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This article in JEQ

  1. Vol. 28 No. 5, p. 1629-1636
    Received: May 27, 1998

    * Corresponding author(s): cm48@umail.umd.edu
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Tropospheric Carbon Dioxide or Ozone Enrichments and Moisture Effects on Soil Organic Carbon Quality

  1. K. R. Islam,
  2. C. L. Mulchi * and
  3. A. A. Ali
  1. Dep. of Natural Resource Sciences and Landscape Architecture, Univ. of Maryland, College Park, MD 20742;
    Dep. of Botany, Zagazig Univ., Zagazig, Egypt.



Carbon, as an active component of organic matter, has considerable effects on soil quality and productivity. The objective of this study was to examine the effect of climate change variables on soil organic C (CT) quality in an agroecosystem. Wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr] plants were grown in 3 m in diam. open-top field chambers and exposed to charcoal-filtered (CF) air at 350 µL CO2 L−1; CF air + 150 µL CO2 L−1; nonfiltered (NF) air + 35 nL O3 L−1; and NF air + 35 nL O3 L−1 + 150 µL CO2 L−1 at two soil moisture levels from 1994 to 1996. The 150 µL CO2 L−1 addition was 18 h d−1 and the 35 nL O3 L−1 was 7 h d−1 from April until late October. In response to treatments, the Cr contents did not change significantly; however, participate, oxidizable, dissolved, humic (CHA) and fulvic (CFA) acid, and carbohydrate C pools increased in soils under CO2 enrichment and well-watered conditions but decreased under O3 stress compared with soils under CF ambient air quality. Tropospheric CO2 enrichment and well-watered condition increased, and O3 stress decreased the log optical density slope for both CHA and CFA fractions more than CF ambient air and restricted moisture treatment. Also, the E465/E665 ratios of both CHA and CFA fractions were higher for the CO2 enrichment and smaller for the O3 stress compared with CF ambient air quality. Results suggest that tropospheric CO2 enrichment and well-watered conditions may favor an accumulation of low molecular weight and more aliphatic quality of C and O3 stress favor high molecular weight and more aromatic quality of C.

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