Estoques de carbono e nitrogênio e fração leve da matéria orgânica em Neossolo Quartzarênico sob uso agrícola

Abstract

Resumo -O objetivo deste trabalho foi avaliar os estoques de C e N do solo e os teores destes elementos na fração leve livre (FLL) da matéria orgânica (MOS) de um Neossolo Quartzarênico, sob diferentes usos agrícolas, no Cerrado. Foram selecionadas cinco áreas para avaliação: cerrado nativo; duas áreas com plantio convencional de soja; uma área ocupada anteriormente com pastagem e convertida em plantio direto de soja; e uma área com pastagem de baixa produtividade. Amostras de solo foram coletadas das camadas de 0-5, 5-10, 10-20 e 20-30 cm de profundidade, para determinação dos estoques de carbono (C) e nitrogênio (N) totais do solo. Os teores destes elementos na FLL foram determinados nas profundidades 0-5 e 5-10 cm. Em comparação à área sob cerrado, foi observado aumento nos estoques de C total do solo nas áreas de soja com até cinco anos de implantação. Houve redução das quantidades de FLL e dos teores de C à profundidade 0-5 cm, nas áreas com plantio de soja e pastagem. Considerando-se o baixo aporte natural de C e N no Neossolo Quartzarênico avaliado, é necessária a adoção de sistemas agrícolas que promovam aporte adequado de resíduos para a manutenção ou incremento da matéria orgânica do solo.Termos para indexação: Cerrado, pastagem, plantio convencional, plantio direto. Carbon and nitrogen stocks and organic matter light fraction in a Typic Quartzipsamment under agricultural useAbstract -The objective of this work was to evaluate C and N stocks in the soil and their contents in the free light fraction (FLL) of the soil organic matter (MOS), in a Typic Quartzipsamment under different land-use in Cerrado. Five areas were selected for evaluation: native cerrado; two areas with soybean under conventional tillage; one area formerly under pasture and afterwards cultivated with soybean under no-tillage; and one area under pasture with low productivity. Soil samples were collected from 0-5, 5-10, 10-20 and 20-30-cm depth layers to determine total C and N stocks of the soil. Contents of C and N in the FLL were determined at 0-5 and 5-10-cm depth. An increase was observed in the total C stocks in soybean areas implemented until five years, in comparison to the native cerrado area. There was a reduction in the amount of FLL and C content at 0-5 cm depth, in areas with soybean and pasture. Considering the low C and N natural input onto the Typic Quartzipsamment, the adoption of agricultural systems that can promote an adequate supply of residues is necessary for maintaining or increasing the soil organic matter.

Organic Matter Labile Fractions and Carbon Stocks in a Typic Quartzipsamment Cultivated With Sugarcane Harvested Without Burning

“…The POCSt and CLOMSt values were also higher in the area under sugarcane crop, which were affected by their higher bulk density values. These results differ from those found by Frazão et al (2010), who reported higher CLOMSt values in the native forest area, compared with areas under different management systems, in Comodoro, Mato Grosso, Brazil. According to these authors, crop systems usually have more favorable conditions for microbial activity due to their higher moisture and soil fertility, promoting a better decomposition and reducing the contents of organic matter.…”

“…Several studies emphasize the decrease of CLOM content in sandy soils subjected to conservationist management systems, in which previous crop residues remain on the soil surface, compared with native forest areas (SOUZA et al, 2006;FRAZÃO et al, 2010). However, this result was not found in the present work, in which the CLOM were not suitable to assess such changes.…”

“…According to Dick et al (2009), clayey soils tend to have high organic matter stocks than sandy soils, due to its high organomineral interactions and low mineralization rates. Therefore, considering the reduced potential for organic matter accumulation of sandy texture soils (FRAZÃO et al, 2010;MUJURU et al, 2013), different management systems must be used to maximize the organic matter supply and maintenance in these soils.…”

Soil Organic Carbon, Carbon Stock and Their Relationships to Physical Attributes Under Forest Soils in Central Amazonia

“…MAIA et al, 2009;FRAZÃO et al, 2010), texture (LUCA et al, 2008 ), mineralogy (ZINN et al, 2007) and soil bulk density (NAVARRETE; TSUTSUKI, 2008) have been described as controlling the magnitude and speed of changing in the content and quality of SOM.…”

Estoques de carbono e nitrogênio no solo cultivado com mamona na Caatinga

“…Atualmente, o carbono (C) e o nitrogênio (N) frequentemente têm sido utilizados como indicadores da qualidade do solo, tanto em sistemas agrícolas como em áreas de vegetação nativa (Jansen, 2005 Em estudos realizados nos diferentes biomas brasileiros, de maneira geral, os autores demonstraram haver relação entre o teor de C e N do solo e o tipo de vegetação (Siqueira Neto et al, 2009Maia et al, 2009Maia et al, , 2010Frazão et al, 2010). Especificamente para o bioma Caatinga, os autores discutem tanto ganhos como perdas nos estoques de C e N nos diferentes usos do solo (Maia et al, , 2007Assis et al, 2010;Sousa et al, 2012), sem que haja consenso sobre a dinâmica da MOS em função da mudança de uso.…”