Evaluation of Chemical Indices of Soil Organic Nitrogen Availability in Calcareous Soils
- M. D. Serna and
- F. Pomares
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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