The homogeneous adjuvant blend is customarily formulated and sold in two and one half (2.5) gallon or larger containers. The adjuvant blend is used to make up the spray mixture, which also includes spray water (about 95% to about 98%) and a herbicidally effective amount of a postemergence herbicide, customarily 4% or less by weight of the aqueous spray mixture. The herbicide is customarily added to the water at the recommended label amount; for example, glyphosate typically is applied in an amount effective for providing an application rate of from about 0.5 to about 4 pounds per acre of the herbicide active ingredient. In this aspect of the invention, the spray applied to the plants is typically:
about 1 to 2 weight percent adjuvant, preferably 1 weight percent with soft and moderate water and 2 weight percent with hard and very hard water;
about 1 to about 4 weight percent herbicide; and
the remainder of the spray being water. All weight percents are based on weight of the total herbicidal spray composition.
Preferably, the herbicide utilized with this invention is glyphosate and other weak acid herbicides, e.g., consisting of 2,4-D [(2,4-dichlorophenoxy)acetic acid], MCPA [(4-chloro-2-methylphenoxy)acetic acid], dicamba (3,6-dichloro-2-methoxybenzoic acid), bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide], glufosinate [2-amino-4-(hydroxymethylphosphinyl) butanoic acid], and mixtures thereof.