I have had some recent questions about calcium nitrate. Calcium nitrate, chemically known as ammonium calcium nitrate decahydrate (5Ca(NO3)2*NH4NO3*10H2O), is a white, hygroscopic, dry water-soluble material. It is 15.5% nitrogen and 19% calcium (15.5-0-0-19Ca). It is produced by reacting nitric acid with crushed phosphate ore and then neutralized with ammonia.
It is considered a 'double growth' fertilizer, since both the calcium and the nitrate contribute to plant growth. It is highly hygroscopic, and needs to be stored in a cool, dry location. Some formulations are coated to help retard moisture absorption during storage.
Compared to other nitrogen fertilizers such as urea or ammonium nitrate, it receives little attention. Many of the discussions I have heard about it originated from biological farmers, and they gave excellent reviews of its attributes. Several commented that using calcium nitrate, and calcium sulfate (SuperCal SO4) together produced some great results.
Because of its hygroscopic properties, I do not recommend mixing calcium nitrate with either SuperCal 98G, or SuperCal SO4, until it is time for application. Storing them as blended material would likely lead to particle degradation in storage.
- Western Fertilizer Handbook, 9th Edition