Resumo -O objetivo deste trabalho foi avaliar as frações húmicas, granulométricas e oxidáveis da matéria orgânica do solo, o conteúdo de matéria orgânica leve no solo, e os teores e estoques de C e N em Latossolo Vermelho, manejado pelos sistemas plantio direto e convencional, para o cultivo de repolho. Áreas de pastagem e de cerrado nativo foram utilizadas como controle. As amostras foram coletadas em 2014, às profundidades 0,0-0,05 e 0,05-0,10 m, após um ciclo de cultivo do repolho sob plantio direto e convencional, em área com longo histórico de cultivo convencional de hortaliças. O sistema plantio direto aumenta os teores de matéria orgânica leve, C e N, assim como os estoques de C e os valores de C orgânico particulado, de C orgânico associado a minerais, e de frações húmicas e oxidáveis da matéria orgânica. O sistema plantio direto melhora a qualidade do solo, em comparação ao plantio convencional, além de proporcionar, para a maioria das variáveis analisadas, maiores valores do que os observados em área de pastagem e valores semelhantes aos da área sob cerrado nativo.Termos para indexação: compartimentos da matéria orgânica, dinâmica da matéria orgânica, manejo do solo, matéria orgânica leve, plantio direto de hortaliças. Storage and fractions of soil organic matter under no-tillage and conventional planting systems of cabbageAbstract -The objective of this work was to evaluate the humic, granulometric, and oxidizable fractions of soil organic matter, the light organic matter content in the soil, and C and N contents and storage in an Oxisol under no-tillage and conventional tillage systems for cabbage cultivation. Pasture areas and native cerrado soil were used as a control. The samples were collected in 2014 at the 0.0-0.05 and 0.05-0.10-m soil depths, after one cabbage crop cycle under no-tillage and conventional tillage systems, in an area with a long history of conventional tillage for vegetable crops. The no-tillage system increases the contents of light organic matter, C and N, as well as C storage and the values of particulate organic C, organic C associated with minerals, and the humic and oxidizable fractions of organic matter. The no-tillage system improves soil quality, in comparison with conventional tillage, besides providing, for most of the variables, higher values than those observed in the pasture area and similar values to those of the area under native cerrado.
ABSTRACT:Highland environments favor accumulation and preservation of soil organic matter (SOM) due to low temperatures, leading to the formation of Histosols. The Itatiaia National Park (INP), Rio de Janeiro, Brazil, offers conditions for preservation of SOM deposited over time, which has led to the formation of these soils. The objective of this study was to characterize Histosols in this environment, with the premise that it may provide evidence of changes in vegetation. Organossolos (Histosols) were sampled, characterized, described, and analyzed for their properties, stable isotopes of 12 C and 13 C, 14 N and 15 N, and dating of organic matter through 14 C. The soils were classified in the Brazilian Soil Classification System as Organossolo Háplico Hêmico típico -RJ-01 (Haplohemists) and Organossolo Fólico Sáprico cambissólico -RJ-02 (Udifolists). The morphological properties, degree of transformation, and chemical fractioning of SOM were consistent with hemic and sapric materials. The δ 13 C and δ 15 N isotopic analyses showed a difference in the contribution of plant materials. In RJ-01, there was previous influence of algae, due to poor drainage, and depletion of δ 13 C, suggesting a mix of C 3 and C 4 plants. RJ-02 showed influence of C 3 type plants. The 14 C dating for RJ-01 was 3280±80 years, and for RJ-02, 2005±5 years (modern age).
RESUMOOs modelos de predição de perda de solo têm se tornado importantes ferramentas no planejamento conservacionista, sendo, para tanto, fundamental a estimativa local dos parâmetros que influenciam o processo erosivo. O objetivo deste trabalho foi determinar a erodibilidade (fator K) e os fatores manejo e cobertura (fator C) e práticas conservacionistas de suporte (fator P) da Equação Universal da Perda de Solo (USLE), em um Argissolo Vermelho-Amarelo. Foram avaliadas as perdas de solo (PS) ocorridas em parcelas-padrão de Wischmeier, no período de 2006 a 2011, com seus respectivos índices de erosividade (EI 30 ). Valores de erodibilidade foram calculados pelo quociente entre PS e EI 30 das chuvas anuais (Ka) e total no período (Kt) e pelo coeficiente angular gerado pela análise de regressão linear entre esses mesmos parâmetros (Kci e Kct). Os fatores C e P foram estimados para a cultura do milho, durante três anos de cultivo em nível (MN). Os valores de Kt e Kct obtidos foram de 0,0090 e 0,0106 Mg ha h ha -1 MJ -1 mm -1 , respectivamente. Os valores médios calculados para os fatores C e P são de 0,0070 Mg ha Mg -1 ha -1 e de 0,45, respectivamente, indicando redução de 55 % na perda de solo do MN, em relação ao MMA. Os valores dos fatores K, C e P encontrados podem ser usados como primeira aproximação para estudos de manejo e conservação do solo e da água na região.
There was no effect of increasing N rates on the sugar concentration, although the sugar yield response was positive and strongly influenced by the stalk production. Results showed the importance of reassessing the adequate N rate for maximizing yield in green cane production systems.
Histosols are a natural reservoir of C in the soil, and their drainage followed by other farming practices leads to subsidence and soil organic matter transformations. The objective of this study was to evaluate the influence of use and management of Histosols, by means of: characterizing chemical and physical properties, and the content of SOM and humic fractions; and quantifying C and N stocks. In addition, to obtain preliminary data on greenhouse gas emissions (CO 2 , N 2 O) in Histosol areas with different agricultural practices. Three areas were selected with similar soil and environment, two in Macaé municipality, under pasture, and with bean annual crop rotation, and the third in Santa Cruz, Rio de Janeiro city, cultivated with cassava (Manihot esculenta). The attributes evaluated were: physical-bulk density (BD), particle density (Dp), organic matter density (OMD), mineral matter (MM), mineral residue (MR), aggregate stability; and chemical-pH, exchangeable cations, soil organic matter (SOM), carbon in the humin (HUM-C), humic acid (HAF-C) and fulvic acid (FAF-C) fractions; stocks of C and N; and flux of CO 2 and N 2 O. In general, the area cultivated with cassava had the highest values for exchangeable cations, as a result of fertilizer and soil management practices. The cassava site showed the highest values of BD and Dp; total volume of pores; MM, MR and OMD and higher degree of transformation of SOM; indicating higher alteration of Histosols properties under this usage. In all sites, the C levels indicated dominance of humin fraction. The SOM and C and N stocks were highest in the pasture, indicating preservation of organic matter, with values from 115.92 to 99.35Mg ha-1 of C e 8.35 to 4.45 Mg ha-1 for N. The values of CO 2-C flux were within the range proposed by the IPCC, where the highest emission was 0.09 Mg CO 2 ha-1 day-1 in the pasture site. The values of N 2 ON flux were lower than proposed by the IPCC, with the highest value (270 g N 2 ON m-2 day-1) in the area under beans (crop rotation). In general, the multivariate analyses discriminated the sites and the pasture was the usage that least affected the Histosols properties.
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