Selenium (Se) is essential to humans and animals due to its antioxidant properties. Although it is not considered an essential nutrient for higher plants. Many studies show that Se in low concentrations (up to 0.5 mg kg) provides beneficial effects to non-hyperaccumulating plants by participating in antioxidant defense systems and enhancing tolerance to abiotic stress. Therefore, this study aimed to evaluate the effects of Se application rates on rice plants under different soil water conditions. The experiment was conducted on an Oxisol using four Se rates (0, 0.5, 1.0 and 2.0 mg kg) and two soil water conditions (irrigated and water deficit). Selenium application via soil up to 0.5 mg kg increased the plant height, chlorophyll index, sulfur and copper accumulation in shoots, carbon dioxide assimilation, superoxide dismutase (EC 1.15.1.1) activity and decreased the hydrogen peroxide concentration in rice leaves. The accumulation of Se in shoot biomass and Se concentration in seeds increased linearly with the applied rates. Water deficit strongly decreased the plant growth and yield. However, rice plants treated with Se showed higher net photosynthesis, water use efficiency and antioxidant system. This study provides useful information about the roles of Se in protecting rice plants from water deficit stress.
INTRODUÇÃOO sistema integrado de produção agropecuária em plantio direto (SIPA-PD) é uma alternativa para a recuperação de áreas degradadas em regiões de clima tropical e subtropical, como o Brasil. Essa recupera- ABSTRACT RESUMOção do solo é possível em função da diversidade de culturas e animais que podem ser utilizados nesse sistema. Entretanto, o manejo de animais nas áreas deve ser realizado de maneira adequada, evitando, assim, os efeitos negativos que o pisoteio pode causar ao solo (Hallett et al. 2003, Souza et al. 2010). A presença de animais em áreas de lavoura pode alterar a estrutura física do solo, sendo que a intensidade de pastejo contribui para esse resultado. Este trabalho objetivou avaliar os atributos físicos do solo e a produtividade de soja e braquiária, em sistema integrado de produção agropecuária, sob plantio direto. Os tratamentos foram distribuídos em blocos casualizados, com três repetições, e consistiram de diferentes alturas de manejo do pasto (0,25 m, 0,35 m e 0,45 m) e uma área sem pastejo. Foi determinada a biomassa seca da parte aérea e raiz da soja e braquiária e a produtividade da soja. Amostras de solo foram coletadas nas camadas de 0-5 cm, 5-10 cm e 10-20 cm de profundidade, sendo determinados os seguintes atributos físicos: densidade, porosidade total, macroporosidade, microporosidade, resistência à penetração e diâmetro médio ponderado de agregados. As intensidades de pastejo não interferiram na densidade do solo em nenhuma das camadas. Houve redução da porosidade total após o segundo ciclo de pastejo, na camada de 0-5 cm. O diâmetro médio ponderado de agregados foi menor nas áreas pastejadas nas camadas de 0-5 cm e 10-20 cm e verificou-se aumento da resistência mecânica à penetração em todas as camadas, principalmente para o pastejo a 0,25 m de altura. A quantidade de biomassa seca total (soja + braquiária) e biomassa seca da parte aérea da braquiária foram menores nas áreas pastejadas, no entanto, a produtividade da soja não foi influenciada pelos ciclos de pastejo. PALAVRAS-CHAVE:Glycine max L.; Urochloa ruziziensis; agregação do solo; porosidade do solo.Influence of the integrated crop-livestock system on soil and soybean and brachiaria yieldThe presence of animals in farming areas can affect soil physical structures depending on grazing intensity. This study aimed to evaluate soil physical attributes, as well as soybean and brachiaria yield, under no-tillage, in an integrated crop-livestock system. Treatments were arranged in a complete randomized blocks design, with three replications, and consisted of different grazing heights (0.25 m, 0.35 m and 0.45 m) and a no-grazing area. The shoot and root dry biomass of soybean and brachiaria and soybean yield were evaluated. Soil samples were collected from 0-5 cm, 5-10 cm and 10-20 cm depth layers and the following soil physical attributes were determined: bulk density, total porosity, macroporosity, microporosity, penetration resistance and mean weight diameter of aggregates. Grazing intensities did not affect soil bulk den...
Crop-livestock integration (CLI) is a management system that has been developed for a variety of soil and climatic conditions, which combined with the no-tillage system (NTS), has many variations in Brazil, particularly regarding grazing intensity. The objective of this study was to assess the effects of different grazing intensities and soybean (Glycine max L.) crops on carbon (Cst) and nitrogen (Nst) stocks, light organic matter (LOM), root content of the LOM (RLOM), and remaining phosphorus ) of pasture grown in a CLI system. Two control areas, an area without grazing (AWG) and a native vegetation area of the Cerrado biome (NCA), which were adjacent to the experimental area, were compared with the cultivated areas. Soil samples were collected from 0.00-0.05, 0.05-0.10, and 0.10-0.20 m beneath each area in a completely randomized design with six replications. Soil characteristics were evaluated in the post-pasture cycle period (PP) and the postsoybean crop period (PC), which coincided with the wet and dry seasons, respectively. The NCA had more LOM in the 0.00-0.05 m layer during the PC and the 0.05-0.10 m layer during both the PP and the PC, C in the LOM in the 0.00-0.20 m layer during the PP and the PC, N in the LOM in the 0.00-0.05 m layer in the PC and the 0.05-0.10 m layer in the PP and the PC, and Cst in the 0.00-0.20 m layer in the PP and the PC than the cultivated areas, but a lower soil density (SD) and Prem in the 0.00-0.20 m layer during both the PP and the PC. Treatment P35 had more Nst in the PC and RLOM in the PP than the other cultivated treatments and the AWG. The absence of grazing in the AWG decreased the SD from the PP to the PC, while the treatments with different grazing intensities had similar values throughout this period. Our results suggest that production could be intensified under light and moderate grazing intensities in the CLI system. Key words: No-tillage system. Grazing intensity. Soil organic matter. Cerrado biome. ResumoA integração lavoura-pecuária (ILP), combinada ao sistema plantio direto (SPD), é um sistema de manejo que tem sido desenvolvido para diversas condições edafoclimáticas, com muitas variações no Brasil, principalmente quanto a intensidade de pastejo. O objetivo deste estudo foi avaliar os efeitos de diferentes intensidades de pastejo e cultivo da soja (Glycine max L.) nos estoques de carbono (EstC) e nitrogênio (EstN), matéria orgânica leve (MOL), conteúdo de raízes na MOL (RMOL) e fósforo remanescente (
The objective of this work was to evaluate the influence of arbuscular mycorrhizal fungi (AMF) on the accumulation of shoot and root biomass and on the nutrient contents of Urochloa decumbens grown in soils with different densities. The experiment was carried out in a randomized complete block design, in a 4x2 factorial arrangement: four soil densities (1.0, 1.2, 1.4, and 1.6 kg dm-3) with and without inoculation of AMF, with four replicates. The biomass accumulation (dry matter weight of shoot and roots) and macro- and micronutrient contents of U. decumbens were determined at different soil densities. The mycorrhizal colonization of the plants was evaluated, and the number of mycorrhizal spores present in the soil was determined. The biomass accumulation of shoot and roots and macro- and micronutrient contents, as well as the number of mycorrhizal spores in the soil, were negatively affected by the increase in soil density. Only root biomass increased with AMF inoculation. There was no interaction between soil density and inoculation for shoot and root biomass accumulation. Arbuscular mycorrhizal fungi influence the accumulation of biomass in the roots and of N and Ca contents in the shoots of Urochloa decumbens even at the highest soil densities.
O objetivo deste estudofoi avaliar diferentes doses de potássio em adubações de cobertura e sua influência sobre fatores de crescimento, sanidade, parâmetros de qualidade, desenvolvimento e produtividade na cultura da cenoura. O experimento foi conduzido na área experimental da Universidade Federal de Mato Grosso em delineamento de blocos casualizados com oito tratamentos, sendo 64, 128, 192, 256, 320, 384, 448 e 512 kg ha-1 de K2Ocomtrês repetições. Foram avaliados comprimento e diâmetro de raiz, área foliar e altura de folha, teor de açúcar (oBrix), acidez total titulável, produtividade além da incidência da doençaMancha de Alternária (Alternaria dauci). A dose de 448 kg ha-1de K2O foi a que mais influenciou no crescimento de raiz. A produtividade apresentou aumento linear em relação às doses de K, sendo que 448 kg ha-1 de K2O representou a maior produtividade, tendo alta correlação com o aumento do comprimento de raiz.A acidez e o teor de açúcar não foram influenciados pelas doses de K2O e a incidência de Mancha de Alternaria (Alternaria dauci) diminuiu em função do aumento das doses de K.
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