Potential Slow Release Fertilizers Based on K2MgSiO4 Obtained from Serpentinite

Fabiane Ballotin,Ottávio Carmignano,Wedisson Santos,Rochel Lago,Edson Mattiello,Ana Paula Teixeira

doi:10.21577/0103-5053.20190229

Abstract

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.

Highlights

Fertilizers use is essential to achieve high crop yields under tropical soil conditions, which are generally poor in nutrients such as K and Mg
As the most of those occurring in tropical agricultural areas, the low cation exchange capacity (CEC)[2] limits the cationic retention, including K+
Upon thermal treatment of pure serpentinite at 700 °C (SER700) the Mg content increased to ca. 18% (Table 1) due to dehydration processes

Summary

Introduction

Fertilizers use is essential to achieve high crop yields under tropical soil conditions, which are generally poor in nutrients such as K and Mg. As the most of those occurring in tropical agricultural areas, the low cation exchange capacity (CEC)[2] limits the cationic retention, including K+ In these conditions, unsuitable managements of traditional K-sources, such as KCl, may lead to risks associated to soil salinity, plant toxicity or losses by leaching across soil profile.[3] these reports evidence the need to prospect fertilizer technologies which release K in a controlled process according to plant demands aiming to improve fertilizer efficiency, including the reduction of both on K loss and the need of split application.[4,5] several studies have been performed into using different materials as slow-release K-fertilizer, such as rice husk ash for the synthesis of Serpentinite, a metamorphic rock with general approximate formula [Mg3Si2O5(OH)4], is found in different places on the surface of the world with global reserves estimated in hundreds of millions kg.[9] The basic serpentine structure is a layer composed of Mg-rich octahedral units [MgO2(OH)4]6– linked to tetrahedral silicate moieties [Si2O5]2–

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Conclusion