MX2008005366A - Hydrogen cyanamide pesticide formulations - Google Patents

Abstract

Agricultural crops are protected from the growth of undesirable vegetation as well as nematode and insect infestations, by the application of hydrogen cyanamide in combination with a short-chain, water-soluble monocarboxylic or polycarboxylic acid, the acid containing 1-3 carboxy groups and either no hydroxy groups or 1-3 hydroxy groups.

Description

PESTICIDE FORMULATIONS OF HYDROGEN CYANAMIDE CROSS REFERENCE TO RELATED REQUEST This application corresponds to a continuation-in-part of the co-pending patent application of the US. Serial No. 11 / 259,435, filed on October 25, 2005, and claims the benefit of priority for all purposes legally capable of being thus provided. The contents of the application Serial No. 11 / 259,435 are hereby incorporated by reference in their entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention resides in materials and methods for crop protection, and particularly relates to soil treatments for controlling the growth of nematodes and herbs. 2. Description of the Prior Art The agricultural industry is based on effective control of insects, plant pathogens, nematodes, and herbs, for abundant and healthy crops. The control of certain forms of nematodes, for example, is an important factor to ensure the viability of the harvest plants in the initial stages of crop growth and also for the production of plants and life span in both annual and perennial crops. Effective control of nematodes is particularly important in view of the ability of nematodes to persist in the soil after removal of the crop. Known methods to control nematodes include crop rotation, fallowing, the use of nematode-resistant crops, and soil fumigation. Of these, soil fumigation is the method that is most economically feasible and the most widely employed, and methyl bromide is the most widely used soil fumigant. Methyl bromide is a highly effective broad spectrum pesticide, which is used in both pre-harvest and post-harvest fumigation. A difficulty with methyl bromide, however, is its volatility, which results in the release of a significant amount of the chemical into the atmosphere when applied to the soil. This reduces the amount of methyl bromide available for pesticidal action in the soil and also causes depletion of the ozone layer due to the reaction of ozone with the bromine atoms that are released when the methyl bromide is subjected to photo-oxidation. The The high volatility of methyl bromide also limits the effectiveness of this fumigant in heavy soils. Cyanamide, a term used to designate both hydrogen cyanamide and calcium cyanamide, is used in Europe as a herbicide and in various parts of the world as a regulator for plant growth. The convenience of using cyanamide as a liquid formulation has increasingly made liquid cyanamide the preferred material, and research has shown that hydrogen cyanamide is an active ingredient in both hydrogen cyanamide and calcium cyanamide preparations. Since its introduction in the 1950s, hydrogen cyanamide is used as a pre-emergence herbicide and a defoliant. The effectiveness of hydrogen cyanamide in plant protection was attributable at least in part to the hydrolysis of calcium cyanamide to hydrogen cyanamide in most soils, although the fact that such hydrolysis occurred was not appreciated at that time. In the environment, hydrogen cyanamide is broken down into urea, followed by decomposition of the urea to ammoniacal forms of nitrogen and carbon dioxide. These metabolites become plant nutrients and their occurrence is mediated by biological organisms and / or physical processes. The rate at which hydrogen cyanamide formulations decompose can be controlled by the incorporation of a stabilizing agent, and phosphoric acid has commonly been employed for this purpose. When drip irrigation was introduced in the 1960s, however, it was discovered that the inclusion of phosphoric acid in a hydrogen cyanamide formulation containing water with a high calcium content caused plugging of the drip emitters. Similar plugging was observed in spray or mist systems, with small diameter spray nozzles. COMPENDIUM OF THE INVENTION This invention resides in a series of discoveries involving the pesticidal use of hydrogen cyanamide. A similar finding is the improvement of pesticidal activity by the addition of a lower alkyl carboxylic acid, with certain combinations of hydrogen cyanamide and the carboxylic acid exhibiting synergistic pesticidal activity. Another discovery is the effectiveness of lower alkyl carboxylic acids as stabilizers of hydrogen cyanamide formulations. The carboxylic acids are found to be effective replacements for the phosphoric acid previously employed, and the stabilization of hydrogen cyanamide formulation can be achieved without the inclusion of phosphoric acid, or with no more than trace amounts. A still further discovery is that soil fumigation and pesticide control in general can be achieved with hydrogen cyanamide without need to cover the soil with a vapor-retaining barrier to control the volatilization of the soil treatment agent. One discovery in connection with the use of citric acid in particular, is the acid's ability to improve the effectiveness of cyanamide herbicide despite the lack of herbicidal activity of the acid itself. This lack of activity is confirmed by the failure of citric acid to demonstrate a response in speed of application, that is to say an increase in its herbicidal effectiveness (if any herbicidal activity were actually shown) with an increase in the speed of application. Another discovery is the utility of citric acid for nematicidal activity in conjunction with the application of cyanamide for herbicidal effect. This is despite the fact that citric acid is not volatile, or at least less volatile than cyanamide, and also despite the fact that citric acid itself is a metabolite of certain soil fungi. Still further discoveries, objects and advantages of the invention will be apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of the test results carried out according to this invention, showing nematicidal activity of combinations of hydrogen cyanamide and propionic acid against reniform nematodes. Figure 2 is a trace of the results of tests performed in accordance with this invention, showing nematicidal activity of combinations of hydrogen cyanamide and propionic acid with spiral nematodes. Figure 3 is a trace of the results of tests performed in accordance with this invention, showing herbicidal activity of combinations of hydrogen cyanamide and propionic acid in pre-emergence application in a collective group of common crop herbs.

Figure 4 is a line of the results of tests carried out in accordance with this invention, showing herbicide activity of combinations of hydrogen cyanamide and propionic acid in pre-emergence application in tiger nut or groundnut. Figure 5 is a line of the results of tests carried out according to this invention, showing herbicidal activity of combinations of hydrogen cyanamide and propionic acid in pre-emergence application in digitaria. Figure 6 is a trace of the results of tests performed in accordance with this invention, showing herbicidal activity of combinations of hydrogen cyanamide and propionic acid in pre-emergence application in Senna obtusifolia. Figure 7 is a trace of the results of tests performed in accordance with this invention, showing herbicidal activity of combinations of hydrogen cyanamide and propionic acid in post-emergence application in a collective group of common crop herbs. Figure 8 is a trace of the results of tests performed in accordance with this invention, showing herbicidal activity of 19 days after the application of pre-emergence of combinations of hydrogen cyanamide and citric acid in a collective group of common crop herbs. Figure 9 is a trace of the results of tests performed in accordance with this invention, showing herbicidal activity of 26 days after the application of pre-emergence combinations of hydrogen cyanamide and citric acid in a collective group of crop weeds common. DETAILED DESCRIPTION OF THE INVENTION AND MODALITIES PREFERRED The term "hydrogen cyanamide" is used here to denote a compound of the formula This compound is also referred to among the chemicals such as cyanamide, cyanogenamide and carbodiimide, and will have to be distinguished from the calcium salt, calcium cyanamide.

Ca = N- C = N The carboxylic acids for use in this invention are straight-chain, water-soluble, lower alkyl carboxylic acids of one to three carboxy groups which optionally contain one to three hydroxy groups in addition to the carboxy group (s). The term "carboxylic acid" is therefore not limited to compounds with simple acid groups or to compounds whose only alkyl substituents are acid groups. By "water soluble" it is meant that at least about 2 parts by weight of the acid, preferably at least about 10 parts by weight, more preferably at least about 30 parts by weight, are soluble in 100 parts by weight of water, and more preferable the acid is liquid and totally miscible with water in all proportions. The term "carboxy group" is used herein to denote a group of the formula -C02H, and the term "hydroxy group" is used herein to denote a group of the formula -OH but does not include the -OH group which is part of the group carboxy. A subgenus of carboxylic acids of particular interest for use in the practice of this invention are those with 1-3 carboxy and zero groups or a hydroxy group. Another sub-genre of particular interest are those with 2-3 carboxy groups and a hydroxy group.

A third subgenus of particular interest are monocarboxylic acids without hydroxy groups. Preferred carboxylic acids are propionic acid, butyric acid, and citric acid (2-hydroxy-1,2,3-propanedicarboxylic acid). Propionic and citric acids are most preferred. Hydrogen cyanamide and carboxylic acid can be applied individually to the agricultural site where pesticide control is desired, or the two chemicals can be applied together in a single application. The chemicals are most conveniently applied in aqueous solution, and thus can be applied as a common aqueous solution. Whether applied individually or in combination, the effectiveness of the two chemicals is not limited to particular proportions by weight, and the proportions by weight can vary widely. In most applications, however, better results will be obtained when the weight ratio of carboxylic acid to hydrogen cyanamide is within the range of about 1: 1 to about 20: 1, and preferably about 2: 1. to approximately 10: 1. Likewise, when chemical products are applied in aqueous solutions, the concentrations The chemicals in the solutions are not critical and can vary widely. The most economical results will generally be achieved when the concentration of hydrogen cyanamide is within the range of from about 0.1% to about 10% by weight, preferably from about 0.3% to about 3% by weight. Similarly, the most economical results with the carboxylic acid will be achieved when the carboxylic acid concentration is within the range of from about 0.1% to about 20% by weight, and preferably from about 1% to about 10% by weight. Hydrogen cyanamide is commercially available and is commonly prepared by the continuous carbonation of calcium cyanamide. When hydrogen cyanamide is supplied in aqueous solution, a stabilizer is typically included in the solution since hydrogen cyanamide is susceptible to decomposition through hydrolysis. As noted above, a phosphate buffer in the form of phosphate ion or phosphoric acid is typically used as the stabilizer. In the practice of the present invention, the phosphate buffer can be retained to result in a solution containing the hydrogen cyanamide, the phosphate buffer, and the carboxylic acid. In alternate form, however, and preferably in many cases, the phosphate buffer can already be completely or substantially eliminated and replaced by the carboxylic acid. Thus, in certain embodiments of the invention, the formulation applied to the soil or agricultural site is an aqueous solution of hydrogen cyanamide and a carboxylic acid of the above description, with at most a trace amount of phosphate ion, or in certain additional embodiments, a solution that is lacking phosphate ion. The term "trace amount" is used herein to mean 1,000 ppm or less, preferably 100 ppm or less. In the practice of this invention, the active ingredients are applied to the soil or to the growth medium of the crop in general to control organisms that are considered harmful to the growth of the crop. These organisms include, but are not limited to, insects, nematodes, and unwanted vegetation. The term "Unwanted vegetation" denotes species of plants that are not harvests, which otherwise tend to grow in the areas where the crops are planted and include both voluntary harvests and herbs. The unwanted vegetation whose control is of greatest interest in the practice of this invention are herbs, and primarily those herbs associated with common crops such as corn, green peppers, tomatoes, soy and vegetables in general, as well as cotton, sorghum, wheat, alfalfa, various ornamentals and various grass grasses. Nematodes that are harmful to crop growth are plant parasitic nematodes that include reniform nematodes (Rotylenchulus reniformus), spiral nematodes (Helicotylenchus dihystera), root knot nematodes. { Meloidogyne arenaria, M. naasi and M. incognita), stubby root nematodes. { Paratrichodorus minor), stubby nematodes. { Tylenchorhynchus claytoni), and others. These are different from nematodes that are beneficial to crop growth, examples are microbivorous (free-living) nematodes and other nematodes, such as those of the order Dorylaimida, which feed on algae, fungi and other nematodes. The term "control" is used here to denote either reducing the growth rate of organisms, preventing organisms from maturing, avoiding that organisms reproduce or exterminate or reduce the viable population of organisms. The term "pesticidally effective amount" is used herein to denote any amount of the active ingredient or ingredients that produce any of these results. In addition to hydrogen cyanamide and carboxylic acid, formulations of the present invention optionally will contain adjuvants or diluents such as formulation aids, buffers and other stabilizers, solubilizing agents, dispersing agents, crop nutrients, and other herbicides, insecticides, nematicides. or fungicides. These additives are well known in the agricultural formulation industry and are readily available from suppliers of agricultural chemicals. The types of soils in which the formulations of this invention can be effective are sandy soils, loamy soils, clays, silt, and combinations such as sandy loam, mud-loam, sandy clay, and the like. When formulations are used to control undesirable vegetation, effective results can be achieved with both pre-emergence application (application directly to the soil before undesirable vegetation emerges from the soil surface) as a post-emergency application (application directly to the undesirable vegetation that has already emerged). Useful methods of application include diffusion or localized spraying, drip irrigation or other forms of irrigation, and any of these methods followed by soil tillage. The rates of application of the active ingredients to the soil can vary over a wide range. The optimal application rates will depend on the crop to be protected, the nature of the infestation, infestation of insects, nematodes or herbs, the stage of growth of the harvest of the infestation, and the way in which it is applied, that is to say already be it by sprinkling, irrigation or other means. For best results in controlling nematodes, the application rate of hydrogen cyanamide will be in the range of from about 25 to about 500, and preferably from about 50 to about 250 kilograms per hectare. For best results in controlling weeds and other undesirable vegetation, the rate of application of hydrogen cyanamide will be in the range of approximately 25 to about 1,000, and preferably about 50 to about 500 kilograms per hectare. The same application speeds apply to control other types of infestation. The carboxylic acid will be applied at speeds that are proportional, by the aforementioned weight proportions. The compositions of this invention will generally be supplied, stored or both, in the form of concentrates with higher proportions of active ingredients that are contemplated for application to the growth site. These concentrates for example may be aqueous solutions containing from about 20% to about 40% each of hydrogen cyanamide and carboxylic acid. The two components can also be stored and shipped as individual aqueous concentrates. The following examples are offered strictly for illustration and are not intended to limit the scope of the invention. EXAMPLE 1 This example demonstrates the nematicidal activity of the combined application of hydrogen cyanamide and propionic acid to a slime-loam in a covered pot, followed twelve days later by planting or planted soybeans in the soil, in this study, the soil was naturally infested with four species of nematodes, two of which were noxious and two beneficial and both survival observations were made of nematodes as growth of soybean plants. Solutions of hydrogen cyanamide at a concentration of 1.0 wt.% And propionic acid at 5.0 wt.% Were prepared, both in water, the hydrogen cyanamide of a 50% aqueous solution buffered with phosphate. Planted pots measuring 10 diameter were used, each containing 1 kg of soil. The soil was silt-loam from a cotton field, pH 6.2, CEC < 10 meq / 100 g of soil, organic matter < 1.0%. The treatment chemicals were combined in various dilutions such that 100 mL of the combined dilutions contained the desired amount of each chemical for each test. The combined dilutions were then applied to the soil surface in each pot, at 100 mL of combined dilution per pot. Dilutions were selected to achieve target application rates expressed in milligrams of the treatment chemical by kilogram of soil, with 1 milligram of treatment chemical per kilogram of soil that is approximately equal to 2 kilograms of chemical per hectare of land or 2 pounds of chemical per acre of land. Immediately after the treatment, in which the chemicals were applied, each pot was covered by a ball of low density, clear polyethylene with a thickness of .038 mm (1.5 mil). After twelve days, the bags were removed and soil samples were taken from each pot for nematological analysis by the salad bowl technique of Rodriguez-Kabana, R., and M.H. Pope, Nematropica, 11: 175-186 (1981). The results of these analyzes are listed in Table I as a result of the pre-planted test. The results for the two harmful nematodes are also illustrated as traces of number of nematodes against the rate of application of hydrogen cyanamide in Figures 1 and 2. After the polyethylene bags are removed, each pot was planted with soybeans. Hutcheson at 5 seeds per pot, and the seeds were allowed to germinate and the plants grew for 45 days. The resulting plants are then removed from the pots, the root system was washed, and the number of plants in each pot was determined. The weights of both fresh shoots and roots were also determined as well as the height of the shoots and the relative health of the root system, using a subjective index. Soil samples were also collected, and soil and roots were incubated to determine nematode populations. The treatments were arranged in a randomized complete block design with seven replications per treatment and statistical evaluation of the data was performed with analysis of variance (ANOVA) and standard regression procedures. The Least Significant Difference of Fischer at p 0.05 was calculated when appropriate. The results of these tests are cited as final test results in Tables II, III and IV, with populations of nematodes on the earth cited in Table II, populations of nematodes in the root system of Table III, and parameters of plants and roots of the soybean sprouts in Table IV. The final test results and pre-planted collectively indicated that propionic acid significantly improved activity nematicide of hydrogen cyanamide both against reniform and spiral nematodes to a degree that exceeds any additive effect of the two products individually. In contrast, the populations of the microbivore nematodes and Dorylaimida were unaffected or increased by the treatments depending on the amounts of cyanamide used. Regarding the conditions of the soybean plants, treatments with cyanamide alone and with cyanamide in combination with propionic acid, both resulted in increased shoot height and increased weights of roots and shoots, all proportional to the amount of cyanamide applied. The relative health of the root systems was also markedly improved by the treatments in a proportional way to the dose. TABLE I Nematicidal Activity of Cyanamide and Propionic Acid in Combination Test Results-Planted: 12 Days After Treatment and Before Planting and Harvesting (Cyanamide at Different Speeds, With and Without Propionic Acid at 250 mg / kg of Earth) TABLE II Nematicidal Activity of Cyanamide and Propionic Acid in Combination Final Test Results: 57 Days After Treatment and 45 Days After Harvest Planted (Cyanamide at Different Speeds, With and Without Propionic Acid at 250 mg / kg of Earth) TABLE II CONTINUES TABLE III Nematodes in Root Systems: 57 Days After Treatment and 45 Days After Harvest Planted (Cyanamide at Different Speeds, With and Without Propionic Acid at 250 mg / kg of Earth) Speed Number of Surviving Nematodes in Root System Per Pot Application Harmful Nematodes (TABLE III CONTINUES) TABLE IV Harvest Conditions (Soybean): 57 Days After Treatment and 45 Days After Planting of Harvest to 5 Seeds of Harvest / Pot (Cyanamide at Different Speeds, With and Without Propionic Acid at 250 mg / kg of Earth) CONTINUOUS TABLE IV Sprout Weight Fresh Index (g) Root Condition EXAMPLE 2 This example demonstrates the herbicidal activity of hydrogen cyanamide and propionic acid in combination, in pre-emergence application to soil seeded with a series of common herbs that germinate in the covered pots. The herbs used in these tests were grown from a package of standard herbal seeds of common annual and perennial herbs representing an extrama grass situation. Herbs include tiger nut (Cyperus esculentus), digitaria (Digitaria sanguinalis), amaranth or red (Amaranthus spp.), Chenopodium or Portulaca (Ipomoea spp.), Senna Obtusifolia. { Senna obtusi folia) and other herbs annual Observations of the effects on the grass population as a whole were made and individual observations are made for Chufa, Digitaria, and Senna obtusifolia. Stock solutions of hydrogen cyanamide at 1.25% by weight and propionic acid at 5.0% by weight were prepared, both in water, the hydrogen cyanamide of 50% aqueous solution buffered with phosphate. The sizes of the pots for planting, the amount of soil per pot, and the type of soil or soil, were all the same as those used in Example 1. As in Example 1, the treatment chemicals were combined in various dilutions, such that 100 mL of the combined dilutions contain the desired amount of each chemical for each test, and the combined dilutions were applied to the soil surface in each pot at 100 mL of combined dilution per pot. Immediately after application of the chemicals, each pot was covered by a clear, low density polyethylene bag with a thickness of .038 mm (1.5 mil). After one week, the bags were removed and herbal counts were made for each pot at intervals of 8, 14, 20 and 27 days after application of the chemical products. Data analysis were performed in the same manner as in Example 1. The results expressed in herbs per pot are cited in Table V for all the herbs, Table VI for tiger nut, Table VII for digitaria and Table VIII for Senna obtusifolia, all at various application rates for both hydrogen cyanamide and propionic acid. The results at 27 days are also plotted for all the herbs in Figure 3, chufa in Figure 4, digitaria in Figure 5, and Senna obtusifolia in Figure 6. The results indicate that the herbicidal activity of hydrogen cyanamide against species of herbs, is improved by propionic acid on a significant of the application speeds used, with much of the data indicating a synergistic effect. Particularly effective results were observed when the rate of application of hydrogen cyanamide was 150 mg / kg of soil. TABLE V Herbicidal Activity of Cyanamide and Propionic Acid in Combination Against All Herb Species in Pre-Emergency Applications in Covered Pots (TABLE V CONTINUES) TABLE VI Herbicidal Activity of Cyanamide and Propionic Acid in Combination Against Chufa in Pre-Emergency Application in Covered Pots TABLE VI CONTINUE TABLE VII Herbicidal Activity of Cyanamide and Propionic Acid in Combination Against Digitaria in Pre-Emergency Application of Covered Flower Pots TABLE VIII Activity Herbicide of Cyanamide and Propionic Acid in Combination Against Senna obtusifolia in Pre-Emergency Application in Covered Flower Pots (TABLE VIII CONTINUES) EXAMPLE 3 example demonstrates the herbicidal activity of hydrogen cyanamide and propionic acid in combination, in application to soil sown with the same species of herbs employed in Example 2. The procedures in this example differ from those of Example 2, however by the use of hydrogen cyanamide crystals free of phosphate ion to prepare the hydrogen cyanamide solution by the use of post-emergence application, and by the omission of any cover of the pots during any part of the test. Observations were made for total herbaceous growth, and individual observations were also made for Chufa, Digitaria, Senna obtusifolia, and mantle of sky corregüela or blue aguinaldo.

Stock solutions of hydrogen cyanamide at 1.25% by weight and propionic acid at 5.0% by weight, both in water, were prepared as before, except that the hydrogen cyanamide solution, as noted above, was prepared by dissolving crystals of hydrogen cyanamide in water in the absence of phosphate ion. The sizes of the pots for planting, the amount of soil per pot, and the type of soil, were all the same as those used in Examples 1 and 2. The treatment chemicals were combined in various dilutions such that 100 mL of the combined dilutions contained the desired amount of each chemical for each test. The herbs were allowed to grow for three weeks before the treatment chemicals were applied. The treatment chemicals were applied to the soil surface in each pot at 100 mL of combined dilution per pot, with the pots that are left uncovered. Herbal counts were taken at intervals of 8, 14, 20 and 27 days after application of the chemicals. Data analyzes were performed in the same manner as in Examples 1 and 2. Table IX cites results in herbs per pot for all herbs, Table X for tiger nut, Table XI for digitaria, Table XII for Senna obtusifolia, and Table XIII for mantle of sky, all with propionic acid only at different rates of application and with propionic acid at the same application rates but in combination with cyanamide. hydrogen at 125 mg / kg of earth. The results at 20 days are also plotted for all herbs in Figure 7. These test results indicate that the application rate of hydrogen cyanamide (125 mg / kg of soil) was sufficient to control the herbs very effectively when applied alone, with less than ten grasses in total per pot at all intervals, including approximately one or less cycad grasses per pot, approximately one or less grasses of Senna obtusifolia per pot, approximately three or less mantle grasses per pot and approximately six or less tigernut weeds per pot. Propionic acid demonstrated herbicide activity by itself, but more significantly, propionic acid does not significantly impair the herbicidal activity of hydrogen cyanamide in any of the tests.

This confirms that the combination of hydrogen cyanamide and propionic acid can be used for effective control of nematodes and herbs (considering these results in combination with those of example 1) with improved nematicidal agility and without loss in herbicidal activity. TABLE IX Herbicidal Activity of Cyanamide (Phosphate Free) and Propionic acid in combination against all Herb Species in Post-Emergency Application in open planters.

(TABLE IX CONTINUES) TABLE X Herbicidal Activity of Cyanamide (Phosphate Free) Propionic Acid in combination against tigernut in post-emergence application in uncovered pots.

TABLE XI Herbicidal activity of Cyanamide (Phosphate Free) and Propionic Acid in combination with Digitaria in Post-Emergence application in discovered pots.

(TABLE XI CONTINUES) TABLE XII Herbicidal Activity of Cyanamide (Phosphate Free) Propionic Acid in combination with Senna Obtusifolia in Post-Emergence application in uncovered pots.

(TABLE XII CONTINUES) Speed Herbs Per Pot: TABLE XIII Herbicidal Activity of Cyanamide (Phosphate Free) Propionic Acid in combination with Cié Mantle in Post-Emergency application in uncovered Pots.

EXAMPLE 4 This example demonstrates the herbicidal activity of hydrogen cyanamide and citric acid in combination in application of pre-emergence soil planted with a series of herbs that germinate in covered pots. The herbs used in these Tests were developed from a package of standard herbal seeds of common annual and perennial herbs that represent an extreme herbal situation. The herbs include digitaria. { . { Digitaria sanguinalis), tiger nut (Cyperus esculentus), Senna obtusifolia (Senna obtusifolia), sky mantle or blue aguinaldo (Ipomoea spp.), Red or amaranth (A aranthus spp.), And other annual herbs. Observations of the effects on the grass population as a whole, were made and individual observations were made for digitaria, tiger nut, Senna obtusifolia, mantle of sky and amaranth. Stock solutions of hydrogen cyanamide at 1.25% by weight and citric acid at 5.0% by weight, both in water, were prepared, the hydrogen cyanamide of a 50% aqueous solution buffered with phosphate. The sizes of the planting pots, the amount of soil per pot and the type of soil, were all the same as those used in example 1. As in example 1, the treatment chemicals were combined in various dilutions, such that 100 ml of the combined dilutions contains the desired amount of each chemical for each test and the combined dilutions were applied to the soil surface in each pot 100 ml of combined dilution per pot. Immediately after application of the chemicals, each pot was covered by a clear low density polyethylene bag, with a thickness of .038 mm (1.5 mils). After one week, the bags were removed and the herb counts were taken for each pot at intervals of 9, 13, 19, and 26 days after application of the chemicals. Analysis of data were performed in the same way as in Example 1. The results expressed in herbs per pot are cited in Table XIV for all herbs, Table XV for digitaria, Table XVI for tiger nut, Table XVII for Senna obtusifolia, Table XVIII for mantle of sky and Table XIX for amaranth, all at different speeds of application for hydrogen cyanamide with and without citric acid. The results at 19 and 26 days are also plotted for all herbs in Figures 7 and 8, respectively. Citric acid when used is applied at a rate of 150 mg / kg. TABLE XIV Herbicidal Activity of Cyanamide and Citric Acid (C6H807) in Combination Against Combined Herb Species in Pre-Emergency Application in Covered Pots.

TABLE XV Herbicidal Activity of Cyanamide and Citric Acid (C6H807) in Combination Against Digitaria in Pre-Emergency Application in Covered Pots.

TABLE XVI Herbicidal Activity of Cyanamide and Citric Acid (C6H807) in Combination Against Chufa in Pre-Emergency Application in Covered Pots.

Speed Herbs per Flowerpot: Applied Cyanamide Chyma-mida Sola tion Days With 1 € G mg CeH807 / kg (mg / kg after land) of treatment TABLE XVII Herbicidal Activity of Cyanamide and Citric Acid (C6H807) in Combination Against Senna Obtusifolia in Pre-Emergency Application in Covered Pots.

TABLE XVIII Herbicidal Activity of Cyanamide and Citric Acid (CsH807) in Combination Against Sky Mantle in Pre-Emergency Application in Covered Flower Pots TABLE XIX Herbicidal Activity of Cyanamide and Citric Acid (C6H807) in Combination Against Amaranth in Pre-Emergency Application in Covered Pots.

VelociHierbas por Maceta: Amaranth day AplicaCianamida Sola de Días CianaAfter m 150 mg C6H807 / kg ground measurement (mg / kg Tratatierra) ment > The results indicate that the herbicidal activity of hydrogen cyanamide against all herbal species is not impaired by co-administration of citric acid. Citric acid actually improves the herbicidal activity of cyanamide and in some cases c: trico acid and cyanamide produce a synergistic herbicidal effect, notably in digitaria at 50-100 mg / kg, and in tigernut at 50 mg / kg. As will be illustrated in Example V below, this additive and synergistic effect is present despite the fact that the herbicidal effect of the citric acid itself is questionable. EXAMPLE 5 This example shows citric acid at various rates of application to the land sown with a series of common herbs that germinate in covered pots. The herbs used in these tests were the same as those used in Example 4 and observations were made of the effects on individual herbs as well as on the herbal population as a whole. A stock solution of citric acid is prepared in the manner described in Example 4, and all other test parameters were also the same as in Example 4. The grass counts were taken from the various pots at intervals of 7, 12 , and 28 days after application of citric acid, and data analysis were performed in the same manner as Example 1. The results expressed in herbs per pot are cited in Table XX for the total herbal population.

TABLE XX Citrus Acid Herbicide Activity (C6H807) Against Combination of Herbs in Pre-Emergency Application in Covered Pots.

The results indicate that the herbicidal activity of citric acid was negligible except at extremely high application concentrations. At application rates of low and medium range, the herbicidal effect does not increase significantly as speed increases. The foregoing is offered primarily for purposes of illustration. People skilled in agricultural chemistry will recognize that additional modifications, additions and substitutions still incorporate the essence of the invention in both spirit and scope as expressed in the claims.

Claims (37)

1. CLAIMS 1. A composition for controlling organisms in the soil, which are harmful to the growth of crops, the composition comprises hydrogen cyanamide and a straight-chain, water-soluble, lower alkyl carboxylic acid containing 1 to 3 carboxy groups and 0 to 3 hydroxy groups, the carboxylic acid in a ratio relative to hydrogen cyanamide which is effective in improving the pesticidal effectiveness of hydrogen cyanamide.
2. 2. The composition according to claim 1, characterized in that the carboxylic acid has 1 to 3 carboxy groups and 0 to 1 hydroxy groups.
3. 3. The composition according to claim 1, characterized in that the carboxylic acid is a monocarboxylic acid without hydroxy groups.
4. 4. The composition according to claim 1, characterized in that the carboxylic acid has 2 to 3 carboxy groups and a hydroxy group.
5. 5. The composition according to claim 1, characterized in that the acid carboxylic is a member selected from the group consisting of propionic acid, butyric acid and citric acid.
6. The composition according to claim 1, characterized in that the carboxylic acid is a member selected from the group consisting of propionic acid and butyric acid.
7. The composition according to claim 1, characterized in that the carboxylic acid is propionic acid.
8. 8. The composition according to claim 1, characterized in that the carboxylic acid is citric acid.
9. 9. The composition according to claim 1, characterized in that the composition is an aqueous solution of hydrogen cyanamide and carboxylic acid.
10. The composition according to claim 9, characterized in that in the weight ratio of the carboxylic acid to hydrogen cyanamide in aqueous solution is from about 1: 1 to about 20: 1.
11. The composition according to claim 9, characterized in that the weight ratio of carboxylic acid to hydrogen cyanamide in the aqueous solution is from about 2: 1 to about 10: 1.
12. The composition according to claim 9, characterized in that the concentration of hydrogen cyanamide in the aqueous solution is from about 0.1% to about 10% by weight and the concentration of the carboxylic acid in the aqueous solution is about 0.1% by weight. about 20% by weight.
13. The composition according to claim 9, characterized in that the concentration of hydrogen cyanamide in the aqueous solution is from about 0.3% to about 3% by weight, and the concentration of the carboxylic acid in the aqueous solution is about 1% to about 10% by weight.
14. The composition according to claim 9, characterized in that the composition does not comprise more than trace amounts of phosphate ion.
15. 15. The composition according to claim 9, characterized in that the composition is devoid of phosphate ion.
16. 16. A method to treat land to control organisms on the earth that are harmful to growth of a crop, the method comprises applying to the soil a pesticidally effective amount of a composition comprising hydrogen cyanamide and a straight-lower alkyl, water-soluble carboxylic acid, containing from 1 to 3 carboxy groups and 0 to 3 hydroxy groups.
17. The method according to claim 16, characterized in that the organisms are species of nematodes that are harmful to crop growth and the composition is applied at a rate that supplies from about 25 to about 500 kilograms of hydrogen cyanamide per hectare.
18. 18. The method according to claim 16, characterized in that the organisms are species of nematodes that are harmful to the growth of crops and from about 50 to about 250 kilograms of hydrogen cyanamide per hectare.
19. 19. The method according to claim 16, characterized in that the organisms are undesirable vegetation and the composition is applied at a rate that provides from about 25 to about 1,000 kilograms of hydrogen cyanamide per hectare.
20. 20. The method according to claim 16, characterized in that the organisms are undesirable vegetation and the composition is applied at a rate that provides from about 50 to about 500 kilograms of hydrogen cyanamide per hectare.
21. 21. The method according to claim 19, characterized in that it comprises applying the composition to the soil before sprouting undesirable vegetation.
22. 22. The method according to claim 19, characterized in that it comprises applying the composition to the soil after the undesirable vegetation springs.
23. The method according to claim 16, characterized in that the organisms are (i) species of nematodes that are harmful to crop growth and (ii) undesirable vegetation and the composition is applied at a rate that supplies from about 25 to about 500 kilograms of hydrogen cyanamide per hectare.
24. 24. The method according to claim 16, characterized in that the organisms are (i) species of nematodes that are Harmful to crop growth and (ii) Undesirable vegetation and the composition is applied at a rate that provides from about 50 to about 250 kilograms of hydrogen cyanamide per hectare.
25. 25. The method according to claim 16, characterized in that the carboxylic acid has 1-3 carboxy groups and 0-1 hydroxy groups.
26. 26. The method according to claim 16, characterized in that the carboxylic acid is a monocarboxylic acid without hydroxy groups.
27. 27. The method according to claim 16, characterized in that the carboxylic acid has 2-3 carboxy groups and a hydroxy group.
28. The method according to claim 16, characterized in that the carboxylic acid is a member selected from the group consisting of propionic acid, butyric acid and citric acid.
29. 29. The method according to claim 16, characterized in that the carboxylic acid is propionic acid.
30. 30. The method according to claim 16, characterized in that the carboxylic acid is citric acid.
31. 31. The method according to claim 16, characterized in that the composition is an aqueous solution of hydrogen cyanamide and carboxylic acid.
32. 32. The method according to claim 31, characterized in that the weight ratio of carboxylic acid to hydrogen cyanamide in the aqueous solution is from about 1: 1 to about 20: 1.
33. 33. The method according to claim 31, characterized in that the weight ratio of carboxylic acid to hydrogen cyanamide in the aqueous solution is from about 2: 1 to about 10: 1. 3 .
34. The method according to claim 31, characterized in that the concentration of hydrogen cyanamide in the aqueous solution is from about 0.1% to about 10% by weight, and the concentration of the carboxylic acid in the aqueous solution is from about 0.1% to about 20% by weight.
35. 35. The method of compliance with the claim 31, characterized in that the concentration of hydrogen cyanamide in the aqueous solution is from about 0.3% to about 3% by weight, and the concentration of the carboxylic acid in the aqueous solution is from about 1% to about 10% by weight.
36. 36. The method according to claim 31, characterized in that the composition comprises only a trace amount of the phosphate ion.
37. 37. The method according to claim 31, characterized in that the composition is devoid of phosphate ion.