What should we pay attention to when applying phosphate fertilizer?

What should we pay attention to when applying phosphate fertilizer? Calcium superphosphate and calcium magnesium phosphate are low-concentration phosphate fertilizers. From the physical and chemical properties, calcium superphosphate is a water-soluble phosphate fertilizer suitable for use in neutral, alkaline and slightly acidic soils; calcium magnesium phosphate is a city-soluble phosphate fertilizer suitable for acidic soils. In general, calcium superphosphate and calcium magnesium phosphate are mainly applied to different crops as basal fertilizers. Calcium superphosphate, also known as ordinary calcium superphosphate, referred to as calcium superphosphate (SSP), is the earliest industrialized fertilizer variety in the world, and is also the main low-concentration phosphate fertilizer product in China. The main effective component of phosphorus is calcium dihydrogen phosphate monohydrate, whose molecular formula is Ca(H2PO4)2? H2O, containing P2O5 12-20%, CaO 28%, S 11-13% , in addition, it also contains a variety of trace elements, as well as a small amount of free acid. The production process is mainly to treat phosphate rock powder with sulfuric acid, and then, after formation, cutting, aging, packaging is the product. Calcium superphosphate is a kind of loose porous powder or granular matter, which is gray, light yellow, gray yellow or brown due to different impurity content of phosphate rock. Because it contains free acid, it is slightly acidic. During storage, moisture will absorb moisture, clump and corrode packaging containers. After moisture absorption, it will also cause a series of chemical changes, so that water-soluble phosphate fertilizer will become insoluble again and reduce fertilizer efficiency. This change is generally called degradation, so pay attention to moisture protection when storing. After calcium superphosphate is applied to the soil, monocalcium phosphate dissolves in water to form saturated phosphoric acid, monocalcium phosphate and dicalcium phosphate solutions. Because the dissolved components are different from the original ones, they are called heterogeneous dissolution. At this time, the solution is very acidic, which can dissolve iron, aluminum, manganese, calcium and magnesium salts in the soil and form insoluble phosphate with them, reducing the effectiveness of phosphorus. This phenomenon is also known as chemical fixation. In acidic soil, insoluble iron phosphate and aluminum phosphate are often formed, and in calcareous soil, octacalcium phosphate or hydroxyapatite are formed, which will reduce the fertilizer efficiency of calcium superphosphate. In acidic soils, especially red and yellow soils, phosphoric acid is also adsorbed and fixed by clay minerals or hydrated trioxides to reduce fertilizer efficiency. The applied superphosphate is easily fixed by soil and has little mobility, and its movement range is generally between 1 and 4 cm. Therefore, the utilization rate of phosphorus fertilizer is very low. According to the nature and characteristics of calcium superphosphate, the specific application methods are as follows: 1. Mixed application with organic fertilizer. When calcium superphosphate is mixed with organic fertilizer, it can reduce contact with soil by using the distribution system of organic fertilizer, so as to improve its fertilizer efficiency. 2. Acid soil can be applied with lime, calcareous soil with ammonium sulfate. In acidic soil, when the pH is below 5.5, it is best to apply lime to neutralize the acidity, so that the pH rises above 6.0 and then apply phosphorus fertilizer; in calcareous soil, it is necessary to cooperate with acidic or physiological acid fertilizers such as ammonium sulfate, and use the effect of sulfate to reduce the calcium ion concentration in the fertilizer circle to improve the effectiveness of phosphorus. 3, although some fertilizers can be mixed, but must be applied immediately after mixing, such as nitrate nitrogen and calcium superphosphate mixed, fertilizer deliquescence moisture absorption, inconvenient to use, if not applied for a long time, nitrogen will be greatly lost, and effective phosphorus into insoluble phosphorus. Mixed use of some fertilizers will cause a large loss of nutrients, resulting in great waste. Alkaline fertilizers such as plant ash and lime should not be mixed with calcium superphosphate, otherwise water-soluble nutrients will be converted into insoluble nutrients, which will reduce the fertilizer efficiency of phosphorus fertilizer. When selecting calcium superphosphate, attention should be paid to distinguishing, and the following points should be achieved: 1. The appearance of unqualified calcium superphosphate is dark gray like qualified calcium superphosphate, loose, dry, hand twisted into a group, greasy. Qualified calcium superphosphate smells slightly sour. The unqualified calcium superphosphate has an irritating odor or peculiar smell. 2. It is best to buy famous products produced by large enterprises. 3. If the purchased calcium superphosphate has an abnormal smell, it should be especially cautious when applied. 4. The price of calcium superphosphate products is mainly determined according to the effective phosphorus pentoxide nutrient content (the national standard requires at least 12%), and calcium and magnesium are only auxiliary components. Second, calcium magnesium phosphate, also known as molten magnesium phosphate, is a silicate glass containing phosphate (PO43-), without a clear molecular formula and molecular weight. Calcium magnesium phosphate not only provides 12%~18% low concentration phosphorus, but also provides a large amount of silicon, calcium and magnesium. Calcium magnesium phosphate fertilizer accounts for about 17% of the total phosphorus fertilizer output in China at present, second only to calcium superphosphate. It is phosphate rock and magnesium-containing, silicon-containing ore, in the blast furnace or electric furnace after high temperature melting, water quenching, drying and grinding. In the selection of attention to the following points: 1, packaging bag identification: packaging bags should have the following contents: product name, trademark, nutrients and their content, net weight, implementation standard number, production license number, factory name, address, telephone, etc., and printed regularly, clear. 2, color and shape identification: calcium magnesium phosphate is mostly gray, light green, dark green, black brown and other different colors, for powder. 3, feel recognition: calcium magnesium phosphate belongs to citric acid soluble phosphate fertilizer, dissolved in weak acid, alkaline, non-corrosive by hand, non-moisture absorption, non-caking. 4, odor and water solubility identification: calcium magnesium phosphate has no odor, insoluble in water. Click for more nitrogen, phosphorus and potassium application techniques Click for more fertilizer application techniques