1 / 27

Soil C Dynamics Following Addition of 13 C-labeled Grain Sorghum ( Sorghum bicolor ) Residue

Soil C Dynamics Following Addition of 13 C-labeled Grain Sorghum ( Sorghum bicolor ) Residue. Paul White and Dr. Charles W. Rice Department of Agronomy Kansas State University Manhattan, KS. Carbon Sequestration. Atmospheric CO 2 levels have increased from 260 to 370 ppmv (IPPC, 2004).

jenis
Download Presentation

Soil C Dynamics Following Addition of 13 C-labeled Grain Sorghum ( Sorghum bicolor ) Residue

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Soil C Dynamics Following Addition of 13C-labeled Grain Sorghum (Sorghum bicolor) Residue Paul White and Dr. Charles W. Rice Department of Agronomy Kansas State University Manhattan, KS

  2. Carbon Sequestration • Atmospheric CO2 levels have increased from 260 to 370 ppmv (IPPC, 2004). • Increasing soil C storage may assist in offsetting increases in CO2 due to fossil fuel emissions until cleaner fuel technology is available on a large scale. • Understanding dynamics of C flow in differently managed ecosystems will be important to forecast C-sequestration effectiveness and extent. • Possible manipulation of ecosystem to increase soil C storage potential

  3. Sunlight Temperature Moisture Nutrients CO2 Inputs Outputs Substrate Quality Soil Belowground Biology

  4. Readily decomposable Moderately decomposable Resistant INPUTS Plant residue CO2 CO2 CO2 Microbial Biomass C Plant and microbial byproducts CO2 = OUTPUTS CO2 CO2 Slow soil C Stable soil C Temporal C changes in soil aggregates? Changes in microbial community dynamics? Adapted from Paul and Clark, 1996

  5. Objectives During one growing season: • Measure the mineralization of 13C-labeled plant residue • Measure the changes in soil TC and TN • Measure the changes in soil TC and 13C in macro- and microaggregates • Determine microbial community changes in response to added residue

  6. Materials and Methods

  7. Ashland Experimental Farm, Manhattan, KS Field Microcosm Experiment • Continuous Sorghum under No-Tillage (NT) and Conventional Tillage (CT) • 4 Blocks • 2 Residue Levels: Control (no residue) and 0.5% by weight • 7 Sample Times: 0, 3, 16, 25, 40, 68, and 159 d • Data analyzed using SAS v9 Proc Mixed and means separated at the 5% significance level (SAS Institute, Cary N.C).

  8. Materials and Methods Sorghum bicolor CV: Mycogen 1506 0.5X Hoagland’s Pulse labeled 5X with 100% 13CO2 Pre-boot stage (about 65 d) Above ground material removed, freeze dried, shredded, and the 4 to 6 mm fraction retained for field experiment Aboveground Residue Characteristics Total C 13C (PDB) ----%---- -----‰----- 42 570

  9. Materials and Methods NT 2.1 g 13C labeled residue placed on soil surface 20 cm deep by 5 cm diameter PVC cores 15 cm CT 2.1 g Mixed evenly with upper 15 cm soil with soil Anion and Cation Exchange Resin bag

  10. Materials and Methods Sample Times: 0 3 16 25 40 68 159d 0 cm Soil separated into 0-5 and 5-15 cm sections and sieved (4 mm) and either air-dried, put in 4 °C cooler, or freeze dried depending on analysis. 5 cm 15 cm Anion and Cation Exchange Resin bag

  11. Materials and Methods C measurements on a scaled approach Total % C and N 13C Whole Soil 13C Aggregates (>1000 m, 250-1000 m, 53-250 m, and 20-53 m) Phospholipid Fatty Acids Neutral Lipid Fatty Acids Overall system stability New input decomposition and retention Temporal C changes in aggregates? Changes in microbial community structure?

  12. Materials and Methods Total % soil C, N by dry combustion & TCD detection 13C whole soil measured by conversion to CO2 using dry combustion and isotopic 13C measured using Europa 20-20 IRMS. 13C Data reported relative to the Pee Dee Belemnite (1.12372% 13C, or 0‰)

  13. Soil Chemical and Physical Parameters and 2004 Climate Data

  14. Soil: Muir silt loam Tillage Depth pH P Ca K Mg Na SO4-S NH4-N NO3-N TC TN 1:1 -----------------------mg/kg------------------------ ----%---- CT0-5 5.4 128 1844 317 281 3.6 7.5 3.6 8.2 1.2 0.11 CT5-15 5.7 52 2209 193 308 6.0 7.6 2.8 3.4 1.2 0.11 NT0-5 5.0 158 1768 262 251 3.7 8.3 2.9 5.4 1.9 0.17 NT5-15 5.8 41 2201 173 291 5.8 6.5 2.5 2.4 1.4 0.13 Bulk Density: NT=1.40 g/cm3 CT=1.36 g/cm3 (G. Doyle, Ph.D. Dissertation) Data reported on a Mg/ha to 15 cm depth basis

  15. 2004 Precipitation Sample Times:

  16. 2004 Temperature 2004 Air Temperature 1980-2003 Air Temp

  17. Results

  18. Time=2 Soil C Time=1 Soil C b 60 50 60 a a 40 50 Time=0 Soil C a MgC/ha 30 40 b 20 MgC/ha 30 a 60 10 20 a a 50 0 10 0-5 5-15 0-5 5-15 40 0 0-5 5-15 0-5 5-15 MgC/ha 30 CT CT NT NT 20 CT CT NT NT Treatment 10 Treatment 0 0-5 5-15 0-5 5-15 Time=4 Soil C CT CT NT NT Time=3 Soil C Treatment 60 50 60 40 50 MgC/ha 30 40 20 MgC/ha 30 10 20 0 10 0-5 5-15 0-5 5-15 0 0-5 5-15 0-5 5-15 CT CT NT NT CT CT NT NT Treatment Time=6 Soil C Treatment 60 50 40 MgC/ha 30 20 10 Time=5 Soil C 0 0-5 5-15 0-5 5-15 60 CT CT NT NT 50 Treatment 40 MgC/ha 30 Treatment 20 10 0 0-5 5-15 0-5 5-15 CT CT NT NT Total Soil C –Tillage X Depth Interaction

  19. Time=1 Soil N 5 Time=2 Soil N T=0 Soil N 4 3 5 5 MgN/ha 2 4 4 1 3 3 MgN/ha MgN/ha 0 2 2 0-5 5-15 0-5 5-15 1 1 CT CT NT NT 0 0 0-5 5-15 0-5 5-15 Treatment 0-5 5-15 0-5 5-15 CT CT NT NT CT CT NT NT Treatment Treatment Time=3 Soil N Time=4 Soil N 5 5 4 4 3 3 MgN/ha MgN/ha 2 2 1 1 0 0 0-5 5-15 0-5 5-15 0-5 5-15 0-5 5-15 Time=6 Soil N CT CT NT NT CT CT NT NT Treatment Treatment 5 4 Time=5 Soil N 3 MgN/ha 2 5 1 4 0 3 0-5 5-15 0-5 5-15 MgN/ha 2 CT CT NT NT 1 Treatment 0 0-5 5-15 0-5 5-15 CT CT NT NT Treatment Total Soil N –Tillage X Depth Interaction

  20. Kinetics modeled as first order having a rapid and slow phase according to: Ct=Co-ekt CT 0-5 13C remaining during experiment 6 5.5 CT0-5block1 ln100+13C CT0-5block2 CT0-5block3 CT0-5block4 5 4.5 0 10 20 30 40 50 60 70 80 Time (d)

  21. CT 5-15 13C remaining during experiment

  22. NT 0-5 13C remaining during experiment

  23. By T=5, no significant difference between tillage or depth in remaining total amount of 13C in soil: 0-15 cm average 13C --------‰ (PDB)-------- CT +28.66 NT +34.63 Rapid Slow ---------k/day------------ -0.0316 -0.0024 Residue Decomposition Kinetics

  24. Conclusions • Addition of 0.5% by weight grain sorghum residue did not have significant impacts on soil C and N dynamics during the growing season Indicating relative macro system stability • Decomposition kinetics and residual 13C levels were not different between tillage regimes Label detectable throughout growing season • 13C Aggregate analysis and microbial lipids analysis may indicate management effects at a finer resolution

  25. Acknowledgments • Geronimo Watson, Karina Fabrizzi, Jamey Duesterhaus, and undergraduate lab techs • Dr. Chuck Rice • Dr. Mary-Beth Kirkham • Dr. Clenton Owensby • Dr. Dallas Pederson This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, Under Agreement No. 2001-38700-11092.

More Related