Marcelo Augusto Batista

Atributos físicos e carbono orgânico em latossolo vermelho sob diferentes sistemas de uso e manejo

Understanding and quantifying the impact of land use and soil management on soil organic carbon (SOC) levels and physical properties is essential for the development of a sustainable agriculture. The purpose of this study was to evaluate some physical properties and SOC of an Oxisol in the Northwest of the state of Parana, under different use and soil management systems, i.e., under native forest, pasture, cassava, and sugarcane. Disturbed soil samples were collected for particle size, particle density, proctor and organic carbon analyses and undisturbed samples (rings) to determine bulk density (Ds) and soil porosity. Results indicated that the land use and management systems induced changes in the soil physical properties in comparison to native forest. This was inferred from the higher values of soil Ds, maximum bulk density, and relative bulk density, and the lower values of macroporosity, total porosity, SOC and soil carbon stock, in the following growing order: pasture, cassava and sugarcane. However, the areas are not considered physically degraded.

MINERALOGICAL, CHEMICAL, AND PHYSICAL CHARACTERIZATION OF SYNTHETIC Al-SUBSTITUTED MAGHEMITES (γ-Fe2−xAlxO3)

Maghemite (γ-Fe2O3) is a ferrimagnetic Fe oxide commonly found in tropical and subtropical soils, especially in the topsoil where it is usually a product of burning. Isomorphic substitution (IS) of the Fe in maghemite by different metals (mainly Al3+) can modify its mineralogical and chemical attributes, and these modifications may be important to understanding the formation and properties of this mineral in soils and sediments. The objective of this work was to evaluate the crystallochemical alterations of synthetic, Al-substituted maghemites prepared by the precipitation of magnetites from alkaline aqueous media containing FeSO4·7H2O with increasing amounts of Al2(SO4)3·7H2O to obtain hypothetical Al3+ for Fe3+ substitutions ranging from 0.0 to 40.0 mol %. The Al-substituted magnetites were washed and dried, and then heated to 250ºC for 4 h to form yellowish red maghemites that were characterized by total chemical analysis, X-ray diffraction, specific surface area (SSA), mass-specific magnetic susceptibility, infrared spectroscopy, transmission electronic microscopy, and color. Increasing Al3+ substitution to an experimental maximum of 15.9 mol % decreased both the a0 dimension of the cubic unit cell (a0 = 0.8339 − 396.157 × 10−16 Al, r2 = 0.99) and the mean crystallite dimension (MCD = 76.4–3.15Al, r2 = 0.79) of the maghemites. With the decrease in MCD came a more yellowish color, an increase in SSA, and a decrease in crystallinity as measured through extraction of the samples with acid ammonium oxalate. The mass-specific magnetic susceptibility of the maghemites increased with Al3+ substitution up to 5.3 mol % and then decreased with further replacement of Fe by Al. Solid-phase aluminum in excess of 16 mol % substitution appeared to occur as a separate, poorly crystalline phase that was X-ray amorphous.

Mineral composition and dry mass production of the corn plants in response to phosphorus sources and aluminum concentration

The corn plants were evaluated with different phosphate fertilizer sources and aluminum (Al) concentrations in a sandy substrate. A totally randomized experiment design was set up with two corn plants in the pots containing 2 kg of a sandy substrate, two phosphate sources (Triple Super Phosphate - TSP or Arad Phosphate - AP) and four Al concentrations. When Al concentrations increased, pH (CaCl2) substrate values decreased. There was an increase in the calcium and phosphorus contents in the sandy substrates that received the TSP and AP sources. The calcium, magnesium, phosphorus, and potassium concentrations of the corn plants shoot were higher in the TSP than without P and AP sources. When the Al concentration increased, the concentration values of the former elements decreased. The dry mass production of the corn plants responded positively to P sources. As the Al concentration increased, the dry mass values decreased significantly in the TSP source.

Aluminum in corn plants: influence on growth and morpho-anatomy of root and leaf

Aluminum (Al) toxicity is one of the most limiting factors for productivity. This research was carried out to assess the influence of Al nutrient solution on plant height, dry weight and morphoanatomical alterations in corn (Zea mays L.) roots and leaves. The experiment was conducted in a greenhouse with five treatments consisting of Al doses (0, 25, 75, 150, and 300 µmol L-1) and six replications. The solutions were constantly aerated, and the pH was initially adjusted to 4.3. The shoot dry matter, root dry matter and plant height decreased significantly with increasing Al concentrations. Compared to the control plants, it was observed that the root growth of corn plants in Al solutions was inhibited, there were fewer lateral roots and the development of the root system reduced. The leaf anatomy of plants grown in solutions containing 75 and 300 µmol L-1 Al differed in few aspects from the control plants. The leaf sheaths of the plants exposed to Al had a uniseriate epidermis coated with a thin cuticle layer, and the cells of both the epidermis and the cortex were less developed. In the vascular bundle, the metaxylem and protoxylem had no secondary walls, and the diameter of both was much smaller than of the control plants.