Biochar in Mediterranean agriculture: Effects on soil greenhouse gas emissions

0 5 10 15 20 25 30 35 -1 0 1 2 3 4 5 November December January February March April May June July mg N2O-N m2day-1 0 5 10 15 20 25 30 35 0 1000 2000 3000 4000 5000 6000 November December January February March April May June July mg CO2-C m2day-1 Biochar in Mediterranean agriculture: EFFECTS ON SOIL GREENHOUSE GAS EMISSIONS Simões-Mota, A.*1, Franco-Luesma, S.2, Álvaro-Fuentes, J.1 1–Spanish National Research Council (CSIC), Zaragoza, Spain * [email protected] 2 –Aragon Agri-Food Research and Technology Center (CITA), Zaragoza, Spain www.pysolo.eu Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Climate, Infrastructure and Environment Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. Timeline of key field operations: November 2024: Basal fertilization NPK 8 15 15 (48kg N ha-1) + Biochar; tillage. Wheat (Triticum durum) sowing. March 2025: Top-dressing (spring) fertilization. July 2025: Harvest. Mediterranean semiarid climate with annual mean air temperature of 14.1 ºC, annual precipitation of 298 mm.The soil is a silty loam, well drained, classified as Typic Xerofluvent (Soil Survey Staff, 2014). RESULTS 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 CMF LB MB LB+MF MB+MF kg N2O-N ha-1 0 1000 2000 3000 4000 5000 6000 CMF LB MB LB+MF MB+MF kg CO2-C ha-1 Fertilization Rainfall CONCLUSIONS INTRODUCTION EXPERIMENTAL DESIGN The biochar used in this study was produced from pine wood chips via slow pyrolysis at 500 °C. Prior to application, it was air-dried, ground, and sieved to <2 mm. Gas flux monitoring: Soil CO₂and N₂O emissions were measured with a static chamber method and analyzed by gas chromatography. Samples were collected every 2 weeks. After each fertilization event every day during the following week. Cumulative seasonal emissions were calculated by linear interpolation between sampling dates. Bulk density (g cm-3) 1,39 ±0,2 pH 8,01 ±0,02 EC (µs cm−3 at 25ºC) 226,83 ±74,1 Phosphorus (mg kg-1) 0,08 ±0,01 Organic Carbon (%) 1,24 ±0,01 Ammonium -N (ppm) 2,86 ±0,25 Nitrate -N (ppm) 2,68 ±1,65 Clay (%) 15 C: Baseline control MF: Fertilizer control (0.6 t ha-1) LB: Low Biochar (2 t ha-1) MB: Medium Biochar (6 t ha-1) LB + MF: Low Biochar + Min Fert (2 + 0.6 t ha-1) MB + MF : Medium Biochar + Min Fert (6 + 0.6 t ha-1) METHODOLOGY Main Objective: Assess the potential of biochar to improve nitrogen management efficiency while maintaining or reducing GHG emissions in Mediterranean cereal systems. Soil main properties: Treatments: Biochar is a carbon-rich material obtained from the thermal decomposition of biomass. Its use in agricultural soils can enhance nutrient retention, improve water-holding capacity, and reduce soil greenhouse gas (GHG) emissions. These benefits are particularly relevant in semiarid regions, where soils are often low in organic matter and vulnerable to degradation. However, the positive results of biochar depends on feedstock type, production temperature, application rate, and its interaction with mineral fertilization. When combined with mineral fertilizers, biochar may reduce N₂O losses by improving nitrogen use efficiency, although results vary with soil type. Understanding these interactions under Mediterranean field conditions is essential to design fertilization strategies that balance crop productivity with climate change mitigation. Daily GHG Emissions Cumulative GHG Emissions (NOV 24 –JUL 25) Zaragoza, Spain Static chamber a c ab ab bc bc *p < 0.05 CO₂: Higher overall fluxes in the co-application of biochar + MF. Biochar-only treatments maintained lower, steadier respiration. N2O: Spring N₂O peaks coincided with rain and warmer temperatures, indicating environmentdriven ‘hot moments’; MF amplified these pulses, but biochar + MF slightly dampened them. Occasional spikes in MB and controls likely reflect rewetting. * * * * * * * Seasonal context: Soil temperature rose from ~6 °C (Feb) to ~30 °C (July), while soil moisture declined from ~20 to ~5%, shaping soil GHG dynamics across treatments. N₂O: Over the season, MF drove the largest cumulative losses. The co-application of biochar with MF lowered emissions by ~16%. Biochar alone kept emissions near control levels, reinforcing its low-N₂O footprint. •MF drives N₂O emissions, especially during warm, wet “hot moments” in spring. •Biochar + MF slightly reduced N₂O losses, showing potential for mitigation. Biochar without MF had minimal N₂O impact. •CO₂fluxes were less responsive to treatments. •Environmental conditions were triggers for emission peaks during spring fertilization. Didn’t’ catch me here and wanna talk? Say hi :)