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This article in SSSAJ

  1. Vol. 52 No. 4, p. 1006-1010
     
    Received: July 27, 1987
    Published: July, 1988


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doi:10.2136/sssaj1988.03615995005200040019x

Net Mineralization of Carbon and Nitrogen Under Aerobic and Anaerobic Conditions

  1. P. M. Gale  and
  2. J. T. Gilmour
  1. Dep. of Agronomy, 115 Plant Sciences, Univ. of Arkansas, Fayetteville, AR 72701

Abstract

Abstract

A study was conducted to compare the net C and net N mineralized during the decomposition of alfalfa (Medicago sativa L.) under aerobic and anaerobic conditions. Dried and ground alfalfa was mixed with soil at a rate of 5 g kg−1 and incubated either aerobically at optimum water in a CO2—free atmosphere or anaerobically (flooded) in an N2 atmosphere. The decomposition process was followed by measuring the CO2 and CH4 evolved, water soluble organic C, and inorganic N. Aerobic C mineralization was best described using CO2 evolution as a first-order kinetic process. Three distinct phases of decomposition were observed (rapid, intermediate, and slow) with rate constants (k) of 0.123, 0.059, and 0.0095 d−1, respectively. Under anaerobic conditions, CO2 evolution remained fairly constant throughout the experiment. The decomposition rate constant for anaerobic CO2 evolution was 0.006 d−1. Carbon mineralization under anaerobic conditions was best described as the sum of CO2 and CH4 evolved plus the water soluble organic C produced. This treatment resulted in three distinct phases of anaerobic decomposition. The C mineralization rate constants for the rapid and intermediate phases were 0.118 and 0.024 d−1, respectively. No rate constant was determined for the slow phase. A computer simulation model was used to estimate the C and N mineralized under both aerobic and anaerobic conditions. The linear relationship between the predicted and observed mineralization was evaluated. For C mineralization the slope was 1.1 and that of N mineralization was 1.0, with R2 values of 0.961 and 0.946, respectively.

Published with the approval of the director of the Univ. of Arkansas Agric. Exp. Stn.

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