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This article in SSSAJ

  1. Vol. 56 No. 5, p. 1486-1491
    Received: Apr 17, 1991

    * Corresponding author(s):
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Evaluation of Chemical Indices of Soil Organic Nitrogen Availability in Calcareous Soils

  1. M. D. Serna  and
  2. F. Pomares
  1. Departamento de Ecologia, Instituto Valenciano de Investigaciones Agrarias, Apartado Oficial, Moncada (Valencia), Spain



Because most of the N in soils is in organic form, information about the rate of N mineralization is required to estimate N availability during a cropping season. Biological and chemical methods to predict the level of plant-available N in soils were investigated under laboratory and growth chamber conditions. Two biological methods (maize [Zea mays L.] plants grown in pots and soils incubated aerobically) and four chemical methods (autoclave, 0.5 M KMnO4, 6 M HCl, and 0.01 M NaHCO3) were compared using 27 different soils from Valencia. Total N mineralized during the incubation periods ranged from −6.1 to 128 mg N kg−1 dry soil, representing from 0 to 9.57% of the soil organic N. The available soil N, defined as the amount taken up by maize, ranged from 12 to 87 mg kg−1, representing from 1.03 to 6.57% of the total soil N; the highest values were obtained from loamy soil. Modified autoclave and HCl methods were more suitable for predicting N availability in these soils than the KMnO4 and NaHCO3 methods. In general, the different extraction methods were not suitable for the clay soils. Prediction of soil N availability to plants in the growth chamber improved if initial mineral N of soils and several chemical and biological methods were combined in a multiple regression analysis; particularly, the multiple regression analysis markedly improved the suitability of the KMnO4 and NaHCO3 methods to predict N uptake by maize.

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