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Quantifying Greenhouse Gas Emissions from Managed and Natural Soils

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Presentation by Klaus Butterbach-Bahl, Björn Ole Sander, David Pelster, and Eugenio Díaz-Pinés.

Presentation of the key elements of the the Quantifying Greenhouse Gas Emissions from Managed and Natural Soils chapter in the recently published book Methods for Measuring Greenhouse Gas Balances and Evaluating Mitigation Options in Smallholder Agriculture

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Quantifying Greenhouse Gas Emissions from Managed and Natural Soils

  1. 1. INSTITUTE OF METEOROLOGY AND CLIMATE RESEARCH, ATMOSPHERIC ENVIRONMENTAL RESEARCH, IMK-IFU DIVISION/Working Group… (change in master view) Quantifying Greenhouse Gas Emissions from Managed and Natural Soils Klaus Butterbach-Bahl1,2, Björn Ole Sander3, David Pelster2, Eugenio Díaz-Pinés1 1: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU) 2: International Livestock Research Institute (ILRI) , Nairobi , Kenya 3: International Rice Research Institute (IRRI) , Los Baños, Philippines
  2. 2. 2 Motivation Worldwide, agriculture is responsible for 47 and 84 % of anthropogenic CH4 and N2O emissions, respectively (Smith et al 2007, IPCC WG III) Smallholder farms are crucial in e.g. Sub-Saharan Africa 75 % of both agricultural and job production (Africa Development Bank 2010) 80 % of farms in SSA are smaller than 2 ha (FAO 2010) Yields are low (ca. 1 Mg ha-1) Evidence-based data of GHG emissions in smallholder farms is scarce Source: Rosenstock et al. 2016. D.O.I. 10.1007/978-3-319-29794-1_1
  3. 3. 3 Chamber methods for measuring GHG fluxes in terrestrial ecosystems Pros + Simple, no in-situ analyzers needed + Allow for treatment-plots experiments + Existence of protocols Cons - Change in the soil environmental conditions - Spatial and temporal variability of fluxes - Accuracy and reliability of measurements
  4. 4. 4 Chamber Placement Terrain Soil Vegetation Management Logistics •Depressions/ ridges/ slope (deposition/ erosion, depth to groundwater) / aspect •Paths (bulk density) •Stones/ terraces (management) •Color (SOC/ flooding) •Texture (water/ nutrient availab.) •Compaction/Plough pan (bulk density) •Natural (vegetation layers/ patchiness, species, coarse woody materialnutrient/ water availability) •Row crops (row/ interrownutrient/ water availability) •Intercropping (nutrient/ water availability) •Irrigation/ flood water inlet/outlet (soil processes) •Fertilization (water/ nutrient availab.) •Compaction/Plough pan (bulk density) •Accessibility •Change of soil properties along access paths •Interference with management
  5. 5. 5 Gas sampling Monitor Timing & interval Vials Sampling Storage •Crop performance in/ outside chamber • Animal activity (e.g. ants, termites, earthworms) •Chamber seals/ maintainance •Approx. at average daily soil-T (e.g. morning 9-11) •Minimize closure time (determine minimum detectable flux) to minimize chamber effects on soil environmental conditions •Flushing (min. 2x volume) or use pre-evacuated vials •Overpressurize •Logical numbering •Minimize disturbance at the plot (plant cover/ soil compaction) •Flush syringe •Ensure headspace mixing •Check seal tightness •Determine max. storage time •Use standards for comparison •Store vials in boxes
  6. 6. 6 Gas analysis and data processing Responsibility Measurement instrument Flux calculation Maintenance Reporting •Hierarchy of responsibility (instrument maintenance/ analysis/ data storage/ reporting) •Understand principles •Optimize sensitivity in terms of accuracy & precision •Coefficient of variation for repeated concentration measurements (e.g. N =5) <1% •Check relationship between instrument signal and concentration •Linear or non-linear (understand advantages and disadvantages of both) •Calculate detection limits •If slope of regression = 0 (check p- value of slope)  flux = 0 •Stock spare parts •Check & service instrument regularly •Clean environment •Do flux calculations immediately •Report back problems to sampling team (e.g. numbering/ unusual noise in concentration changes across sampling interval •Check logic of fluxes with observations of auxilliary measurements
  7. 7. 7 Auxilliary Measurements & Reporting Socio- economy Meteorology Soil properties Soil hydrology Crop/ plant performance •Precipitation •Air temperature •Photosynthetic active radiation •Wind speed/ direction •Relative humidity •Evapotranspiration rates •Soil-temperature/ moisture (different layers down to 1m if possible) Multi-layer (0-10, 10-20, 20-50, 50- 100 cm) •Texture/ SOC/ total N / inorganic N/ bulk density/ pH •Water saturated conductivity •Microbial biomass C and N •Litter type / depth / C and N content (if applicable) •Water infiltration / hydraulic conductivity / water holding capacity •Distance to groundwater •Floodwater depth (e.g. rice paddies) •Depth of drainage tiles •Biomass development (monthly) •Pests/ diseases/ weeds •Development stages (e.g. tillering/ flowering) •LAI •Harvest index •Yield / N content Management •Field operations (e.g. ploughing, seeding, weeding, fertilization, irrigation, harvesting, pesticide applic.) •Fertilizer types & amounts •Crop type / rotation, variety and planting density •Residue management
  8. 8. 8 Spatial and temporal variability of soil GHG fluxes Source: Barton et al. 2015, Scientific Reports, D.O.I. 10.1038/srep15912 Source: Cowan et al. 2015, Biogeosciences, D.O.I. 10.5194/bg-12-1585-2015
  9. 9. 9 Chamber 1 The gas pooling technique Arias-Navarro et al. 2013, Soil Biol Biochem, D.O.I. 10.1016/j.soilbio.2013.08.011 Close Mixing of the gas sample Pressurize/ Expand T0 Inject, flush & overpressurize glass vial T0 T0 T1T2T3 T2 T1T3 Gas Chromatograph
  10. 10. 10 Chamber-based methods are recommended in complex landscapes such as smallholder agriculture. Spatial and temporal variability remains a huge challenge  adequate design and sampling frequency are crucial. QA/QC is essential at all steps. Chamber design and positioning Gas sampling and analysis Calculations and reporting Conclusions Voice: David Pelster, Klaus Butterbach-Bahl & Allison Kolar

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