Organic carbon determination in histosols and soil horizons with high organic matter content from Brazil

Abstract

Soil taxonomy systems distinguish mineral soils from organic soils based on the amount of soil organic carbon. Procedures adopted in soil surveys for organic carbon measurement are therefore of major importance to classify the soils, and to correlate their properties with data from other studies. To evaluate different methods for measuring organic carbon and organic matter content in Histosols and soils with histic horizons, from different regions of Brazil, 53 soil samples were comparatively analyzed by the methods of Walkley & Black (modified), Embrapa, Yeomans & Bremner, modified Yeomans & Bremner, muffle furnace, and CHN. The modified Walkley & Black (C-W & B md) and the combustion of organic matter in the muffle furnace (OM-Muffle) were the most suitable for the samples with high organic carbon content. Based on regression analysis data, the OM-muffle may be estimated from C-W & B md by applying a factor that ranges from 2.00 to 2.19 with 95% of probability. The factor 2.10, the average value, is suggested to convert results obtained by these methods.

Caracterização de Organossolos em ambientes de várzea do nordeste do Brasil

“…Esse método é mais adequado para solos com elevados teores de MO (Embrapa, 2006;Pereira et al, 2006), em detrimento aos métodos de oxidação via úmida (com uso de dicromato de potássio). Adicionalmente, a presença de pirita em alguns dos solos estudados pode levar a superestimativa dos teores de CO pelo método da via úmida (Souza Jr. et al, 2001b …”

“…Apesar de já terem sido realizados estudos com o objetivo de caracterizar os Organossolos em alguns estados da região Nordeste do Brasil, como Bahia e Alagoas (Couto & Resende, 1985;Souza Jr et al, 2001a,b;Pereira et al, 2006;Valladares et al, 2008a,b) e Maranhão (Ebeling et al, 2013), pouco são os estudos sobre a gênese e a ocorrência desses solos nos Estados do Ceará, do Rio Grande do Norte e da Paraíba. As áreas de turfeiras das planícies, com Organossolos de ambiente de várzea, influenciam na dinâmica e qualidade da água do ambiente.…”

Methods of soil organic carbon determination in Brazilian savannah soils

“…This mass loss resulting from the volatilization of hygroscopic and structural water is accounted for along with the mass of organic compounds lost in the form of CO 2 , which implies overestimation of the organic component of the sample (Davies, 1974;Miyazawa et al, 2000;Melo et al, 2008). Jankauskas et al (2006) worked with only two soils and Pereira et al (2006) used samples with high OC content. These authors found correlations of 0.80 and 0.94, respectively, between the C obtained by the gravimetric method and elemental analysis.…”

Bulk Density Prediction for Histosols and Soil Horizons with High Organic Matter Content

“…The methods used for chemical and physical analysis of organic soils have been called into question in other studies (Pereira et al, 2006;Gatto et al, 2009). Most procedures are calibrated to mineral soils, hindering interpretation of results.…”

“…Carbon content in soils that make up the database was determined by different methods, such as combustion in a muffle furnace, titration with dichromate (Walkley and Black, 1934;Yeomans and Bremner, 1988), and automatic elemental analyzers (CHN), which commonly increases variation in C content among the samples (Pereira et al, 2006;Gatto et al, 2009). These variations may have affected the validation parameters of the equations produced.…”