Potential slow release fertilizers based on K₂MgSiO₄ obtained from serpentinite

In this work, a potassium magnesium silicate mineral based on phase K₂MgSiO₄ was prepared from serpentinite rock and studied as a potential K and Mg slow-release fertilizer. The material was prepared by impregnation of serpentinite/KOH and calcination at 700 °C to produce K₂MgSiO₄ phase, olivine and forsterite. The release patterns of K and Mg in the stirred-flow trial and leaching through the soil columns showed that K₂MgSiO₄-based materials released K on lower rates than KCl and MgSO₄.7H₂O, however, there was no evidence of Mg release. The extraction with 1 mol L^-1 NH₄OAc showed a considerable content of Mg and K for K₂MgSiO₄-based materials, due to exchange of NH₄⁺ and Mg²⁺. X-ray diffraction (XRD) analysis of materials impregnated with K and calcined showed peaks relative to K₂MgSiO₄. After leaching, the peaks intensity diminished, supporting that part of K leached. Therefore, the samples showed great potential as slow-release K-fertilizers when compared with KCl source. (author)