Slow calcium release fertilizers and methods for their synthesis are described. Organic materials, particularly from manure are used for coating to achieve slow release forms of the fertilizer. Desirably, low temperature kinetic treatments are used to prepare pulverized forms having small size yet well coated with natural (non-denatured) molecular material to achieve the slow release. A desired embodiment is made from kinetic processing of rock gypsum and manure at low temperatures with added acid. Use of the fertilizers leads to acceleration of microbial viability.