Short-term carbon dioxide emission under contrasting soil disturbance levels and organic amendments

• A first-order decay model was used to assess CO2 emissions from a Nitisol.
• Soil temperature was the main abiotic factor regulating CO2 emissions.
• Soil disruption and crop residue incorporation increased CO2 emissions by up to 13%.
• Application of composted or digested swine slurry can offset soil CO2 emissions.
• Composted swine slurry presented a genuine potential for soil organic C accumulation.

Agriculture can be either a source or sink of atmospheric CO2 depending on soil management. The application of swine slurry in conventional tilled soils could enhance soil CO2 emission depleting soil organic C stocks. However, the use of recalcitrant C-rich organic fertilizers in no-till soils can offset soil CO2 emission promoting soil C sequestration. This hypothesis was tested by evaluating short-term CO2-C emissions from a Rhodic Nitisol under contrasting soil disturbance levels (disturbed (DS) and undisturbed soil (US)) top-dressed with mineral or organic fertilizers (urea (UR), raw swine slurry (RS), anaerobically digested swine slurry (ADS), and composted swine slurry (CS)). Soil CO2 emission was evaluated for 64 days using static chambers where gas samples were collected and analysed by photoacoustic infrared spectroscopy. Soil water-filled pore space (WFPS), temperature and meteorological data were concomitantly registered and a first-order exponential decay model was used to assess the decomposition of organic fertilizers and CO2 emissions induced by soil disturbance. Soil CO2-C emission was correlated with soil temperature, while limiting soil aeration impaired CO2-C efflux when WFPS >0.6 cm3 cm−3. Disturbance increased soil CO2-C efflux (36.3 ± 2.2 kg CO2-C ha−1 day−1) in relation to US (33.3 ± 1.6 kg CO2-C ha−1 day−1). Extra labile C input through RS amendment induced an increased soil CO2-C efflux for a longer period (t1/2 = 16.9 and 9.6 days in DS and US treatments, respectively), resulting in higher CO2-C emissions than soil amended with other fertilizers. The recalcitrant C input by ADS and CS had limited effect on soil CO2-C emissions. CS presented a genuine potential for substantial soil organic C accumulation while offsetting increased CO2-C emissions in comparison to RS amended soils.