Background and overview[1 Ink adhesion promoter]
A magnesium-nitrogen-phosphorus compound fertilizer made from a compound of phosphoric acid and magnesium [MgCl2·Mg(OH)2]. The main component is the double salt of magnesium ammonium phosphate monohydrate [Mg(NH4)PO4·H2O], containing magnesium (Mg )15% to 16%, nitrogen 10% to 11%, and phosphoric acid (P2O5) 39% to 40%. It has low solubility in water and is a slow-release fertilizer. Mostly made into granular form. The dissolution rate after being applied to the soil can be controlled by the particle size, and it can supply the nitrogen, phosphorus, and magnesium required by crops for a longer period of time. Mainly used in orchards, grasslands, flowers and seedbeds, etc. Generally only used as base fertilizer.
Properties and uses[2]
Magnesium ammonium phosphate belongs to the colorless orthorhombic crystal system. Appearance: white crystalline fine particles or powder, density 1.71g/ml. Slightly soluble in cold water, soluble in hot water and dilute acid, insoluble in ethanol, and soluble in alkaline solutions. break down. When magnesium ammonium phosphate is heated to 100°C in ammonia flow, 5 molecules of crystal water are removed and becomes monohydrate; when heated to 100°C in the air, it is dehydrated into anhydrous substance; when heated to 600°C, it decomposes into pyrophosphoric acid Magnesium; its aqueous solution is heated to 48-50°C to precipitate monohydrate. Magnesium ammonium phosphate is used as a feed additive, fertilizer additive, and is also used in medicine. It can also be used in the manufacture of coatings, urethanes, and soft foam flame retardants. Magnesium ammonium phosphate has been included in the list of fertilizers abroad and is used as a long-lasting inorganic nitrogen fertilizer. It is mainly used for fruit trees, lawns, flowers, etc.
Preparation[2]
1. Phosphate method
1) Ammonium dihydrogen phosphate (sodium) method Method 1: Ammonium dihydrogen phosphate and magnesium hydroxide react in a certain ratio at 40 to 65°C to generate magnesium ammonium phosphate. The reaction formula is as follows:
The above reaction is carried out at 75~100℃ to generate NH4MgPO4·H2O, the reaction formula is as follows:
Method 2: Add magnesium chloride or magnesium sulfate solution to ammonium dihydrogen phosphate (sodium) solution, add ammonium bicarbonate while stirring, and control the pH value of the solution between 6.0 and 6.5 to obtain magnesium ammonium phosphate. The reaction formula is as follows :
2. Diammonium hydrogen phosphate (sodium) method: Add magnesium chloride or magnesium sulfate solution to diammonium hydrogen phosphate (sodium) solution, add ammonia while stirring, and control the pH value at 6.0 to 6.5 to obtain magnesium ammonium phosphate. , the reaction formula is as follows:
In addition, magnesium ammonium phosphate can also be produced by reacting magnesium phosphate and ammonium hydroxide. The 2·2 phosphoric acid method produces magnesium ammonium phosphate by direct reaction of phosphoric acid, magnesium oxide or magnesium hydroxide, and ammonia water. The reaction formula is as follows:
Laboratory method: Use phosphoric acid and magnesium hydroxide to prepare magnesium ammonium phosphate (NH4MgPO4·H2O) in 2 steps. First, magnesium hydroxide reacts with phosphoric acid at 50-65°C and pH=4-6 to form magnesium hydrogen phosphate trihydrate; then it is ammoniated with concentrated ammonia at 75-100°C and pH=6-8 to form ammonium magnesium phosphate. The reaction formula is as follows:
3. Ammonium sulfate superphosphate method: First, ammonium sulfate and calcium superphosphate are reacted to prepare ammonium dihydrogen phosphate, and then in the presence of magnesium ions, ammonium bicarbonate is used to adjust the pH value of the solution to 6.0 to 6.5. Magnesium ammonium phosphate is obtained, and its reaction formula is as follows:
4. Other methods: (1) Using bitter brine as raw material: react phosphoric acid (salt) and ammonia (ammonium salt) with the magnesium in bitter brine to prepare magnesium ammonium phosphate. The process has low cost and high output. High efficiency and other advantages. (2) Use the alkali plant filtered mother liquor as raw material: use the free ammonia and combined ammonia in the heavy alkali mother liquor separated by the alkali plant to react with industrial phosphoric acid and magnesium to produce magnesium ammonium phosphate. (3) Use phosphorus (ammonia) wastewater as raw material: add magnesium salt and ammonia (ammonium salt) to the phosphorus wastewater to prepare magnesium ammonium phosphate.
Application of magnesium ammonium phosphate in agriculture[2-3]
Magnesium ammonium phosphate is a multi-element compound fertilizer containing N, P, and Mg, and all ingredients are effective. Its solubility in water is extremely low. Because of its citrus solubility, it can store nitrogen in the soil after application, and Under the action of microorganisms, nitrification gradually occurs, slowly decomposing and providing plant nutrients. Different particle sizes have different nitrification rates, and the nutrient needs of crops can be met by controlling the particle size.
1) As base fertilizer and top dressing, magnesium ammonium phosphate can be used as base fertilizer and top dressing. It should be applied together with other fertilizers. When used as base fertilizer, it should be applied shallowly on acidic soil. Calculated in terms of magnesium, 1 to 1.5 kg per 667 m2 is generally applied. . One application can meet the nutritional needs of crops throughout the growth period without the need for top dressing. Even if the dosage is too large, it will not easily cause seedling burning, leggy growth, lodging, etc. Even if the dosage is applied for several years at a time, it will not cause seedling burning. When used for vegetables and cereal crops, some quick-acting chemical nitrogen fertilizers should be mixed. Top dressing should be applied early. Magnesium ammonium phosphate has the characteristics of slow release and resistance to leaching, and is particularly suitable for sandy soils that are deficient in magnesium and prone to leaching of nutrients, as well as southern red soils that are deficient in magnesium, subject to high temperatures and rainy weather. ,
2) If magnesium ammonium phosphate is used as the coating material (additive) for long-term fertilizer, the slow-release performance is better than that of sulfur-coated urea, and the entire coating is composed of plant nutrients. When applied to the soil It will not cause any residual substances and is better than polymer-coated fertilizers in preventing secondary pollution. In Japan, magnesium ammonium phosphate is used to coat the surface of water-soluble granular fertilizers to extend storage stability and improve fertilizer utilization. In order to reduce the volatilization of ammonium bicarbonate fertilizer and improve its fertilizer efficiency in China, 5% to 9% magnesium ammonium phosphate is added to ammonium bicarbonate containing 3% to 5% water to make growing fertilizers.Effective ammonium bicarbonate makes ammonium bicarbonate have better stability and its active ingredients are significantly improved. Zhengzhou LUXECOTE Phosphate and Compound Fertilizer Technology Research and Promotion Center develops LUXECOTE@ series of controlled release fertilizers with magnesium ammonium phosphate as the main coating layer. It is used in golf courses, sports fields, landscape lawns in Australia, the United States, Singapore and other countries. Good results have been achieved; in China, compared with conventional fertilization, the one-time full-amount basal fertilizer used for summer corn can save 1/3 to 1/2 of the fertilizer. A field comparison test of the one-time basal fertilizer for rice has shown that it can save 1/3 of the fertilizer. .
3) Agricultural effects Magnesium ammonium phosphate has low solubility, does not damage the root system, and can be absorbed by crops as much as it needs. It is not easily lost by water, promotes crop growth, enhances disease resistance, and improves the quality of fruits, vegetables, flowers, etc. and yield, making the fruits of the crops brighter in color, more mellow in taste, more nutritious, and completely free of environmental pollution. France uses this compound fertilizer to double potato production, increase wheat production by 50%, and increase clover and vegetable crop production by 40%.
Main reference materials
[1] Agricultural Dictionary
[2] Properties, preparation methods and applications of magnesium ammonium phosphate
[3] Research on the application of magnesium ammonium phosphate precipitation-zeolite adsorption method in ammonia nitrogen treatment in marine aquaculture
