Nitrous oxide (N2O) is a potent greenhouse gas. Agriculture is the largest anthropogenic source of N2O due to fertilizer use and soil microbial activity. Clay-rich soils, such as Vertisols, develop deep desiccation cracks that remain open to the atmosphere, creating direct gas pathways. Thermal gradients between crack and ambient air can drive convective airflow and enhance gas exchange, potentially increasing N2O and CO2 emissions from the soil.
To our knowledge, no field study has quantified whether such cracks increase these emissions or their share in total soil-atmosphere fluxes. This study aims to quantify the contribution of desiccation cracks to N2O and CO2 emissions from cultivated Vertisols.
Field measurements at Neve Ya’ar, Israel, using a static closed-loop chamber and MIRA Ultra gas analyzer to measure N2O and CO2 fluxes from active cracks and adjacent matrix soil. Recorded parameters included crack geometry, soil moisture and temperature profiles, crack air temperature, and nitrogen species in porewater. Preliminary results show higher N2O-N and CO2-C fluxes from cracks than matrix (N2O-N: 0.0025 µg m2 d-1 vs. 0.00070 µg m2 d-1 (p = 0.00284); CO2-C: 11.2 µg m2 d-1 vs. 6.5 µg m2 d-1 (p = 0.0719), respectively), suggesting cracks are emission hotspots.
To gain deeper insights into the impact of desiccation cracks on N2O and CO2 emissions, a synthetic crack system is being developed for controlled laboratory experiments. In these experiments the impact of crack aperture, soil water content, soil nitrate (NO3-) concentration, and air thermal gradients on N2O and CO2 fluxes will be studied.
