Effects of different humic substances concentrations on root anatomy and Cd accumulation in seedlings of Avicennia germinans (black mangrove).

This study explores, in controlled conditions, the effect of humic substances on Avicennia germinans seedlings, with or without cadmium contamination. Humic compounds significantly changed plant root architecture, and, when coupled with cadmium, root anatomy and Cortex to Vascular Cylinder diameter ratio

Can co-application of silicate rock powder and humic-like acids increase nutrient uptake and plant growth in weathered tropical soil?

Silicate rock powder (SRP) restores the fertility of weathered soils. However, its slow nutrientrelease is a disadvantage for short-duration crops. Humic-like acids (HLAs) are plantbiostimulants that enhance root development and nutrient uptake. This work evaluates theeffects of the co-application of HLA extracted from a vermicompost and SRP on the nutrientuptake and growth of maize cultivated in weathered soil in Brazil. The chemical composition ofHLA was assessed using Fourier-transform infrared spectroscopy and13Carbon-nuclear magneticresonance, revealing an overall characteristic of hydrophobicity. A preliminary trial with differentHLA concentrations (0, 20, 40, 80, and 160 mg L−1) revealed that 40 mg L−1HLA resulted in thehighest increase in the root area, dry root weight, H+efflux, and the number of lateral roots,compared with other concentrations. The main experiment using soil treated with SRP atdifferent rates (0, 600, 1200, 1800, and 2400 kg ha−1) showed that the co-application of SRP andHLA caused a significant difference in the root and total plant weights, compared with the soleSRP application. Furthermore, it increased the nutrient content of the plants. These effects aremainly because of increased proton pump activity and the hydrophobicity of HL

Soil characterization and drainage effects in a savanna palm swamp (vereda) of an agricultural area from Central Brazil.

Brazilian palm swamps (veredas) are fundamentals in the hydrological balance of watercourses in the Brazilian savanna (Cerrado). The "sponge effect" of their soils is the main factor controlling local hydrology, storing rainwater, and functioning as headwaters. The restricted knowledge of these tropical ecosystems has led to increased losses, poor preservation, and reduction in their ecosystem services. Veredas have become refuges surrounded by croplands, often drained and inappropriately managed. This study shows the impacts of anthropization on soil processes and properties of a vereda in an agricultural area. Two soil profiles were selected and characterized as preserved and anthropized, respectively upstream and downstream of the studied vereda. Morphological, physical, chemical and microbiological properties were analyzed. Principal Components Analysis (PCA) was applied to synthesize the data and provide evidence of the main properties and underlying processes that most responded to the degradation action. The arrangement of this analysis shows three main distinguish drivers: one joining the properties related to the humification of organic matter and relative accumulation of mineral matter versus accumulation of organic matter; the second with properties related to soil chemical reactivity; and the third reflecting the mineralization of organic matter. Our results suggest that the anthropic action has strongly caused the organic carbon reduction (~22 %). After 20 years, the anthropized soil presents not only a great decline in carbon stock (~14 kg m-2), but also strong impacts on several other ecologic functions, such as water holding capacity. Veredas are complex and fragile environments, and they should be fully protected to maintain their ecosystem services

Grazing management strategies for Xaraés grass (Brachiaria brizantha cv. Xaraés)

The objective of this study was to evaluate the effects of two intermittent grazing strategies, with 24 fixed resting days and 95% light interception in Xaraés grass. For evaluation of productive, structural and nutritive characteristics, we used a completely randomized design with repeated measures in the time, with four grazing cycles and two grazing strategies. For consumption by the animals, we used a completely randomized design, in a 2 x 3 factorial, with two grazing strategies and three days of occupation. There was no effect for the variables: availability, structure and chemical composition of forage, except for light interception and crude protein, in which treatment with LI showed the highest value of light interception and lower content of CP. There was effect for dry matter intake between the days of occupation, and the highest values found on the first day and the lowest on the third day of occupation. Thus, taking into account practicality of adoption, good soil and climatic conditions, grazing management with intensification of fixed days shows great potential for pasture use.Objetivou-se com este estudo, avaliar os efeitos de duas estratégias de pastejo intermitente, com 24 dias fixos de descanso e com 95% de interceptação luminosa em capim-xaraés. Para a avaliação das características produtivas, estruturais e bromatológicas foi utilizado o delineamento inteiramente casualizado com medidas repetidas no tempo, com quatro ciclos de pastejo e duas estratégias de pastejo. Para o consumo dos animais foi utilizado o delineamento inteiramente casualizado em arranjo fatorial 2 x 3, sendo duas estratégias de pastejo e três dias de ocupação, e para a taxa de lotação utilizou-se o arranjo 2 x 4 (duas estratégias e quatro ciclos de pastejo). Não houve efeito para as variáveis: disponibilidade, estrutura e composição bromatológica da forragem, com exceção para interceptação luminosa e proteína bruta, onde o tratamento com IL obteve maior valor de interceptação luminosa (2,73% superior que o DF) e menor teor de PB (1,08% inferior ao tratamento DF). Para o consumo de matéria seca houve efeito (

Sementes de leguminosas submetidas a diferentes períodos de estresse salino

Este estudo foi conduzido com o objetivo de avaliar os efeitos do estresse salino sobre o teor de umidade e sobre a germinação de sementes de cunhã, soja perene, macrotiloma e calo-pogônio. O delineamento experimental foi inteiramente casualizado em esquema fatorial 4x5 (quatro espécies, cinco tratamentos) com quatro repetições. As sementes permaneceram em sal por: 0, 6, 12, 18 e 24 horas. O estresse salino, até 18 horas, não apresentou risco para a germinação das sementesThis study was led with the objective of evaluating the saline stress effect over humidity rate and germination of butterfly pea, perennial soybean, archer and calopo seeds. A completely randomized design at factorial scheme 4x5 with four repetitions was used. Seeds stated in salt for, 6, 12, 18 and 24 hrs. The saline stress did not show risk to seed germination even up to 18 hr