JPS6330389A - Slow active nitrogen fertilizer-containing granular fertilizer - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a granular slow-release fertilizer containing a slow-release nitrogen fertilizer.

[Background of the invention] Ammonium sulfate, urea, ammonium chloride, ammonium nitrate, etc., which have traditionally been used as nitrogen fertilizers, are all easily dissolved in water and often run off before being absorbed by plants in the soil, especially in rice fields. When using nitrogen fertilizer as described above under such flooded conditions, it is difficult to effectively prevent the loss of fertilizer due to runoff.

Therefore, a technique is already known in which a nitrogen-containing organic substance that is sparingly soluble in water is used as a nitrogen fertilizer, and such nitrogen fertilizer is called a slow-release nitrogen fertilizer. Slow-release nitrogen fertilizers include oxamide, ureaform, imbutylidene diurea, guanylurea, difurfurylidene triurea,
Urea 2, glycoluril, crotonylidene urea, etc. are known. Among these slow-release nitrogen fertilizers, oxamide [(CONH2)2], for example, has excellent characteristics as a slow-release nitrogen fertilizer, such as low solubility in water and no phytotoxicity to crops. Slow-release nitrogen fertilizers such as oxamide are usually obtained in the form of powder.

However, powdered slow-release nitrogen fertilizers are decomposed and mineralized relatively quickly by decomposing bacteria in the soil (slow-release nitrogen fertilizers are decomposed into a form that plants can absorb), and they become inorganic. As with the above-mentioned ordinary nitrogen fertilizers, the converted components are easily lost due to runoff, etc., so the slow-release characteristics of slow-release nitrogen fertilizers may not be fully utilized.

Therefore, by controlling the elution of slow-release nitrogen fertilizer and suppressing the contact between slow-release nitrogen fertilizer and slow-release nitrogen fertilizer decomposing bacteria, we can reduce the mineralization rate of slow-release nitrogen fertilizer and A technology is being used that maintains the effectiveness of nitrogen fertilizer over a long period of time.

For example, as a method for producing granular powder,
Publication No. 98 is characterized in that a small amount of phosphoric acid, ammonia, an aluminum reactant, an ionic alkaline earth metal compound is added in the production of a granular chemical fertilizer containing one or more of N, P20s, and K2O. An invention related to a method for manufacturing granular fertilizer that does not disintegrate in water was further developed by
No. 8-16301 discloses an invention in which a compound based on silicic anhydride is used instead of the ionic alkaline earth metal compound mentioned above.

In other words, these inventions basically improve fertilizer components ( Specifically, the slow-release nitrogen fertilizer is mainly characterized by suppressing the elution amount of CDU, imbutylidene urea).

However, the granular fertilizer produced by the method described in the above-mentioned publication has some characteristics such as particle strength under submerged conditions and the ability of particles to maintain their shape without disintegrating in water (shape stability in water). It may not be said that the various characteristics are sufficient.

This is because powdered slow-release nitrogen fertilizers are generally difficult to mold compared to fertilizers other than slow-release nitrogen fertilizers, and even among slow-release nitrogen fertilizers, the characteristics when molding into granules are different. Therefore, if you use the conventional granulation method,
For example, powdered oxamide is particularly difficult to mold even among slow-release nitrogen fertilizers, and when oxamide is used as a slow-release nitrogen fertilizer, the above invention Even if the fertilizer is granulated using a small amount of phosphoric acid, ammonia, and aluminum reactant, it is difficult to produce a granular fertilizer with 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 excipients according to the characteristics of the slow-release nitrogen fertilizer 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 a slow-release nitrogen fertilizer 100
Slow-release nitrogen fertilizer-containing granules obtained by granulating a composition containing 10 to 350 parts by weight of an iron compound and 2 mol or more of an ammonium salt of phosphoric acid per 1 mol of the iron compound. It's in fertilizer.

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

[Detailed Description of the Invention] The granular fertilizer of the present invention basically comprises a slow-release nitrogen fertilizer;
This slow-release nitrogen fertilizer is a fertilizer made by granulating a composition containing a specific amount of an iron compound and an ammonium salt of phosphoric acid.

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

The content of slow-release nitrogen fertilizer is usually 60% by weight or less. Further, the content is preferably in the range of 5 to 40% by weight, and if the content of the slow-release nitrogen fertilizer is higher than 60% by weight, the blending ratio of components such as iron compounds and ammonium salts of phosphoric acid As a result, the hardness of the resulting particles may be low and, therefore, the mineralization of slow-release nitrogen fertilizers may not be effectively controlled.

In the present invention, ordinary slow-release nitrogen fertilizers are used.

Examples of slow-release nitrogen fertilizers include poorly soluble synthetic nitrogen compounds such as amide compounds, aldehyde and urea condensates, guanidine compounds, triazine compounds, and urea condensates. can. More specifically, an example of a poorly soluble amide compound is oxamide (Ox), and an example of a condensate of aldehyde and urea is
Ureaform (UF), imbutylidene urea (more)
, crotonylidene diurea (CDU), urea-Z, glycoluril, difurfurylidene triurea (2F3U), and examples of guanidine compounds include phosphates and sulfates of guanylurea (GU). An example of the triazine compound is cyanuric acid, and an example of its urea condensate is triuret. The slow-release nitrogen fertilizer may contain these alone or in combination of two or more types. In particular, the granular fertilizer of the present invention may use any of the above-mentioned slow-release nitrogen fertilizers. Although it has good properties even when the fertilizer contains granular fertilizers, it is possible to obtain a granular fertilizer that has good properties even when the main component is oxamide, which has poor formability even among slow-release nitrogen fertilizers. Therefore, the granular fertilizer of the present invention is suitable when using oxamide 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) per 100 parts by weight of the above slow-release nitrogen fertilizer.
Blend. If the amount of iron compound exceeds the above range, the shape stability of the fertilizer particles in water will decrease.

Although various iron compounds can be used, it is preferable to use a strong acid salt of iron.

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 from these. It is particularly preferable to use iron sulfate.
It has a composition formula of 2O, and the Fe2(SOa)s content is 50
~60% by weight is easy to use.

The ammonium salt of phosphoric acid is used in an amount of 2 moles or more per mole of the iron compound. In particular, it is preferable that the amount of ammonium salt of phosphoric acid used is within the range of 5 to 60 mol per 1 mol of the above iron compound.At least a part of this ammonium salt of phosphoric acid reacts with the above iron compound to produce It is presumed that the below-mentioned water-insoluble compound that is sparingly soluble in phosphoric acid is formed, so if the ammonium salt of phosphoric acid is less than 2 moles, the content of the phosphoric acid fertilizer component in a form that can be substantially absorbed by plants will be low. Furthermore, the underwater shape stability and hardness of the obtained granular fertilizer are reduced. In addition, if it is more than 60 moles,
Since the blending ratio of iron compounds and the like in the granular fertilizer may be low, it may not be possible to sufficiently control the elution amount of the slow-release nitrogen fertilizer.

Examples of ammonium salts of phosphoric acid include monoammonium phosphate, niummonium phosphate and ammonium polyphosphate. It is particularly preferred to use monoammonium phosphate (-ammonium phosphate), ie monoammonium phosphate has better reactivity with the above-mentioned iron compounds compared to 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 a salt as exemplified above, but may form the above-mentioned salt 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.

Although the granular fertilizer of the present invention does not require the use of an excipient, the use of an excipient such as gypsum improves the particle strength and underwater shape stability of the granular fertilizer obtained. When using gypsum, which further improves various properties, it is usually used in an amount of 5 to 200 parts by weight per 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 using gypsum, common ones such as hemihydrate gypsum and gypsum can be used.

In addition, when using gypsum, 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 adjusting the total weight of gypsum and 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, an ammonium salt of phosphoric acid, and optionally mixed gypsum, etc., and fertilizer components described below.

That is, the above components are mixed and an appropriate amount (usually 10 to 20 parts by weight of water per 100 parts by weight of the mixture) is added to the mixture.
is added, granulated using a conventional method (for example, a granulation method using a dish granulator, an extrusion granulator, etc.), and dried.

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

This water-insoluble compound has the characteristics of being insoluble or poorly soluble in water and having high hardness. By granulating as described above, the crystals become porous.The granular fertilizer of the present invention basically utilizes such characteristics of the produced water-insoluble compound,
It controls the leaching of slow-release nitrogen fertilizer from granular fertilizer.

That is, the porous crystals of the above-mentioned water-insoluble compound develop into a network, giving the granular fertilizer strength and shape stability in water. The slow-release nitrogen fertilizer (and other fertilizer components added as desired) is present in a matrix-like dispersed state in the water-insoluble compound.

When gypsum is used, the gypsum and the above-mentioned water-insoluble compounds work together to form a granular fertilizer with even higher strength and good shape stability in water. In addition, by using gypsum, the gypsum has the effect of blocking decomposing bacteria from infiltrating into the granular fertilizer, making it advantageous to control the mineralization rate of slow-release nitrogen fertilizer under field conditions. be able to do it.

The surface conditions of the porous crystals and fertilizer particles can be confirmed by depositing gold on the surface of the fertilizer particles and then observing the surface using an electron microscope at a magnification of 100 to 10,000 times. Can be done.

One of the characteristics of the granular fertilizer of the present invention is that it uses a large amount of iron compound. The use of this iron compound not only forms a water-insoluble compound in the fertilizer particles and acts to impart hardness to the fertilizer particles, but also improves the pH of the atmosphere surrounding the fertilizer when the granular fertilizer of the present invention is placed in water. It acts to lower the value. That is, when oxamide is used as a slow-release nitrogen fertilizer, its elution rate is controlled by lowering the pH value around the fertilizer particles, and furthermore, lowering the pH value also reduces the activity of oxamide-degrading bacteria. There was found.

In the granular fertilizer of the present invention, by using a large amount of iron compound as described above, it has become possible to effectively lower the pH value. That is, when oxamide is used as a slow-release nitrogen fertilizer in the granular fertilizer of the present invention, in addition to the action of the water-insoluble compound described above,
This effect of lowering the pH value lowers the elution rate and decomposition rate of oxamide.

In addition, in the granular fertilizer of the present invention, an aluminum compound may be used as a part of the above-mentioned iron compound. In other words, even if an aluminum compound is used instead of an iron compound if the amount is below a certain amount, the elution rate of the slow-release nitrogen fertilizer component is suitably suppressed, and the property that the fertilizer particles have good hardness is particularly changed. There's nothing to do.

However, in terms of effects on plants, iron is an essential element in minute amounts for plants, whereas aluminum is not an essential element in trace amounts. Therefore, the granular fertilizer of the present invention containing iron may cause chlorosis due to iron deficiency. However, as the aluminum content increases, such an effect can no longer be expected.

As an aluminum compound that can be used in place of an iron compound, a strong acid salt of aluminum is suitable;
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 preferred to use aluminum sulfate.

In addition, when using an aluminum compound, the blending ratio of the aluminum compound in the composition is usually 5% higher than that of the iron compound.
The content shall be 0 mol% or less.

It is presumed that by using the aluminum compound in this manner, some of the iron atoms in the water-insoluble compound are replaced with aluminum atoms.

In the present invention, some of the iron atoms or ammonium atoms in the water-insoluble compound may be further substituted with other atoms within a range that does not impair the properties of the water-insoluble compound.

The granular fertilizer of the present invention is a granulated product of a composition whose main components are a specific amount of slow-release nitrogen fertilizer, an iron compound, and an ammonium salt of phosphoric acid, so the explanation has focused on these, but the present invention The granular fertilizer can also be made into a composite granular fertilizer by preparing a composition containing fertilizer components other than the slow-release nitrogen fertilizer and granulating the composition.

That is, the granular fertilizer of the present invention contains nitrogen fertilizers other than slow-release nitrogen fertilizers (e.g., ammonium sulfate, ammonium nitrate, ammonium chloride, lime nitrogen, urea), phosphate fertilizers (e.g., superphosphate lime, phosphorus fertilizer), potassium fertilizer (e.g., potassium chloride), organic fertilizer (e.g., oil cake, fishmeal), trace elements (e.g., Mn, B, Cu, Zn, (
, Q) may also be included.

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

The granular fertilizer of the present invention may also contain a synthetic resin such as polyvinyl alcohol for the purpose of increasing the hardness of each particle and improving the shape stability in water.

A specific example of a composite granular fertilizer is slow-release nitrogen fertilizer5.
~20 parts by weight, 20 to 40 parts by weight of ammonium salts of phosphoric acid (preferably primary ammonium phosphate), 10 to 30 parts by weight of nitrogen fertilizers other than slow-release nitrogen fertilizers (preferably ammonium sulfate),
Examples include granulated compositions containing 10 to 30 parts by weight of a potassium fertilizer (preferably potassium chloride), 3 to 30 parts by weight of an iron compound (preferably WL iron acid), and 0.1 to 30 parts by weight of gypsum. .

Further, specific examples of compound fertilizers containing urea include 5 to 20 parts by weight of urea, 10 to 25 parts by weight of slow-release nitrogen fertilizer (preferably oxamide), and ammonium salts of phosphoric acid (preferably primary ammonium phosphate). 25-45 parts by weight, slow-release nitrogen fertilizer and nitrogen fertilizer other than urea (ammonium sulfate is preferred)5
~10 parts by weight, potassium fertilizer (preferably potassium chloride) 10~
Mention may be made of compositions comprising 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.

There are no particular restrictions on the shape and size of the granular fertilizer of the present invention, but it is usually granular or granular with a particle size within the range of 1 to 10 mm. Especially when the particle size is 1.5
Particulate or granular materials within the range of ~5.5 mm are preferable because they have good workability, such as reducing scattering during fertilization.

The granular fertilizer of the present invention has high hardness of each particle, and the particles have a particle size of 3.5 to 4.
5 mm) has an average hardness of 5 kg or more. Furthermore, it has excellent shape stability in water, as fertilizer particles are less likely to disintegrate in a short period of time when placed in water. Therefore, the mineralization rate of slow-release nitrogen fertilizer in flooded soil is reduced.

When the granular fertilizer of the present invention is used, the short-term leaching of slow-release nitrogen fertilizer in water and the outflow, which are the biggest drawbacks of conventional fertilizers, are eliminated.

It is extremely useful in practice as it exhibits extremely efficient fertilizer effects over a long period of time.

Next, Examples and Comparative Examples of the present invention will be shown.

[Example 1] Oxamide powder 10.4 parts by weight, monoammonium phosphate 3 parts
0 parts by weight, ammonium sulfate 22.1 parts by weight, chloride treatment 18.2 parts by weight, iron sulfate [Fe2(SOa) s
・XH2O, Fe2(SOa)3
Content rate 55% by weight] 17.2 parts by weight and gypsum2.
1 part by weight was thoroughly mixed using a mixer. The amount of monoammonium phosphate blended is 11.0 mol per 1 mol of iron sulfate.

Next, 13 parts by weight of water was added to 100 parts by weight of this mixture, granulated using a plate 5 granulator, and the granules were heated and dried to form loose particles having a diameter within the range of 2 to 5 mm. A granular fertilizer containing effective nitrogen fertilizer was obtained.

The obtained granular fertilizer was subjected to gold vapor deposition according to a conventional method, and then subjected to an electron microscope (JXA-50A, manufactured by JEOL Ltd.).
When observed at a magnification of 5,000 times, it was confirmed that porous crystals had grown in each fertilizer particle.

In addition, in the Examples and Comparative Examples described below, the observation of fertilizer particles was carried out by the above-mentioned method.

[Example 2] 2~
A slow-release nitrogen fertilizer-containing granular fertilizer with a diameter in the range of 5 mm was obtained. Note that the blending amount of monoammonium phosphate is 22.2 mol per 1 mol of iron sulfate.

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

[Example 3] 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 slow-release nitrogen fertilizer-containing granular fertilizer with a diameter in the range of 5 mm was obtained. The amount of monoammonium phosphate blended is 32.5 moles per mole of iron sulfate.

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

[Comparative Example 1] A slow-release nitrogen fertilizer having a diameter within 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 gypsum was changed to 19.3 parts by weight. A containing granular fertilizer was obtained.

[Evaluation Items] Each of the slow-release nitrogen fertilizer-containing granular fertilizers obtained in Examples 1 to 3 and Comparative Example 1 was evaluated as a slow-release nitrogen fertilizer based on hardness, pH value, shape stability in water, and inorganic This was carried out by testing each item of conversion rate. These test methods are as follows. In addition, in the test described below, among the obtained granular fertilizers, those having particle diameters in the range of 3.5 to 4.5 mm were selected and used.

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

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

Shape stability in water: 10 granular fertilizer particles containing slow-release nitrogen fertilizer were placed in a beaker containing 100 m of water (25°C) to prepare four samples, and after 1 hour, the particles in each beaker were The disintegration rate was calculated by determining the number of particles whose shape had disintegrated, and was expressed as the average value of the calculated disintegration rates.

Mineralization rate of oxamide in flooded soil: Air drying ± [from Futsukaichi soil (sandy loam)] Take 15g in a 50mJL beaker, add 25ml of water, stir well to expel air, and slowly 0.13 g of granular fertilizer containing effective nitrogen fertilizer was added and left to stand for 1 hour. Next, 45 g of the above air-dried fertilizer was further added to make it flooded, and it was left to stand in a constant temperature room at 30°C. After a predetermined period of time had elapsed, the amount of oxamide remaining in water, soil, and fertilizer was quantified to determine the proportion of oxamide that had been decomposed and mineralized (mineralization rate).

The evaluation results are shown in Table 1.

All white Table 1 below (kg) Stability ($) 1 week 2 weeks 3 weeks 4i
! Example 1 7.4 2.5 10 13.332.55
0.759.22 7.3 3.1 15 14
．． 935.055.261.33 7.0 3.6
25 15.836.857.366.2 Comparative Example 1 2.8 4.4 85 20.139.36
1.170.7 [Example 4] In Example 1, the blending amount of oxamide was 14.0 parts by weight, the blending amount of ammonium phosphate was 3'7.0 parts by weight, and the blending amount of ammonium sulfate was 8.8 parts by weight. Part by weight, the amount of iron sulfate is 8.
6 parts by weight, the amount of chloride treatment was 20.8 parts by weight, the amount of gypsum was 0.8 parts by weight, and the amount of urea was 10.8 parts by weight.
A slow-release nitrogen fertilizer-containing granular fertilizer having a diameter within the range of 2 to 5 mm was obtained in the same manner except that 0 weight parts were combined. The amount of monoammonium phosphate blended is 26.8 moles per mole of iron sulfate.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer include:
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 slow-release nitrogen fertilizer-containing granular fertilizer with a diameter in the range of 5 mm was obtained. The amount of monoammonium phosphate blended per 1 mole of iron sulfate is 41.2 moles.

The fertilizer particles of the obtained granular fertilizer containing slow-release nitrogen fertilizer include:
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 amount of monoammonium phosphate blended is 52.7 moles per mole of iron sulfate.

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

[Comparative Example 2] Containing slow-release nitrogen fertilizer having a diameter within the range of 2 to 5 mm in the same manner as in Example 4, except that iron sulfate was not mixed and the amount of gypsum was changed to 9.4 parts by weight. Granular fertilizer was produced.

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

The evaluation results are shown in Table 2.

Table 2 (kg) Stability (z) 1 week 2 weeks 3 weeks
4 Week Example 4 G, 8 3.0 0 1? ,83125
4.373.85 6.9 3.2 5 21
．． 637.255.7711126 7.5 3.0
? 0 31551.978.394.2 Comparative example

Claims (1)

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