Carbon and Nitrogen Stocks and Humic Fractions in Brazilian Organosols

Abstract

ABSTRACT:Despite limited geographic expression of Organosols in Brazil, their high carbon storage capacity and natural environmental vulnerability justifies further studies on C and N stocks in these soils and their relationship to the nature of organic matter. Evaluation of physical and chemical properties of organic soils and their ability to store C is important so as to develop sustainable management practices for their preservation. The objectives of the study were to measure the total organic carbon stock (OCst), total nitrogen stock (Nst), and humic fractions in Organosols from different environments and regions of Brazil, and to correlate the data with soil chemical (pH, P, K, Ca 2+ , Mg 2+ , Al 3+ , H+Al, CEC, V) and physical properties (soil bulk density, Bd; organic matter density, OMd; total pore space, TPS; minimum residue, MinR; and proportion of mineral matter, MM), and degree of organic matter decomposition (rubbed fiber content; pyrophosphate index, PyI; and von Post index). For that purpose, 18 Organosol profiles, in a total of 49 horizons, were sampled under different land usage and plant coverage conditions. The profiles were located in the following Brazilian states -Alagoas, Bahia, Distrito Federal, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Paraná, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, and São Paulo. The OCst and Nst varied significantly among horizons and profiles. The Organosols exhibited, on average, 203.59 Mg ha -1 OCst and 8.30 Mg ha -1 Nst, and the highest values were found in profiles with pasture usage. The content of the humic fraction (humin, HUM; fulvic acid, FAF; and humic acid, HAF) and C storage varied in the soil horizons and profiles according to the degree of decomposition and other factors of soil formation. The OCst, Nst, OMd and the C stocks in the humic fractions were positively correlated. The values of acidity were lower in the soils with higher contents of mineral material, and low pH values were related to a high C/N ratio. The OCst and Nst were correlated with different soil properties, the most important being the degree of soil organic matter decomposition, which was inversely correlated.

Cenários Geográficos do Norte e Nordeste em Debate

“…Embora tenham sido realizados alguns trabalhos com solos, podendo ser citados os de Lepsch et al (1990), Benites (1998), Souza Júnior et al (2001, Benites (2002), procurando relacionar variáveis do espaço ou do ambiente com atributos de Organossolos e solos com elevado conteúdo de matéria orgânica de determinadas regiões, poucos trataram esse tema com abrangência nacional (VALLADA-RES, 2003;VALLADARES et al, 2016;CANTO et al, 2020).…”

“…O estudo dos solos com altos teores de material orgânico se justifica pela sua fragilidade natural, potencial de estoque de carbono para a atmosfera e recomendações de uso e manejo, conforme enfatizado por Valladares et al (2016), que demonstraram no Brasil a grande quantidade de carbono estocado nesses ambientes, apesar da pequena área ocupada e sua correlação com outros atributos dos solos. O risco de subsidência, que consiste na perda de volume e massa em função da drenagem excessiva, é outro problema recorrente em Organossolos no Brasil, pois diminui a capacidade de suporte hídrico, e o potencial de uso dos solos é avaliado por Valladares et al (2008) e Cipriano- Silva et al (2014), que utilizaram diferentes métodos quantitativos com a finalidade de mensurar os efeitos da subsidência, além de fazer inferência aos atributos desses solos.…”

Impact of land use on Histosols properties in urban agriculture ecosystems of Rio de Janeiro, Brazil

“…According to the Brazilian Soil Classification System, peatland soils (Histosols) are classified as Organossolos (Santos et al, 2018). It is estimated that Brazil has about 0.6-1.0 million hectares of Histosols distributed across tropical and subtropical areas, with an average of 204 Mg ha -1 of organic carbon stock in the 1.00 m of topsoil (Valladares et al, 2016). Considering that the country has more than 12,200 km 2 of mangrove areas, distributed over 7,000 km of coast with likely presence of organic soils, the exact area of Histosols is still uncertain (Minasny et al, 2019).…”

Fertilidade de um organossolo e produtividade do feijoeiro influenciados pela calagem e inoculação

“…Os Organossolos apresentam grande importância ambiental e ecológica devido à capacidade de armazenamento de carbono e água que apresentam e são muito utilizados pela agricultura familiar (Scheer et al, 2011;Ebeling et al, 2013;Cipriano-Silva et al, 2014). Estes solos possuem elevados teores de carbono na forma de humina, ácidos húmicos e ácidos fúlvicos (Valladares et al, 2007;Loss et al, 2015;Valladares et al, 2016), bem como ISSN: 1984ISSN: -2538 Pereira et al, v.13, n.48, p. 211-221, Dourados, 2020 apresentam elevada acidez trocável (Perez et al, 2009) e potencial (Silva et al, 2008;Ebeling et al, 2008). Sendo assim, para que as culturas agrícolas expressem seu máximo potencial quando cultivadas em Organossolos, alguns autores relatam que deve ser feita a calagem e uso de adubação fosfatada (Mattiello et al, 2006;Schultz et al, 2011).…”