|Schumacher, Thomas - SD STATE UNIV.|
|Lobb, David - UNIV. OF MANITOBA|
|Malo, D - SD STATE UNIV.|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 18, 2004
Publication Date: April 1, 2005
Citation: Reicosky, D.C., Lindstrom, M.J., Schumacher, T.E., Lobb, D.E., Malo, D.D. 2005. Tillage-induced CO2 losses across an eroded landscape. Soil & Tillage Research. 81:183-194. Interpretive Summary: Increased carbon dioxide (CO2) in the atmosphere relates to concerns about potential global warming and prospects of using soil as a sink for carbon (C). The cumulative effect of tillage and many cropping rotations has caused a 30-50% decrease in soil C that causes undesirable changes in soil physical, chemical and biological properties. Recent studies involving tillage methods indicate major gaseous loss of C immediately after tillage. This work describes spatial variation and differences in CO2 losses as a result of tillage methods across an eroded landscape that were related to tillage intensity or soil fracturing that facilitated the movement of CO2 out and oxygen into the soil. The measured CO2 fluxes were largest with the moldboard plow > chisel plow > not tilled (before tillage). The spatial variation in CO2 flux in the north-south transect was nearly four-fold immediately after plowing. Similar results were shown on the west-east transect. The CO2 loss was partially related to soil chemical properties with lower CO2 flux on the severely eroded sites. The CO2 loss partially reflected the degradation of soil properties from tillage-induced soil translocation and wind and water erosion. These results are significant to farmers and policy makers in that intensive tillage results in substantial short-term CO2 loss. This information will assist scientists and engineers in developing improved tillage methods to minimize the gaseous loss and to improve soil C management. Farmers can develop and utilize new management techniques for enhancing soil C by increasing the quantity and quality of crop residues and by changing the type and intensity of tillage. This information will be of direct benefit to the farmers to enable them to maintain crop production with minimal impact on air quality and the environment.
Technical Abstract: Soil carbon (C) loss and soil translocation from tillage operations have been identified as causes of soil degradation and soil erosion. The objective of this work was to quantify the variability in tillage-induced carbon dioxide (CO2) loss by moldboard (MP) and chisel (CP) plowing across an eroded landscape and to relate the C loss to soil properties. The study site was a 4-ha wheat (Triticum aestivum L. cv. Marshall) field with rolling topography and five soil types in the Svea-Barnes complex in west central Minnesota (N. Lat. = 45 deg 41', W. Long. = 95 deg 43'). Soil properties were measured at several depths at a 10-m spacing along north-south (N-S) and west-east (W-E) transects through severely eroded, moderately eroded and non-eroded sites. Conventional MP (25 cm deep) and CP (15 cm deep) equipment were used along the pre-marked transects. Gas exchange measurements were obtained with a large, portable chamber within 2 m of each sample site following tillage. The measured CO2 fluxes were highest with the MP > CP > not tilled (before tillage). The variation in 24-h cumulative CO2 flux from MP on the N-S transect was nearly three-fold and four-fold on the W-E transect. The surface soil organic C on the transects was lowest on the eroded knolls at 5.1 g C kg**-1 and increased to 19.6 g C kg**-1 in the depositional areas. The lowest CO2 fluxes were measured from severely eroded sites. This indicated that the variation in CO2 loss partially reflected the degradation of soil properties caused by historic tillage-induced soil translocation with some wind and water erosion. The spatial variation across the rolling landscape complicates the determination of non-point sources of soil C loss and suggests the need for improved conservation tillage methods to maintain soil and air quality in agricultural production systems.