JPS6323159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated urea fertilizer, and more particularly to a fertilizer coated with urea particles mixed with dicyandiamide to control the dissolution rate of fertilizer components.

The main components of fertilizers used for growing crops in agriculture and horticulture are nitrogen, phosphoric acid, and potassium, and nitrogen components are usually utilized in the form of ammonia and nitric acid when plants absorb them through their roots. Nitrogen components in soil are chemically susceptible to various changes in form and are more difficult to retain in soil than other components such as phosphoric acid and potassium. For example, even if nitrogen components are fertilized in the form of ammonia, ammonium salts, or urea, the majority of them will change to nitrate within a few weeks and disappear through leaching, or will be reduced and become nitrogen gas and volatilize into the air. is large. Furthermore, when large amounts of nitrogen components are applied at once in the form of ammonia, ammonium salts, or urea, they tend to cause concentration problems more easily than other fertilizer components, so managing the application of nitrogen fertilizers is time-consuming in terms of the number of times of application, the amount of fertilizer applied, etc. Requires.

Urea, which is used in large quantities as a simple nitrogen fertilizer, has been developed to coat urea with mineral oil, wax, sulfur, synthetic resin, mineral powder, etc. in order to prevent concentration disturbances and make fertilization easier. . In the process of absorption and utilization of these coated ureas by crops, water passes through the coating film and dissolves the urea inside, urea is eluted out of the coating film, and urease, etc. in the soil decomposes the urea and turns it into ammonia. There is a process in which microorganisms in the soil convert ammonia to nitrite and then to nitric acid. Among these processes, the rate of morphological change differs depending on soil conditions because the action of microorganisms in the soil is involved.
When the field conditions are favorable for crop growth, the urea eluted from the coated urea quickly changes to nitric acid and almost no ammonia is present. Therefore, considering the changes in the form of urea, in many fields, applying coated urea as fertilizer has the same effect on plants as gradually supplying nitric acid.

The question of whether ammonia or nitric acid is preferable for plants as a nitrogen fertilizer source is of great concern to agricultural engineers and those directly involved in agriculture, and it is a matter of great concern to agricultural engineers and those directly involved in agriculture, and it is important to consider the question of whether ammonia or nitric acid is better for plants as a source of nitrogen fertilizer.
From the viewpoints of quality, disease resistance, cultivation environment, fertilizer utilization rate, etc., research and tests have been conducted on soil fertilization, crop cultivation, plant physiology, and crop pathology. Judging from the results of these studies, the evaluation of the superiority of ammonia and nitric acid varies depending on the preconditions, but considering its versatility as a fertilizer, it is desirable for both ammonia and nitric acid to coexist in the soil.

It is known that nitrification of ammonia in soil can be controlled by using a nitrification inhibitor such as dicyandiamide together with nitrogen fertilizer. In order to control the amount of ammonia and nitric acid present in the soil over a long period of time, it is necessary that an appropriate amount of ammonia and/or an ammonia source and a nitrate formation inhibitor be present in the soil. Furthermore, it is desired to be able to compensate for the difference in dissolution rate (elution rate) in water between ammonia from fertilizer and/or the ammonia source and the nitrification inhibitor. The present invention has been made to solve the above problems.

The primary objective of the present invention is to provide a fertilizer that can supply both ammonia and nitric acid as nitrogen fertilizer components in controlled amounts and proportions to crops over an extended period of time. Another object of the present invention is to provide a urea-based fertilizer whose components are unlikely to be washed away even by rain or the like. Still another object of the present invention is to provide a urea-based fertilizer that does not cause concentration problems to crops. Other objects of the invention will become apparent from the following description.

The fertilizer according to the present invention is a fertilizer in which the surface of granules made of urea mixed with dicyandiamide is coated with a film that is difficult to disintegrate with water, and the dissolution rate of fertilizer components is adjusted so that ammonia and nitric acid can be supplied to plants in a well-balanced manner. It is.

The urea granules in the present invention can be produced as follows. Granulation can be carried out while cooling a melt containing or encapsulating dicyandiamide, or by evaporating the solvent from a concentrated solution or slurry or powder using a binder. The method of granulating the melt while cooling it is advantageous in terms of the amount of heat used. The method for producing the melt is, for example, a method of mixing urea powder (formed) and dicyandiamide powder and heating and melting the mixture (mixing equipment includes, for example, a mixing tank, a rotating drum type mixer, a ribbon blender, a V-type blender). For heating and melting, for example, a tank having a jacket or coil using a stirring blade and a heat medium such as pressurized steam can be used.) A method of melting powdered urea and then adding dicyandiamide. (The melting point of urea is 132℃, and the steam used for heating and melting is 140-150℃, so the melting point is 132℃.
Dicyandiamide at 207-209°C was dissolved in molten urea, and analysis of the solution after it remained in the molten state for about 50 minutes revealed that only slight decomposition of urea and dicyandiamide occurred. ), a method in which dicyandiamide powder is melted and then urea powder is added and melted, a method in which dicyandiamide powder and urea powder are melted separately and then the two are mixed, etc., which requires complicated equipment and processes. It is advantageous to use the method of and in that it does not cause
Further, water, lower alcohol, etc. can be used as a solvent for a concentrated solution or slurry containing or encapsulating dicyandiamide.

The following method can be used to granulate a melt containing or encapsulating dicyandiamide, a concentrated solution or slurry, and a powder used in combination with a binder. For granulating the molten material, for example, the molten material can be injected from the top of a vertical tower using a rotating disk, pressurized nozzle, etc., and cooled air can be sent from below to solidify it within the tower. Examples include granulation methods such as granulation in a fluidized bed, granulation in a fluidized bed, and granulation in a spouted bed. Preferably, a spouted bed is used. Good results can be obtained when granulating concentrated solutions or slurries using a spouted bed, as in the case of granulating melts. When granulating the powder, a rotary pan or the like can be used. It is industrially advantageous to granulate a melt because granulation can be carried out quickly, the amount of heat transferred in a granulation device is small, and no treatment of a solvent is required.

Materials for coating fertilizer granules include synthetic resins, sulfur wax, asphalt, etc. For example, coating compositions containing polyolefin resin as a main component (for example, Japanese Patent Publication No. 3104/1983), polyvinylidene chloride, or ethylene copolymer. A composition obtained by uniformly dispersing talc and sulfur in a coating composition containing a polymer (for example, JP-A-51-75674), a resin composition containing a polyolefin resin, an ethylene-vinyl acetate copolymer resin, or a polyvinylidene chloride resin. Compositions containing alkyd resins (for example, Japanese Patent Publication No. 49-46748), compositions containing polyalkylene with a molecular weight of 10,000 or less and paraffin wax (for example, Japanese Patent Publication No. 45-922), emulsified polymers such as vinyl acetate resin latex, etc. Examples include compositions containing coalescence (for example, Japanese Patent Publication No. 37-15832), and compositions in which a first layer is coated with sulfur and a second layer thereon is coated with a wax-like substance (for example, U.S. Pat. No. 3,295,950). The coating is applied by turning the coating material into a liquid fluid such as a solution, melt, emulsion, or powder, and rolling it in a fluidized bed, spouted bed, rotating pan, rotating drum, etc., or spraying it into particles. The material is brought into contact with and adhered to the body, and then heated, cooled, and solvent removed as necessary to form a coating. It is desirable to use the coating material shown in (2) above because it is easy to control the dissolution rate of fertilizer components.

The characteristic of the fertilizer coated with urea granulated together with dicyandiamide obtained in the present invention is that when the fertilizer dissolves in water in soil and exhibits a fertilizing effect, the dissolution rate of dicyandiamide in water increases and becomes similar to that of urea. It is to show the percentage dissolution rate. Therefore, nitrification of urea can be effectively suppressed for a long period of time. These effects are observed in either granules made from molten urea mixed with dicyandiamide or concentrated solutions or slurries of urea mixed with dicyandiamide. The dicyandiamide in the coating film is not easily washed away by rain, nor does it decompose in the soil in a short period of time, maintaining its nitrification inhibiting effect.

The invention will now be illustrated by way of example.

Preparation of granules (1) Granulation (A) Granular urea containing dicyandiamide Urea powder and dicyandiamide were mixed uniformly in a V-type mixer, and then heated using steam at 4 kg/cm ² G in a tank equipped with a jacket that can be heated with steam. It is melted and sprayed onto 10 to 14 meshes of prill urea in a jet tower to adhere to it and granulate it, then cooled and
7 mesh grains were obtained.

(B) Granular Urea Urea powder was melted and granulated as described above to obtain 5 to 7 mesh granules.

(C) Granular dicyandiamide 0.5% by weight in finely powdered dicyandiamide
An aqueous polyvinyl alcohol solution was sprayed onto the mixture, and the mixture was granulated using a pan-type granulator and dried to obtain granules of 5 to 7 meshes.

(2) Coating the granules: 60 parts by weight of talc, 20 parts by weight of low-density polyethylene, 20 parts by weight of ethylene-vinyl acetate copolymer,
A hot solution of 0.5 parts by weight of a surfactant (polyoxyethylene nonyl phenyl ether) dissolved in tetrachlorethylene to give a concentration of 7% by weight is sprayed onto the granules using a jet tower and then dried to form a 5% by weight coating film. We made grains with

EXAMPLE 1 The tests in this example show that the dissolution rate of the urea coated fertilizer with dicyandiamide is close to the dissolution rate of the coated urea.

Dry soil with 2mm pass air-dried soil (cultivated soil with humic volcanic ash and alluvial soil, Gomi Island, Fuji City, Shizuoka Prefecture)
Add 200 mg of total nitrogen to 500 g of the sample obtained by the method described above.
A considerable amount of water was added, 60% of the maximum water capacity (85g water/100g dry soil) was added, and the upper edge of the container was covered with polyethylene film and left in a thermostatic chamber at 25°C. After a predetermined period had elapsed, all the samples were collected and crushed, and the components remaining inside the shell of the coating film were analyzed to calculate the elution rate. All tests were conducted in triplicate. The results are shown in Figure 1A.
and shown in B.

Figure 1-A shows the elution rate of a product in which dicyandiamide nitrogen is melted with urea and coated after granulation so that it accounts for 7% by weight of the total nitrogen, and the elution rate of urea shows the elution rate of dicyandiamide. . In FIG. 1B, the elution rate of urea is obtained when a coating is applied after melt granulation of urea alone, and the elution rate of dicyandiamide is obtained when a coating is applied to a granulation of dicyandiamide alone.

From the test of this example, it is observed that the dissolution rate (dissolution rate) of the coated dicyandiamide grains is much smaller than the dissolution amount of the coated urea grains, as shown in Figure 1-B. As shown in -A, it has been shown that when dicyandiamide is melted and granulated together with urea and coated, the elution rate of dicyandiamide is almost the same as the elution rate of urea. This indirectly indicates that dicyandiamide, a nitrification inhibitor, is eluted into the soil and exerts its effect in response to the leaching of urea.

Example 2 The tests in this example show that the coated urea fertilizer according to the invention allows a balanced presence of ammonia and nitric acid in the soil over a long period of time.

Mix fertilizer with soil under conditions similar to Example 1, pour in water, and after a predetermined period of time, add the entire amount of the fertilizer and soil mixture to a 10% potassium chloride aqueous solution that is 5 times the weight of the dry soil and leave for 30 minutes at room temperature. The solution was shaken for a minute and then the filtrate was analyzed for ammonia nitrogen and nitrate nitrogen. The results are shown in Figures 2A, B and C.

Figure 2-A shows the results when 200 mg of dicyandiamide nitrogen was melted together with urea and coated after granulation to make it 7% by weight of the total nitrogen; nitrogen,
is recovered nitrate nitrogen.

FIG. 2-B shows the results of a product coated with urea alone and granulated with dicyandiamide alone. When 200 mg of total nitrogen is added to particles coated with urea alone, recovered ammonia nitrogen indicates recovered nitrate nitrogen. When 186 mg of total nitrogen was added to the granules coated with urea alone and 14 mg of dicyandiamide nitrogen was added to the granules coated with dicyandiamide alone (equivalent to 7% by weight of dicyandiamide nitrogen), the total recovered ammonia nitrogen was recovered. Indicates nitrate nitrogen.

Figure 2-C shows the total nitrogen content of 186 mg of urea alone coated after melt granulation, and 14 mg of dicyandiamide fine powder added with dicyandiamide nitrogen, total recovered ammonia nitrogen, and recovered nitrate nitrogen. shows.

According to the test in this example, when urea alone was fused into granules and then coated, both ammonia nitrogen and nitrate nitrogen were present in the soil at the same time. It turns out that things can be kept for a long time.
When urea alone is granulated and coated, and dicyandiamide is granulated and then coated, the amount of ammonia nitrogen present is much lower than that of nitrate nitrogen in the soil.
When dicyandiamide powder is used in combination, it can be observed that the amount of ammonia nitrogen becomes smaller than that of nitrate nitrogen after about one month.

Example 3 The test of this example shows the effect of granulated and coated urea on inhibiting nitrification when the content of dicyandiamide is varied.

According to the method of Example 1, granular coated urea containing dicyandiamide containing 3%, 5%, and 15% by weight of dicyandiamide nitrogen was prepared based on the total nitrogen content.
Ammonia nitrogen and nitrate nitrogen eluted into the soil after a predetermined period of time using 200 mg were measured.
The results are shown in Figures 3A, B and C. In the figure,
, indicates ammonia nitrogen, and , indicates nitrate nitrogen.

From the results of this example, it can be observed that as the amount of dicyandiamide contained in the granular coated urea increases, the amount of ammonia nitrogen increases in the soil after 70 days, for example, and nitrification is suppressed.

Example 4 The test in this example shows damage caused by fertilization.

Air-dried soil (same soil used in Example 1)
3.5Kg and total nitrogen 1.0g in test fertilizer, P ₂ O ₅ 0.5g in superphosphate right ash, K _{2 O} 0.5g in potassium sulfate
The mixture was mixed and packed in 1/5000 are pots, and 1 g of Italian ryegrass seeds were sown and cultivated for 30 days. Urea containing 10% by weight of dicyandiamide nitrogen as a nitrogen source is fused and granulated and coated, dicyandiamide nitrogen
Melt granulated urea containing 10% by weight,
Uncoated fused granulated urea, 10% by weight of total nitrogen (equivalent to 0.1g) fertilized with dicyandiamide nitrogen
Tests were conducted using powdered dicyandiamide and coated melt-granulated urea.

Pasture grass grew normally when and was used as the nitrogen source, but when and was used as the nitrogen source, problems such as yellowing of the tips of the grass were observed.

[Brief explanation of the drawing]

Figure 1-A shows the fertilizer according to the invention in Figure 1-B.
Figure 2-A is the elution rate of urea (and) and dicyandiamide (and) of the comparison product, Figure 2-B and C are the recovered ammonia nitrogen (, and) and recovered nitrate nitrogen of the fertilizer according to the present invention. (, and) Figure 3-A, B, and C are ammonia nitrogen (, and) and nitrate nitrogen (, and) leached into the soil of the fertilizer according to the present invention.
and nitrate nitrogen (, and).

Claims (1)

[Claims] 1. A urea-based coated fertilizer characterized by having a structure in which granules obtained from a mixture of urea and dicyandiamide are coated with a film that is difficult to disintegrate with water.