HK40108392A - Intermediate-release fertilizers and methods for making same - Google Patents

Description

Medium-release fertilizers and their preparation methods

Cross-references to related applications

This application claims priority to U.S. Application No. 63/262968, filed October 23, 2021, entitled “INTERMEDIATE-RELEASE FERTILIZERS AND METHODS FOR MAKING SAME,” which is incorporated herein by reference for all purposes. For U.S. purposes, this application claims the benefit of U.S. Application No. 63/262968, filed October 23, 2021, entitled “INTERMEDIATE-RELEASE FERTILIZERS AND METHODS FOR MAKING SAME,” pursuant to 35 U.S.C. § 119, which is incorporated herein by reference for all purposes.

Technical Field

This invention relates to plant fertilizers. Some embodiments of the invention provide nutrient release over an intermediate timescale. Some embodiments of the invention provide methods for manufacturing such fertilizers.

background

Nitrogen (N), phosphorus (P), and potassium (K) are the main nutrients required for plant growth and development. For example, phosphorus helps transfer energy from sunlight to plants, stimulates early root and plant growth, and accelerates maturation. Fertilizers provide nutrients to plants in an available form so that plants can absorb them as needed, thereby promoting plant growth and development. Fertilizers may also contain other active substances, including minor nutrients such as magnesium (Mg), sulfur (S), and calcium (Ca); micronutrients such as boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), and nickel (Ni); pesticides; herbicides; etc.

A problem with some fertilizers is that their composition contains one or more substances that can damage plant roots and/or seedlings when applied. This can reduce germination rates or harm developing root systems, thereby reducing crop yields.

Ideal fertilizers release nutrients efficiently, providing optimal plant growth throughout or part of the growing season. Some fertilizers contain water-soluble components. Highly water-soluble components rapidly penetrate the soil and can be lost through leaching, runoff, or chemical binding with soil minerals. Other fertilizers contain components that are essentially insoluble in water. These components can be released over longer timescales, providing nutrients to plants over a longer period. Fertilizers that deliver nutrients to plants at the optimal release rate offer plants a better chance of nutrient uptake. Such fertilizers minimize the leaching, runoff, or chemical binding of fertilizer components.

There is a need for improved fertilizer compositions that can efficiently provide nutrients (especially phosphorus) to plants. There is also a need for improved fertilizer compositions that reduce damage to roots and/or seedlings caused by fertilizer application.

The foregoing examples and related limitations of the related art are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those skilled in the art upon reading the specification and studying the accompanying drawings.

Overview

This invention has several aspects. One aspect provides a fertilizer that, upon application, tends to release phosphorus in a plant-available form at a rate faster than slow-release fertilizers that provide phosphorus in the form of slightly water-soluble compounds such as struvite, and slower than fast-release fertilizers that provide phosphorus in the form of highly water-soluble compounds such as monoammonium phosphate (MAP) or diammonium phosphate (DAP). Such fertilizers may be referred to as “medium-release” fertilizers. Medium-release fertilizers may contain one or more “medium-release” phosphorus sources. The solubility of medium-release phosphorus sources in water is greater than that of slightly soluble compounds such as struvite, and less than that of highly water-soluble compounds such as MAP or DAP. The medium-release fertilizers described herein are capable of releasing plant-available phosphorus and other nutrients to crops at a rate higher than that of fertilizers containing only slow-release phosphorus sources but lower than that of fertilizers containing only fast-release phosphorus sources.

The inventors have identified schertelite as a good source of moderately released phosphorus. Schertelite is a compound having the following composition: Mg( _NH₄ ) _₂H₂ ( _PO₄ ) _₂ - _{4H₂O .}

In some implementation schemes:

• The fertilizer consists of granules that include a medium-release phosphorus source (e.g., magnesium phosphate rock);

• The fertilizer consists of granules that include both a medium-release phosphorus source (e.g., magnesium hydride) and a slow-release phosphorus source (e.g., struvite).

• The fertilizer consists of granules comprising both a medium-release phosphorus source (e.g., magnesium hydride phosphate rock) and a fast-release phosphorus source (e.g., water-soluble phosphorus-containing materials such as MAP and/or DAP); and

• The fertilizer consists of granules that include medium-release phosphorus sources (e.g., magnesium hydride phosphate), slow-release phosphorus sources (e.g., struvite), and fast-release phosphorus sources (e.g., water-soluble phosphorus-containing materials such as MAP and/or DAP).

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent from the accompanying drawings and the following detailed description.

Brief description of the attached diagram

Exemplary embodiments are shown in the accompanying drawings. The embodiments and drawings disclosed herein are intended to be illustrative and not restrictive.

Figure 1 is a graph illustrating the release curve of an exemplary fertilizer according to the implementation scheme.

Figure 2 is an enlarged view of the fertilizer granules according to the first embodiment.

Figure 3 is an enlarged view of the fertilizer granules according to the second embodiment.

Figure 4 is an enlarged view of the fertilizer granules according to the third embodiment.

Figure 5 is an enlarged view of the fertilizer granules according to the fourth embodiment.

Figure 6 is a process flow diagram illustrating a first exemplary method for manufacturing fertilizer granules.

Figure 7 is a process flow diagram illustrating a second exemplary method for manufacturing fertilizer granules.

Figure 8 is a graph showing the germination rate of rapeseed as a function of phosphate application rate for the various phosphorus sources listed in Table 2.

describe

Specific details are set forth throughout the following description to provide a more complete understanding to those skilled in the art. However, well-known elements may not have been shown or described in detail to avoid unnecessarily obscuring the contents of this disclosure. Therefore, this specification and drawings should be viewed in an illustrative rather than restrictive sense.

Fertilizers containing moderate phosphorus sources (especially magnesium phosphate rock).

This invention relates to fertilizers comprising a moderately released phosphorus source. The moderately released phosphorus source releases phosphorus for plant uptake at a rate between that of a fast-release phosphorus source (such as MAP or DAP) and that of a slow-release phosphorus source (such as struvite). In some embodiments, the moderately released phosphorus source comprises or is composed of magnesium phosphate dihydrogen phosphate.

Magnesium phosphate hydride has the chemical formula ( _NH₄ ) _₂MgH₂ ( _{PO₄ ) ₂} ·4( _H₂O ). It consists of approximately 8.6 wt% nitrogen, 43.8 wt% _P₂O₅ , and 7.5 wt% magnesium _. Magnesium phosphate hydride can be formed by reacting a phosphorus source with a magnesium source. The phosphorus source can be, for example, monoammonium phosphate (MAP), diammonium phosphate (DAP), struvite (or magnesium ammonium phosphate with the chemical formula _MgNH₄PO₄ · _6H₂O ), and/or raw materials for forming these compounds such as phosphoric acid and ammonia. The magnesium source can be, for example, _periclase (also known as magnesium oxide with the chemical formula MgO) and/or brucite (also known as magnesium hydroxide Mg(OH) _₂ ).

In some embodiments, the content of magnesium phosphate rock in the fertilizer ranges from about 2% by weight to about 80% by weight or from about 5% by weight to about 80% by weight. In some embodiments, the content of magnesium phosphate rock in the fertilizer is at least 10% by weight or greater than about 10% by weight. In some embodiments, the content of magnesium phosphate rock in the fertilizer is about 45% by weight.

Fast-release phosphorus sources have high water solubility, which allows them to penetrate rapidly into the soil upon application. Fast-release phosphorus sources can have a solubility in water at 20°C, for example, exceeding 300 g/L (e.g., in the range of about 300 g/L to about 600 g/L or higher).

Slow-release phosphorus sources have low water solubility, which allows them to be released into the soil over a longer period of time. For example, slow-release phosphorus sources can have a solubility in water at 25°C in the range of approximately 170 mg/L or less, up to approximately 180 mg/L.

Intermediate-release phosphorus sources can have solubility in water at 20°C between that of fast-release and slow-release phosphorus sources. For example, intermediate-release phosphorus sources can have solubility in water at 20°C in the range of greater than 180 mg/L to less than 300 g/L, in the range of about 200 mg/L to about 200 g/L, or in the range of about 400 mg/L to about 40 g/L.

In some embodiments, the intermediate-release phosphorus source has a water-soluble phosphorus content in the range of 20% to 80%, or in the range of 40% to 75%, or in the range of 50% to 70%, or about 58%, relative to its total phosphorus content.

In some embodiments, the intermediate-release phosphorus source has a water-soluble phosphorus content of at least two-thirds of the phosphorus content of the MAP, relative to its total phosphorus content. In some embodiments, the intermediate-release phosphorus source has a water-soluble phosphorus content in the range of about 25% to about 95% of the phosphorus content of the MAP, relative to its total phosphorus content.

In some embodiments, virtually all available phosphorus nutrients in the fertilizer are provided by a medium-release phosphorus source. In some embodiments, the fertilizer contains a medium-release phosphorus source as the primary source of phosphorus in the fertilizer (i.e., the medium-release phosphorus source provides more than half of the total phosphorus provided by the fertilizer). In some embodiments, the medium-release phosphorus source accounts for more than 70%, 80%, or 90% of the total available phosphorus in the fertilizer.

Fertilizers that combine moderate-release phosphorus sources with other phosphorus sources

In other embodiments, the fertilizer may contain other phosphorus sources besides a moderately released phosphorus source. For example, the fertilizer may contain one of a slow-release phosphorus source and a fast-release phosphorus source, or a combination of both with a moderately released phosphorus source.

Fertilizers combining medium-release and fast-release phosphorus sources

In embodiments where the fertilizer contains a fast-release phosphorus source, the fast-release phosphorus source can be, for example, a water-soluble phosphorus-containing material that comprises or is derived from a suitable phosphate. Suitable phosphates include, for example, phosphoric acid, single superphosphate (SSP), double superphosphate (DSP), triple superphosphate (TSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), dicalcium phosphate, or combinations of two or more of the above. In an exemplary embodiment, the fast-release phosphorus source is MAP. In other exemplary embodiments, the fast-release phosphorus source is a combination of MAP and DAP. The content of the fast-release phosphorus source in the fertilizer can, for example, range from slightly above 0% by weight to about 75% by weight.

In some embodiments combining one or more intermediate-release phosphorus sources with one or more rapid-release phosphorus sources, the water-soluble phosphorus pentoxide ( _P₂O₅ ) content in the intermediate-release phosphorus source is lower than the water-soluble _P₂O₅ content in _the rapid-release phosphorus source. In some embodiments, the water-soluble _P₂O₅ content of the intermediate-release phosphorus source is about 5% to about 70% lower than _the water-soluble _P₂O₅ content of the rapid-release phosphorus _source . In some embodiments, the water-soluble _P₂O₅ content of the intermediate-release phosphorus source is about _{40 % to about 70% lower than the water-soluble P₂O₅ content of} the rapid-release phosphorus source. In some embodiments, the water-soluble _P₂O₅ content of the intermediate-release phosphorus source is 10% or more lower than _{the water-soluble P₂O₅ content} of _the rapid-release phosphorus source.

Fertilizers combining medium-release and slow-release phosphorus sources

In some embodiments where the fertilizer contains a slow-release phosphorus source, the slow-release phosphorus source may be, for example, struvite or dittmarite having the chemical formula ( _NH₄ )Mg( _PO₄ )· _H₂O . In some embodiments, the fertilizer additionally or alternatively contains one or more other slow-release phosphorus sources, such as phosphate rock or hydroxyapatite.

In some embodiments, the fertilizer comprises both one or more medium-release phosphorus sources and one or more slow-release phosphorus sources, such as struvite, magnesium ammonium phosphate rock, phosphate rock, or hydroxyapatite. For example, the fertilizer may contain magnesium ammonium phosphate rock with struvite or magnesium ammonium phosphate rock in a desired proportion. For example, the fertilizer may contain magnesium ammonium phosphate rock with struvite or magnesium ammonium phosphate rock with magnesium ammonium phosphate rock in a molar ratio ranging from 10:90 to 90:10, or be substantially composed of them.

In some embodiments combining one or more intermediate-release phosphorus sources and one or more slow-release phosphorus sources, _the water-soluble _P₂O₅ content of the _intermediate -release phosphorus source is at least twice the water-soluble _P₂O₅ content of the slow-release phosphorus source. In some embodiments, the water-soluble _P₂O₅ content of the intermediate-release phosphorus source is about two to five times _the water-soluble _P₂O₅ content of _the slow-release phosphorus source.

Other fertilizer characteristics

In some embodiments, the fertilizer described herein has a water-soluble phosphorus _pentoxide ( _P₂O₅ ) content greater than about 25% of the total _P₂O₅ in the _fertilizer . In some embodiments, the water-soluble _P₂O₅ content in the fertilizer _is in the range of about 15% to about 85%, or 25% to 75% _, or 40% to 70% of the total _P₂O₅ in the fertilizer.

In some embodiments, the fertilizer described herein has a free water content or ground moisture content of less than about 10% by weight. In some embodiments, the free water content or ground moisture content of the fertilizer is less than about 4% by weight.

In some embodiments, the fertilizers described herein contain additional materials to provide other inorganic or micronutrients (e.g., zinc, boron, and sulfur) and/or additional sources of nitrogen, potassium _, and magnesium that are beneficial to plant growth or health. For example, carnallite (a naturally occurring evaporating mineral with the molecular formula _K₂Ca₂Mg ( _SO₄ ) _₄ · _2H₂O ) may be mixed with other substances in the fertilizer to provide the crop with a source of sulfur (S) and calcium (Ca), as well as additional sources of potassium (K) and magnesium (Mg). Alternatively, other active materials such as pesticides, selective herbicides, etc., may be included in the fertilizer.

Figure 1 is a graph showing the release curves (cumulative release of nutrients as a function of time) determined by accelerated release tests, for example, of fertilizers containing a moderately releasing phosphorus source (Sample 1 - Composition #3 in Table 1 and Sample 2 - Composition #1 in Table 1). Release curves of fertilizers containing a fast-release phosphorus source (Control 1 - MAP) and fertilizers containing a slow-release phosphorus source (Control 2 - pure struvite) are provided as controls.

In accelerated release tests, columns containing fertilizer or other test substances are rinsed several times with a weakly acidic solution to determine how many rinse cycles are required for complete fertilizer dissolution. Accelerated release tests simulate the release of nutrients from fertilizer in cultivated soil, providing a basis for comparing the expected release rates of different fertilizers in cultivated soil.

The data in Figure 1 are results obtained through testing using the ANRT method. Each material (Sample 1, Sample 2, Control 1, Control 2) was tested in duplicate. For all materials, 3 grams of poly-fil was placed at the bottom of each column. 3 grams of sample of each material were weighed and loaded into each column. An additional 3 grams of poly-fil was placed at the top of each column to prevent solid particles from escaping during the test.

The columns were indirectly heated to 50°C using a hot water circulation system (jacketed column). A 0.2% citric acid solution was continuously circulated through each test column using a peristaltic metering pump at a flow rate of 4.017 mL/min to release product nutrients. After each test cycle at each time interval, the citric acid solution was drained and stored for analysis. As testing resumed, fresh citric acid solution was loaded into each test column. This continuous replacement of the citric acid solution was performed at the following time intervals:

1. First extraction = 2 hours at 50℃

2. Second extraction = 2 hours at 50℃

3. Third extraction = 2 hours at 50℃

4. Fourth extraction = 2 hours at 50℃

5. Fifth extraction = 2 hours at 50℃

6. Sixth extraction = 4 hours at 50℃

7. Seventh extraction = after 8 hours at 50℃

8. Eighth extraction = 4 hours at 50°C

9. Ninth extraction = 4 hours at 50°C

Once the 30-hour accelerated nutrient release test is complete, total phosphorus and magnesium are analyzed in each citric acid filtrate sample using approved analytical methods. _Perkin -Elmer ICP-OES is used to measure magnesium, and a scalar-segmented flow analyzer is used to measure _P₂O₅ .

The release curves in Figure 1 show the percentage of total phosphorus pentoxide ( _P₂O₅ ) released from each fertilizer over time. The release curves in Figure 1 show that medium-release phosphorus sources should release phosphorus into the soil at a rate between that _of fast-release and slow-release phosphorus sources.

The fertilizer described in this article provides highly efficient phosphate release to crops throughout the growing season. Compared to conventional water-soluble phosphate fertilizers, this fertilizer produces crops with improved root development and/or increased germination rates and/or crop yields. Less water-soluble phosphorus is also observed to leach and/or runoff from the soil from this fertilizer compared to the application of conventional water-soluble phosphate fertilizers. This fertilizer is particularly beneficial for sensitive crops where seedlings are easily damaged, or in areas where nearby water bodies are sensitive to nutrient runoff or eutrophication.

The fertilizer provides at least one of the major inorganic nutrients required by crops: nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg). In some embodiments, the fertilizer contains nitrogen in the range of about 3% by weight to about 20% by weight. In some embodiments, the fertilizer contains phosphorus (expressed as _P₂O₅ ) in the range of about 20% _by weight to about 50% by weight. In some embodiments, the fertilizer contains potassium in the range of about 0% by weight to about 20% by weight. In some embodiments, the magnesium content in the fertilizer is in the range of about 1% by weight to about 20% by weight. In an exemplary embodiment, the fertilizer has an NPK level of about 8-43-0+3.5Mg, where N is the nitrogen content by weight percentage, P is the phosphorus content as _P₂O₅ by weight _percentage , and K is the potassium content as _K₂O by weight percentage. In another embodiment, the fertilizer has an NPK level of about 5-28-0+10Mg.

Table 1 below lists exemplary fertilizer compositions comprising one or both of magnesium hydride, struvite, and a fast-release phosphorus source, as well as one or more other intermediates. The content of each substance present is expressed as a percentage by weight of the fertilizer.

Table 1A lists some additional illustrative fertilizer compositions. The weight percent values in Table 1A do not take into account non-nutrient substances such as non-nutrient binders that may be present in some embodiments.

fertilizer form

The fertilizers described herein may be in the form of granules or uniform microspheres. Figures 2-5 are schematic diagrams showing exemplary fertilizer granules 10, 20, 24, and 28, respectively. Figure 2 shows fertilizer granule 10 containing magnesium phosphate phosphate rock granules 12. The magnesium phosphate phosphate phosphate rock granules 12 may be uniformly distributed throughout the fertilizer granule 10. In some embodiments, the magnesium phosphate phosphate phosphate phosphate rock 12 provides substantially all available phosphorus nutrients in the fertilizer granule 10.

Figure 3 shows fertilizer granules 20, which contain struvite granules 22 mixed with magnesium phosphate phosphate granules 12.

Figure 4 shows fertilizer granules 24, which contain fast-release phosphorus source granules 26 mixed with magnesium hydride phosphate granules 12.

Figure 5 shows fertilizer granules 28, which contain fast-release phosphorus source 26 and slow-release phosphorus source (e.g., struvite) 22 mixed with magnesium hydride phosphate granules 12.

In exemplary embodiments, fertilizer particles 10, 20, 24, and 28 are characterized by a diameter ranging from about 0.2 mm to about 20 mm. In some embodiments, fertilizer particles 10, 20, 24, and 28 have a diameter ranging from about 2 mm to about 4 mm. Particle size can be described by a size guide number (SGN). The SGN is obtained by multiplying the median particle size in millimeters by 100. For example, an SGN of 311 corresponds to a median particle size of 3.11 mm. In some embodiments, the size of fertilizer particles 10, 20, 24, and 28 is a size guide number (SGN) of about 250 and about 350 SGN, or between.

Particle size can also be described using a uniformity index. The uniformity index compares large particles to small particles. This index is represented by an integer between 1 and 100, with higher numbers indicating better uniformity and a narrower particle size range. In one embodiment, the uniformity index of fertilizer particles 10, 20, 24, and 28 is greater than about 45. In another embodiment, the uniformity index of fertilizer particles 10, 20, 24, and 28 is greater than about 50.

Fertilizer granules 10, 20, 24, and 28 with an SGN of approximately 300 may have a hardness or crushing strength of at least about 3 lbf. In an exemplary embodiment, fertilizer granules 10, 20, 24, and 28 with an SGN of approximately 300 may have a hardness or crushing strength greater than about 5 lbf.

In some embodiments, fertilizer granules 10, 20, 24, and 28 are spherical or substantially spherical in shape. In some embodiments, fertilizer granules 10, 20, 24, and 28 are elliptical or substantially elliptical in shape. Fertilizer granules 10, 20, 24, and 28 may have an angular shape (i.e., a shape having one or more angles). Fertilizer granules 10, 20, 24, and 28 may have other shapes.

Fertilizer granules 10, 20, 24, and 28 may have a crystallinity level in the range of about 87% to about 94%.

In some embodiments, the struvite 22 and/or fast-release phosphorus source 26 particles and magnesium hydride phosphate particles 12 are in a distinguishable particulate form within fertilizer particles 20, 24, and 28. Fertilizer particles 20, 24, and 28 may, for example, be in the form of layers of struvite 22 and/or fast-release phosphorus source 26 and magnesium hydride phosphate 12. Fertilizer particles 20, 24, and 28 may have a structure comprising alternating layers of minerals.

In other embodiments, the struvite 22 and/or the fast-release phosphorus source 26 and magnesium hydride phosphate rock 12 are indistinguishable particles in fertilizers 20, 24, and 28 (i.e., very small particles that are indistinguishable without a microscope). In such embodiments, struvite 22 and/or the fast-release phosphorus source 26 may be combined with magnesium hydride phosphate rock 12 to form a generally or substantially homogeneous mixture of mineral particles within fertilizer particles 20, 24, and 28.

Magnesium phosphate hydride 12 and/or struvite and/or fast-release phosphorus 26 may have self-adhesive properties (i.e., the granules can bind together to form fertilizer granules 10, 20, 24, 28), so that no additional material is needed to bind the granules together. In other embodiments, fertilizer granules 10, 20, 24, 28 optionally include an adhesive for binding the granules of magnesium phosphate hydride 12 and struvite 22 and/or fast-release phosphorus 26 (if present) together. Suitable adhesives may include, for example, calcium lignosulfonate, starch, molasses, and/or MAP.

Fertilizer granules 10, 20, 24, and 28 may optionally be coated. In some embodiments, the coating comprises a dust-proof material. The dust-proof material helps reduce or trap dust generated during the production, transportation, and application of fertilizer granules 10, 20, 24, and 28. In some embodiments, the coating comprises an anti-caking agent. The anti-caking agent helps reduce the tendency of fertilizer granules 10, 20, 24, and 28 to clump and form bulky lumps. The dust-proof material and/or anti-caking agent may include, for example, waxes, petroleum products, and polymers.

Another example of the fertilizer described herein is a blend of a first particle primarily composed of one or more moderately released phosphorus sources and a second particle containing one or more fast-release phosphorus sources and/or one or more slow-release phosphorus sources. The first particle may, for example, consist essentially of magnesium phosphate rock or a mixture of magnesium phosphate rock with one or more of struvite and magnesium phosphate rock.

Depending on the intended application, granular fertilizers may include, for example:

• Magnesium phosphate hydrometallurgite (5% to 85% by weight),

· guano (0% to 80% by weight) and

• Fast-release phosphorus source (0% to 65% by weight).

In some embodiments, the fertilizer granules contain about 100% by weight of magnesium phosphate rock. In some embodiments, the fertilizer granules contain magnesium phosphate rock ranging from about 2% to about 100% by weight, struvite ranging from about 0% to about 70% by weight, and a fast-release phosphorus source ranging from about 0.2% to about 70% by weight.

Source of materials

Slow-release phosphorus sources can be generated by reacting two or more feedstocks. Slow-release phosphorus sources can optionally or additionally be obtained as a byproduct of wastewater treatment. For example, struvite can be generated by reacting a phosphorus source with a magnesium source. Struvite can also be obtained from wastewater containing a sufficient concentration of nutrients. Struvite from one or both of these sources can be used in the fertilizers described herein. In such embodiments, the content of the slow-release phosphorus source in the fertilizer ranges from 0% by weight to approximately 70% by weight.

Conveniently, magnesium phosphate hydrate can be produced as an intermediate in the reaction for producing struvite. Furthermore, the reaction can be controlled to produce a desired mixture of magnesium phosphate hydrate and struvite.

In one exemplary embodiment, magnesium hydride phosphate is formed by reacting MAP with MgO in the presence of water. The theoretical reaction mechanism for the formation of magnesium hydride phosphate from MAP (i.e., the phosphorus source) and MgO (i.e., the magnesium source) is as follows:

MgO+2NH ₄ (H ₂ PO ₄ )+3H ₂ O→Mg(NH ₄ ) ₂ (HPO ₄ ) ₂ ·4H ₂ O

Magnesium phosphate hydride is unstable in the presence of water. In the presence of excess magnesium and water, magnesium phosphate hydride transforms into struvite. The theoretical reaction mechanism for this transformation is as follows:

Mg(NH ₄ ) ₂ (HPO ₄ ) ₂ ·4H ₂ O+MgO+7H ₂ O→2MgNH ₄ PO ₄ ·6H ₂ O

As illustrated in the exemplary theoretical reaction mechanism above, magnesium hydride (MgH2O) is an intermediate product formed during struvite production. In some embodiments, the fertilizer described herein comprises a combination of struvite and MgH2O. In those embodiments, struvite can be a slow-release phosphorus source. The desired concentration of MgH2O in the fertilizer can be achieved by favoring or disfavoring the conversion of MgH2O to struvite. Reaction factors that can affect the final concentrations of struvite and MgH2O include, for example:

• The addition rate of magnesium and phosphorus;

• Free water content;

• Reaction conditions, such as temperature and pH value;

• Quantity and/or type and/or form of other input materials.

• Input material reactivity and particle size distribution

• The form of the raw material (i.e., dry particles versus dissolved particles or slurry).

The desired concentration of magnesium hydride in the fertilizer can be obtained by controlling the molar ratio of magnesium to phosphorus (Mg:P ratio). Decreasing the Mg:P ratio increases the formation of magnesium hydride, thereby reducing struvite formation. Increasing the Mg:P ratio reduces the formation of magnesium hydride, thereby increasing struvite formation. In some embodiments, the Mg:P ratio of the fertilizer is less than about 1.5. In some embodiments, the Mg:P ratio of the fertilizer is between about 0.1 and about 1.5. In some embodiments, the Mg:P ratio of the fertilizer is between about 0.2 and about 1.2.

In addition to magnesium phosphate rock, the fertilizer may contain one or more other intermediate products. These intermediate products may be formed during the production of moderately released and/or slow-release phosphorus sources. They may provide additional nutrient sources beneficial to crops. Such intermediate products may include, for example, one or more of the following: magnesium phosphate rock having the formula ( _NH₄ ) _MgPO₄ - _H₂O ; magnesium phosphate rock having the formula ( _NH₄ ) _₂Mg₃H₄ ( _PO₄ ) _₄ · _{8H₂O ; and} magnesium phosphate rock having the formula Mg( _HPO₄ )· _3H₂O .

In some implementations, the fertilizer may contain impurities that may be present in the raw materials, such as small amounts of ammonium sulfate and/or calcined gypsum, which are impurities commonly found in MAP and DAP.

In some embodiments, the fertilizer does not contain significant amounts (e.g., more than about 4% by weight) of any of the aforementioned additional intermediates. In some embodiments, the total content of one or more other intermediates in the fertilizer is, for example, less than about 20% by weight. In some embodiments, a larger amount of such intermediates is retained in the fertilizer. The content of magnesium ammonium phosphate in the fertilizer can range from about 0% by weight to about 60% by weight. The content of magnesium ammonium phosphate relative to struvite can be controlled by operating the granulation system at a higher temperature. For example, temperatures above about 56 degrees Celsius favor the formation of more magnesium ammonium phosphate than struvite. For example, the content of magnesium phosphate hydrophosphate and magnesium phosphate (if any one or more of these compounds are present) in the fertilizer can each range from 0% by weight to about 10% by weight.

Manufacturing method

Particles or uniform spheres such as fertilizer granules 10, 20, 24, and 28 can be made in various ways. The following are some non-limiting exemplary methods for manufacturing the fertilizers described herein.

Figure 6 illustrates a process 100 according to an exemplary embodiment. Process 100 includes chemical granulation. In process 100, particles or uniform microspheres may be formed by stacking. In process 100, raw material 102 may be powdered, for example, by crushing or grinding in a suitable grinder 104 (unless raw material 102 is already in a suitable small particle form). In some embodiments, raw material 102 may have a size distribution of less than about 200 mesh. In some embodiments, raw material 102 may have a size distribution of less than about 325 mesh.

Raw material 102 may include fine particles 12 of magnesium hydride phosphate and optional fine particles 22 of struvite and/or fine particles 26 of fast-release phosphorus source. Alternatively, raw material 102 may include a combination of inorganic compounds that will react to form magnesium hydride phosphate 12 and/or struvite 22 and/or fast-release phosphorus source 26.

For example, in some embodiments, raw material 102 includes a phosphorus source and a magnesium source to form magnesium phosphate 12 and/or struvite 22. _{The phosphorus source may be one or more of monoammonium phosphate (MAP), diammonium phosphate (DAP), struvite (or magnesium ammonium phosphate with the chemical formula MgNH₄PO₄·6H₂O ) and} /or raw materials such as phosphoric acid and ammonia that form these compounds. The magnesium source may be one or more of periclase (also known as magnesium oxide with the chemical formula MgO) and/or brucite (also known as magnesium hydroxide Mg(OH) _₂ ), or may be obtained as an impurity in phosphoric acid or MAP/DAP, particularly if manufactured from low-grade ores with high magnesium content. The input struvite may be obtained, for example, as a byproduct of wastewater treatment.

In embodiments where _the fertilizer includes a fast-release phosphorus material source 26, raw material 102 may include _, for example, _monoammonium phosphate ( _{NH₄H₂PO₄} ), diammonium phosphate (( _NH₄ ) _₂HPO₄ ), triporite (also known as monocalcium phosphate with the chemical formula ( _{CaH₄P₂O₈} ), anhydrous ammonia, phosphoric acid, or a combination of two or more of these inorganic compounds to form fast-release phosphorus material source 26. Raw material 102 may be in any suitable form, such _as solid, gas _, liquid, or slurry (i.e., a semi-liquid mixture).

Raw material 102 is introduced into granulator 106. Suitable granulators that can be used include rotary drum granulators, disc granulators, mechanical mixers, and roller presses/compactors. In some embodiments, raw material 102 is premixed before being introduced into granulator 106. Mechanical mixers such as pug mills or pipe cross reactors (not shown) can be used for premixing. In some embodiments, raw material 102 is mixed directly in granulator 106. Mixing helps to achieve uniform distribution of the raw material, promotes the chemical reaction for the formation of magnesium hydride phosphate and/or struvite and/or fast-release phosphorus material sources by bringing the raw materials into close contact with each other, and helps to encapsulate or agglomerate particles. In some embodiments, one or more raw materials 102 are introduced into granulator 106 as a slurry (i.e., a mixture of one or more raw materials and water) or a binder material.

In some embodiments, water and/or steam 108 is introduced into granulator 106 in an amount sufficient to cause the raw material to form the desired amount of magnesium phosphate hydride and/or struvite and/or fast-release phosphorus material source, and agglomerate into particles having the desired size and properties. Water and/or steam 108 can be introduced into granulator 106 by injection using, for example, a sprayer or sprayers. In some embodiments, a sufficient amount of water and/or steam 108 is added to raw material 102 to form particles (particles output from granulator 106).

The specific composition of the fertilizer granules depends on the reaction conditions of the granulation process. Non-exhaustive reaction conditions include 1) temperature, 2) pH, 3) moisture content, and 4) reaction time. In an exemplary embodiment, the operating temperature of the granulation process is maintained between approximately 10°C and 70°C. The operating temperature of the granulation process can be obtained by changing the temperature of the raw materials and/or controlling the temperature of the granulator 106.

Process 100 may include a curing period. During the curing period, a certain proportion of intermediate products may continue to react to form struvite. Curing typically results in an increase in the hardness of the fertilizer granules. Exposing the fertilizer granules to increased moisture/humidity during the curing period tends to accelerate curing. The curing period can be, for example, approximately 24 to 96 hours.

Optionally, binder 112 is added to pellet mill 106. Compounds such as calcium lignosulfonate, starch, guar gum, molasses binder, etc., can be used as binders. One or more binders can enhance pellet strength and adhesion, accelerate pellet formation, and/or provide improved physical properties of the pellets (e.g., density, hardness, resistance to breakage/fracture during handling and storage).

The granules output from granulator 106 are dried at 114 to increase granule strength, stop the chemical reaction, and reduce excess moisture content in the granules. In some embodiments, the excess moisture content in the dried granule product 116 is less than about 10%. In some embodiments, the excess moisture content in the dried granule product 116 is less than about 4%.

The dried granules are then screened at 118 to produce the material in the desired product size. Particles that are out of the required size range (too large and/or too small) can be returned to granulator 106. In some embodiments, oversized and/or undersized particles can be crushed or pulverized before being returned to granulator 106.

Optionally, product 116 may be coated at 120 with a coating agent to reduce dust and/or agglomeration and enhance product strength. Examples of suitable coating agents include waxes, petroleum products, and polymers.

Figure 7 illustrates a method 200 according to another exemplary embodiment, which produces fertilizer granules by steam/water granulation. In process 200, the raw material 202 is powdered, for example, by crushing or grinding in a suitable grinder 204 (unless the raw material 202 is already in a suitable small particle form). A binder 212 (e.g., MAP, calcium lignosulfonate, starch, or molasses, etc.) may be introduced into the granulator 106 to enhance agglomeration.

Optionally, for example, the raw material, which may optionally contain one or more liquids, may be premixed in a ply mill or similar device (not shown) before being fed into the pellet mill 206. The raw material 202 may also be added to the pellet mill 206 via a circulation route (the circulation route may carry, for example, circulating dry products and/or pulverized materials that are too large or too small).

Steam and/or water 208 and/or binder 212 are introduced into the pellet mill 206 in an amount sufficient to agglomerate the dry raw material into particles with the desired size and properties.

The granules are dried in dryer 214 and screened in sieve 218 or other size selector to separate product-sized granules from those that are too large or too small. Oversized and undersized granules can be crushed and recycled back to granulator 206. If desired, the product can be coated to reduce dust and/or agglomeration and increase product strength.

Field test results

rape

In a field trial of rapeseed, the fertilizer described herein, comprising uniform microspheres of magnesium phosphate dihydrogen phosphate co-granulated with struvite, magnesium phosphate dihydrogen phosphate, and MAP, was applied. Control plots were fertilized with a fertilizer containing a blend of struvite and MAP particles. It was found that the fertilizer containing magnesium phosphate dihydrogen phosphate produced a 12.3% higher yield than the struvite-MAP blend. In both cases, the total amount of phosphate was the same as that provided by struvite and MAP alone.

This field trial showed that rapeseed germination was less inhibited by MAP when combined with struvite and magnesium hydride in a single pellet. Seedlings germinating on media containing increased phosphate concentrations (from uniform pellets of 25% or 38% struvite combined with 75% or 62% MAP, respectively) exhibited statistically similar germination rates to those germinating on 100% struvite of the three different species. Even at the lowest application rates, seedling germination was inhibited on media containing only DAP or MAP.

Table 2 describes the sources of phosphate used in these field trials.

Figure 8 is a graph showing the germination rate of rapeseed as a function of phosphate application rate for the various phosphorus sources listed in Table 2.

beet

In field trials of sugar beets, the fertilizers described herein were applied, comprising uniform granules of magnesium phosphate dihydrogen phosphate co-granulated with struvite, magnesium phosphate dihydrogen phosphate, and MAP, and uniform granules of magnesium phosphate dihydrogen phosphate co-granulated with struvite, magnesium phosphate dihydrogen phosphate, and DAP. A fertilizer containing uniform granules of magnesium phosphate dihydrogen phosphate and MAP was prepared using 25% struvite and ₇₅ % MAP (expressed as a percentage of total _{P₂O₅ )} . A fertilizer containing uniform granules of magnesium phosphate dihydrogen phosphate and DAP was prepared using 27% struvite and 73% DAP (expressed as a percentage of total _P₂O₅ ). Control plots were fertilized with a fertilizer containing a blend of struvite and MAP particles. The struvite-MAP blend contained 25% struvite and 75% MAP (expressed as a percentage _of total _P₂O₅ ). The struvite in the struvite-MAP blend was obtained as a byproduct of wastewater treatment. It has been found that fertilizers containing uniform microspheres of magnesium phosphate and MAP produce 4.8% higher yields than fertilizers containing uniform microspheres of magnesium phosphate and DAP, and 5.2% higher yields than struvite-MAP blends.

wheat

In field trials of wheat, the fertilizer described herein, comprising uniform microspheres of magnesium phosphate dihydrogen phosphate co-granulated with struvite, magnesium phosphate dihydrogen phosphate, and MAP, was applied. Control plots were fertilized with a fertilizer containing a blend of struvite and MAP particles. It was found that the fertilizer containing magnesium phosphate dihydrogen phosphate produced a 2.6% higher yield than the struvite-MAP blend. In both cases, the total amount of phosphate was the same as that provided by struvite and MAP.

These trials found that uniform pellet products containing magnesium phosphate (i.e., uniform products containing slow-release, medium-release, and fast-release phosphorus in each pellet) are more effective in releasing phosphorus content than comparable co-blended fertilizers without magnesium phosphate (i.e., products that provide slow-release and fast-release phosphorus in each individual pellet).

One application of the fertilizer described herein is in the cultivation of crops that yield carbohydrates such as grains, starch, and sugars. Examples of such crops include corn, wheat, rice, barley, oats, potatoes, sweet potatoes, sugarcane, sugar beets, or other similar plants. Another application of the fertilizer described herein is in the cultivation of oilseeds such as rapeseed and soybeans, or other similar plants. Yet another application of the fertilizer described herein is in the cultivation of turf or other similar plants. It is preferable to apply this fertilizer below the soil line, close to the root zone. The fertilizer can be placed near the seeds.

Terminology Explanation

Unless the context explicitly requires otherwise, throughout the specification and claims:

• The terms “comprise” and “comprise” should be interpreted in the sense of inclusion rather than exclusivity or exhaustiveness; that is, in the sense of “including but not limited to”.

• “connected,” “coupled,” or any variation thereof means any direct or indirect connection or coupling between two or more elements; the coupling or connection between elements can be physical, logical, or a combination thereof; the elements as a whole can be considered connected or coupled.

When used to describe this specification, the words “in this document,” “above,” “below,” and similar terms refer to the entire specification and not any particular part thereof;

• When referring to a list of two or more items, “or” covers all of the following interpretations of the word: any item in the list, all items in the list, and any combination of items in the list;

• The singular forms “a”, “an”, and “the” also include the meaning of any appropriate plural form.

• “And/or” is used to indicate that one or two situations may occur, such as A and/or β including (A and B) and (A or B).

When applied to numerical values, “approximately” means ±10% of the value.

When a feature is described as "optional" or "optionally" present, or as present "in some embodiments," this disclosure is intended to cover embodiments in which the feature is present, as well as other embodiments in which the feature is not necessarily present, and other embodiments in which the feature is excluded. Furthermore, in the case of any combination of features described in this application, this statement is intended to serve as a basis for the use of proprietary terms associated with the combination of features, such as "alone," "only," etc., and proprietary terms using one or more "negative" limitations to exclude the presence of other features.

• The terms “first” and “second” are used for descriptive purposes and should not be construed as indicating or implying relative importance or the number of technical features indicated.

The directional terms used in this specification and any appended claims (if any), such as “vertical,” “lateral,” “horizontal,” “upward,” “downward,” “forward,” “backward,” “inward,” “outward,” “vertical,” “lateral,” “left,” “right,” “front,” “backward,” “top,” “bottom,” “below,” “up,” “under,” etc., depend on the specific orientation of the described and shown device. Various alternative orientations may be used for the subject matter described herein. Therefore, these directional terms are not strictly defined and should not be interpreted narrowly.

When stating a range of values, the stated range includes all subranges of that range. Unless the context explicitly specifies otherwise or any one or more portions of the range are explicitly excluded, the statement of a range is intended to support values at the endpoints of the range, as well as any intermediate values at one-tenth of the units to the lower limit of the range, and any subranges or groups of subranges of the range. When the range includes one or both endpoints of the range, ranges that do not include one or both of these endpoints are also included in this invention.

Certain numerical values mentioned herein are preceded by "about". In such cases, "about" provides literal support for the following exact value, the exact value ±5%, and all other values that are close to or approximately equal to that value. Unless otherwise stated, a specific value is included among the values specifically listed by "about", where the specific value provides a basic equivalent of the listed value in the context in which the listed value appears. For example, a statement that something has a value of "about 10" should be interpreted as: This set of statements:

• In some implementations, this value is 10;

• In some implementations, this value is in the range of 9.5 to 10.5;

And if, based on the context, a person skilled in the art would understand that a range of values is substantially equal to 10, since values within that range would be understood to provide substantially the same result as the value 10, then "approximately 10" also includes:

• In some implementations, the value is in the range of C to D, where C and D are the lower and upper endpoints of the range, respectively, which covers all those values that provide substantially equal value 10.

For illustrative purposes, specific examples of systems, methods, and apparatus have been described herein. These are merely examples. The techniques provided herein can be applied to systems other than those exemplified above. Many changes, modifications, additions, omissions, and substitutions are possible in the practice of this invention. This invention includes variations of the described embodiments that will be apparent to those skilled in the art, including variations obtained by: replacing features, elements, and/or actions with equivalent features, elements, and/or actions; mixing and matching features, elements, and/or actions from different embodiments; combining features, elements, and/or actions of the embodiments described herein with features, elements, and/or actions of other technologies; and/or omitting combined features, elements, and/or actions from the embodiments.

Therefore, the appended claims and the claims introduced herein are intended to be construed as including all such modifications, substitutions, additions, omissions, and sub-combinations that can be reasonably inferred. The scope of the claims should not be limited to the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the specification as a whole.

Various features are described herein as existing in “some embodiments.” Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one, or any combination of two or more of such features. This is limited only to the extent that it would be impossible for someone skilled in the art to construct an actual embodiment combining such incompatible features, in which some features are incompatible with others. Therefore, the description of “some embodiments” having feature A and “some embodiments” having feature B should be interpreted as the inventors also considering an explicit indication of embodiments combining features A and B (unless otherwise stated or features A and B are fundamentally incompatible). This is true even if features A and B are shown in different figures and/or mentioned in different paragraphs, sections, or sentences.

While this document discusses many exemplary aspects and implementations, those skilled in the art will recognize certain modifications, substitutions, additions, and sub-combinations thereof.

While many exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain modifications, substitutions, additions, and sub-combinations thereof. Therefore, the appended claims and the subsequently introduced claims are intended to be construed as including all such modifications, substitutions, additions, and sub-combinations within their true spirit and scope.

It should be emphasized that the present invention relates to all combinations of the above features, even if these features are referenced in different claims.

Claims (57)

1. A fertilizer composition comprising magnesium phosphate phosphate particles, wherein the content of magnesium phosphate phosphate in the fertilizer composition is at least 10% by weight of the fertilizer composition. 2. The fertilizer composition as defined in any of the preceding claims, wherein the content of magnesium phosphate hydrometallurgical in the fertilizer composition is in the range of 10% to 80% by weight. 3. The fertilizer composition as defined in any of the preceding claims, wherein the molar ratio of magnesium to phosphorus in the fertilizer composition is less than 1.5. 4. The fertilizer composition as defined in any of the preceding claims, wherein the molar ratio of magnesium to phosphorus in the fertilizer composition is between 0.2 and 1.1. 5. The fertilizer composition as defined in any of the preceding claims, wherein _the water-soluble _P₂O₅ content is greater than 25% of the total _P₂O₅ available in the fertilizer _composition . 6. The fertilizer composition as defined in any of the preceding claims, wherein the water-soluble _P₂O₅ content is in the range of about 25% of _the total _P₂O₅ available in the fertilizer _composition . 7. The fertilizer composition as defined in any of the preceding claims, wherein the water content of the fertilizer is less than 10% by weight. 8. The fertilizer composition as defined in any of the preceding claims, wherein the water content of the fertilizer is less than 4% by weight. 9. The fertilizer composition as defined in any of the preceding claims further comprises slow-release phosphorus source particles. 10. The fertilizer composition as defined in the preceding claims, wherein the slow-release phosphorus source comprises struvite. 11. The fertilizer composition as defined in claim 9 or 10, wherein the content of the slow-release phosphorus source in the fertilizer composition is in the range of 0% to 40%. 12. The fertilizer composition as defined in any of the preceding claims further comprises fast-release phosphorus source particles. 13. The fertilizer composition as defined in the preceding claims, wherein the fast-release phosphorus source is one or more of phosphoric acid, monosuperphosphate (SSP), dospermium superphosphate (DSP), trisuperphosphate (TSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), and dicalcium phosphate. 14. The fertilizer composition as defined in claim 12 or 13, wherein the content of the fast-release phosphorus source in the fertilizer composition is in the range of 0% by weight to 65% by weight. 15. The fertilizer composition as defined in any of the preceding claims further comprises one or more intermediate products, said one or more intermediate products being formed from the production of one or more of magnesium phosphate, slow-release phosphorus sources and fast-release phosphorus sources. 16. The fertilizer composition as defined in claim 15, wherein the total content of said one or more intermediate products is less than 20% by weight of the fertilizer composition. 17. The fertilizer composition as defined in any of the preceding claims, wherein the fertilizer composition comprises one or more of magnesium ammonium phosphate rock, magnesium ammonium phosphate rock, magnesium phosphate rock, ammonium sulfate rock, and calcined gypsum. 18. The fertilizer composition as defined in any of the preceding claims, wherein the content of magnesium ammonium diphosphate in the fertilizer composition is in the range of 1% to 20%. 19. The fertilizer composition as defined in any of the preceding claims, wherein the nitrogen content in the fertilizer composition is in the range of 3% by weight to 20% by weight. 20. The fertilizer composition as defined in any of the preceding claims, wherein the magnesium content in the fertilizer composition is in the range of 0% by weight to 15% by weight. 21. The fertilizer composition as defined in any of the preceding claims, wherein the magnesium content in the fertilizer composition is in the range of 0% by weight to 20% by weight. 22. The fertilizer composition as defined in any of the preceding claims, wherein the fertilizer composition has an N-P-K rating of 8-43-0. 23. The fertilizer composition as defined in any of the preceding claims, wherein the fertilizer composition has an N-P-K rating of 5-28-0. 24. The fertilizer composition as defined in any of the preceding claims further comprises particles of one or more additional minerals. 25. The fertilizer composition as defined in claim 24, wherein the one or more additional minerals include carnallite. 26. The fertilizer composition as defined in any of the preceding claims, wherein the fertilizer composition is in the form of fertilizer granules. 27. The fertilizer according to the preceding claim, wherein the fertilizer particles are granules or uniform small balls. 28. The fertilizer according to claim 26 or 27, wherein the fertilizer particles are substantially composed of magnesium phosphate hydromonium phosphate rock. 29. The fertilizer according to claim 26 or 27, wherein the fertilizer particles are substantially composed of magnesium phosphate hydromonite and the slow-release phosphorus source. 30. The fertilizer according to claim 26 or 27, wherein the fertilizer particles are substantially composed of magnesium phosphate hydromonium phosphate rock and the fast-release phosphorus source. 31. The fertilizer according to claim 26 or 27, wherein the fertilizer particles are substantially composed of magnesium phosphate hydromonium phosphate rock, the slow-release phosphorus source, and the fast-release phosphorus source. 32. The fertilizer according to any one of claims 26 to 31, further comprising a coating layer surrounding the outer layer of the fertilizer particles. 33. The fertilizer according to the preceding claim, wherein the coating layer comprises a dustproof material and/or an anti-caking agent. 34. The fertilizer according to any one of claims 26 to 33, wherein the diameter of the fertilizer particles is in the range of 0.2 mm to 20 mm. 35. The fertilizer according to any one of claims 26 to 34, wherein the diameter of the fertilizer particles is in the range of 2 mm to 4 mm. 36. The fertilizer according to any one of claims 26 to 35, wherein the particle size index (SGN) of the fertilizer particles is in the range of 250 SGN to 350 SGN. 37. The fertilizer according to any one of claims 26 to 36, wherein the uniformity index of the fertilizer particles is greater than 45. 38. The fertilizer according to any one of claims 26 to 36, wherein the uniformity index of the fertilizer particles is greater than 50. 39. The fertilizer according to any one of claims 26 to 38, wherein the crushing strength of the fertilizer particles is at least about 3 lbf. 40. The fertilizer according to any one of claims 26 to 39, wherein the fertilizer particles have a crystallinity level in the range of 87% to 94%. 41. A fertilizer composition comprising: The phosphorus source particles have a moderate release rate, wherein the solubility of the moderate release phosphorus source is greater than that of a slow-release phosphorus source characterized as low water solubility and less than that of a fast-release phosphorus source characterized as high water solubility. The content of the moderately released phosphorus source in the fertilizer composition is greater than 10% by weight of the fertilizer composition. 42. The fertilizer composition according to the preceding claims, wherein the slow-release phosphorus source has a solubility of less than 100 g/L in water at 25°C. 43. The fertilizer composition according to the preceding claims, wherein the fast-release phosphorus source has a solubility of greater than 300 g/L in water at 25°C. 44. The fertilizer composition according to the preceding claims, wherein the solubility of the intermediate-release phosphorus source is 15% to 50% lower than that of the fast-release phosphorus source. 45. The fertilizer composition according to the preceding claims, wherein the solubility of the intermediate-release phosphorus source is 30% to 60% higher than that of the fast-release phosphorus source. 46. The fertilizer composition according to the preceding claims, wherein the moderately released phosphorus source is formed by reacting a phosphorus source with a magnesium source. 47. The fertilizer composition according to the preceding claims, wherein the phosphorus source is one or more selected from monoammonium phosphate (MAP), diammonium phosphate (DAP), struvite, phosphoric acid, and ammonia. 48. The fertilizer composition according to the preceding claims, wherein the magnesium source is one or more of magnesium oxide and magnesium hydroxide. 49. The fertilizer composition as defined in any of the preceding claims, wherein the molar ratio of magnesium to phosphorus in the fertilizer composition is less than 1.5. 50. A method for producing fertilizer, the method comprising: Two or more raw materials are added together, wherein the two or more raw materials include a phosphorus source and a magnesium source; The two or more raw materials are mixed to form a mixture, wherein the mixture contains a source of moderately released phosphorus. Granulation of the mixture into fertilizer pellets; and Select the fertilizer granules according to their size. 51. The method according to the preceding claim, wherein the phosphorus source is added at a rate 80% to 99% faster than the magnesium source. 52. The method according to the preceding claim, wherein the phosphorus source is added at a rate 90% to 97% faster than the magnesium source. 53. The method according to the preceding claim, wherein the phosphorus source is one or more selected from monoammonium phosphate (MAP), diammonium phosphate (DAP), struvite, phosphoric acid, and ammonia. 54. The method according to the preceding claim, wherein the magnesium source is one or more of magnesium oxide and magnesium hydroxide. 55. The method according to the preceding claim, wherein the mixture comprises one or both of a slow-release phosphorus source and a fast-release phosphorus source. 56. A fertilizer having any of the novel inventive features, combinations of features, or sub-combinations of features described herein. 57. A method having any of the novel inventive steps, actions, combinations of steps and/or actions, or sub-combinations of steps and/or actions described herein.