“…the increase in soil carbon stocks represents a relevant strategy for mitigating climate change.”
Jéssica Pereira de Souza is a postdoctoral researcher at the Department of Soil Science at UFRGS, studying isotopic techniques (¹³C) to trace carbon derived from crop residues and roots. She holds a degree in Agronomy from UniCatólica, a master’s in Soil Science from UFPR and a PhD in Soil Science from UFRGS. She has experience in carbon dynamics and the management of sustainable agricultural systems.
Jéssica Pereira de Souza, postdoctoral researcher in Soil Science.
AgriBrasilis – What is the importance of soil organic carbon accumulation?
Jéssica – Soil organic carbon (SOC) is the main component of soil organic matter (SOM) and plays a central role in maintaining the quality and sustainability of agricultural systems. Its accumulation is directly related to improvements in soil structure, promoting the formation and stability of aggregates, which enhances water infiltration and retention, reduces erosion, and increases resilience to extreme climate events. In addition, SOC acts as an important reservoir of nutrients and energy for microorganisms, contributing to nutrient cycling and crop productivity. From an environmental perspective, increasing soil carbon stocks represents a relevant strategy for mitigating climate change.
AgriBrasilis – In this context, which agricultural practices are most recommended?
Jéssica – The foundation of agricultural management to increase SOC stocks is to boost carbon inputs through plant production and reduce losses through SOM mineralization. In general, minimal soil disturbance and continuous plant cover are recommended. Practices such as no-till farming, which minimizes soil disturbance and reduces SOM mineralization rates; the use of cover crops, which ensures continuous residue input; and crop rotation, which diversifies the quality of organic compounds added to the soil, stand out. Integrated systems, such as crop-livestock-forestry integration and agroforestry systems (AFS), have also proven effective by promoting greater biomass input, especially from roots and consequently greater carbon accumulation.
AgriBrasilis – How do microorganisms contribute to carbon sequestration or mineralization?
Jéssica – Soil microorganisms play a central role in carbon dynamics, acting simultaneously in both sequestration and mineralization processes. They use organic compounds derived from plant residues and root exudates, regulating the fate of carbon through their metabolic activities. Carbon mineralization occurs mainly through catabolic processes, in which microorganisms decompose organic matter via extracellular enzymes, releasing CO₂ into the atmosphere.
On the other hand, microorganisms also contribute to carbon sequestration through anabolic processes. During microbial growth, part of the assimilated carbon is incorporated into microbial biomass and later transformed into necromass and microbial metabolites. These microbial products constitute a significant fraction of stable soil organic matter. Carbon stabilization occurs mainly through its association with soil minerals, occlusion within aggregates and physical protection in microenvironments where microbial access is limited.
The balance between sequestration and mineralization is directly related to microbial physiology, especially carbon use efficiency (CUE), which determines how much of the assimilated carbon is converted into biomass or lost as CO₂. Factors such as the type of plant residue, temperature, moisture, pH, oxygen availability and soil mineralogy modulate microbial activity and community composition, directly influencing these processes.
AgriBrasilis – How does land-use change influence the loss or accumulation of this element in the soil?
Jéssica – Land-use change is one of the main factors affecting soil carbon stocks. The conversion of natural ecosystems, such as forests, into agricultural areas generally results in significant carbon losses due to reduced residue input and increased organic matter decomposition, especially when associated with soil disturbance. Conversely, the adoption of conservation practices and the restoration of degraded areas can partially reverse these losses, promoting gradual carbon accumulation over time, particularly in systems with high root biomass production.
AgriBrasilis – What are the challenges to expanding the adoption of practices that increase soil carbon sequestration in Brazil?
Jéssica – Despite the widely recognized benefits, expanding the adoption of practices that promote soil carbon sequestration in Brazil still faces several challenges. These include initial implementation costs, lack of specialized technical assistance and difficulties in adapting practices to the country’s diverse soil and climate conditions. In addition, cultural factors, such as resistance to changing traditional management systems and institutional limitations, such as the absence of robust public policies and economic incentives, hinder the dissemination of these practices. Therefore, promoting soil carbon sequestration in Brazil depends not only on scientific advances but also on integrated strategies involving technical training, incentive policies and awareness among farmers.
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