Soil CO2 emission and short-term soil pore class distribution after tillage operations

Alongside the agricultural development in Brazil, concerns have arisen about its environmental impacts, such as the emissions of CO₂ resulting from soil cultivation and management practices in agricultural production systems. The aim of this study was to investigate the temporal variation in CO₂ emissions and soil physical attributes in response to the process of soil particle rearrangement after soil tillage operations. The study was conducted in three adjacent areas of 10 × 3 m, subjected to two soil tillage systems: (i) rotary hoe + conventional leveling harrow, representing an intensive soil tillage (IT); (ii) disc harrow + leveling harrow, characterizing a reduced tillage (RT). The soil of the third area was not tilled, representing the no-tillage (NT) system. Daily measurements of soil CO₂ emission (FCO₂), soil temperature, soil moisture, pore class distribution, bulk density, penetration resistance, water-free pore space, weighted mean diameter, aggregate stability index, total organic carbon, and particulate organic carbon were performed during a period of 29 days after soil tillage. On the first day after tillage, FCO₂ was 87% higher in the plot under IT (3.86 μmol m⁻² s⁻¹) than RT (2.06 μmol m⁻² s⁻¹) and 147% higher than in the plot under NT (1.56 μmol m⁻² s⁻¹). The variations in soil density and penetration resistance declined as of the 12th day after tillage. This effect was considered a natural process of soil consolidation and influenced the temporal variation of soil CO₂ emissions. Pore class distribution is an essential physical attribute to explain the temporal variations of soil CO₂ emissions, and these classes are influenced by the applied management. Therefore, the study of these attributes must be taken into account when assessing the variation of CO₂ emissions from agricultural soils.