Granulated organo-mineral fertilizers: the process of formation and investigation of porous phosphate-diatomite shell

Climate change and shortages of mineral fertilizer supplies for the future of agriculture are raising fears of a global food crisis. There is a need for proactive innovations in fertilizer research to maintain soil fertility. Using granules with special properties, particularly organic-mineral fertilizers with the nanoporous structure of the shell (coating), is a promising solution to the possibility of controlled dissolution in the soil. A review of the composition of organic-mineral fertilizers' shells showed that despite elements that are feasible to provide a nanoporous structure, an additional search for pore-forming elements is a significant task. Microscopic studies of diatomaceous earth showed that the size of individual particles is not more than 20 μm, and most of them have a porous structure. In addition, diatomaceous earth has the necessary characteristics that increase soil fertility. Based on this fact, a new composition of the organic shell with the inclusion of diatomite has been proposed. Shell nanoporous structure of the organo-mineral fertilizer with the inclusion of diatomite has a developed network of nanopores that prolong the action of the granule’s nitrogen component. Using spectrometry and electron microscopy, studies of the phase and chemical composition and crystal structure of encapsulated fertilizers showed a uniform distribution of chemical elements through the coating thickness. It also supports the prolonged action of carbamide granule core and accumulation of soil humidity that gives the possibility to increase stress tolerance of plants during the dry periods of vegetation due to the addition of Si-containing compounds into the shell of fertilizers.