Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 23, 2004
Publication Date: November 1, 2004
Citation: Gollany, H.T., Baker, A.A., Oviatt, H.S. 2004. Carbon sequestration in the semi-arid Pacific Northwest: effects of land management and landscape position. Agronomy Abstracts. CD-ROM, S03-gollany4540. Madison, WI. Technical Abstract: Soil organic C (SOC) is the most important soil quality indicator due to its role in biological, chemical and physical processes. Depletion of SOC leads to declines in soil quality and sustainability. Our objective was to examine influences of land management practices on SOC accretion on 12 soil series at five northeastern and north central Oregon counties (Umatilla, Morrow, Gilliam, Sherman, and Wasco). Georeferenced soil samples were collected from fields along a climosequence transect with average annual precipitation ranging from 258 to 610 mm, temperature ranging from 7 to 11 degrees Celsius, and elevations ranging from 310 to 912 m. Fields are managed as winter wheat/fallow (WW/F), reduced tillage winter wheat/fallow (RT), wheat pea rotation (WP) or Conservation Reserve Program (CRP). In the top 30-cm, SOC was 23 g C/kg soil for soils at the back slope position and managed as WW/F. While SOC was 120 g C/kg for soils at the toe slope position and managed as CRP. Total N was 2 g /kg soil for soils at the summit position, and 9 g N/kg soil for soils at the toe slope position and managed as CRP. SOC decreased in the order CRP, WP, RT and WW/F. SOC loss continues in intensely cultivated systems in semi-arid regions of the inland Pacific Northwest. High biological oxidation of SOC and absence of C inputs in fallow years are reasons for SOC losses in these cropping systems.