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MONS: Mechanisms of nitrous oxide emission in tropical soil

Grant number: 23/08814-9
Support Opportunities:Scholarships in Brazil - Post-Doctoral
Effective date (Start): January 01, 2024
Effective date (End): December 31, 2025
Field of knowledge:Agronomical Sciences - Agronomy - Soil Science
Principal Investigator:Maurício Roberto Cherubin
Grantee:Lucas Pecci Canisares
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

Abstract

The humanity faces a challenging moment of meeting the food demand, increase the ecosystem services and mitigate the anthropogenic impact in the climate crisis. Increasing soil organic matter is a key component to improve soil health, increase food production and mitigate the causes of the climate crisis in tropical agricultural systems. Using forage as cover crops growing in the inter-season of the Brazilian cash crops has an enormous potential of sequestering carbon into the soil. However, the greenhouse gas emission can be higher in these systems, especially for the higher nitrous oxide emissions (N2O), due to its impact on the soil microbiome and, consequently, the processes related to nitrogen (N) cycling. The mechanisms of niche differentiation of N2O producer microorganisms due to the higher plant residue, such as higher plant residue inputs and N mineralization, especially in tropical soils. The main goal of this project is to evaluate the impact of N mineralization from cover crop residues on different groups of N2O producers, specifically ammonia oxidizing microorganisms (AOM) because they typically control the rate-limiting process of N2O production in well aerated soils, as well as evaluate different strategies to mitigate N2O emission in contrasting ammonium sources (organic vs inorganic). This project will perform a meta-analysis to quantify the impact of quantity, quality and time of cover cropping on N2O emission through different functional groups of AOM (AOA, AOB and comammox). The project will use two soil microcosm incubations, one especially to understand the impact of the source of ammonium on the different groups of AOM, as well as the conversion of the ammonium into N2O and test the efficacy of different nitrification inhibitors to reduce the activity of these different groups in soils with contrasting ammonium sources (organic vs inorganic). This study will use a state-of-the-art technique to quantify the different functional groups of AOMs (AOB, AOA and comammox), DNA-qSIP combines stable isotopes with heavier mass to increase the density of the DNA of microorganisms that are actively using the substrate. The DNA extracted from the soil will be fractionated according with the bouncy density and the number of DNA copies will be quantified in each fraction using qPCR. This project will use the flux of N2O and the variations in the soil NO3- as supporting information to complement the molecular data. This combination of molecular and isotopic techniques is the state-of-the-art of microbial ecology because it quantifies directly the number of active microorganisms in the soil incubations and will contribute to improving the understanding of the mechanisms of N2O emissions from tropical soil. The results of the projects will crucial to improve the ability of the process-based models to predict the N2O emissions in different scenarios, it will further contribute with evaluating the efficacy of different mitigation strategies in contrasting soil N conditions in the context of the Centro de Pesquisa de Carbono em Agricultura Tropical (CCARBON, processo No 2021/10573-4). Thus, this project will improve the understanding of biological process related to soil health and agricultural sustainable intensification so the national and global goals to mitigate climate change can be achieved.

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