ABSTRACT The recent approach of eliminating the usage of fire for sugarcane harvesting resulted in managing the crop on a trashblanketed soil, to which a proper recommendation of N fertilization is lacking, a problem that remains in the coastal tablelands of the Espírito Santo State, Brazil. This study aimed at evaluating the effect of increasing N rates on stalk and sugar yields and the N use efficiency by the crop. The experimental area planted with sugarcane, at the first ratoon, is located in Linhares, Espírito Santo State. The treatments consisted of N rates varying from 80 to 160 kg N∙ha−1 as ammonium sulphate, and a control without N, in a completely randomized blocks experimental design. Stalk yield increased with the N rate, and fitting the results to a quadratic function suggests no response to fertilizer rates above 130 kg N∙ha−1. The highest margin of agricultural contribution was obtained at the rate of 100 kg N∙ha−1. The N use efficiency decreased from almost 49 to 38%, when the N rate increased from 100 to 160 kg N∙ha−1. 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.

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.

Abstract 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 12C and 13 14 15 14 C, N and N, and dating of organic matter through 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 δ13C and δ15N 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 δ13C, suggesting a mix of C3 and C4 plants. RJ-02 showed influence of C3 type plants. The 14C dating for RJ-01 was 3280±80 years, and for RJ-02, 2005±5 years (modern age).

Os 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 (EI30). Valores de erodibilidade foram calculados pelo quociente entre PS e EI30 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.

The soil loss prediction models have become important tools for conservation planning, being fundamental the local estimation of the parameters that influence the erosion processes. The objective of this work was to determine the soil erodibility (K factor), soil cover and management factor (C factor) and conservation practice factor (P factor) of the Universal Soil Erosion Equation (USLE), in an Ultisol. Soil losses (SL) were measured in Wischmeier standard-plots from 2006 to 2011, with the respective erosivity index (EI30). Soil erodibility was calculated by the ratio of SL and the annual (Ka) and total period EI30 (Kt), considering the angular coefficient generated from the linear regression analysis between those parameters (Kci, for each rainy period, and Kct, for the studied period). The factors C and P were estimated for three years of maize in contour cultivation (MCL) and down in the slope (MDS). The Kt and Kct values were 0.0090 and 0.0106 Mg ha h ha-1 MJ-1 mm-1, respectively. The average calculated values for factors C and P are 0.0070 Mg ha Mg-1 ha-1 and 0.45, respectively, indicating a soil loss reduction of 55 % in MCL, compared to MDS. The values of the factors K, C and P obtained can be used as first approximation to soil and water conservation management projects in the region.