Superphosphate is a type of phosphate fertilizer, and the two are inclusive. Phosphate fertilizer: Phosphate fertilizer refers to fertilizers with phosphorus as the main nutrient, such as superphosphate, double superphosphate, calcium magnesium phosphate, bone meal, phosphate rock powder, etc. Superphosphate: The main component of superphosphate is monocalcium phosphate, which is an acidic chemical phosphate fertilizer with a phosphorus content of about 16-18%.

I. Phosphate fertilizer Phosphate fertilizer refers to fertilizers with phosphorus as the main nutrient. Its fertilizer effect depends on the effective content of phosphorus pentoxide in the fertilizer. It can be classified according to its source and the solubility of the phosphate it contains, as follows: 

1. Classification based on solubility

(1) Water-soluble phosphate fertilizer: The main component is monocalcium phosphate, which has good water solubility and fast fertilizer effect, such as ordinary superphosphate, double superphosphate, etc.

(2) Citrate-soluble phosphate fertilizer: The main component is dicalcium phosphate, which is slightly soluble in water and soluble in 2% citric acid solution. The fertilizer effect is slow, such as calcium magnesium phosphate fertilizer, defluorinated phosphate fertilizer, precipitated phosphate fertilizer, steel slag phosphate fertilizer, etc.

(3) Insoluble phosphate fertilizer: The main component is tricalcium phosphate, which is slightly soluble in water and 2% citric acid solution. It needs to be converted into monocalcium phosphate or dicalcium phosphate before it can exert its fertilizer effect, such as bone meal, phosphate rock powder, etc.

2. Classification by source

(1) Chemical phosphate fertilizer: such as superphosphate, double superphosphate, calcium magnesium phosphate fertilizer, phosphate rock powder, etc.

(2) Natural phosphate fertilizer: such as seabird droppings, animal bone meal, fish bone meal, etc.

II. Superphosphate

1. Superphosphate (monocalcium phosphate) is a loose, porous, acidic chemical phosphate fertilizer made by reacting phosphate rock with dilute sulfuric acid. Its primary component is monocalcium phosphate, with a phosphorus content of approximately 16-18%. The secondary component is calcium sulfate, which accounts for approximately 50% by weight.

2. Superphosphate appears as a dark gray or off-white powder and is mostly soluble in water. It can be used as a base fertilizer, topdressing, or seed fertilizer for crops.

3. Superphosphate is suitable for alkaline, slightly alkaline, and neutral soils. It should not be mixed with alkaline fertilizers such as lime and wood ash.

4. Superphosphate, when mixed with nitrogen fertilizers, has a nitrogen-fixing effect, reducing nitrogen loss.