Calcium magnesium phosphate fertilizer is an alkaline slow-release phosphorus fertilizer, suitable for application on acidic soils.

Calcium magnesium phosphate fertilizer is an alkaline phosphorus fertilizer that is based mainly on phosphorus and also contains various nutrients such as calcium, magnesium and silicon. It is usually made by melting phosphate rock together with magnesium-bearing minerals at high temperature, quenching rapidly in water, and then grinding fine. It belongs to the citrate-soluble slow-release fertilizer category; the phosphorus it contains is insoluble in water, but can be gradually decomposed by the weak acids secreted by crop roots and by acidic substances in the soil, so that crops can absorb and use it continuously.

In appearance, calcium magnesium phosphate fertilizer is mostly grayish-white, grayish-green or grayish-black powder. It is stable in nature, not prone to absorbing moisture or caking, and is easy to transport and store. Because its fertilizer effect is gentle and long-lasting, besides supplying phosphorus it can also supplement medium elements such as calcium, magnesium and silicon, and it has a good compensatory effect on magnesium-deficient soils and on silicon-loving crops such as rice. Its alkalinity can neutralize soil acidity, and it also has certain value in improving acidic soils.

As for application, calcium magnesium phosphate fertilizer is most suitable as a base fertilizer in acidic or slightly acidic soils; applying it early, deep and in concentrated spots gives better results, and applying it together with farmyard manure after composting can raise its utilization rate. It responds well to crops such as rice, rapeseed, beans and green manure, and dipping seedling roots or mixing with seed during seedling raising are also common methods of use. On calcareous or alkaline soils, however, its phosphorus is difficult to release and the application effect is poor, so water-soluble phosphorus fertilizer should be used instead.

It should be noted that calcium magnesium phosphate fertilizer is alkaline and should not be stored or applied directly mixed with ammonium nitrogen fertilizer, so as to avoid loss of ammonia through volatilization. When storing, it should be kept in a dry, ventilated place and protected from rain and moisture. As long as base application is arranged reasonably according to soil properties, its characteristics of complete nutrients and long-lasting fertilizer effect can be brought into full play.