319-6 Cumulative Soil Carbon Dioxide Emissions: Accounting for Intra-Crop Spatial and Temporal Variability.

See more from this Division: S11 Soils & Environmental Quality
See more from this Session: S11 General Soils & Environmental Quality: II
Tuesday, October 23, 2012: 9:45 AM
Duke Energy Convention Center, Room 251, Level 2
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Aaron Daigh, Agronomy, Iowa State University, Ames, IA, Thomas Sauer, USDA-ARS National Laboratory for Agriculture & the Environment, Ames, IA and Robert Horton, Iowa State University, Ames, IA
Since soil-gas emissions are dynamic, high-resolution data are needed to capture their spatial and temporal relations and variability.  The objectives of this study are to 1) quantify and test relationships among soil-surface CO2 effluxes to soil physical conditions both spatially and temporally and 2) evaluate soil-surface CO2 effluxes among various cropping systems.  Near Ames, Iowa, six no-till cropping systems of mixed prairie (nitrogen fertilized and unfertilized), continuous maize with 50 % stover removal (with and without cover crop), and maize-soybean rotation (each crop type grown each year) was initiated with four replications in a randomized complete block design.  Various cropping systems and intra-crop management positions were instrumented with sensors to measure soil-surface CO2 efflux, soil water content and soil temperature.  Soil-surface CO2 effluxes differed among intra-crop management positions at times mid and late in the growing season in continuous maize systems but did not differ throughout the growing season in maize-soybean systems.  Soil-surface CO2 efflux was affected by physical conditions especially soil temperature and water content and/or management practice events.  The temporal structure of soil-surface CO2 efflux associated with soil temperature variations greatly differ when soil water content is either stationary or non-stationary over time.  Cumulative soil-surface CO2 emissions were greatest for the unfertilized prairie releasing 5.2 Mg CO2-C ha-1 from the soil.  All other cropping system soils released 4.0 (+/- 0.3) Mg CO2-C ha-1.  These data are a critical component of the carbon balance and thus their intra-crop spatial and temporal trends need to be considered when attempting to determine net carbon gain or loss among cropping systems.
See more from this Division: S11 Soils & Environmental Quality
See more from this Session: S11 General Soils & Environmental Quality: II