Method of preparing a composition to be sprayed on plant leaves or fruits

Abstract: In order to prevent biological lesions of plants caused by a deficiency in calcium, there is provided a method of preparing at low cost a composition containing saccharides, an organic acid and a high concentration of a calcium component, to be sprayed on plant leaves or fruits. In an aqueous solution containing glucose and an organic acid, calcium hydroxide or a substance capable of forming calcium hydroxide upon hydration in an aqueous solution is dissolved. The amount of glucose is from 15 to 40 wt.% and that of the organic acid is from 3 to less than 20 wt.%, based on the water.

Description: The present invention relates to a method of preparing a composition to be sprayed on plant leaves or fruits for the purpose of preventing biological lesions caused by deficiency of the calcium component, and specifically relates to a method of preparing a composition having an increased content of a water-soluble calcium component. The calcium component is quite important for plant growth causing translocation of nutrients and improvement in cell assimilation. Also the calcium component is effective in neutralizing organic acids formed in plant bodies, and a deficiency thereof brings about acidification of the humor to result in a hindered synthesis or translocation of hydrocarbons. The calcium component is generally recognized as difficultly movable in plant bodies, being contained more in old leaves than in young leaves, and movable scarcely into fruiting bodies. Biological lesions caused by the deficiency in calcium component include bitter pit of apple and blossom-end rot incidence of tomato and core rot incidence of celery or Chinese cabbage, for example. Calcium component existing in soil is not necessarily absorbed and utilized fully by plants, as will be apparent from the fact that biological lesion is caused by a deficiency in calcium despite the soil was supplied beforehand with calcareous fertilizers. In order to balance the deficiency in calcium and to cope directly and aggressively with the biological lesion caused by deficiency in calcium, there is a method of rendering the calcium to be absorbed by spraying a water-soluble calcium component directly on plant leaves or fruits. The water-soluble calcium component employed generally is calcium chloride or calcium primary phosphate. However, these compounds are not satisfactory to plants for supplying them with the calcium component, as the former sometimes cause phytotoxicity and the latter has problems of the inferior solubility and a lowered pH. For solving the problem of inferior solubility, various calcium compounds highly soluble in water have been proposed for compositions to be sprayed on plant leaves or fruits. There are proposed methods using, for example, calcium formate in JP-A-59-137384, calcium acetate in JP-A-60-260487 and calcium propionate in JP-A-4-202080. However, as these calcium compounds are rather expensive, it is desirous of having a method of preparing an inexpensive composition for spraying on plants, in which the composition has a calcium solubility equivalent to or larger than that of these calcium compounds and causes no phytotoxicity. JP-A-4-8231 discloses a composition containing a water-soluble calcium component, a saccharide and an organic acid to be sprayed on plant leaves or fruits. The reference teaches that the organic acid is absorbed to lower the pH and acidifies the plant, the calcium component is absorbed and adjusts or neutralizes the lowered pH of the plant and the saccharide stimulates absorption of the calcium component by its effect on the osmotic pressure. As to preparation methods of the composition, mention is made in the Example for adding an aqueous solution of an organic acid (propionic acid, citric acid) to an aqueous solution of monocalcium saccharose or adding a saccharide (glucose) to an aqueous solution of an organic acid (propionic acid, citric acid) calcium salt. However, the disclosed concentration of calcium is 4.0% as CaO, and no mention is made on the intention or the method for enhancing the concentration of calcium component. WO 91/13844 describes a composition for and a method of treating vegetation to promote its growth or its crop yield, to control pathogenic attack and to mitigate frost damage. The composition according to this reference comprises, as the major constituent by weight, a source of carbon skeleton and energy, also a macro-nutrient component and a micro-nutrient component, also preferably a vitamin/co-factor component and a complexing agent. The composition of WO 91/13844 may be applied as an aqueous solution, as a foliar spray, as a soil amendment, or as a root or seed dip. Alternatively, it may be applied in dry form as a soil mix. When applied properly during periods of stress the composition assists plants in overcoming such things as attack by pathogens, high energy demands during critical periods of growth and/or maturation and frost damage. JP-A-61025458 refers to the preparation of calcium-enriched soybean milk. According to this reference, soybean milk or a soybean protein drink is blended with 100 to 110 mg% (calculated as Ca) saccharide lime salt (e.g. a complex of glucose or xylose and Ca(OH) 2 ), and mixed with an organic acid (e.g., malic acid) with vigorous stirring, and adjusted to pH 7.0 ± 0.4. From EP-A-0 658 529 there is known a plant nutrient composition for providing plants with one or more metal ions in a form in which said metal ions can be absorbed by plants. The composition comprises a product obtained by mixing said one or more metal ions with a reducing sugar following heating of the sugar under alkaline conditions. The present inventors gave attention to an increased solubility of the calcium component in an aqueous solution of .glucose, due to formation of a water soluble calcium complex when Ca(OH) 2 was added to the glucose solution. A further study on the increased solubility made them find out that it was possible to increase the solubility of the calcium component and the stability of the solution by means of preparing firstly an aqueous solution containing glucose and an organic acid, and then adding to the solution calcium hydroxide or a substance capable of forming calcium hydroxide upon hydration. In view of the above, the present invention is directed to a method of preparing at a low cost a composition containing saccharides, an organic acid and a high concentration of the calcium component, usable for spraying on plant leaves or fruits. The present invention provides a method for preparing a composition to be sprayed on plant leaves or fruits according to independent claim 1. The adding order of glucose and the organic acid to the water is not restricted, for which either can be the first and the concurrent addition is allowable. The calcium hydroxide is added at last. For preparing a composition containing a highly concentrated water-soluble calcium component, the amount of glucose is from 15 to 40 wt.%, preferably from 20 to 35 w.%, based on water. The amount of organic acid is from 3 to less than 20 wt.%, preferably from 5 to 15 wt.%, based on water. A too large amount of the organic acid causes gelation of the solution prior to completely dissolving a sufficient amount of calcium hydroxide . As to the raw material for Ca(OH) 2 (calcium hydroxide), slaked lime can also be used. It is reasoned that Ca(OH) 2 dissolved in an aqueous solution of glucose exists not only in a form of dissociated Ca 2+ but also in a dissolved state of a complex formed with Ca(OH) 2 and glucose, and that the complex has an intense solubility in the solution. The reason why the solubility of the calcium component increases in an aqueous solution containing both glucose and the organic acid is not clear.However, it is guessed that a possible coexistence of the dissolved calcium component of the calcium complex formed with glucose and the dissociated Ca 2+ in the solution contributes to increase the solubility of the calcium component. Thus, according to the method of this invention, the resulting solution has not only an increased amount of calcium component but also has an improved storage stability being affected little by the temperature and gaseous carbon dioxide. when Ca(OH) 2 is dissolved in an aqueous solution of glucose, the saturated solution obtained shows a strong alkaline pH of about 13. However, when Ca(OH) 2 is dissolved in an aqueous solution of glucose containing an organic acid, not only an increased solubility of Ca(OH) 2 but also a lowered pH are attainable (for a solution dissolving more Ca(OH) 2 than the above, pH of about 12 is attainable). In the preparation of the composition to be sprayed on plant leaves or fruits according to the present method, when disaccharides such as saccharose (cane sugar) and maltose, polysaccharides such as maltotriose and maltotetrose are hydrolyzed by use of an organic acid and converted partly or wholly into monosaccharides like glucose and fructose, the composition employing the resulted monosaccharides in place of glucose can exhibit the same effect as that exhibited by use of glucose. For the present invention, the organic acid is not only useful for adjusting the pH of the composition to be sprayed on plant leaves or fruits but also is effective in increasing the absorption of the calcium component by plants. As for the organic acid, at least one selected from formic acid, acetic acid and propionic acid is preferred. The present invention will be explained in detail hereunder by reference to the Examples. Example 1 Into an aqueous solution of 20°C containing 25 wt.% (per total) of glucose (guaranteed reagent) and 5 wt.% (per total) of formic acid (guaranteed reagent) was dissolved slaked lime (JIS [Japanese Industrial Standard] guaranteed) to prepare a solution composition saturated with the slaked lime. The amount of slaked lime for saturating 100 g of the glucose-formic acid aqueous solution was 13.70 g, and the amount of water-soluble calcium component in the saturated solution composition was 9.12 wt.% (as CaO). pH of the composition was 11.10. No precipitation was formed from the solution during its storage at room temperature for 6 months. Example 2 Into an aqueous solution of 20°C containing 25 wt.% (per total) of glucose (guaranteed reagent) and 5 wt.% (per total) of acetic acid (guaranteed reagent) was dissolved slaked lime (JIS guaranteed) to prepare a solution composition saturated with the slaked lime. The amount of slaked lime for saturating 100 g of the glucose·acetic acid aqueous solution was 14.25 g, and the amount of water-soluble calcium component in the saturated solution composition was 9.44 wt.% (as CaO). pH of the composition was 12.45. No precipitation was formed in the composition during its storage at room temperature for 6 months. Example 3 Into an aqueous solution of 20°C containing 25 wt.% (per total) of glucose (guaranteed reagent) and 5 wt.% (per total) of propionic acid (guaranteed reagent) was dissolved slaked lime (JIS guaranteed) to prepare a solution composition saturated with the slaked lime. The amount of slaked lime for saturating 100 g of the glucose·propionic acid aqueous solution was 13.53 g, and the amount of water-soluble calcium component in the saturated solution composition was 9.02 wt.% (as CaO). pH of the composition was 11.40. No precipitation was formed in the composition during its storage at room temperature for 6 months. Comparative Example 1 Into an aqueous solution of 20°C containing 25 wt.% (per total) of glucose (guaranteed reagent) was dissolved slaked lime (JIS guaranteed) to prepare a solution composition saturated with the slaked lime. The amount of slaked lime for saturating 100 g of the aqueous glucose solution was 10.18 g, and the amount of water-soluble calcium component in the saturated solution composition was 6.98 wt.% (as CaO). pH of the composition was 13.81. A slight precipitation was formed in the composition after its storage at room temperature for one month. Comparative Example 2 Into a clean water of 20°C was dissolved slaked lime (JIS guaranteed) to prepare a solution composition saturated with the slaked lime. The amount of. slaked lime for saturating 100 g of the water was 0.165 g, and the amount of water-soluble calcium component in the saturated solution composition was 0.125 wt.% (as CaO). pH of the composition was 13.2. Comparative Example 3 Into an aqueous solution of 20°C containing 25 wt.% (per total) of glucose (guaranteed reagent) was dissolved calcium formate (guaranteed reagent) to prepare a solution composition saturated with the calcium formate. The amount of water-soluble calcium component in the saturated solution was 4.44 wt.% (as CaO). pH of the composition was 6.74. Comparative Example 4 Into a clean water of 20°C was dissolved calcium formate (guaranteed reagent) to prepare a solution composition saturated with the calcium formate. The amount of water-soluble calcium component in the saturated solution was 7.15 wt.% (as CaO). pH of the composition was 7.02. Comparative Example 5 Into a clean water of 20°C was dissolved calcium acetate monohydrate (guaranteed reagent) to prepare a solution composition saturated with the calcium acetate. The amount of water-soluble calcium component in the saturated solution was 7.48 wt.% (as CaO). pH of the composition was 7.32. Comparative Example 6 Into a clean water of 20°C was dissolved calcium propionate (guaranteed reagent) to prepare a solution composition saturated with the calcium propionate. The amount of water-soluble calcium component in the saturated solution was 8.58 wt.% (as CaO). pH of the composition was 7.36. The results obtained in Examples 1-3 and Comparative Examples 1-6 are summarized in Table 1. The amount of water-soluble calcium component (as CaO) for saturating the aqueous solutions containing glucose and the organic acid with calcium hydroxide (Example 1-3) is larger respectively than the amount of water-soluble calcium component (as CaO) for saturating an aqueous solution containing glucose only with calcium hydroxide (Comparative Example 1), for saturating a clean water with calcium hydroxide (Comparative Example 2), for saturating an aqueous solution containing glucose and the calcium salt of an organic acid with the calcium salt of the organic acid (Comparative Example 3), and for saturating an aqueous solution of the calcium salt of an organic acid with the calcium salt of the organic acid (Comparative Examples 4-6). The influence of the kind of the organic acid is not so remarkable. Aqueous solution of glucose-acid Ca(OH) 2 dissolved (g/100g) CaO in composition (wt.%) pH Glucose concentration (wt.%) Acid concentration (wt.%) Example 1 25 5 13.70 9.12 11.10 Example 2 25 5 14.25 9.44 12.45 Example 3 25 5 13.53 9.02 11.40 Comp.Ex.1 25 0 10.18 6.98 13.81 Comp.Ex.2 0 0 0.165 0.125 13.2 Comp.Ex.3 25 0 4.44 6.74 Comp.Ex.4 0 0 7.15 7.02 Comp.Ex.5 0 0 7.48 7.32 Comp.Ex.6 0 0 8.58 7.36 Example 4 Into an aqueous solution containing glucose and acetic acid having concentrations shown in Table 2 was dissolved at 20°C slaked lime to obtain the saturated solution. The amount of slaked lime for saturating 100 g of the aqueous solution and the resulted pH are shown in Table 2. Aqueous solution of glucose-acid Ca(OH) 2 dissolved (g/100g) pH Glucose concentration (wt.%) Acid concentration (wt.%) 20 0 8.20 13.75 20 5 11.32 12.21 20 10 14.65 12.04 20 15 17.39 11.90 20 20 gelation - 25 0 10.18 13.81 25 5 14.25 12.45 25 10 18.16 12.24 25 15 20.58 12.07 25 20 gelation - 30 0 12.12 13.78 30 5 14.69 12.28 30 10 19.40 12.12 30 15 21.40 12.00 30 20 gelation - 35 0 14.15 13.80 35 5 15.87 12.19 35 10 20.80 11.99 35 15 gelation - The relation between the concentration of glucose, concentration of acetic acid and the saturation solubility of slaked lime is summarized in Table 3. Glucose concentration (g/100g) 20 25 30 35 Acetic acid concentration (g/100g) 0 8.20 10.18 12.12 14.15 5 11.32 14.25 14.69 15.87 10 14.65 18.16 19.40 20.80 15 17.39 20.58 21.40 gelation 20 gelation gelation gelation gelation It is understood from Table 3 that the amount of glucose in the aqueous solution is from 15 to 40 wt.%, preferably from 20 to 35 wt.%, and the amount of the organic acid in the aqueous solution is from 3 to less than 20 wt.%, preferably from 5 to 15 wt.%. Example 5 An aqueous solution containing 17 wt.% (per total) of maltose (guaranteed reagent) and 11.5 wt.% (per total) of acetic acid (guaranteed reagent) was provided. Maltose was hydrolyzed in the solution and an aqueous solution containing glucose and acetic acid was obtained. To the resulted solution was added slaked lime (JIS guaranteed) to prepare a saturated solution composition. The amount of water-soluble calcium component in the composition was 9.08 wt.% (as CaO). pH of the composition was 11.44. Comparative Example 7 Into an aqueous solution of 20°C containing 100 parts by weight of water and 25 parts by weight of maltose (guaranteed reagent) was dissolved slaked lime (JIS guaranteed) to prepare a solution composition saturated with calcium hydroxide. The concentration of water-soluble calcium component in the composition was 3.19 % (as CaO). pH of the composition was 12.38. By virtue of the present invention, it is possible to prepare economically a high calcium content composition for spraying on plant leaves or fruits.

Claims: A method for preparing a composition to be sprayed on plant leaves or fruits, which composition contains a water-soluble calcium component, saccharides and at least one organic acid, characterized in that the water-soluble calcium component is calcium hydroxide or quick lime, which is present in the composition in an amount of 11.32 to 21.40 g/100 g, calculated as Ca(OH) 2 , glucose is present in an amount of 15 to 40 wt.%, based on water, and the organic acid is present in an amount of from 3 to less than 20 wt.%, based on water, with the steps that an aqueous solution containing glucose and at least one organic acid is provided, and calcium hydroxide or quick lime .is dissolved in said aqueous solution. The method according to claim 1, wherein said organic acid is at least one selected from the group consisting of formic acid, acetic acid and propionic acid.

Inventors: MIYAJI HIROSHI, URANO TERUO, MIYAJI, HIROSHI, URANO, TERUO
Applicants: MURAKASHI LIME IND, MURAKASHI LIME INDUSTRY CO., LTD
Application year: 1997
Main classification: C05D3
IPC codes: A01N25, C05G1, C05G3, A01N37, C05G5, A01G7, A01N59, C05D3