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This article in SSSAJ

  1. Vol. 62 No. 4, p. 942-951
     
    Received: Jan 3, 1997


    * Corresponding author(s): cwrice@ksu.edu
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doi:10.2136/sssaj1998.03615995006200040014x

Carbon and Nitrogen Mineralization in Tallgrass Prairie and Agricultural Soil Profiles

  1. H. A. Ajwa,
  2. C. W. Rice  and
  3. D. Sotomayor
  1. USDA-ARS, Water Management Research Lab., Fresno, CA 93727
    Dep. of Agronomy, Throckmorton Hall, Kansas State Univ., Manhattan, KS 66506-5501
    Univ. of Puerto Rico, Mayagüez, PR 00681

Abstract

Abstract

In situ mineralization of N may contribute significantly to total inorganic-N pools deep in the soil profile. We conducted long-term laboratory incubation experiments to evaluate the net C and N mineralization in soils collected from various depths in tallgrass prairie and agricultural fields of the same geological materials and soil type. Samples were packed to a bulk density of 1.4 g cm-3 in 5-cm-diameter by 10-cm-long cores. The cores were incubated at 35°C for 40 wk in sealed containers. Net C mineralization was measured by evolved CO2, and N mineralized was measured by periodic leaching with NH+4 and NO-3 measured in the leachate. Carbon and N mineralization in the surface horizon were greater in the tallgrass prairie than in the agricultural soil. In both the tallgrass prairie and agricultural soil profiles, C mineralization was least at the water-table depth. Carbon mineralization was described by a first-order kinetic model, but N mineralization was described better by a consecutive (sigmoidal) reaction model. At most depths, the ratios of potentially mineralizable organic C (C0) to total organic C (C0/TOC) and potentially mineralizable organic N (N0) to total N (N0/TN) were greater in the agricultural soil profile than in the tallgrass prairie soil profile. The C0 and N0 in the surface soil (0–0.2 m) represented 11.6 and 12.2% of the total organic C and N pools for the tallgrass prairie soil profile, respectively, and 21.0 and 10.2% of the total organic C and N pools for the agricultural soil profile. Management practices affected the mineralization potentials and rates of both the surface and subsurface soils.

This work was carried out at the Inst. of Arctic Biology, Univ. of Alaska, Fairbanks, AK 99775.

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