HR: 1340h
AN: B13B-1202    [Abstracts]
TI: Linking Temporal Decomposition Dynamics of Crop Residues to Soil Tillage Intensity in Manitoba, Canada
AU: * Glenn, A J
EM: umglenn@cc.umanitoba.ca
AF: Department of Soil Science, Rm. 362 Ellis Building University of Manitoba, Winnipeg, MB R3T 2N2, Canada
AU: Tenuta, M
EM: tenutam@cc.umanitoba.ca
AF: Department of Soil Science, Rm. 362 Ellis Building University of Manitoba, Winnipeg, MB R3T 2N2, Canada
AU: Amiro, B D
EM: brian_amiro@umanitoba.ca
AF: Department of Soil Science, Rm. 362 Ellis Building University of Manitoba, Winnipeg, MB R3T 2N2, Canada
AU: Wagner-Riddle, C
EM: cwagnerr@uoguelph.ca
AF: Department of Land Resource Science, University of Guelph, Guelph, ON N1G 2W1, Canada
AU: Warland, J S
EM: jwarland@uoguelph.ca
AF: Department of Land Resource Science, University of Guelph, Guelph, ON N1G 2W1, Canada
AU: Drewitt, G B
EM: gdrewitt@uoguelph.ca
AF: Department of Land Resource Science, University of Guelph, Guelph, ON N1G 2W1, Canada
AB: Heterotrophic respiration from agricultural soils may be differentiated as originating from microbial decomposition of recent litter inputs (crop residue carbon) and resident soil organic matter (SOM) pools of varying age and stages of decomposition. Differences in preferential C isotope discrimination between C₃ and C₄ photosynthetic pathways has application to determining temporal C cycling dynamics in agroecosystems. Addition of crop residues with a different δ¹³C than SOM facilitates determining the contribution of residue to soil emissions of CO₂ and discrimination of SOM derived emissions. In the present study, a tunable diode laser trace gas analyzer was used to determine δ¹³C values and ¹²CO₂ and ¹³CO ₂ fluxes over an agricultural field in the Red River Valley of southern Manitoba, Canada. Soil emissions of δ¹³CO₂ were also measured on select days using a static chamber method. Measurement campaigns were conducted in the fall/early winter of 2006 and spring of 2007 following harvest of a maize crop. Stable isotopic CO₂ gradients were measured from the center of four 200 by 200m plots and fluxes were calculated using the aerodynamic flux gradient method. The soil in two of the experimental plots underwent intensive tillage, while the other two plots received reduced tillage. In fall/early winter of 2006 an increase in δ¹³C (becoming less negative) over plots indicates the contribution to respiration originating from the fresh corn residue. The influence of soil tillage on C sequestration is being evaluated from respiratory loss of residue and SOM from the reduced and intensive tillage treatments.
DE: 0402 Agricultural systems
DE: 0428 Carbon cycling (4806)
DE: 0490 Trace gases
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting