& Tadeu Takeyshi Inoue (5) RESUMOA compreensão e a quantificação do impacto dos sistemas de uso e manejo nos teores de C orgânico do solo (COS) e em propriedades físicas são fundamentais para o desenvolvimento de sistemas agrícolas sustentáveis. O objetivo deste trabalho foi avaliar alterações em alguns atributos físicos e COS de um Latossolo Vermelho da região noroeste do Paraná sob diferentes sistemas de uso e manejo: mata nativa, pastagem e as culturas de mandioca e de cana-de-açúcar. Foram coletadas amostras deformadas para determinação da textura, da densidade de partículas, do ensaio de Proctor normal e dos teores de matéria orgânica; e amostras indeformadas, para determinação da densidade do solo (Ds) e porosidade do solo. Os resultados indicaram que os sistemas de manejo estudados induziram alterações nos atributos físicos do solo em relação à mata nativa, o que foi verificado pelos maiores valores de Ds, densidade relativa do solo e densidade máxima do solo e menores valores de macroposidade, porosidade total, COS e estoque de C do solo, na seguinte ordem crescente: pastagem, mandioca e cana-de-açúcar. Contudo, as áreas não são consideradas fisicamente degradadas.

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.

This research investigated the efficiency and residual effects of two solid organomineral fertilizers on corn (Zea mays L.) shoot dry matter (SDM), P uptake, P recovery index, P use efficiency index, accumulated SDM (ASDM), and total P uptake. This was a greenhouse pot study where organomineral‐granulated (OG) fertilizer, organomineral‐pelletized (OM) fertilizer, and inorganic fertilizer mix (MM) were tested on a Eutropherric Red Latossol clay soil (Oxisol). Phosphorus (P) rates were 0, 25, 50, 100, and 200 mg kg−1. Two plants were grown in each pot for 35 d before harvest; this cropping cycle was repeated consecutively four times on the same pots. Corn SDM for OM in the first cropping cycle was three times lower than for OG and MM at the highest P rate, was similar among all sources in the second and third cycles, and in the last cropping cycle was on average two times higher for the OM and MM compared with OG. Tissue P uptake was on average 50% greater for OM and MM than for OG. Corn ASDM and total P uptake were significantly greater (on average 35% for ASDM and 40% for total P uptake) with MM and OM than with OG for the majority of the rates. The P recovery index was the same in the first cropping cycle among all sources; however, it was significantly higher (60% on average) for MM and OM in the last two cycles than for OG. No difference in P use efficiency of corn plants was observed between fertilizer sources. Organomineral fertilizers made with different techniques yield fertilizers with different P availability. We observed a different residual effect among the mineral and organomineral fertilizers. The P release kinetics of the mineral fertilizer are different compared with the organomineral. The P content extracted by water in the fertilizers is the main index of the phosphate fertilizer efficiency.

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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.

Nanofertilizers are increasingly explored for sustainable micronutrient delivery in agriculture. Pre-treating seeds with nanofertilizers prior to planting (i.e., seed priming) reduces concerns about nanoparticle (NP) fertilizer non-target dispersion; however, priming formulations and concentrations must be carefully selected to avoid germination inhibition and toxicity. Here we investigate changes in corn seed germination and seedling development after seed priming with ZnO NPs, ZnO bulk and ZnCl2. To evaluate the effects sterile seeds were immersed in priming solutions of 0, 20, 40, 80, 160 mg L−1 Zn for the three Zn sources. Following an 8 h priming the seeds were evaluated for germination and vigor for 5 days on germination paper. Root and shoot lengths were measured as well as fresh and dry biomass. Compared to the control, the ZnO NP and ZnCl2 seed priming promoted beneficial effects. ZnO NP seed-priming exhibited a concentration dependent profile in improving seedling growth, with greatest benefit around 80 mg L−1, providing 17%, 25% and 12% higher values than control for germination, root length, and dry biomass production, respectively. In contrast, seeds primed with bulk ZnO did not differ from the control. These findings support NP-seed priming as an alternative to delivery of essential micronutrients, such as zinc, to corn seedlings.

On the other hand, the mean crystallite dimension and mass-specific magnetic susceptibility of the studied maghemites decreased with increasing isomorphic substitution.

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