Comparison of carbon and nitrogen determination methods for samples of a Paleudult subjected to no-till cropping systems

Scientia Agricola

Jeferson Dieckow²  João Mielniczuk¹  Heike Knicker¹  Cimélio Bayer¹  Deborah Pinheiro Dick¹  Ingrid Kögel-knabner¹ 

[1] ,UFPR Depto. de Solos e Engenharia Agrícola Curitiba PR ,Brasil

关键词: Walkley-Black;    Kjeldahl;    wet combustion;    dry combustion;    Walkley-Black;    Kjeldahl;    combustão úmida;    combustão seca;   

DOI  :  10.1590/S0103-90162007000500011

来源: SciELO

【 摘 要 】

Organic carbon (C) concentration evaluated by the Walkley-Black method, and total nitrogen(N)concentration determined by Kjeldahl method, were compared with corresponding results of C and N concentrations obtained through the dry combustion method (Elementar Vario EL analyzer), using samples of ten soil layers down to the depth of 107.5 cm of a kaolinitic Typic Paleudult (220-418 g clay kg-1 along the profile) subjected to no-till cropping systems [fallow bare soil, pigeon pea (Cajanus cajan L. Millsp.) plus maize, and lablab (Lablab purpureum L. Sweet) plus maize]. A close correlation (R² > 0.96) was observed between the C results of the Walkley-Black and dry combustion methods, but a correction was suggested to be applied to C results of Walkley-Black (C = 1.05C W.Black + 0.47). A close correlation (R² > 0.96) was also found between results of Kjeldahl-N and dry combustion-N, but no correction was necessary to be applied. The relationships between results of Walkley-Black and dry combustion and between results of Kjeldahl and dry combustion did not change among soil samples from different management systems, in disagreement to findings of a previous study where results of analytical C recovery were influenced by samples from different managements, supposedly because changes in lability or recalcitrance of organic matter might have affected the wet combustion reactions. A poor correlation (R² = 0.42) was found between the C:N ratios based on Walkley-Black and Kjeldahl analysis and the C:N ratios based on dry combustion analysis. The methods for C and N determination did not affect the interpretation of the effects of management systems on soil C and N stocks.

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