Agricultural repurposing of nickel slag residue
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Thermomagnesium (TM) or magnesium silicate (MgSiO3), is originally from the nickel (Ni) industry, and is a by-product that provides magnesium (Mg) and silicon (Si) to plants and corrects soil acidity. Some studies verify its solubility in tropical soils. This study evaluated the application of TM in two particle sizes (20 and 100 mesh), in sandy and medium-texture soils (Typical Oxisol), and a clayey texture soil (Typical Ultisol), in a six-month incubation experiment in a greenhouse. The soil samples were dried and sieved, placed in plastic pots, and incubated from 60 to 80% of the moisture retention capacity. Samples for pH analysis (CaCl2 extraction), Mg2+ (resin extraction) and Si4+ (CaCl2 extraction) were taken at 10, 20, 30, 40, 50, 60, 70, 85, 100, 115, 130, 150, and 180 days of TM incubation in the soils. The application of 100 mesh TM was superior owing to its greater contact surface, which increased the soil content of Mg and Si, and corrected the acidity in the three soils that were studied. The controlled release of TM (100 mesh) increased Mg fertilization efficiency, since less Mg2+ is lost by leaching, owing to the slower dissolution kinetics than soluble sources. The TM adjusts to the demand of the plants and has a residual effect for subsequent crop seasons.