Sustainability via soil remineralization: blend of diabase, shale, and dolostone in Ferralsol and nutrient dynamics.

Abstract

Rock powders are increasingly considered a sustainable alternative to soluble fertilizers, particularly in highly weathered tropical soils. In this context, this study aimed to evaluate the short-term chemical and mineralogical changes induced by a diabase-shale-dolostone blend applied as a soil remineralizer to a Ferralsol under controlled laboratory conditions. Specifically, the experiment assessed nutrient release, changes in soil chemical attributes, and dissolution-precipitation features on mineral surfaces. A 1-year pot experiment was conducted in Rio Claro (SP, Brazil), using four remineralizer treatments and a control, each with three replicates. The treatments combined two application rates (15 and 20 t ha^-1) with two particle-size fractions: filler (< 0.3 mm) and powder (0.3-2.0 mm). Additionally, individual fragments of diabase and dolostone (2-5 mm) were enclosed in mesh bags to monitor surface weathering. Soil and fragments were sampled twice a year, while leached water was collected monthly. The remineralizer's application positively affected the soil, raising pH, base saturation, and the available levels of SO₄^2-, Ca²⁺, and Mg²⁺, as well as reducing Al³⁺ and Al saturation. New phases of clay minerals such as chlorite, vermiculite, and hydroxy-interlayered minerals (HIMs) were observed. The leachate evaluations showed the availability of K⁺, Ca²⁺, Mg²⁺, and Na⁺, along with the soil's permanence of Al³⁺, Si, and P. In fragments, the rapid precipitation of poor crystalline material-kaolinite-like phase (KLP)-demonstrates that rock powder reduced exchangeable acidity. The rock powder blend holds potential as a nutrient source for soil, especially secondary macronutrients, warranting future agronomic testing.