REMINERALIZATION OF AGRICULTURAL SOIL: STUDY OF CHEMICAL CHANGES RESULTING FROM ACCELERATED WEATHERING

Abstract

Soil remineralization in Brazil has gained prominence in the world for being a source of nutrients for the soil, due to its ability to form new crystalline phases. Also known as accelerated weathering of rocks, this practice has shown potential for chemical and physical recovery of agricultural soils. It also has the appeal of decarbonization via rock weathering, which in fact tends to occur faster when compared to natural conditions of soil formation. This research aimed to analyze the effects and remineralization potential of two agricultural soils using a sustainable solution of Compact Shale with Ca and Mg contents from mining tailings in the region of Itabira/MG. The experiment was conducted in two locations. One in Nazareno, Minas Gerais, and the other in Piracicaba, São Paulo. The rock dust was ground at 0.106mm and applied at a rate of 22 tons/ha. In both locations, the material was deposited under the soil and incorporated with the aid of a plow harrow up to a depth of 30cm. The experiment installed in Piracicaba was irrigated to field capacity and the trial in Nazareno waited for the regularity of the rainfall in the region. In both locations, the experimental design was in randomized blocks with 5 treatments and 6 replications. For the experiments, the following treatments were adopted: control (T1 without application), T2 of pure compact shale, T3 dolomitic limestone in Nazareno-MG and pure calcitics in Piracicaba-SP, T4 of compact shale added of dolomitic and calcitic limestone (Nazareno-MG and Piracicaba-SP respectively), and T5 of market remineralizer (Agrifértil Mg+ in Nazareno-MG and ErgoFert Grow+ in Piracicaba-SP. The chemical/agronomic indicators of soil quality were analyzed. Compact shale modified soil pH during the experimental period. The compact shale showed superior behavior to the commercial limestone for the indicators of pH (CaCl2 and H2O), saturation by base, exchangeable aluminum (Al3+) and potential acidity (H+Al).  These results were similar to those of the isolated and combined limestones for the Effective CTC (t) and Sum of bases (SB) indicators.