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This article in SSSAJ

  1. Vol. 38 No. 2, p. 313-315
    Received: Mar 27, 1973
    Accepted: Dec 18, 1973

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Mineralization of Carbon and Nitrogen in Soil Amended with Carbon-13 and Nitrogen-15 Labeled Plant Material1

  1. F. E. Broadbent and
  2. T. Nakashima2



Doubly labeled barley (Hordeum vulgare L.) plants were grown in a closed chamber containing 13C-enriched CO2 and 15N-enriched nutrient solution. Tops and roots were separated, ground, and added to Columbia fine sandy loam in fritted glass filter tubes. Soil samples were incubated with continuous flow aeration for 5 years. Evolved CO2 was trapped for 22 weeks. Mineral nitrogen was leached from the samples at intervals throughout the 5-year period. After 5 years, only 12% of the carbon from tops and 16% of that from roots remained in soil, compared with 38% of the nitrogen in tops and 57% of the root nitrogen. Average annual losses of carbon from soil organic matter were 6.1–6.8%; annual turnover of nitrogen varied from 6.3 to 7.4%. Availability ratios for nitrogen decreased as a function of time from about 2.5 initially to 1.2 at the end of the incubation period. Unaccounted-for losses of nitrogen from barley tops and from soil organic matter were 15–17%, but only 2% from roots.

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