Use of Limestone Mining Pickling to Improve Soil Conditions and Resilience of Sandy Soils to Climate Change

• Grant number: 24/05622-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2024
• End date: July 04, 2025
• Field of knowledge: Agronomical Sciences - Agronomy
• Principal Investigator: Antonio Carlos de Azevedo
• Grantee: Leonardo Fontoura Crevelim
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated research grant: 21/10573-4 - Center for Carbon Research in Tropical Agriculture (CCARBON), AP.CEPID
• Associated scholarship(s): 24/21466-2 - Mineralogical Characterization of Potassic Clays in Overburden Material for Agricultural Use, BE.EP.IC

Abstract

Strategies to cope with climate change are urgent, particularly for fragile ecosystems such as those developed on sandy soils (those with 15% or less clay). These soils have a small capacity for biomass production because they have a small amount of clay, limiting their capacity to store nutrientes (CEC), water (WRC) and carbon. Prolonged periods of drought, the greater frequency of which results from ongoing climate change, are especially stressful for the already nutrient-starved vegetation. In pasture agroecosystems, usually established on these soils, it is not common to invest in water and nutrient supplementation, aggravating their degradation. Because of this context, the Federal Government published in December 2023 the National Program for the Conversion of Degraded Pastures into Sustainable Agricultural and Forestry Production Systems (PNCPD, Decree 11,815). The addition of clay to sandy soils is a technology that has been scarcely considered in Brazil. The resulting increase in Specific Surface Area (SSA) can potentially increase soil water and nutrient retention, aggregation and carbon sequestration. Sedimentary formations in the Paulista Peripheral Depression (PPD) in the State of São Paulo, such as Itararé, Tatui, Irati and Corumbatai, which have facies with the presence of K-clays (2:1 phyllosilicates with potassium interlayers), are often overlapped with basalt deposits (mined for the production of construction aggregates) and limestone (for the production of agricultural limestone). The material from these formations is removed, and when it does not have the potential for use in the ceramic industry of São Paulo, it accumulates in the yards of the mining companies, without destination (mine overburden). The PPD surrounds the Western Plateau of São Paulo (PWP), where sandy soils developed over the sandstones of the Bauru Group, enabling freight between source (PPD) and destination (PWP). The objective of this proposal is to evaluate the ability of K release from the K-clays from a limestone mining overburden applied to a sandy soil from the PWP, as well as the increase of soil ASE, CEC, WRC, aggregation, and carbon capture in the soil. This evaluation will take place in pots under constant moisture regime and also under a regime alternating cycles of wetting and drying. It isanticipatedthat these cycles should accelerate the release of K from the clay interlayers. If this exploratory investigation is successful, developments may result in the transformation of mining overburden into a lowcost and long-lasting input to improve soil conditions and carbon capture in sandy soils, becoming a nature-based technology. By improving edaphic conditions, this technology would contribute to promoting the circular economy at the state level, to the objectives of the PNCPD and to the increase of Animal Units (number of animals ha-1) in pasturelands, reducing the pressure for deforestation of new areas for grazing.