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Title: CARBON BUDGET IN DRYLAND AGROECOSYSTEMS AFTER 12 YEARS IN NO-TILL AS AFFECTED BY CLIMATE GRADIENT, SLOPE POSITION, AND CROPPING INTENSITY

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

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2004
Publication Date: 3/2/2004
Citation: Sherrod, L.A., Peterson, G.A., Westfall, D.G., Ahuja, L.R. 2004. Carbon budget in dryland agroecosystems after 12 years in no-till as affected by climate gradient, slope position, and cropping intensity. Great Plains Fertility Conf. Proceedings. Denver, CO. March 2-3, 2004. pp. 234-239.

Interpretive Summary: No-till management allows for greater frequency of cropping and less fallow by enhancing water storage. This study was conducted to determine what C pools were impacted by cropping intensity under no-till management across climate and landscape positions. Soil organic carbon was separated into three pools of active, intermediate, and stable, based on turnover time. Cropping systems of increasing intensity were imposed across a topographic sequence across three potential ET locations of low, medium, and high. Increases in SOC due to cropping intensity were due to increases in the active and intermediate carbon pools as estimated by mineralized C and particulate organic matter C as no significant increases were found in the stable fractions as hypothesized. Location and slope position strongly influenced these pools but were independent of cropping intensity in the 0-10 cm depth.

Technical Abstract: Soil organic carbon (SOC) has decreased under cultivated wheat-fallow (WF) in the Great Plains. We evaluated the effect of no-till cropping systems of WF, wheat-corn-fallow (WCF), wheat-corn-millet-fallow (WCMF), continuous cropping (CC), and native grass species (G) on SOC changes over 12-years at three locations in eastern Colorado. The SOC sequestration rate increase was shown to have a linear response (R2=0.99) to cropping intensity going from 30 in WF to 170 kg C/ha/yr in CC in the 0-5 cm depth. Changes in SOC sequestration rates were also compared for WF, WCMF, and G. The SOC sequestration rates fluctuated within sites. Averaged across sites G had the highest SOC sequestration rates for all 3 rates with WCMF showing a trend to decrease with time and WF started to gain SOC over time. No-till cropping systems can increase the rate and amount of SOC sequestered in soils previously managed under tilled WF systems. The amount of SOC sequestered is maximized by cropping that eliminates summer fallow.