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Title: SOIL ORGANIC CARBON POOLS AFTER 12 YEARS IN NO-TILL DRYLAND AGROECOSYSTEMS

Author
item Sherrod, Lucretia
item PETERSON, G - COLORADO STATE UNIVERSITY
item WESTFALL, D - COLORADO STATE UNIVERSITY
item Ahuja, Lajpat

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2003
Publication Date: 9/1/2005
Citation: Sherrod, L.A., Peterson, G.A., Westfall, D.G., Ahuja, L.R. 2005. Soil organic carbon pools after 12 years in no-till dryland agroecosystems. Soil Science Society of America Journal. Vol. 69:1600-1608. 2005.

Interpretive Summary: Previous studies of no-till management in the Great Plains have shown that increased cropping intensity increased soil organic carbon (SOC). The objectives of this study were to (i) determine which soil C pools (active, slow, and passive) were impacted by cropping intensity after 12 yr of no-till across potential evapotranspiration (PET) and slope position gradients; (ii) relate C pool sizes to the levels found in total SOC; and (iii) determine C pool sizes relative to C levels found in a grass treatment (G). Cropping systems were wheat (Triticum aestivum)-fallow (WF), wheat-corn (Zea mays L.)-fallow (WCF), wheat-corn-millet (Panicum miliaceum)-fallow (WCMF), and continuous cropping (CC) at three PET sites in Colorado. Active C (Soil microbial biomass C); and slow pool C (particulate organic matter C) increased as cropping intensity increased, dependent on PET. Passive C (mineral associated organic C) was strongly influenced by a site-by-slope position interaction but not by cropping system. Toeslope soils had 35% higher POM-C compared with summits and sideslopes. All C pools were strongly correlated with total SOC, with the variability decreasing as C pool turnover time increased. Carbon pool sizes in cropping systems relative to levels found in G were independently influenced by cropping system. The highest were found in the CC system, which had 91, 78, and 90% of the amounts of C found in the perennial G system in the acive, slow, and passive C pools, respectively.

Technical Abstract: Previous studies of no-till management in the Great Plains have shown that increased cropping intensity increased soil organic carbon (SOC). The objectives of this study were to (i) determine which soil C pools (active, slow, and passive) were impacted by cropping intensity after 12 yr of no-till across potential evapotranspiration (PET) and slope position gradients; (ii) relate C pool sizes to the levels found in total SOC; and (iii) determine C pool sizes relative to C levels found in a grass treatment (G). Cropping systems were wheat (Triticum aestivum)-fallow (WF), wheat-corn (Zea mays L.)-fallow (WCF), wheat-corn-millet (Panicum miliaceum)-fallow (WCMF), and continuous cropping (CC) at three PET sites in Colorado. Active C (Soil microbial biomass C); and slow pool C (particulate organic matter C) increased as cropping intensity increased, dependent on PET. Passive C (mineral associated organic C) was strongly influenced by a site-by-slope position interaction but not by cropping system. Toeslope soils had 35% higher POM-C compared with summits and sideslopes. All C pools were strongly correlated with total SOC, with the variability decreasing as C pool turnover time increased. Carbon pool sizes in cropping systems relative to levels found in G were independently influenced by cropping system. The highest were found in the CC system, which had 91, 78, and 90% of the amounts of C found in the perennial G system in the acive, slow, and passive C pools, respectively.