Alterações nos compartimentos de carbono do solo pela aplicação de biochar : visão global e tendências locais

Abstract

Biochar application has emerged as a promising strategy to enhance soil carbon (C) sequestration, improve soil health, and mitigate climate change. However, its effects on soil C pools vary widely due to differences in feedstock, pyrolysis conditions, application rates, soil types, and environmental factors. This study aimed to quantify the potential of biochars to alter soil C pools under different conditions through a global meta-analysis and to understand the direct and indirect contributions of sewage sludge biochar (SSB) to soil C storage in a sevenyear field trial on a tropical Oxisol. In the first chapter, a meta-analysis of 586 paired comparisons from 169 studies worldwide was conducted. The results showed significant increases in total C (TC), organic C, microbial biomass C, labile C, and fulvic acid following biochar application, with factors such as biochar properties, soil characteristics, and experimental conditions influencing these effects. The second chapter detailed a seven-year field trial assessing the effects of SSB pyrolyzed at 300°C and 500°C on soil C pools and crop yield. SSB application increased soil TC and total nitrogen levels, enhanced the non-oxidizable organic C pool, and improved soil fertility. However, positive effects on crop yield declined over time without supplemental mineral fertilization. In the third chapter, the global metaanalysis findings were integrated with the local field trial results. The comparison revealed discrepancies, highlighting the importance of tailoring biochar applications to local conditions. Despite lower percent increases in soil C fractions in the field trial, the absolute TC gains were substantial, suggesting that SSB can effectively enhance soil C stocks in tropical soils when appropriately managed. This study confirms that biochar can enhance soil C sequestration, but its effectiveness is highly context-dependent, emphasizing the need to understand the factors influencing its impact on soil C pools for sustainable agriculture and climate change mitigation.