Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2003
Publication Date: 11/4/2003
Citation: Sherrod, L.A., Peterson, G.A., Westfall, D.G., Ahuja, L.R. 2003. Soil organic carbon pools after 12 years in no-till agroecosystem as impacted by cropping intensity. Meeting Abstract. Amer. Soc. of Agronomy. Nov. 2-6, 2003. Denver, CO. Interpretive Summary: No-till management allows for greater frequency of cropping and less fallow by enhancing water storage. Twelve years after conversion from a conventional tillage crop-fallow system to no-till cropping systems with increasing intensity, increases in soil organic C have been found due to increases in production with increasing cropping intensity. Total soil C is comprised of active, slow, and passive C pools based on the turnover time in the soil. Increases in soil organic C where due to increases in the active and slow C pools as represented by C mineralized after a 3 day incubation and particulate organic matter C (size fraction between 2-mm and 53-um) respectively, as no significant increases were found in the passive soil C pool represented by the mineral associated organic C in the silt and clay size fraction. In general, location and slope position influenced the active and slow C pools with the highest levels found in the toeslope positions in the low and medium PET locations. Continuous cropping showed the highest active and slow C pools at each PET location and slope position, with wheat-fallow showing the lowest levels.
Technical Abstract: No-till management allows for greater frequency of cropping and less fallow by enhancing water storage. The objectives of this study was (i) determine what C pools were impacted by cropping intensity under no-till management across climate and landscape positions and (ii) relate the C mineralized (CMIN) and water soluble organic C (WSOC) to the amount of particulate organic matter C (POM-C) found. We determined the amount of SOC, POM-C, mineral associated organic C (MAOC), CMIN and WSOC in the cropping systems of wheat (Triticum aestivum) - fallow (WF), wheat-corn (Zea Mays)-fallow (WCF), wheat-corn-millet (Panicum miliaceum) - fallow(WCMF), and continuous cropping (CC) at three ET locations in Colorado. Locations are all within a 420 mm annual precipitation but increase in ET going from north to south. Cropping systems were imposed across a topographic sequence within each location. Increases in SOC due to cropping intensity are due to increases in the active and intermediate carbon pools as estimated by WSOC / CMIN, and POM-C whereas no significant increases were found in the MAOC fractions down to10 cm depth. Location and slope position strongly influenced these pools but did not significantly interact with cropping intensity in summed depths. Continuous cropping had 37 % of the SOC as POM-C whereas WF only had 27% . Regressions of CMIN vs. POM-C in the 0-10 cm soil depth showed a strong correlation (r= 0.76), as did WSOC vs. POM-C (r =0.77).