Algenor da Silva Gomes

Resistência mecânica à penetração de um Planossolo submetido a diferentes sistemas de cultivo

O conhecimento das caracteristicas e propriedades dos solos de varzea do RS, utilizados atualmente com a cultura do arroz irrigado, torna-se essencial para a adocao de praticas que envolvam irrigacao, drenagem, correcao da acidez e da fertilidade, principalmente quando se deseja obter altos niveis de produtividade, com menor custo e com menores possibilidades de degradacao destes solos e do ambiente onde estao situados. Dentro deste panorama, avaliou-se a compactacao de um Planossolo cultivado sob diferentes sistemas de manejo, atraves da resistencia mecânica do solo a penetracao. Camadas compactadas foram identificadas, de forma mais acentuada, na profundidade intermediaria (0,10-0,20 m) nos sistemas com maior utilizacao da mecanizacao agricola (T2 - sistema de cultivo continuo de arroz e T3 - sistema de cultivo de arroz x rotacao de culturas). Observou-se que, em todos os sistemas, houve aumento dos valores de resistencia mecânica do solo a penetracao em relacao a testemunha (T6 - solo mantido sem cultivo), principalmente na camada intermediaria (0,10-0,20 m), quando o solo foi submetido ao sistema de cultivo continuo de arroz (T2). Os tratamentos T3 (sistema de cultivo de arroz x rotacao de culturas) e T5 (sucessao de culturas: soja (sistema convencional) x arroz (sistema de semeadura direta)) apresentaram os valores mais altos de resistencia a penetracao, provavelmente em decorrencia da baixa umidade e dos efeitos do cultivo e da utilizacao de maquinas responsaveis pela deformacao da estrutura do solo.

ESTABILIDADE DE AGREGADOS DE UM PLANOSSOLO SOB DIFERENTES SISTEMAS DE MANEJO

The wetland soils in the state of Rio Grande do Sul present wide variation in their morphological, physical, chemical and mineralogical characteristics due to the heterogeneity of the parent material and different degrees of hydromorphism. Since their main uses for flooded rice and cattle breeding are frequently low-profit activities, the introduction of dry land crop species in rotation and/or succession with flooded rice has been called for. By broadening the spectrum of wetland soil use, a better weed control for flooded rice and an enhanced physical state of the degraded soil by management systems of reduced soil disturbance would become possible. In this context, the effect of tillage systems on the aggregation state of an Albaqualf has been evaluated: conventional tillage (CT), minimum tillage (MT), no tillage (NT) and pre-germinated (PG), by means of the following attributes: distribution of stable water aggregates in different size classes and mean weight diameter (MWD) of the aggregates. The experiment has been conducted since 1995/96 and is installed in the Estacao Experimental de Terras Baixas (Experimental Station Lowlands-ESL) of Embrapa (Brazilian agricultural research organization), Clima Temperado, district of Capao do Leao (RS). After three years, the NT system favored an aggregate formation of larger sizes, originating largest MWD, while the system PG pushed the largest aggregate concentration of the soil into the smallest size class, with the smallest aggregate MWD. The MWD was lineal and positively correlated with the organic C, not presenting any correlation with the clay dispersed in water.

Densidade de um planossolo sob sistemas de cultivo avaliada por meio da tomografia computadorizada de raios gama

A sustentabilidade do arroz (Oryza sativa L.) irrigado em solos de varzea esta alicercada na utilizacao da rotacao e sucessao de culturas, fundamentais para o controle do arroz-vermelho e preto. Os reflexos sobre os atributos dos solos de varzea merecem estudos em especial sobre a compactacao do solo. O objetivo deste trabalho foi identificar camadas compactadas em Planossolo submetido a diferentes sistemas de cultivo e preparo, avaliando-se a densidade do solo (Ds) pela Tomografia Computadorizada de Raios Gama (TC). A analise foi realizada em um experimento de longa duracao, conduzido de 1985 a 2004, na Estacao Experimental da Embrapa Clima Temperado, Capao do Leao, RS, num delineamento experimental em blocos ao acaso, com sete tratamentos, cada um com quatro repeticoes (T1 - um ano de arroz com preparo convencional do solo seguido de dois anos de pousio; T2 - cultivo continuo de arroz com preparo convencional do solo; T4 - rotacao de arroz e soja (Glycine max L.) com preparo convencional do solo; T5 - rotacao de arroz, soja e milho (Zea maiz L.) em preparo convencional do solo; T6 - plantio direto de arroz no verao em sucessao do azevem (Lolium multiflorum L.) no inverno; T7 - rotacao de arroz sob plantio direto e soja sob preparo convencional do solo; T8 - testemunha: solo sem cultivo). A Tomografia Computadorizada de Raios Gama permitiu detectar que o plantio direto de arroz no verao em sucessao do azevem no inverno nao resultou na formacao de camadas compactadas; a utilizacao de dois anos de pousio, no sistema de producao de arroz irrigado, nao foi suficiente para evitar a formacao de uma camada superficial compactada; e a rotacao de arroz, soja e milho com preparo convencional do solo apresentou duas camadas compactadas (0,0 a 1,5 cm e 11 a 14 cm), indicando que essas podem limitar a producao agricola nesse sistema de producao em Planossolos.

Sustentabilidade de sistemas de rotação e sucessão de culturas em solos de várzea no Sul do Brasil

The quantitative analysis with different types of indicators is crucial in determining the sustainability of crop succession. This study aimed to appraise that in tilled plain areas. The research was carried out in Pelotas, RS, Brazil at Embrapa Clima Temperado research area. The treatments consisted of successions of winter and spring-summer crops species for five years, followed by two years of fallow and three years of rice cropping. The spring-summer crops were corn and soybean, besides rice; the winter crops were cereals, leguminous pastures, mixtures species, turnip and native grass species. Seeding was performed either by no-till (NT) or conventional (CT). The experiment was planned in a split-plot randomized blocks design with three replications, where the summer crops occupied the plots, while the winters species were allocated to the subplots. The parameters measured were transformed into index to standardize the variables, each one in relation to the better measurement behavior, and arranged in four categories of analysis: (a) Agronomics indices (dry weight and grain yield); (b) Environmental indicators (soil fertility); (c) Energy Indicators (gain and energy efficiency); d) Economic Indicators (profitability and gross value of production). Through harmonic average rates calculated for each indicator, comparisons to the crop succession were then performed, and its sustainability inferred. Analyses of contrasts between the crop successions were accomplished too. The results provided the following conclusions: (a) All crop succession which had maize participation had a higher index sustainability; (b) the crops successions S1 [Cereals x soybean x rice(NT)] and S4 [Turnip x soybean x rice(NT)] had, respectively, the highest and the lowest sustainability among the ones with the soybean crop participation; (c) S5 [Native grass x soybean x rice(CT)] showed the lowest sustainability level, (d) S8 [Species mixtures x corn x rice(NT)] presented the best distribution and balance between the different classes of sustainability considered; (e) S10 [Native grass x corn x rice(CT)] has the worst performance, regarding the sustainability of the ones which included maize; (f) the NT system gives greater sustainability to the crop succession.

Teor e qualidade de substâncias húmicas de planossolo sob diferentes sistemas de cultivo

The objective of this study was to evaluate and compare the content and chemical characteristics of humic substances (SHs) of an Albaqualf under different soil management systems. Soil samples were collected in a long-term field experiment (19 years) from the 0-0.025; 0.025-0.05 and 0.05-0.20m layers and from the top of the B horizon. The following treatments were evaluated: APC-continuous rice crop system under conventional tillage and weed control with herbicides; APD-no-tillage system with rye-grass in the winter and rice in the summer, and SN-soil under natural condition with native grassland. The SHs and the non-humic fraction (NH) were obtained by chemical fractioning. The content of total soil carbon and those occurring as SHs and NH were determined by the Walkley-Black and spectrophotometric methods, respectively. To determine the chemical and molecular characteristics of the SHs, UV-visible and infrared spectroscopy techniques and elementar analyses were employed. In comparison to the soil under natural condition (SN), the no-tillage system (APD) maintained total soil organic carbon concentrations as well as the content of SHs. The conventional tillage reduced soil total organic carbon and the content of SH in the upper layers (<0.05m). The proportion of fulvic acid in relation to the total soil organic carbon increased with soil depth, suggesting the mobilization of this fraction along the profile. The soil management system affected the composition of the organic matter mainly in the 0 to 0.025m layer, where the SH showed a lower decomposition and higher polaricity degree and contained smaller proportion of aliphatic structures than SH in the APD system.

CO066. DHEA/CORTISOL RATIO IN RELATION TO ANXIETY

a glicemia do jejum, a glicemia as 2 horas e a HbA1c. A berberina tambem diminui significativamente a razao Leptina/Adiponectina nos grupos tratados. Relativamente a funcao endotelial, houve uma melhoria acentuada do relaxamento dependente do endotelio nos animais tratados com berberina. Concluimos que a berberina apresenta um elevado potencial terapeutico no tratamento das complicacoes associadas a diabetes tipo 2.