What Is Phosphate Fertilizer? Types and Functions of Phosphate Fertilizer Explained

Phosphate fertilizer (full name: phosphatic fertilizer), a fertilizer with phosphorus as its main nutrient. The size and speed of its fertilizer effect depend on the available phosphorus pentoxide content, soil properties, application method, crop type, etc.

Classification of phosphate fertilizer:

The size and speed of the fertilizer effect depend on the available phosphorus pentoxide content, soil properties, application method, crop type, etc.

According to source, it can be divided into:

(1) Natural phosphate fertilizers, such as guano, bone meal and fish bone meal, etc.

(2) Chemical phosphate fertilizers, such as superphosphate, calcium magnesium phosphate, etc.

Classification according to the solubility of the phosphate salts contained

(1) Water-soluble phosphate fertilizers, such as ordinary superphosphate, triple superphosphate, etc. Their main component is monocalcium phosphate. Easily soluble in water, with a relatively fast fertilizer effect.

(2) Citrate-soluble phosphate fertilizers, such as precipitated phosphate fertilizer, steel slag phosphate fertilizer, calcium magnesium phosphate fertilizer, defluorinated phosphate fertilizer, etc. Their main component is dicalcium phosphate. Slightly soluble in water but soluble in 2% citric acid solution, with a relatively slow fertilizer effect.

(3) Sparingly soluble phosphate fertilizers, such as bone meal and phosphate rock powder. Their main component is tricalcium phosphate. Slightly soluble in water and 2% citric acid solution, and can only produce a fertilizer effect after gradually transforming into monocalcium phosphate or dicalcium phosphate in the soil.

Rational application of phosphate fertilizer can increase crop yield, improve crop quality, accelerate tillering of cereal crops and promote full grain filling; promote flowering and fruiting of cotton, melons, solanaceous vegetables and fruit trees, and increase the fruiting rate; increase the sugar content of sugar beet, sugarcane, watermelon, etc.; and the oil content of rapeseed.

How exactly should phosphate fertilizer be applied for the best effect?

No need to apply it every year

After phosphate fertilizer is applied, crops in the current season generally can only absorb and use a small part of it, while the later effect can last for several years. Therefore, in the years after phosphate fertilizer is applied, there is no need to apply it every year.

Apply phosphate fertilizer early

Crops absorb phosphorus fastest at the seedling stage, accounting for half of the total phosphorus absorbed during the entire growth period of the crop. If crops lack phosphorus at the seedling stage, it will affect later growth, and even if phosphorus is supplemented later, it is difficult to make up for the loss caused by early phosphorus deficiency. Therefore, attention should be paid to ensuring no phosphorus deficiency at the seedling stage of crops.

Apply phosphate fertilizer finely

Superphosphate easily absorbs moisture and clumps during storage, so when applying it, it must be crushed and sieved to facilitate absorption by crop roots.

Apply in holes or bands

Concentrated application of phosphorus makes it easy for it to be fixed and rendered ineffective by elements such as iron, aluminum and calcium in the soil. Therefore, when applying it, hole application or band application should be carried out so that the phosphorus is fixed around the seeds and root system. In this way, the phosphorus can be prevented from being fixed by elements such as iron, aluminum and calcium in the surrounding soil, and it is also beneficial to absorption by crop roots.

Mix phosphate fertilizer with organic fertilizer

Mixing phosphate fertilizer, especially calcium magnesium phosphate fertilizer, with organic fertilizer can convert the sparingly soluble phosphorus in the phosphate fertilizer into available phosphorus that crops can easily absorb.

Deep and shallow application

Layered application of phosphate fertilizer has little mobility in the soil; basically it stays wherever it is applied. Therefore, phosphate fertilizer     should be applied both in deep and shallow layers. Applying phosphate fertilizer in the shallow layer is beneficial to absorption by seedlings, thereby enabling crops to turn green early and tiller quickly. For phosphate fertilizer application, generally 1/3 is applied in the shallow layer and 2/3 in the deep layer.

Combined application of nitrogen and phosphorus and mixed application with nitrogen fertilizer

Crops absorb various nutrients in a certain proportion; if the proportion is unbalanced, they will not grow well. Nitrogen and phosphorus should also be applied in combination, which can both balance nutrients and promote root growth, laying the foundation for a high yield.

Foliar spraying

When crops reach the late growth stage, the root system gradually ages and its ability to absorb nutrients weakens, often causing phosphorus deficiency. At this time, water-soluble superphosphate can be sprayed on crop leaves, allowing phosphorus to enter the plant body through the stomata or cuticle of the leaf surface.

Simple identification methods for phosphate fertilizer

1. Identification from packaging

1. Check the markings. Fertilizer packaging bags must indicate the product name, nutrient content, grade, trademark, net weight, standard code, factory name, factory address, production license number and other markings. 2. Check the sealing of the packaging bag. Special attention should be paid to fertilizers whose packaging bag seals have obvious signs of being opened; such fertilizers may be adulterated.

2. Identification by shape and color

1. Urea: white or light yellow, in granular, needle-like or prismatic crystals. 2. Ammonium sulfate: white crystals. 3. Superphosphate: gray-white or light skin-colored powder. 4. Triple superphosphate: dark gray or gray-white granules or powder. 5. Calcium magnesium phosphate fertilizer: gray-brown or dark green powder. 6. Potassium sulfate: white crystals or powder. 7. Potassium chloride: white or light red granules. 8. Monoammonium phosphate: gray-white or dark gray granules. 9. Diammonium phosphate: white or light yellow granules.

3. Identification by smell

Fine granules with an obvious pungent ammonia smell are ammonium bicarbonate. Fine powder with a sour smell is triple superphosphate, and that with a special fishy odor is calcium cyanamide. If superphosphate has a very pungent strange sour smell, it indicates that waste sulfuric acid was very likely used in the production process; such fertilizer can easily damage or burn crops to death.

4. Identification method by dissolving in water

Take 1 gram of fertilizer, place it in a clean glass cup or white porcelain bowl, add 10 mg of distilled water (or clean cooled boiled water), shake fully, and observe its dissolution. What dissolves completely is nitrogen fertilizer or potassium fertilizer; what dissolves in water but leaves residue is superphosphate; what dissolves in water with no residue or very little residue is triple superphosphate; what dissolves in water but has a relatively strong ammonia smell is ammonium bicarbonate.

5. Identification method by burning

Take a small spoonful of fertilizer and place it on red-hot charcoal; if it burns violently, observe carefully: if it smokes, catches fire and has an ammonia smell, it is ammonium nitrate; if it explodes with a crack and has no ammonia smell, it is potassium chloride; if there is no violent reaction and it has an ammonia smell, it is urea and ammonium chloride; if a little ammonium sulfate is added and there is no ammonia smell, it is phosphate rock powder.