Concept of use of comprehensive fertilizers of long-term action on the basis of waste processing of potassium-magnesium ore as a new paradigm in improving soil fertility

Technology for the production and use of new multiple slow-release fertilizers from clay-salt waste (sludge) remaining as a result of potassium fertilizers production from natural K-Mg ores, is elaborated in Perm Federal Research Center. The main processes in the technology are waste enrichment and subsequent high-temperature calcination of the enriched concentrate. As a result, the product, received the name the calcine of clay-salt sludge, was formed having the properties of multiple slow-release fertilizer and ameliorant. Laboratory and field experiments on the calcine use as a potassium fertilizer were fulfilled. The studied crops were spring wheat, barley, and potato. The experimental scheme included such treatments: control (without fertilizers), NP – background; NP + KCl and NP + calcine. The use of calcine for grain crops (wheat, barley) on the NP background promoted the yield gains by 1.7–1.9 t/ha compared with the control, the use of standard NPK fertilizers – by 1.8–2.0 t/ha, the difference was within the error of the experiment (HCP05 = 0.21; 0.38 t/ha). The content of nitrogen, phosphorus and potassium in the grain and straw of both crops in the treatments using calcine was approximately equal to the variants using standard fertilizer and significantly higher compared to the control. Differences between calcine treatments were not significant. The application of N90P90 and full mineral fertilizer (N90P90K90) contributed to the yield increase of potato tubers by 1.43–4.51 t/ha respectively. The use of unconventional potassium fertilizer – calcine on the background of NP was not inferior in efficiency to the use of traditional fertilizer – potassium chloride. The quality parameters of the potato crop (dry matter and starch content in tubers, the content of heavy metals) were also not inferior compared to the use of traditional potassium fertilizer. The use of calcine for potato and cereals in rates equal to K60-120 did not lead to deterioration of the fertility indicators of sod-podzolic soil. Upon receipt of the cinder, one can use the additional unlimited set of components. In other words, this is a conceptual model for creating new types of mineral fertilizers with desired properties for different soil and climatic conditions and crops with different requirements for mineral nutrition