Soil carbon and greenhouse gas fluxes in soybean cultivation: comparing organic, conventional, no-tillage, and liquid swine manure management

• Ano de defesa: 2024
• Autor(a) principal: Santos, Carolina Ferraz dos
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Carbon sequestration; Emissão de gases; Gas emissions; Manejo do solo; Sequestro de carbono; Soil management
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/64/64133/tde-27082024-104210/

The movement of organic agricultural production has been gaining more prominence in Brazil and worldwide as these products are increasingly associated with higher levels of safety and health for consumers and lower social and environmental impacts. Soybean, a primary source of protein for organic and non-organic animal feed, sees Brazil responsible for 42% of global production. Soil management practices, such as tillage versus no-tillage and mineral versus organic fertilization, play key roles in organic matter decomposition and may influence greenhouse gas (GHG) emissions. Aiming to advance this subject, the present study assessed four different soybean production systems, being organic with soil tillage and non-organic with no-till, soil tillage and no-till with swine liquid manure. We examined soil carbon (C) stocks in two functionally different fractions: particulate organic matter (POM) and mineral-associated organic matter (MAOM). Additionally, we analyzed C stable isotopes to identify C origins (C3 and C4 plants) in these fractions. Furthermore, GHG fluxes (CO2, N2O, and CH4) were quantified weekly to capture emissions throughout the growing season. Our central hypothesis posits that systems fertilized with organic amendments accumulate more soil C despite higher GHG fluxes. The outcomes suggest differences in C on POM mainly on the first soil layers, with treatments NTS (2.55 ± 0.26 a) and OT (3.36 ± 0.59 ab) showing the highest variations. MAOM was the main contributor to long-term C sequestration in soil for both 0-30 cm and 0-60 cm. We hypothesized lower MAOC values for NTS and OT due to the priming effect, which consumes MAOM stocks and triggers soil emissions. The measured CH4 fluxes did not show statistical differences between treatments, but CO2 and N2O fluxes did. GHG fluxes, expressed as CO2eq, were higher for treatments with organic amendments (OT and NTS), likely due to the high organic matter turnover resulting from large C inputs in these systems (priming effect).