JPH062628B2 - Granular fertilizer containing slow-release nitrogen fertilizer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a granular slow-release fertilizer containing a slow-release nitrogen fertilizer.

BACKGROUND OF THE INVENTION Ammonium sulfate, urea, ammonium salt, ammonium nitrate, etc., which have been conventionally used as nitrogen fertilizers, are all easily dissolved in water and often flow out in soil before they are absorbed by plants. Particularly, when the above nitrogen fertilizer is used under the flooded condition such as a paddy field, it is difficult to effectively prevent the loss of the fertilizer flowing out.

Therefore, there is already known a technique of using a nitrogen-containing poorly soluble organic substance as a nitrogen fertilizer, and such a nitrogen fertilizer is called a slow-release nitrogen fertilizer. Slow-acting nitrogen fertilizers include oxamide, ureaform, isobutylidene diurea, guanylurea, diflufurylidene triurea,
Urea-Z, glycoluril, crotonylidene diurea and the like are known. Among such slow-release nitrogen fertilizers, for example, oxamide [(CONH ₂ ) ₂ ] has excellent properties as a slow-release nitrogen fertilizer, such as low solubility in water and no chemical damage to crops. It has, and has already been put to practical use in some areas. Slow-release nitrogen fertilizers such as oxamide are usually obtained as powders.

However, powder-form slow-release nitrogen fertilizers are relatively quickly decomposed by degrading bacteria in soil and mineralized (meaning that slow-release nitrogen fertilizers are decomposed to a form that can be absorbed by plants). The converted components are likely to be lost due to runoff as in the case of the above-mentioned ordinary nitrogen fertilizers, so that the slow-acting characteristics of the slow-release nitrogen fertilizers may not be fully utilized.

Therefore, by controlling the elution of the slow-release nitrogen fertilizer to suppress the contact between the slow-release nitrogen fertilizer and the slow-release nitrogen fertilizer-decomposing bacteria, the mineralization rate of the slow-release nitrogen fertilizer is reduced and the slow-release nitrogen fertilizer is released. The technology is used to maintain the fertilizing effect of nitrogenous fertilizers for a long period of time.

For example, as a method for producing granular fertilizer, Japanese Patent Publication No. 48-162
In Japanese Patent Publication No. 98, a small amount of phosphoric acid, ammonia, and ammonia in the production of granular compound fertilizer containing one or more of N, P ₂ O ₅ and K ₂ O.
An invention relating to a method for producing granular fertilizer which does not disintegrate in water, which is characterized by adding an ionic alkaline earth metal compound to an aluminum reactant, is further disclosed in JP-B-48-163.
No. 01 discloses an invention in which a compound mainly containing silicic acid anhydride is used in place of the above ionic alkaline earth metal compound.

That is, these inventions basically include a small amount of phosphoric acid / ammonia / aluminum reaction product necessary for maintaining the shape of the granular fertilizer in the submerged condition in the granular fertilizer to thereby improve the fertilizer component ( Specifically, the slow-release nitrogen fertilizer is mainly characterized by suppressing the elution amount of CDU and isobutylidene urea.

However, the granular fertilizer produced by the method described in the above publication has the following characteristics: particle strength under flooded conditions and characteristics that particles maintain their shape without collapsing in water (underwater shape stability). In some characteristics, it may not be said to be sufficient. This is a powder of slow-release nitrogen fertilizer,
Compared with fertilizers other than slow-release nitrogen fertilizers, it is generally difficult to form, and even among slow-release nitrogen fertilizers, the characteristics when forming into granules are different, so using the conventional granulation method, This is because the type and amount of excipient component are often inappropriate. For example, powdery oxamide is particularly difficult to mold among slow-release nitrogen fertilizers, and when oxamide is used as the slow-release nitrogen fertilizer, a small amount of phosphoric acid / ammonia / aluminum reactant is used by utilizing the above invention. Even if granulated, it is difficult to produce granular fertilizer having good particle hardness and shape stability in water.

Therefore, when granulating using a slow-release nitrogen fertilizer, it is necessary to select the type and amount of the excipient according to the characteristics of the slow-release nitrogen fertilizer to be used.

[Object of the Invention] An object of the present invention is to provide a granular slow-release fertilizer containing a slow-release nitrogen fertilizer having sufficient hardness and good shape stability in water.

SUMMARY OF THE INVENTION The present invention provides a slow-release nitrogen fertilizer and the slow-release nitrogen fertilizer 100.
Granules containing slow-release nitrogen fertilizer obtained by granulating a composition containing 10 to 350 parts by weight with respect to parts by weight of an iron compound and 2 mol or more of ammonium salt of phosphoric acid per 1 mol of the iron compound It is in fertilizer.

[Effects of the Invention] Since the granular fertilizer of the present invention has high hardness of each particle and is less likely to disintegrate in water, the elution rate of the slow-release nitrogen fertilizer can be effectively suppressed. Therefore, the rate of mineralization of the slow-release nitrogen fertilizer can be effectively controlled.

DETAILED DESCRIPTION OF THE INVENTION The granular fertilizer of the present invention is basically a slow-release nitrogen fertilizer,
This is a fertilizer in which a composition containing a specific amount of an iron compound and an ammonium salt of phosphoric acid is granulated with respect to the slow-release nitrogen fertilizer.

The granular fertilizer of the present invention contains a slow-release nitrogen fertilizer.

The content rate of the slow-release nitrogen fertilizer is usually 60% by weight or less. Further, it is preferable that the content is in the range of 5 to 40% by weight. When the content rate of the slow-release nitrogen fertilizer is higher than 60% by weight, the compounding rate of components such as iron compounds and ammonium salts of phosphoric acid becomes low, so that the hardness of the obtained particles may be low, Therefore, it may not be possible to effectively control the mineralization of the slow-release nitrogen fertilizer.

In the present invention, as the slow-release nitrogen fertilizer, usual one is used.

Examples of slow-release nitrogen fertilizers include sparingly soluble synthetic nitrogen compounds and sparingly soluble amide compounds, condensates of aldehydes and urea, or guanidine-based compounds, triazine-based compounds, and urea-type condensates. it can. More specifically, examples of the sparingly soluble amide compound include oxamide (OX), and examples of the condensate of aldehyde and urea include
Ureaform (UF), isobutylidene diurea (I
B), crotonylidene diurea (CDU), urea-Z,
Glycoluril, diflufurylidene triurea (2F3
U), and examples of guanidine compounds include guanylurea (GU) phosphates and sulfates. Moreover, cyanuric acid can be mentioned as an example of a triazine-based compound, and triuret can be mentioned as an example of its urea condensate. The slow-release nitrogen fertilizer may be a single type of these or a combination of two or more types.
In particular, the granular fertilizer of the present invention has good characteristics even when any of the slow-release nitrogen fertilizers described above is used, but particularly, among the slow-release nitrogen fertilizers, the formability is excellent. Even if the main component is bad oxamide, it is possible to obtain a granular fertilizer having good characteristics. Therefore, the granular fertilizer of the present invention is suitable when oxamide is used as a main component as a slow-release nitrogen fertilizer.

The iron compound is 10 to 350 parts by weight (preferably 40 to 200 parts by weight) with respect to 100 parts by weight of the above-mentioned slow-release nitrogen fertilizer.
Compound. If the amount of the iron compound deviates from the above range, the shape stability of the fertilizer particles in water will deteriorate.

Although various kinds of iron compounds can be used, it is preferable to use a strong iron acid salt. Examples of such iron compounds include iron sulfate, iron chloride and iron nitrate. In the present invention, one or more iron compounds are appropriately selected and used.
It is particularly preferable to use iron sulfate. Further, iron sulfate has a composition formula of Fe ₂ (SO ₄ ) ₃ · xH ₂ O and F
e ₂ (SO ₄ ) ₃ content of 50 to 60% by weight is easy to use.

The ammonium salt of phosphoric acid is used in an amount of 2 mol or more per 1 mol of the iron compound. In particular, the amount of ammonium salt of phosphoric acid used is preferably in the range of 5 to 60 mol per 1 mol of the iron compound. It is speculated that at least a part of the ammonium salt of phosphoric acid reacts with the iron compound to form a water-insoluble compound which will be described later and is sparingly soluble in water. The content of the phosphate fertilizer component in a form that can be substantially absorbed by the plant is reduced, and further the shape stability and hardness of the obtained granular fertilizer in water are reduced. On the other hand, if it is more than 60 mols, the compounding ratio of the iron compound or the like in the granular fertilizer may be low, so that the elution amount of the slow-release nitrogen fertilizer may not be sufficiently controlled.

Examples of ammonium salts of phosphoric acid include monoammonium phosphate, diammonium phosphate and ammonium polyphosphate. Particularly, it is preferable to use monoammonium phosphate (monophosphorous ammonium). That is, monoammonium phosphate has better reactivity with the above-mentioned iron compound than other ammonium salts of phosphoric acid.

However, in the present invention, the ammonium salt of phosphoric acid does not need to be added to the composition in the form of the salts exemplified above, and may form the above salts such as phosphoric acid and ammonia. It may be added in the form of an acid and a base (eg phosphoric acid and aqueous ammonia), or two or more salts.

The granular fertilizer of the present invention does not require the use of excipients, but by using an excipient such as gypsum, the granular strength and the underwater shape stability of the obtained granular fertilizer can be obtained. The various characteristics of are further improved. When gypsum is used, it is usually used in an amount of 5 to 200 parts by weight based on 100 parts by weight of the above-mentioned slow-release nitrogen fertilizer. If it deviates from the above range, the strength and shape stability in water of the obtained granular fertilizer may not be sufficiently improved.

When gypsum is used, ordinary ones such as hemihydrate gypsum and dihydrate gypsum can be used.

When gypsum is used, the total weight of gypsum and iron compound in the granular fertilizer of the present invention is 0.5 to 2.5 times the weight of the slow-release nitrogen fertilizer contained in the granular fertilizer. It is particularly preferable to adjust the blending amount of each component so that it falls within the range. By setting the total weight of the gypsum and the iron compound as described above, the underwater shape stability and hardness of the granular fertilizer are further improved.

The granular fertilizer of the present invention is a granulated product of a composition containing a slow-release nitrogen fertilizer, an iron compound and an ammonium salt of phosphoric acid, optionally mixed gypsum, and the fertilizer components described below.
That is, the above-mentioned components are mixed, an appropriate amount (usually 10 to 20 parts by weight of water relative to 100 parts by weight of the mixture) is added thereto, and a conventional method (for example, a plate type granulator, an extrusion granulator) is added. It is obtained by granulating using a granulation method using the above) and drying.

By granulating the composition in this manner, in the granular fertilizer of the present invention, at least a part of the above-mentioned iron compound and ammonium salt of phosphoric acid react to form a compound insoluble or hardly soluble in water. It is presumed to be a thing.

This water-insoluble compound is insoluble or sparingly soluble in water and has a property of high hardness. Then, by granulating as described above, the crystal becomes porous. The granular fertilizer of the present invention basically utilizes such characteristics of the produced water-insoluble compound,
It controls the release of slow-release nitrogen fertilizers from granular fertilizers.

That is, the above-described porous crystals of the water-insoluble compound develop in a mesh shape to give strength and shape stability in water to the granular fertilizer. The slow-release nitrogen fertilizer (and other fertilizer components optionally mixed) is present in the above water-insoluble compound in a matrix-like dispersed state.

When gypsum is used, the gypsum and the above water-insoluble compound work together to form a granular fertilizer having higher strength and good shape stability in water. Further, by using gypsum, gypsum has the effect of blocking the invasion of degrading bacteria into the granular fertilizer, so it is advantageous to control the mineralization rate of slow-release nitrogen fertilizer in field conditions. You will be able to do it.

The state of the surface of the porous crystals and the fertilizer particles should be confirmed by performing gold vapor deposition on the surface of the fertilizer particles and then observing the surface at a magnification within a range of 1000 to 10000 using, for example, an electron microscope. You can

One of the characteristics of the granular fertilizer of the present invention is that a large amount of iron compound is used. The use of this iron compound simply acts to form a water-insoluble compound in the fertilizer particles and impart hardness to the fertilizer particles, and the pH of the atmosphere around the fertilizer in which the granular fertilizer of the present invention is put into water. It acts to reduce the value. That is, when oxamide is used as a slow-release nitrogen fertilizer, its dissolution rate is controlled by lowering the pH value around the fertilizer particles, and further lowering of the pH value also reduces the activity of oxamide-degrading bacteria. There was found.

Then, in the granular fertilizer of the present invention, it becomes possible to effectively lower the pH value by using a large amount of iron compound as described above. That is, when oxamide is used as the slow-release nitrogen fertilizer in the granular fertilizer of the present invention, in addition to the action of the above water-insoluble compound, the action of decreasing the pH value causes the dissolution rate and decomposition rate of oxamide. It will decrease.

In the granular fertilizer of the present invention, an aluminum compound may be used as a part of the above iron compound. That is, even if an aluminum compound is used instead of the iron compound if the amount is a certain amount or less, the elution rate of the slow-release nitrogen fertilizer component is suitably suppressed, and the characteristics that the fertilizer particles have good hardness are particularly changed. There is nothing to do.

However, in the action on plants, iron is a trace essential element of plants, whereas aluminum is not a trace essential element of plants. Therefore, while the granular fertilizer of the present invention contains iron, an effect of preventing the occurrence of chlorosis and the like due to iron deficiency can be expected, whereas such an effect cannot be expected as the content rate of aluminum increases.

As the aluminum compound that can be used instead of the iron compound, a strong acid salt of aluminum is preferable,
Specific examples include aluminum sulfate, aluminum chloride and aluminum nitrate, and one or more aluminum compounds can be selected from these and used. It is particularly preferable to use aluminum sulfate.

When an aluminum compound is used, the compounding ratio of the aluminum compound in the composition is usually 5 times that of the iron compound.
It is 0 mol% or less.

It is presumed that a part of iron atoms in the water-insoluble compound is replaced with aluminum atoms by using the aluminum compound in this way. In the present invention, within the range that does not impair the properties of the water-insoluble compound,
A part of iron atom or ammonium atom in the water-insoluble compound may be further substituted with another atom.

Since the granular fertilizer of the present invention is a granulated product of a composition containing a specific amount of a slow-release nitrogen fertilizer, an iron compound and an ammonium salt of phosphoric acid as main components, the explanation has been given centering on these. The granular fertilizer can also be prepared as a composite granular fertilizer by preparing a composition containing a fertilizer component other than the slow-release nitrogen fertilizer and granulating the composition.

That is, the granular fertilizer of the present invention includes, in addition to the above components, nitrogen fertilizers other than slow-release nitrogen fertilizers (eg, ammonium sulfate, ammonium nitrate, ammonium nitrate, lime nitrogen, urea), phosphate fertilizers (eg, superphosphate lime iodine). Phosphorus fertilizer), potash fertilizer (eg, potassium chloride), organic fertilizer (eg, oil residue, fish meal), trace elements (eg, Mn, B, Cu, Zn,)
Cl) may be included.

When the above-mentioned fertilizer is mixed, the total content of the above-mentioned fertilizer components is usually 80% by weight or less (preferably 60% by weight or less).

The granular fertilizer of the present invention may be mixed with a synthetic resin such as polyvinyl alcohol for the purpose of increasing the hardness of each particle to improve the shape stability in water.

A specific example of compound granular fertilizer is slow-release nitrogen fertilizer 5
˜20 parts by weight, ammonium salt of phosphoric acid (preferably primary ammonium phosphate) 20 to 40 parts by weight, nitrogen fertilizer other than slow-release nitrogen fertilizer (preferably ammonium sulfate) 10 to 30 parts by weight,
An example is a granulated product of a composition containing 10 to 30 parts by weight of potassium fertilizer (preferably potassium chloride), 3 to 30 parts by weight of an iron compound (preferably iron sulfate), and 0.1 to 30 parts by weight of gypsum.

Further, as specific examples of the compound fertilizer containing urea, 5 to 20 parts by weight of urea, 10 to 25 parts by weight of slow-release nitrogen fertilizer (preferably oxamide), ammonium salt of phosphoric acid (preferred ammonium phosphate) are preferable. 25 to 45 parts by weight, slow-release nitrogen fertilizer and nitrogen fertilizers other than urea (ammonium sulfate is preferred) 5
-10 parts by weight, potassium fertilizer (preferably potassium chloride) 10
A composition containing 30 parts by weight, 2 to 20 parts by weight of an iron compound (preferably iron sulfate), and 0.1 to 15 parts by weight of gypsum can be mentioned.

There is no particular limitation on the shape and size of the granular fertilizer of the present invention, but it is usually granular or granular having a particle diameter within the range of 1 to 10 mm. Especially the particle size is 1.5 ~
Granules or granules within the range of 5.5 mm are
It is preferable because it has good workability such as scattering during fertilization.

In the granular fertilizer of the present invention, the hardness of each particle is high, and the particles (particle diameter 3.5 to 4.
The average hardness of 5 mm) is 5 kg or more. further,
Excellent shape stability in water, such as when fertilizer particles are less likely to collapse in a short time when placed in water. Therefore, the mineralization rate of the slow-release nitrogen fertilizer in flooded soil is reduced.

When the granular fertilizer of the present invention is used, short-term leaching and runoff of the slow-release nitrogen fertilizer in water, which has been the biggest drawback of conventional fertilizers, is eliminated, and extremely long-term fertilization effect is exhibited. In that respect, it is very useful in practice.

Next, examples and comparative examples of the present invention will be shown.

[Example] 10.4 parts by weight of oxamide powder, monoammonium phosphate 3
0 parts by weight, ammonium sulfate 22.1 parts by weight, potassium chloride 18.2 parts by weight, iron sulfate [Fe ₂ (SO ₄ ) ₃ xH ₂ O,
Fe ₂ (SO ₄ ) ₃ content of 55% by weight] 17.2 parts by weight and gypsum 2.1 parts by weight were thoroughly mixed with a mixer. In addition,
The amount of monoammonium phosphate mixed with 1 mol of iron sulfate is
11.0 mol.

Then, 13 parts by weight of water was added to 100 parts by weight of this mixture, and the mixture was granulated using a plate-type granulator, and the granulated product was heat-dried to have a slow-release property having a diameter in the range of 2 to 5 mm. A granular fertilizer containing nitrogen fertilizer was obtained.

After subjecting the obtained granular fertilizer to a gold vapor deposition treatment according to a conventional method, it was observed with an electron microscope (JXA-50A, manufactured by JEOL Ltd.) at a magnification of 5000 times.
It was confirmed that porous crystals were growing.

In the examples and comparative examples described below, the fertilizer particles were observed by the above method.

[Example 2] In the same manner as in Example 1 except that the amount of iron sulfate was 8.6 parts by weight and the amount of gypsum was 10.7 parts by weight.
A granular fertilizer containing slow-release nitrogen fertilizer with a diameter in the range of 5 mm was obtained. The amount of primary ammonium phosphate mixed with 1 mol of iron sulfate was 22.2 mol.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer,
It was confirmed that porous crystals were growing.

[Example] In the same manner as in Example 1 except that the amount of iron sulfate was 5.8 parts by weight and the amount of gypsum was 13.5 parts by weight.
A granular fertilizer containing slow-release nitrogen fertilizer with a diameter in the range of 5 mm was obtained. The compounding amount of monoammonium phosphate with respect to 1 mol of iron sulfate was 32.5 mol.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer,
It was confirmed that porous crystals were growing.

[Comparative Example 1] A slow-release nitrogen fertilizer having a diameter in the range of 2 to 5 mm in the same manner as in Example 1 except that iron sulfate was not used and the amount of plaster was 19.3 parts by weight. The contained granular fertilizer was obtained.

[Evaluation Items] Evaluation of each of the slow-release nitrogen fertilizer-containing granular fertilizers obtained in Examples 1 to 3 and Comparative Example 1 as a slow-release nitrogen fertilizer was carried out using hardness, pH value, shape stability in water and inorganic content. It was carried out by testing each item of the conversion rate. These test methods are as follows. In the tests described below, the particle size of the obtained granular fertilizer was 3.
Those in the range of 5 to 4.5 mm were selected and used.

Hardness: The average value of 10 particles of slow-release nitrogen fertilizer-containing granular fertilizer particles measured with a Kiya type hardness meter is shown.

pH value: 1 g of granular fertilizer particles containing slow-release nitrogen fertilizer was added to 100 ml of water (25 ° C.) and sufficiently stirred to obtain a suspended state, and the pH of this aqueous suspension was measured.

Underwater shape stability: 10 beakers containing 100 ml of water (25 ° C) were charged with 10 granular fertilizer particles containing slow-release nitrogen fertilizer to prepare 4 particles, and after 1 hour, the shape of the particles in each beaker The number of particles disintegrated was calculated to calculate the disintegration rate, and the average disintegration rate was shown.

Mineralization rate of oxamide in flooded soil: 15 g of air-dried soil [from Fukkaichi soil (sand loam soil)]
It was taken in a 0 ml beaker, 25 ml of water was added thereto, and the mixture was well stirred to expel air, then 0.13 g of granular fertilizer containing slow-release nitrogen fertilizer was added and left for 1 hour. Next, add 45 g of the above-mentioned air-dried soil to make a submerged state, and 30 ° C.
It was left standing in a constant temperature room. After a lapse of a predetermined time, quantify the amount of oxamide remaining in water, soil and fertilizer,
The ratio of the decomposed and mineralized oxamide (mineralization rate) was determined.

The evaluation results are shown in Table 1.

Example 4 In Example 1, the compounding amount of oxamide was 14.0 parts by weight, and the compounding amount of primary ammonium phosphate was 37.0 parts by weight.
The amount of ammonium sulfate is 8.8 parts by weight, and the amount of iron sulfate is 8.6.
Parts by weight, the amount of potassium chloride added is 20.8 parts by weight, and the amount of gypsum is 0.8 parts by weight.
A granular fertilizer containing slow-release nitrogen fertilizer having a diameter within the range of 2 to 5 mm was obtained in the same manner except that the weight ratio was mixed. In addition,
The amount of monoammonium phosphate mixed with 1 mol of iron sulfate is
It is 26.8 mol.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer,
It was confirmed that porous crystals were growing.

[Example 5] In the same manner as in Example 4 except that the amount of iron sulfate was 5.7 parts by weight and the amount of gypsum was 3.7 parts by weight.
A granular fertilizer containing slow-release nitrogen fertilizer with a diameter in the range of 5 mm was obtained. The compounding amount of monoammonium phosphate with respect to 1 mol of iron sulfate was 41.2 mol.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer,
It was confirmed that porous crystals were growing.

[Example 6] In the same manner as in Example 4, except that the amount of iron sulfate was 4.4 parts by weight and the amount of gypsum was 5.0 parts by weight.
A slow-release nitrogen-containing granular fertilizer with a diameter in the range of 5 mm was obtained. The compounding amount of monoammonium phosphate with respect to 1 mol of iron sulfate was 52.7 mol.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer,
It was confirmed that porous crystals were growing.

[Comparative Example 2] In Example 4, similarly containing a slow-release nitrogen fertilizer having a diameter in the range of 2 to 5 mm, except that the amount of gypsum was 9.4 parts by weight without adding iron sulfate. Granulated fertilizer was produced.

Regarding the slow-release nitrogenous fertilizer-containing granular fertilizers obtained in Examples 4 to 6 and Comparative Example 2 described above, the hardness of fertilizer particles, the pH value, the shape stability in water, and the inorganic content of oxamide in flooded soil were determined in the same manner as above. The rate of conversion was evaluated.

The evaluation results are shown in Table 2.

Claims (5)

[Claims] 1. A slow-release nitrogen fertilizer, and said slow-release nitrogen fertilizer 10.
10 to 350 parts by weight of an iron compound with respect to 0 parts by weight,
Granular fertilizer containing slow-release nitrogen fertilizer obtained by granulating a composition containing 2 mol or more of ammonium salt of phosphoric acid per 1 mol of the iron compound. 2. The composition further comprises the slow-release nitrogen fertilizer 100.
The granular fertilizer containing slow-release nitrogen fertilizer according to claim 1, which contains 5 to 200 parts by weight of gypsum with respect to parts by weight. 3. The slow-release nitrogen fertilizer according to claim 1, wherein the iron compound is at least one iron compound selected from the group consisting of iron sulfate, iron chloride and iron nitrate. Granular fertilizer. 4. The slow-release nitrogenous fertilizer-containing granular fertilizer according to claim 1, wherein the ammonium salt of phosphoric acid is monoammonium phosphate. 5. The slow-release nitrogen fertilizer-containing granular fertilizer according to claim 1, wherein the slow-release nitrogen fertilizer contains oxamide.