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As florestas da costa atlântica brasileira são pouco estudadas quanto às quantidades e à dinâmica de nutrientes. Os objetivos deste trabalho foram estimar os teores e conteúdos de carbono orgânico, Ca, Mg, K, Na, P e N no solo e na serapilheira dos ambientes de encosta e fundos de vale do Parque Nacional da Tijuca, Rio de Janeiro, RJ. Os processos de ciclagem de nutrientes nas encostas (ambientes mais oligotróficos) e dos fundos de vale (ambientes menos oligotróficos) também foram comparados. Foram estabelecidas 15 parcelas de amostragem, cada uma com 100 m², 10 em encostas (vertentes do Conde, das Cobras e da Tijuca), e cinco em fundos de vale (fundos de vale 1 e 2). O compartimento solo (nutrientes trocáveis/disponíveis e totais até a profundidade de 0,30 m) e o compartimento serapilheira (separada em horizontes O1 e O2) foram avaliados. O teor de carbono orgânico total no solo das encostas foi maior que o nos fundos de vale. Nas encostas, a serapilheira também apresentou maior biomassa, com separação nítida dos horizontes O1 e O2, o que não ocorreu nos fundos de vale. Aparentemente, a disponibilidade de nutrientes nos dois ambientes foi o que gerou tais diferenças, com a tendência de aumento nos teores no solo nos fundos de vale. Diferenças entre fundos de vale e encostas foram mais evidentes para o K. Os resultados deste estudo caracterizaram a área estudada como oligotrófica, embora com considerável potencial de reposição dos elementos perdidos por lixiviação.

The extent by which the contribution of eucalypt harvest residues (HR) to soil organic carbon (SOC) is impacted by soil disturbance during and/or after harvesting is unclear. We addressed this question by following the decomposition of HR in microplots (15-cm diameter, 15-cm height) and determining their contribution to SOC in 10 sites across southeastern Brazil. The experiment was set up according to a complete randomized block design arranged into a 3 × 2 factorial scheme including: HR removal (HR0), only bark removal (HR − B) and HR including bark (HR + B) applied to: undisturbed soil (US) with HR left on the soil surface or disturbed soil with HR mixed into the first 5 cm of the topsoil. We had eight blocks as replicates. Following a 12-month field decomposition, soil samples were fractionated to isolate SOC within the particle-size fractions (PSF) greater and lower than 53 µm. Subsequently, we used 13C to quantify the effects of the treatments in C3-derived SOC content (C3-SOC) within each PSF. For both PSF, their C3-SOC content increased in response to HR − B or HR + B relative to HR0, depending on soil disturbance and HR half-life time (t0.5). For HR − B, net increments in C3-SOC within the PSF > 53 µm increased significantly with HR t0.5, regardless of soil disturbance. Otherwise, the C3-SOC content within the PSF

Boron (B) can easily leach into the soil when added in the form of a soluble fertilizer such as borax or boric acid (H3BO3); however, large quantities of B can cause toxicity in plants. The use of a slow release source of B such as layered double hydroxides intercalated with borate may minimize leaching/toxicity of B. The objectives of this study are to evaluate the availability and leaching of B from magnesium–aluminium layered double hydroxides intercalated with borate anions (Mg2Al-B-LDH) and H3BO3 in a sandy soil, and the B bioavailability of these two sources in consecutive cultivations of sunflower. Mg2Al-B-LDH and H3BO3 at two rates (10 and 20 mg dm−3 of B) were incubated for 1, 2, 3, 5, 10, 20 and 40 days. After incubation, the soil B availability was evaluated using the hot-water extraction method. For the leaching study, 20 mg dm−3 of B from the two sources was incorporated into the top 0.5 cm of soil and incubated for 1, 5, 10, 15, 20, 25 and 30 days before leaching with water volume equivalent to the total soil-pore space. Sunflower plants were cultivated for two consecutive seasons in greenhouse using Mg2Al-B-LDH and H3BO3 and six rates (0, 0.5, 1, 2, 3 and 5 mg dm−3) in a factorial 2 × 6, with four replicates. Plants received a single application of B before sowing at the first cultivation. H3BO3 had greater availability of B in the soil than Mg2Al-B-LDH regardless of the applied rate or time of incubation. The slow release of B by Mg2Al-B-LDH resulted in a significant reduction in B leached compared to H3BO3. There was a quadratic and linear response of sunflower aboveground biomass and B accumulation with increasing rates of H3BO3 and Mg2Al-B-LDH, respectively, in the second cultivation only. A boron rate of 5 mg dm−3 applied as H3BO3 resulted in plant toxicity, while Mg2Al-B-LDH promoted a slow release of B to the plants throughout the cultivation period.

The aim of this study was to evaluate the effect of forms of application and application rates of phosphate fertilizer on the agronomic characteristics of carrot. A field experiment was car...

Phosphorus (P) is a nutrient necessary for agricultural production and a potential originator for eutrophication in water bodies, resulting in qualitative changes; it may also affect the aquatic ecosystem and human health. In addition, as a finite resource, the importance of studying strategies to remove it from water is evident, thus making possible its recycling. Many studies have used powdered materials, including biochars, for P water decontamination; however, the difficulty of separating and collecting these materials from water after adsorption may be difficult. Therefore, using hybrid materials in which the fine particles (powder) are impregnated into larger, solid particles by means of a polymeric host can facilitate collection and reuse after P adsorption. In this context, this study aimed the synthesis and characterization of a new hybrid film formed by the biopolymer cellulose acetate (CA) and biochar (FAC-B) for P adsorption in aqueous solution. We obtained biochar from the pyrolysis of carrot residue (Daucus carota L.) and doped it with magnesium. As a biodegradable polymer and the most abundant natural polysaccharide in the environment, using CA as a biochar support material is an environmentally friendly alternative. We prepared the CA film with the casting method, and the biochar was inserted into the filmogenic solution in the same amount as the CA. The film was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), molecular absorption spectroscopy in the infrared region with an attenuated total reflectance (FTIR/ATR) accessory, and X-ray Photoelectron Spectroscopy (XPS). We evaluated the thickness, weight, density, H2O uptake and H2O solubility of the produced FAC-B. The maximum adsorption capacity of P by FAC-B was 21.57 mg g−1, in agreement with the Langmuir isotherm model. The adsorption value suggests that the film has the potential to be used as an efficient P adsorbent in water.

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A saturação por base do solo pode influenciar a disponibilidade de zinco para as plantas. Portanto, objetivou-se avaliar a influência de doses de zinco e de crescentes saturações por bases de solo sobre a disponibilidade deste para plantas de milho. Para tal conduziu-se dois experimentos em casa de vegetação, sendo um referente a um solo arenoso e outro argiloso. Ambos em esquema fatorial 6 x 3, em delineamento inteiramente casualizados, com três repetições. O primeiro fator correspondeu a saturação por bases (V%) de cada solo, após curva de incubação com doses crescentes de calcário, e o segundo fator às doses estudadas de zinco (0, 5 e 25 mg dm-3). Avaliou-se a produção de matéria seca da parte área de plantas de milho, o teor e o acúmulo foliar de zinco, e o teor de zinco no solo após a condução dos experimentos. O aumento da dose de zinco proporcionou aumento de todas variáveis em estudos, em ambos experimentos, exceto para a matéria seca no solo arenoso. Esta, também, foi a única situação que os fatores atuaram de forma independente. O aumento da saturação por bases do solo proporcionou decréscimo das variáveis analisadas, sendo que o tipo de solo influencia na amplitude da resposta. Conclui-se que o aumento da dose de zinco contribui para aumento da disponibilidade e acúmulo de zinco para as plantas, sendo esta é afetada negativamente pelo aumento da saturação por bases do solo.

Plants with different photosynthetic cycles (C3 and C4) and different plant parts (root or shoot) contribute in different ways to soil organic carbon (SOC). In addition, phosphate and nitrogen fert...

The increase of the absorption efficiency of boron (B) by plants is essential for increasing crop productivity. The intercalation of B in MgAl layered double hydroxides (LDHs) is an alternative to evaluating how these materials can provide B to plants. In this work, a MgAl LDH intercalated with borate ions (Mg2Al-B-LDH) was synthesized by the constant pH coprecipitation method, and the material produced was evaluated as a matrix for storage and as a source of B for plants. The Mg2Al-B-LDH was characterized by XRD, ATR-FTIR, TGA-DTA, specific surface area, pore size and volume, and SEM. A bioassay was performed to verify the supply of B to plants from the two sources in the forms of H3BO3 and of Mg2Al-B-LDH to sunflower plants grown in pots. The LDH basal spacing value of 12.0 Å is characteristic of intercalation of tetraborate octahydrate ions [B4O5(OH)42−]·8H2O between the layers. There was an increase in the dry matter (DM) and B content of the plants relative to those treatments where no B was added. The lack of statistical difference for plant yield between the two sources of B suggests a lack of stability of the Mg2Al-B-LDH structure under the acidic condition of the soil.

Made available in DSpace on 2022-04-29T08:32:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-15 Phosphorus (P) is one of the nutrients applied in high amounts to vegetable crops due to high soil clays fixation. In view of the onion plant's limitations, the present study was formulated to access whether doses and forms of P splitting increase the efficiency of phosphate fertilization and influence physiological and growth characteristics of onion. Two experiments were carried out, one in a Red Yellow Latosol with a clay texture and the other in a Yellow Latosol with medium texture, both in a greenhouse. Evaluation was done on the interactions between two P doses and five split forms arranged in a factorial scheme (2 × 5) + 1 (control without P) in a completely randomized design and five replications. The agronomic efficiency, the recovery efficiency of P, the P-available in soil at the end of cultivation, the photosynthetic pigment content and the dry matter were positively influenced by P split, especially in clayey soil. Split application of P was strategic to reduce contact time of P with soil and prevent fixation guarantying greater nutrient availability in soil throughout the crop cycle. In medium-textured soil, the P movement became less problematic because of the lower P-fixing capacity, therefore low splitting effect. Master in Agronomy from the Federal University of Viçosa Rio Paranaíba campus Doctor in Agronomy (Vegetable Production) from the State University of São Paulo “Julio de Mesquita Filho” Jaboticabal Professor Federal University of Viçosa Department of Agronomy Institute of Agricultural Federal University of Viçosa Rio Paranaíba campus Retired Professor at the Federal University of Viçosa Department of Soils Doctor in Agronomy (Vegetable Production) from the State University of São Paulo “Julio de Mesquita Filho” Jaboticabal

We assessed the sensitivity of mixed exchange resin (MER) and Mehlich-3 (M3) to calcium-bound phosphate (Ca-P) in Oxisols. These methods were compared with Mehlich-1 (M1) and anion exchange resin (AER), which have high and low sensitivity, respectively, to this soil P form. We used maize (Zea mays L.) as a test plant. Three samples from two Oxisols were treated with five ratios of Triple Superphosphate—TS and Bayovar Phosphate Rock—BPR (0 + 100; 25 + 75, 50 + 50, 75 + 25 and 100 + 0% TS + BPR). The MER extracted more P than AER and M3 at the highest BPR:TS ratios (high Ca-P) and similar quantities at the higher TS:BPR ratios (low Ca-P) for two soil samples. Unlike M1-extracted P, M3-P, AER-P, and MER-P positively correlated with maize dry matter production and P uptake. Mehlich-3 and MER were suitable to assess P availability in high Ca-P Oxisols.

Natural phosphate rock (NP) solubilization in soils is dependent on the soil pH and its power to remove or drain (sink effect) P and Ca of the solution that is in equilibrium with the NP. The aim of this work was to evaluate the effect of acidity and P- and Ca-sinks on the solubilization of bayovar reactive rock phosphate (a phosphorite). Samples of this NP in aqueous suspension were placed in a cassette (Slide-A-Lyzzer G2 Dialysis Cassette) compartment and immersed in a beaker containing 150 mL of an aqueous solution with pH adjusted at 4.5 or 6.0, where P- and Ca-sinks individually or in their combinations, were applied. The tested sinks were: Anionic Resin (AR); Cationic Resin (CR); Mixed Resin (MR: AR + CR); Goethite (Goe); Goe + AR; Goe + CR and one control (NP only) in five replicates. Beakers (experimental units) were shaken for 12 h daily, at 130 rpm, until completing 30 days of equilibrium. The suspensions were filtered to extract solution-P from the residue on the filter paper; the labile-P was extracted from this residue using 0.8 mol·L-1 NH4Cl in 2 mol·L-1 HCl and, finally, the remainder P in the same residue together with the filter paper were subjected to nitric-perchloric acid digestion, to determine the P-residual in the extract. Goe caused greater solubilization of the NP, indicating that this P-sink was more effective than AR, causing similar or greater solubilization than CR. AR and CR, in a similar way, significantly restricted the trait characteristic of Goe (p < 0.05), at both pH values, in the solubilization of NP. Although Goe generally caused greater solubilization of the NP, it also caused the lower formation of labile-P. The CR presented, in general, the highest contents of solution-P, thus it triggered solubilization of NP without the immobilization of the solution-P, unlike the one with the AR that adsorbs it. In the lower pH condition (4.5), the solubilization of NP tended to be higher than at pH 6.0, although in a little effective way, compared to the effects of the sinks.

Across southeastern Brazil, eucalypt plantations have been established in areas with predominantly low-fertility soils, in which nutrient cycling is critical for forest sustainability. However, despite continuous research on harvest residues (HR) over the last 30 years or more, the extent by which its decomposition rate is affected by management practices, climate conditions and soil properties is not well understood. We evaluated the decomposition of HR in 10 sites under eucalypt plantations within the Mata Atlântica and the Cerrado (savanna-like) biomes, which account for more than 60% of the area under eucalypt plantations in Brazil. In each site, we assessed the decomposition of HR as affected by three major management practices, namely bark removal or its maintenance, HR left on the soil surface or mixed into the topsoil, and N fertilization at 0 or 200 kg ha−1, in a complete factorial scheme, using 4 replicates per treatment. The remaining mass of HR was assessed at 0, 3, 6, 12 and 36 months after the installation of the experiments, yielding a total of 320 samples. HR decomposed 22% faster when it was mixed into the topsoil or when the bark was included, but it was minimally affected by N fertilization. While increasing precipitation, temperature, soil pH, exchangeable Ca and Mg, and sand content led to faster decomposition rates, the opposite occurred with increasing exchangeable Al and clay content. The mean annual precipitation and soil pH combined by multiple linear regressions explained approximately 70% of the variability in the decomposition of HR across the sites. Interestingly, the decomposition rate was inversely correlated to the soil carbon content in our study. Bark maintenance in the fields under eucalypt plantations reduces off-site nutrient exportation and contributes to an increase in the decomposition rate almost by the same extent as by incorporating HR into the topsoil. Additionally, environmental conditions and soil properties also exert strong influence over the decomposition of HR and should be considered for managing nutrient cycling and fertilization programs. This is particularly important for the sustainability of eucalypt plantations established in low-fertility soils across tropical regions.

The continuous increase in the world population requires more agricultural production; therefore, phosphorus compounds (P) are essentials. Considering that P reserves are finite, studying its recycling and reusing is essential. Biochar made from agricultural residues is an interesting material to be studied for P recovery and reuse in agriculture. This study shows the preparation and characterization of a biochar obtained from the pyrolysis of carrot residue for P adsorption studies in aqueous solution. Carrot was pyrolyzed at different temperatures values, with and without pretreatment with MgCl2. Biochar impregnated with Mg and pyrolyzed at 400 °C showed higher efficiency in P removal in aqueous solution (138 mg g−1). The characterization techniques indicated that after P adsorption by biochar, a chemical reaction occurred between Mg and P species with formation of Mg(H2PO4)2. The biochar from carrot residue obtained in this work is a promising adsorbent for P recycling and has potential to be used as soil fertilizer.

Vale do Rio Doce shoot dieback (VRDSD) is an anomaly whose cause seems to be associated with hypoxic conditions and their consequences (excess Mn and Fe) triggered by elevation of the water table in areas with poor drainage. Different plants have distinct survival strategies under this form of stress. The objective of this study was to understand the physiological responses involved in the differential tolerance of eucalyptus clones to VRDSD and their relationship to hypoxia and excess Mn. A hydroponic experiment was carried out using a 2 × 2 × 2 factorial arrangement, two eucalyptus clones with different levels of tolerance to VRDSD (sensitive Urograndis hybrid - 1213; and the tolerant Rio Claro hybrid - Eucalyptus grandis x unknown - 2719), two concentrations of O2 (8 and 4 mg L-1), and two Mn concentrations (1.39 and 300 mg L-1) in a randomized block design (RBD) with three replicates. Forty-day-old clones were maintained in Clark nutrient solution for 30 days. After this period, the treatments were applied for 11 days. Plant gaseous exchange shoot and root production, and the quantity of enzymes related to oxidative stress in leaves and roots were evaluated. In the tolerant clone, reactive oxygen species (ROS) were produced under hypoxic conditions, accompanied by reduction in production of dry matter, malondialdehyde (MDA), and in activity of the enzyme alcohol dehydrogenase (ADH). However, this clone had greater production of superoxide dismutase (SOD) under these conditions, an enzyme responsible for detoxification of ROS, which acts as part of the Low Oxygen Quiescence Syndrome (LOQS). In contrast, sensitive clones did not exhibit expressive reductions in growth or changes in the leaf/root ratio. These clones formed large quantities of adventitious roots and had high levels of MDA and ADH and low levels of SOD. Therefore, sensitive clones appear not to be prepared for detoxification of ROS and other toxic metabolites, but rather adopt morphological escape mechanisms, the Low Oxygen Escape Syndrome (LOES), in response to hypoxia. Thus, the period of soil waterlogging may cause the death of large numbers of roots in sensitive clones, limiting their ability to absorb water and nutrients and culminating in the death of these plants. Excess Mn seems to aggravate the damage caused by hypoxia, but it is not the causal agent of VRDSD.

http://dx.doi.org/10.5902/1980509816607A busca de sistemas sustentáveis de manejo do solo tem levado pesquisadores a desenvolverem novas técnicas de cultivo. Dentre elas, destacam-se no Brasil estudos realizados com espécies florestais capazes de fixar N2 atmosférico e aumentar o estoque de C e N em frações lábeis e estáveis da matéria orgânica do solo (MOS). O presente estudo teve por objetivo avaliar as alterações nos estoques de C e N em frações das substâncias húmicas, da fração leve da MOS e da matéria microbiana em solos cultivados com Eucalyptus urograndis em rotação curta, eucalipto em rotação longa e povoamentos de Acacia mangium que sucederam plantios de eucalipto em rotação curta, tendo como referência o solo de floresta nativa (Mata Atlântica) adjacente. Foram quantificados os estoques de C orgânico total e N total (COT e NT), nas frações das substâncias húmicas (fração ácido fúlvico-AF, fração ácido húmico-AH e fração humina-H), C e N da fração leve da MOS (C-MOL e N-MOL) e estoque de C e N da matéria microbiana (C-BM e N-BM). Os resultados indicaram que o cultivo do eucalipto em rotação curta apresentou menores estoques de COT e NT, nas frações das substâncias húmicas e, de N na matéria microbiana em comparação ao solo sob rotação com Acacia mangium. O cultivo de Acacia mangium e o aumento do tempo da rotação do eucalipto incrementaram os estoques de C e N da maioria das frações lábeis (C-MOL, N-MOL e C-BM) e estáveis (C e N nas substâncias húmicas). Indicando tendência de recuperação dos seus estoques para valores próximos daqueles originais (mata nativa), sendo superiores aos estoques obtidos na área de eucalipto em rotação curta.

O critério atualmente adotado para a indicação de adubação da soja, embasado no estabelecimento de níveis críticos, tem permitido a obtenção de produtividades médias em torno de 3.600 kg ha-1. Contudo, para a obtenção de produtividades mais elevadas e econômicas, sem prejuízos ao equilíbrio ambiental, deve-se visar à definição de modelos quantitativos que permitam estimar a demanda por nutrientes, em função do potencial de produção almejado. Modelos desta natureza vêm sendo estabelecidos no Departamento de Solos da Universidade Federal de Viçosa, para o desenvolvimento de sistemas de recomendação de corretivos e fertilizantes, denominados genericamente de FERTCALC® e NUTRICALC®. A partir de um banco de dados, formado pelo monitoramento nutricional de lavouras comerciais em Mato Grosso do Sul, foram estabelecidos modelos matemáticos para a estimativa da demanda nutricional, em função da produtividade e do acúmulo de nutrientes no terceiro trifólio com pecíolo, ou, então, do coeficiente de utilização biológica (CUB). Demonstrou-se que, para uma dada produtividade, o produto da matéria seca da folha índice com os teores de nutrientes, considerados como suficientes para a cultura, resulta no conteúdo nutricional desta, que, por sua vez, apresenta relação com o conteúdo nutricional no caule, folhas, vagens e nos grãos. A quantidade de nutrientes imobilizada na planta de soja também pode ser calculada a partir do quociente entre a produção de grãos e de matéria seca de parte aérea e os valores de CUB estabelecidos. Os métodos propostos permitem estimativa de valores próximos da demanda nutricional pela soja. The criteria currently adopted for soybean fertilizer recommendation, based on the established of critical levels, has allowed obtaining productivity average around 3600 kg ha-1. However, in order to obtain greater and more profitable yields without harming the environment, it is necessary to establish new quantitative models to estimate correctly the demand for nutrients, depending on the desired production potential. This kind of models has been established in the Department of Soil Science at the Universidade Federal de Viçosa, for the development of recommendation systems of fertilizers generically called FERTCALC® and NUTRICALC®. Mathematical models were established from a database formed by nutritional monitoring of commercial crops in Mato Grosso do Sul State, Brazil, in order to estimate the nutrient demand. In these mathematical models, the nutrient demand was a function of potential of production and of nutrient accumulation in the third leaflet with petiole or as a function of the coefficient of biological use (CUB). It was found that, given a certain grain yield, the product between the dry matter of the index leaf and the nutrient levels considered as sufficient or great for the soybean crop results in its nutritional status; this last one is related to the nutritional status of stems, petioles, leaflet, pods and grains. The amount of nutrients in soybean plants can also be calculated by the ratio between grain yield and dry matter of shoot and established values of CUB. The proposed methods allow the estimation of values close to the nutritional demand for soybeans.

A diagnose dos estados nutricionais do algodoeiro e da soja, pelo método de níveis críticos, tem-se embasado em faixas de suficiência estabelecidas há muitos anos, com pequenas adequações no período. Contudo, considerando-se que os teores foliares podem variar, dentre outros fatores, em função do tipo de amostra coletada e do potencial produtivo da cultura, torna-se importante a definição de valores de referência regionais. Este trabalho teve como objetivo estabelecer os teores adequados de nutrientes para algodoeiro e soja, por meio do ajuste de modelos de regressão para o teor foliar em função do índice de equilíbrio nutricional definido pelo Sistema Integrado de Diagnose e Recomendação (DRIS). Utilizou-se um banco de dados, constituído das produtividades e dos teores de nutrientes em amostras foliares de ambas as espécies, coletadas em talhões de lavouras comerciais e em parcelas experimentais, em Mato Grosso do Sul e Mato Grosso. Foram obtidas faixas de suficiência para as folhas índice de algodoeiro (quinta folha totalmente formada, a partir do ápice) e de soja (terceiro trifólio sem e com pecíolo), com amplitude menor do que aquela estabelecida na literatura para estas culturas. Especificamente, para a soja, confirmou-se a existência de diferenças nos valores de referência em função do tipo de folha índice amostrado. Amostras de folha índice sem pecíolo produzem teores significativamente maiores de N, P, B, Fe, Mn e Zn e menores de K, em relação aos das amostras com pecíolo. A desconsideração do modo de amostragem pode induzir a falsos diagnósticos de deficiências ou excessos nutricionais. Nutritional status diagnosis of cotton and soybean crops through critical level methods is based on sufficiency ranges established many years ago, with little advances since then. However, as nutrient contents in leaves are influenced by sample type and crop yield potential among other factors, it is important to establish regional reference values. The aim of this study was to establish optimum nutrient concentrations in cotton and soybean leaves by adjusting a regression model to nutrient concentration based on DRIS indexes. Database consisted of yield and nutrient content in leaf samples collected in commercial cotton and soybean crops and soybean experimental plots in Mato Grosso do Sul and Mato Grosso States. On each selected place, chemical composition of leaves and crop production (whole cottonseeds or soybean grains) were evaluated at full blooming stage and physiological maturity, respectively. Based on the proposed methodology, sufficiency ranges for indexes leaves of cotton (fifth fully formed leaf) and soybean (third trifoliate leaf, without or with petiole) were determined, whith variation smaller than that presented in other papers reviewed. Specifically for the soybean crop, in addition to confirming the differences in the reference values according to the type of index leaf sampled. Samples without petiole produce significantly higher levels of N, P, B, Fe, Mn and Zn and lower K level, compared with samples with petiole. If disregarded, the manner of sampling can induce false diagnosis of nutritional deficiency or excesss in the crop.

Changes in amino acid composition are frequently observed in plants under various conditions of stress, such as nutrient deficiencies. Hence, amino acids have been proposed as more sensitive indicators of N status than total N concentration. The goal of this study was to evaluate alterations in amino acid composition of young eucalyptus clones as a result of variable N supply. An experiment was carried out in a greenhouse with two Eucalyptus clones (VM-01 and I-144) and six N application rates (0, 0.74, 2.93, 4.39, 5.85, and 8 mmol L -1 of NH4NO3) grown in a nutrient solution in a randomized block design. Amino acid concentrations varied greatly as a function of N supply and depended on the organ (root or leaf) and the genotype evaluated. Roots showed greater number of amino acids than leaves (17 and 14, respectively), probably because of a higher amino acids synthesis or translocation to the roots. For both clones, N deficiency induced a significant decrease in proline, arginine, and methionine concentration in roots and a decrease in tyrosine, alanine, threonine, and methionine in leaves. These decreases were also associated with lower total N concentration and total dry matter of the eucalyptus clones. In conclusion, N supply affects amino acid composition, and the amino acids listed above are likely to be more sensitive indicators of N status than total N in eucalyptus clones.

Land-use changes with natural vegetation removal may impact the quantity and quality of humic substances (HS), including their molecular nature. Nuclear magnetic resonance (NMR) experiments were used in the present study to evaluate the alterations in the molecular composition of fulvic (FA) and humic (HA) acids from soils under eucalypt plantations in three major biomes in Brazil: Atlantic Forest, Cerrado, and Grassland. The major NMR-identifiable components in these HS were aromatics including aromatic C-O, COO/NC = O groups, peptides, carbohydrates, lignin-derived moieties and nonpolar alkyls. In all biomes the dipolar dephasing technique indicated the presence of significant amounts of condensed aromatic C, possibly inherited from charred materials derived from natural and anthropogenic fires in the region. The nonpolar alkyl C to O-alkyl C ratio averaged 1.4 for HA and 1.1 for FA. Humic substances from eucalypt soils showed greater contribution of nonpolar alkyl groups and a smaller abundance of O-alkyl groups in comparison to the native vegetation soil. Sugarcane (Saccharum officinarum L.) cultivation increased HA aromatics in comparison to those from the native Atlantic Forest soil, but when sugarcane was substituted by eucalypt the aromatics decreased and O-alkyl C recovered in HA and FA. There was evidence of greater contribution of lignin-derived C for HA and FA in sites planted with Brachiaria spp. pastures. Except for the HA from one Cerrado soil (Itacambira), aromaticity of HA decreased following planting to eucalypt. These changes in HS molecular composition across biomes may have impact on soil organic matter processes and they should be taken into account in future studies.

Phosphorus deficiency is well known as a major agronomic constraint in the highly weathered Oxisols of Brazil and reasonable economic returns are not possible without application of high rates of phosphorus. Poultry litter, which is enriched in P, is increasingly being used in organic management of cultivated lands. Due to the great P fixing capacity of these soils, any limit to the soil sink of P is not recognized. The study was undertaken to evaluate the risk of P loss due to increase in phosphorus sorption saturation (PSS) from land application of poultry litter and to establish a relationship between PSS and water soluble phosphorus. No till corn-fallow rotation was followed for three years with annual application of 0, 5, 10, 25, 50 and 100 Mg ha −1 of poultry litter in a highly weathered clayey dystrophic red-yellow Argisol of Brazil. The effect of poultry litter application on soil was evaluated and Mehlich-3 P (P M-3 ) concentrations increased 3–134 times over control after three years of poultry litter application. Poultry litter application increased pH and decreased the concentration of exchangeable Al; whereas concentrations of K + , Na + , Zn 2+ , Mg 2+ and Ca 2+ increased substantially over control. Increase in soil pH and total organic carbon due to poultry litter application reduced the P sorption capacity of soils and P sorption. The PSS increased considerably at higher rates of poultry litter application (>10 Mg ha −1 ) and strongly increased the amount of desorbable P. Total water extractable P was mostly accounted for by reactive P forms and increased with poultry litter rates. In a plot of dissolved reactive P (DRP) against PSS, a change point was observed at 22.7% PSS corresponding to a dissolved reactive P (DRP) concentration of 0.92 mg kg −1 soil after which a sharp increase in DRP was observed. P concentration >0.1 mg L −1 was observed in soil solution at 60 cm soil depth with increasing rates of poultry litter application, thus providing evidence of P leaching. In the absence of an environmental soil test criteria for P, the break point PSS of 22.7% could be used to practically monitor whether soils have reached a level of P loading that constitutes an environmental risk of P losses from soil to surface and ground waters.

Nutrient resorption in plants influences nutrient availability and cycling and is a key process in biogeochemical models. Improved estimates of resorption parameters are needed for predicting long-term primary productivity and for improving such models. Currently, most models assume a value of 50% resorption for nitrogen (N) and phosphorus (P) and lack resorption data for other nutrients and for specific vegetation types. We provide global estimates of resorption efficiencies and nutrient concentrations for carbon (C), N, and P and the first global-scale estimates for essential nutrients such as potassium (K), calcium (Ca), and magnesium (Mg). We also examine leaf mass loss during senescence (LML) globally and for different plant types, thus defining a mass loss correction factor (MLCF) needed to quantify unbiased resorption values. We used a global meta-analysis of 86 studies and ∼1000 data points across climates for green and senesced leaves in six plant types: ferns, forbs, graminoids, conifers, and ev...

A matéria orgânica do solo (MOS) tem importantes funções no ciclo de C e na qualidade do solo. Considerando a complexidade dos fatores que controlam a ciclagem da MOS e o tempo necessário para que as mudanças sejam nela observadas, a modelagem constitui uma ferramenta muito importante para entender a ciclagem da MOS em solos florestais. As hipóteses do estudo foram: o cultivo do eucalipto por várias rotações resultaria no aumento dos estoques de C do solo, quando comparado a pastagens degradadas; e os valores dos estoques de C do solo simulados pelo modelo Century descreveriam a realidade melhor que a média das observações. Assim, os objetivos do presente estudo foram: avaliar a dinâmica da MOS utilizando o modelo Century para simular as mudanças dos estoques de C para duas cronossequências de plantações de eucalipto no Vale do Rio Doce, Minas Gerais, Brasil; e comparar os estoques de C simulados pelo Century com os estoques de C determinados em diferentes ordens de solo em distintas regiões do Vale do Rio Doce cultivadas com eucalipto. Em Belo Oriente (BO), região de menor altitude e temperatura mais elevada, as plantações de eucalipto têm sido cultivadas por 4, 13, 22, 32 e 34 anos, ao passo que em Virginópolis (VG) - região de maior altitude e temperatura mais baixa - os tempos de cultivos com eucalipto foram de 8, 19 e 33 anos. Assim, foram determinados os estoques de C do solo na camada de 0-20 cm. Os resultados indicaram que os estoques de C simulados pelo modelo Century decresceram após 37 anos de pastagem mal manejada em áreas previamente cobertas por mata nativa nas regiões de BO e VG. A substituição da pastagem mal manejada por eucalipto nos anos 70 resultou, em geral, no aumento de 0,28 e 0,42 t ha-1 ano-1 de C em BO e VG, respectivamente. Os estoques de C determinados sob eucalipto cultivado em distintas ordens de solo e independentes regiões com variáveis condições edafoclimáticas foram ligeiramente próximos aos valores estimados pelo modelo Century (RMSE = 20,9; eficiência do modelo - EF = 0,29), apesar do oposto resultado obtido com o procedimento estatístico para testar a identidade de métodos analíticos. Apenas sob condições de menores estoques de C no solo, o modelo superestimou os estoques de C na camada de 0-20 cm. Assim, o modelo Century tem grande potencial para detectar mudanças nos estoques de C em distintas ordens do solo sob eucalipto em futuras rotações, além de indicar o impacto do manejo do resíduo da colheita na MOS. Soil organic matter (SOM) plays an important role in carbon (C) cycle and soil quality. Considering the complexity of factors that control SOM cycling and the long time it usually takes to observe changes in SOM stocks, modeling constitutes a very important tool to understand SOM cycling in forest soils. The following hypotheses were tested: (i) soil organic carbon (SOC) stocks would be higher after several rotations of eucalyptus than in low-productivity pastures; (ii) SOC values simulated by the Century model would describe the data better than the mean of observations. So, the aims of the current study were: (i) to evaluate the SOM dynamics using the Century model to simulate the changes of C stocks for two eucalyptus chronosequences in the Rio Doce Valley, Minas Gerais State, Brazil; and (ii) to compare the C stocks simulated by Century with the C stocks measured in soils of different Orders and regions of the Rio Doce Valley growing eucalyptus. In Belo Oriente (BO), short-rotation eucalyptus plantations had been cultivated for 4.0; 13.0, 22.0, 32.0 and 34.0 years, at a lower elevation and in a warmer climate, while in Virginópolis (VG), these time periods were 8.0, 19.0 and 33.0 years, at a higher elevation and in a milder climate. Soil samples were collected from the 0-20 cm layer to estimate C stocks. Results indicate that the C stocks simulated by the Century model decreased after 37 years of poorly managed pastures in areas previously covered by native forest in the regions of BO and VG. The substitution of poorly managed pastures by eucalyptus in the early 1970´s led to an average increase of C of 0.28 and 0.42 t ha-1 year-1 in BO and VG, respectively. The measured C stocks under eucalyptus in distinct soil Orders and independent regions with variable edapho-climate conditions were not far from the values estimated by the Century model (root mean square error - RMSE = 20.9; model efficiency - EF = 0.29) despite the opposite result obtained with the statistical procedure to test the identity of analytical methods. Only for lower soil C stocks, the model over-estimated the C stock in the 0-20 cm layer. Thus, the Century model is highly promising to detect changes in C stocks in distinct soil orders under eucalyptus, as well as to indicate the impact of harvest residue management on SOM in future rotations.

Eucalyptus is the most widely planted forest species in Brazil (∼3.4 million hectares). Ongoing rotations and high yields lead to the occurrence of copper (Cu), manganese (Mn), iron (Fe), and zinc (Zn) deficiency symptoms. The objectives of this work were to identify the most appropriate extractant for evaluating micronutrient availability in commercial Eucalyptus plantations and to evaluate the influence of soil properties on Eucalyptus foliar micronutrient contents. Soil micronutrient contents were extracted by Mehlich 1, Mehlich 3, and diethylenetriaminepentaacetic acid (DTPA). Mehlich 1 and Mehlich 3 extracted the greatest amounts for all micronutrients analyzed. Foliar Cu, Mn, and Zn contents showed significant and positive relationships with soil Cu, Mn, and Zn contents extracted by the three solutions. Soil organic carbon (SOC), soil clay content, and soil pH improved significantly the power of regression models in estimating foliar micronutrient contents. The improvement was greater for Mehlich 3 ...

No Brasil, com a intensificação da silvicultura clonal, o plantio de materiais genéticos mais produtivos e exigentes nutricionalmente tem aumentado o aparecimento de sintomas de deficiência de micronutrientes, principalmente de B e, mais recentemente, de Cu e de Zn, sobretudo em áreas de Cerrado. Este trabalho teve por objetivo avaliar três métodos de determinação da disponibilidade de Cu (Mehlich-1, Mehlich-3 e DTPA pH 7,3) para mudas de eucalipto cultivadas em casa de vegetação, em amostras de seis solos de Cerrado, e a influência de propriedades do solo na eficiência desses extratores. Os tratamentos foram arranjados no esquema fatorial 6 x 5, correspondendo a seis solos e cinco doses de Cu (0, 2, 4, 8 e 16 mg dm-3), com quatro repetições, em blocos ao acaso. Os níveis críticos de Cu em solos de Cerrado, para o crescimento de mudas de eucalipto, são iguais ou inferiores a 0,12 e 0,09 mg dm-3; pelos extratores Mehlich-1 e DTPA, respectivamente. Os teores e conteúdos de Cu na planta mostram estreita relação com os teores de Cu no solo pelos três extratores. Os teores de Cu pelo Mehlich-1, Mehlich-3 e DTPA são altamente correlacionados entre si. A avaliação da disponibilidade de Cu para mudas de eucalipto pode ser feita com qualquer um dos três extratores. Entretanto, o Mehlich-1 é o extrator mais recomendado, pela facilidade operacional deste método em relação aos outros e por ele já ser usado na grande maioria dos laboratórios do País.

Orchid fertilization is fundamental for a satisfactory plant growth and development for commercial orchid production as well as in collections. Mineral and/or organic sources can be used for fertilization. The objective of this study was to evaluate the effect of the use of organic and/or mineral fertilizers on the nutrition and growth of orchid (Laelia purpurata 'werkhanserii' x L. lobata 'Jeni') seedlings in greenhouse. The following fertilizers were tested: an NPK fertilizer + micronutrients; a Ca source in the form of calcium nitrate; two organic fertilizers, one prepared with a mixture of bone meal, castor meal and ash, and a similar commercial fertilizer. The organic fertilizers were distributed on the surface of the pots every two months and the minerals were applied weekly to the substrate in 25 mL aliquots of a solution containing 1 g L-1 of the respective fertilizer. The plant response to the application of mineral together with organic fertilizer was better, with higher dry matter production than by the isolated application of each fertilizer (organic or mineral). The treatments with calcium nitrate + NPK fertilizer did not differ significantly from the use of NPK fertilizer, probably due to the S deficiency detected in a mineral analysis of the tissues. Commercial organic fertilizer had a very elevated B level, leading to toxicity symptoms, reduced growth and necrotized tips of the older leaves in all fertilized treatments. A fertilização de orquídeas é fundamental para crescimento e desenvolvimento satisfatórios tanto em orquidários comerciais quanto em coleções. Essa fertilização pode ser realizada com fontes minerais e, ou, orgânicas. Este trabalho teve como objetivo avaliar o efeito do uso de fertilizantes orgânicos e, ou, minerais sobre a nutrição e crescimento de mudas de orquídeas (Laelia purpurata 'werkhanserii' x L. lobata 'Jeni') em casa de vegetação. Foram utilizados: um fertilizante mineral NPK + micronutrientes; uma fonte de Ca na forma de nitrato de cálcio; e dois fertilizantes orgânicos, um preparado com a mistura de farinha de ossos, torta de mamona e cinzas e outro semelhante a esse último adquirido no comércio (comercial). Os fertilizantes orgânicos foram distribuídos sobre a superfície dos vasos a cada dois meses, e os minerais foram aplicados semanalmente no substrato em alíquotas de 25 mL de uma solução contendo 1 g L-1 do respectivo fertilizante. Os resultados demonstraram melhores respostas para uso do fertilizante mineral juntamente com o fertilizante orgânico, apresentando maior produção de matéria seca das plantas em relação ao uso isolado de cada fertilizante (orgânico ou mineral). Os tratamentos que receberam nitrato de cálcio adicionalmente ao fertilizante NPK não apresentaram diferenças significativas em comparação ao uso do fertilizante NPK, provavelmente por deficiência de S, evidenciada na análise mineral dos tecidos. O fertilizante orgânico comercial mostrou teor muito elevado de B, refletindo em sintomas de toxidez, crescimento reduzido e extremidades de folhas mais velhas necrosadas, em todos os tratamentos que receberam esse fertilizante.

Little is currently known about modifications in edaphic characteristics caused by short-rotation eucalyptus and the impacts of these alterations on the sustainability of eucalyptus wood production. This study was carried out to identify theses changes at five sites of eucalyptus plantation in the region of the Rio Doce Valley, state of Minas Gerais, Brazil. Areas with more than three previous eucalyptus cycles, adjacent to pasture land or native forest, were chosen. Soil samples were collected and soil fertility analyzed by routine methods and other fractionation methods in order to measure alterations in the K, Ca and Mg contents as a consequence of eucalyptus cultivation. In the eucalyptus areas, reductions in the exchangeable Ca2+, Mg2+ and K+ contents and pH were observed and increased Al3+ and H + Al contents. Of all nutrients, only P contents (Mehlich-1 P) increased in the eucalyptus areas. The reduction in exchangeable forms and in medium-term soil nutrient pools indicates the need for higher nutrient rates than the currently applied in order to prevent nutritional limitations and soil nutrient exhaustion. After several eucalyptus rotations there was a recovery in the SOM content in comparison to degraded pasture soils, although not to the level of the native forest soil. The positive correlation between effective CEC and medium-term non-exchangeable Ca, Mg and K with SOM emphasizes the need for adequate fertilizer and plant residue management to sustain or even increase forest productivity in future cycles.

A substituição da vegetação nativa na região de Cerrado por florestas plantadas de eucalipto pode levar a mudanças nos estoques de C e N das diferentes frações da matéria orgânica do solo (MOS). Contudo, a intensidade e a direção da mudança nos teores de MOS dependem do tipo de solo, clima e manejo da área plantada. O objetivo deste trabalho foi determinar o efeito do plantio de eucalipto nos estoques de C e N em frações lábeis e estáveis da MOS em região de Cerrado no Vale do Jequitinhonha, MG. O estudo foi desenvolvido utilizando-se amostras de solos provenientes de povoamentos de Eucalyptus urophylla e de áreas adjacentes com vegetação natural de Cerrado e cultivo de pastagem. Para o plantio do eucalipto, a vegetação do Cerrado foi cortada, a lenha removida e os resíduos enleirados e queimados. As plantações de eucalipto com 20 anos apresentaram teores de carbono orgânico total (COT) similares aos da vegetação de Cerrado e pastagem. Nas frações ácido húmico e ácido fúlvico (FAH e FAF), os teores de C foram de 16,6 e 17,5 % maiores para o solo de eucalipto em comparação com os solos da pastagem, e 17,5 e 36,9 % com os solos do Cerrado, respectivamente. O cultivo do eucalipto não reduziu o estoque de C e N da biomassa microbiana do solo (BMS) em comparação com a do Cerrado e pastagem, e proporcionou incremento nas quantidades de C e N na matéria orgânica leve (MOL), o que contribuiu para o aumento da MOS. A contribuição do C derivado do eucalipto para a MOS, após 20 anos de cultivo, foi de 5 %. Isso indica uma baixa taxa de substituição do C nativo pelo C derivado do eucalipto, com uma média anual de 0,25 %. Assim, a substituição da vegetação nativa do Cerrado por eucalipto não resultou na diminuição do estoque de C nas frações FAH, FAF, MOL e BMS da MOS. The substitution of the native Cerrado (Brazilian savanna) vegetation by planted eucalyptus forests can influence the C and N pools in the different soil organic matter (SOM) fractions. However, the intensity and direction of this change depend on the soil type, climate, and management techniques in the planted area. The objective of this study was to determine the effect of eucalypt plantations on the C and N pool of labile and stable SOM fractions in an area previously occupied with savanna-like vegetation in the Vale do Jequitinhonha, MG, Brazil. Soil samples were collected from Eucalyptus urophylla plantations and adjacent areas with natural savanna vegetation, and managed pasture. The eucalypt plantation was 20-year old, and had succeeded the savanna vegetation, which was cut, the firewood removed and the residues burned. The pasture had been planted about 15 years earlier using the same site preparation procedures. There were no differences in total organic carbon (TOC) among soil samples of the three vegetation types. In the humic acid (HA) and fulvic acid (FA) fractions, the C contents were about 16.6 and 17.5 % higher for the eucalypt soil in comparison with the soils from the pasture and, 17.5 and 36.9 % higher than in soils from the savanna, respectively. Replacing the savanna vegetation by eucalypt did not reduce the C and N pools of the soil microbial biomass of the soil, but increased the amounts of C and N in the light organic matter (LOM), contributing to an increase in SOM. The estimated contribution of C derived from eucalypt to SOM based on 13C natural abundance was 5 %. This indicates a low substitution rate of native C by C derived from eucalypt, with an mean annual rate of 0.25 %. It can be concluded that substituting the native savanna vegetation by eucalypt did not reduce the C pools in the different SOM fractions.

A formação de P não-lábil a partir de formas lábeis, adsorvidas aos oxihidróxidos de Fe e Al, é razão para o baixo efeito residual da fertilização fosfatada em solos tropicais. A reversibilidade do P não-lábil para formas lábeis nesses solos pode ser favorecida pela redução do Fe^3+ e, ou, pela diminuição da atividade dos oxihidróxidos de Fe e Al. Neste trabalho, objetivou-se avaliar a adsorção e dessorção de P, sua transformação em não-lábil e reversibilidade dessa forma em amostras de solos submetidas à redução microbiana ou química. Para isso, amostras de 11 solos foram homogeneizadas com 300 mg kg^-1 de P na forma de NaH2PO4 em solução, incubadas por 30 dias e, então, submetidas a dez extrações sucessivas de P com resina de troca aniônica (RTA) (tratamento sem redução). Em seguida, outras amostras dos solos foram submetidas à ambiente redutor em solução de sacarose 0,1 mol L^-1 com posterior aplicação da doses de P (300 mg kg^-1) e as dez extrações sucessivas de P (tratamento redução microbiana). Depois, outras amostras foram reduzidas/complexadas com oxalato de amônio (Ox) ou com citrato-ditionito-bicarbonato (CDB), e os solos/resíduos receberam a mesma dose de P dos experimentos anteriores. Foram então incubados por 30 dias e submetidos às extrações sucessivas com RTA (tratamento redução química). A capacidade máxima de adsorção de P (CMAP) dos solos mostrou-se mais dependente da goethita (com 70,8 % de contribuição para seu valor) do que da gibbsita (com contribuição de 29,2 %). A correlação negativa entre os teores de P obtidos na segunda extração com a RTA, nos solos em condição natural, sem redução, e os teores de gibbsita sugere que este, e não a goethita, é o oxihidróxido responsável pela maior restrição à dessorção do P. Os valores de CMAP, estimados por meio do P remanescente (P-rem), mostraram, nas amostras submetidas ao tratamento com redução microbiana, pequena alteração para o grupo dos solos menos oxídicos, com menor CMAP. Todavia, nos solos mais oxídicos, com maior CMAP, o efeito prévio da sacarose foi o aumenta do P-rem (diminuição da CMAP) 10 vezes em relação aos solos para o tratamento sem redução. Entretanto, a redução gerada pela sacarose não alterou a dessorção do P anteriormente adsorvido. A expectativa de que ocorreria significativa reversibilidade de P não-lábil com a redução microbiana ou química dos solos não se concretizou, demonstrando a grande estabilidade dessas formas. The formation of non-labile from labile P forms, adsorbed onto Fe and Al oxyhydroxides, is the reason for low residual of phosphate fertilization in tropical soils. The reversibility of non-labile P to labile forms in these soils may be favored by the reduction of Fe^3+ and, or,by the reduced activity of Fe and Al oxyhydroxides. This study aimed to evaluate P adsorption and desorption, the transformation into non-labile forms and reversibility of these forms in soil samples from environments of microbial or chemical reduction. Samples of 11 soils were homogenized with 300 mg kg^-1 P (NaH2PO4) in solution and incubated for 30 days. P was extracted in 10 successive extractions with anion-exchange resin (AER) (treatment without reduction). In a second experiment, the soil samples were treated with 0.1 mol L^-1 sucrose solution to create a reduction enrviroment and subsequent application of P dose (300 mg kg^-1) and 10 successive P extractions (treatment microbial reduction). In a third experiment, the samples were complexed/reduced with ammonium oxalate (Ox) or with citrate-dithionite-bicarbonate (CDB). The soils/residues were treated with the above P dose, incubated for 30 days and subjected to successive extractions with AER (chemical reduction). It was observed that maximum P adsorption capacity (MPAC) of the soils was closer related with goethite, (which accounted for 70.8 % of the value), than gibbsite (with a contribution of 29.2 %). The negative correlation between the P contents in the second AER extraction for the soils in natural condition without reduction, and the contents of gibbsite only, indicated that gibbsite and not goethite is the oxyhydroxide that restricts P desorption most. The MPAC values estimated by equilibrium P showed, in the samples treated with microbial reduction, a slight alteration for the group of the less oxidic soils, with lower MPAC. But for more oxidic soils with higher MPAC, the previous effect of sucrose, which increased equilibrium P (reducing the MPAC), was high, about 10 times higher than in soils of the treatment without reduction. However, the reduction caused by sucrose did not alter the desorption of previously adsorbed P. The expectation of a significant reversibility of non-labile P due to microbial or chemical reduction of the soils was not confirmed, demonstrating the great stability of this form.

Alterações no potencial redox (Eh) de solos, como ocorrem em solos hidromórficos, causam alterações significativas nas características químicas e mineralógicas dos solos e têm forte influência sobre o comportamento do P, alterando a relação entre suas formas lábil e não-lábil. O objetivo deste trabalho foi verificar o efeito de condições de baixo Eh na dissolução/reversibilidade de formas não-lábeis de P e solubilização/comportamento dos oxihidróxidos de Fe e Al. Para isso, amostras de 11 solos foram incubadas com 300 mg kg^-1 de P por 30 dias, com posterior exaustão do P-lábil por extrações sucessivas com resina de troca aniônica (RTA). Posteriormente, elas foram submetidas a um tratamento denominado redução microbiana com 0,1 mol L^-1 de sacarose, por 60 dias, com trocas desta solução a cada 15 dias. Os resultados obtidos foram comparados com outros quando a mesma dose de P foi aplicada após essa redução microbiana, seguida por extrações sucessivas do P-lábil com RTA. Mediram-se, ainda, em ambas as condições, na solução de sacarose em equilíbrio com os solos, os valores de Eh e pH, teores de Fe, Al e P, ao final de cada período de 15 dias, por ocasião da troca da solução. As amostras originais - não tratadas - dos solos foram, também, submetidas à complexação/redução com oxalato de amônio (Ox) ou com citrato-ditionito-bicarbonato de sódio (CDB). Foram feitas quatro extrações sucessivas com Ox e duas como CDB, determinando-se, após cada extração, em ambos os métodos, os valores de Eh, pH e os teores de Fe, Al e P. Posteriormente, as amostras residuais dos solos submetidos aos tratamentos com Ox e CDB receberam 300 mg kg^-1 de P. A diminuição dos valores de Eh pela adição de sacarose ou pelas extrações com Ox e CDB não favoreceu a reversibilidade de formas não-lábeis de P. A adição de P aos solos aparentemente promoveu maior estabilidade para a goethita, restringindo sua interferência no valor de Eh do solo, como, também, estabilizou a gibbsita, que passou a não interferir no pH do solo. Os resultados permitem aventar a hipótese de que o P aplicado proporcionaria efeito restritivo ao comportamento de oxihidróxidos. Alterations in the redox potential (Eh) of soils, as observed in hydromorphic soils, cause significant alterations in the chemical and mineralogical soil characteristics and have a strong influence on the behavior of P, altering the ratio of the labile and non-labile forms. The purpose of this study was to verify the effect of conditions of low Eh on the dissolution/reversibility of non-labile P forms and solubilization/behavior of Fe and Al oxyhydroxides. Samples of 11 soils were incubated with 300 mg kg^-1 P for 30 days. Then the labile P was exhausted by successive extractions with anion exchange resin (AER). In a next step, the samples were treated by microbial reduction with 0.1 mol L^-1 sucrose for 60 days, with solution exchanges every 15 days. The results were compared with others where the same P dose was applied after microbial reduction, followed by successive AER extractions of labile P. In both conditions the Eh and pH values, Fe, Al and P contents were measured in the sucrose solution in equilibrium with the soils, at the end of each period of 15 days when the solution was changed. The original untreated soil samples were also subjected to complexation/reduction with ammonium oxalate (Ox) or with sodium citrate-dithionite-bicarbonate (CDB). Four successive extractions with Ox and two with CDB were performed and values of Eh and pH and Fe, Al and P concentrations were determined after each extraction for both methods. Thereafter, 300 mg kg^-1 P was applied to the residual soil samples of the Ox and CDB treatments. The decrease of Eh values due to sucrose addition or extractions with Ox and CDB did not favor the reversibility of non-labile P forms. P addition to the soil apparently resulted in a greater stability of goethite, which restricted the interference with Eh value, and also stabilized gibbsite, which ceased to influence the soil pH. Results led to the hypothesis that the applied P has a restrictive effect on the behavior of oxyhydroxides.

A eficiência de utilização de um nutriente, expressa pela relação entre a biomassa produzida e a quantidade absorvida, é uma importante característica adaptativa das plantas, particularmente daquelas cultivadas em solos com baixa disponibilidade desse nutriente. Maior eficiência de utilização de P (EUP) é conferida pela maior taxa de remobilização de P, que consiste na translocação desse nutriente para regiões de maior demanda metabólica na planta. Maiores taxas de remobilização têm sido associadas a maiores atividades das enzimas: fosfatase ácida (APase) e ribonuclease (RNase). Neste trabalho, avaliou-se a atividade dessas enzimas em plantas de Brachiaria decumbens, pouco exigente, e de Panicum maximum cv. Tanzânia, mais exigente em P, cultivadas em solos que receberam diferentes doses desse nutriente e submetidas a diferentes alturas de corte. O ensaio foi realizado em casa de vegetação, utilizando amostra do horizonte B de um Latossolo Vermelho-Amarelo argiloso. Os tratamentos resultaram da combinação fatorial das duas gramíneas, das doses de 100, 200 e 500 mg dm^-3 de P e das três alturas de corte: sem corte e corte a 15 e 30 cm a partir da superfície do solo para Brachiaria; e sem corte e corte a 20 e 40 cm para Panicum. As unidades experimentais consistiram de vasos com 10 dm^3 de solo, com 10 plantas. Os resultados indicaram que não houve diferença significativa na produção de biomassa das duas gramíneas, mas a adição de P propiciou maior produção e maior teor desse nutriente na parte aérea de ambas. As plantas submetidas a cortes mais severos apresentaram menor produção e maiores teores de P na parte aérea. Ocorreu efeito negativo das doses de P na atividade da APase e da RNase nas duas forrageiras. As plantas cultivadas com a menor dose de P apresentaram maior atividade dessas enzimas e maior EUP. A atividade de ambas as fosfatases decresceu com a idade das plantas. No tratamento com o corte mais intenso, independentemente da dose de P, tanto Brachiaria quanto Panicum apresentaram menor EUP. Isso ocorreu associado à maior atividade das enzimas APase e RNase, indicando que outros mecanismos relacionados com a adaptação das plantas a baixas disponibilidades de P podem estar envolvidos. The nutrient use efficiency, expressed by the ratio between the produced biomass and nutrient content, is an important adaptive characteristic of plants, particularly of those cultivated in low-fertility soils. A high P-use efficiency (PUE) is conferred by high P remobilization rates, i.e., P transport to regions of greater metabolic demand in the plant. High P remobilization rates have been associated with high acid phosphatase (APase) and ribonuclease (RNase) enzyme activities. In our study, we evaluated the activity of these enzymes in Brachiaria decumbens, with a low, and Panicum maximum cv Tanzânia, with a high P demand, cultivated in soil treated with different P rates and cut at different heights. The experiment was carried out in a greenhouse, using B-horizon samples of a clayey Yellow-Red Latosol. The treatments consisted of a factorial combination of two grasses, three P rates (100, 200 and 500 mg dm^-3) and three cutting heights: no cutting, 15 and 30 cm above the soil surface for Brachiaria, and no cutting, 20 and 40 cm for Panicum. The experimental units consisted of pots with 10 dm^3 soil, with 10 plants each. Results indicated that there was no significant difference between biomass production of the two grasses, but the P application resulted in a higher biomass yield and P shoot concentration. The biomass production of plants cut at a lower height was smaller and P concentrations in shoots were higher. A significant effect of P rates on the APase and the RNase activities was observed in both forages. In plants grown at the lowest P rate enzyme activities and PUE were the highest. The activity of both phosphatases decreased with plant aging. In the treatment with the lowest cutting height, the PUE in both Brachiaria and Panicum plants was lower, independent of the P rate. At the same time, a higher APase and RNase activity was observed, indicating that other mechanisms may be involved in the plant adaptation to low P availability.

Uma população é composta por indivíduos, e a amostragem correta dos indivíduos estima adequadamente as características da população. Porém, para avaliar a fertilidade do solo, quem seria o indivíduo solo (unidades de amostra) e qual sua dimensão? Com o objetivo de definir a dimensão do indivíduo solo componente de determinada população, sob plantio direto (PD) ou sob plantio convencional antes (PCAA) ou depois da aração (PCDA), visando avaliar a fertilidade do solo e desenvolver um método de amostragem de solos, determinando o número de amostras simples necessário à formação de uma amostra composta que caracterize o indivíduo solo (unidade de amostra), foram coletadas amostras simples de solo (5,4 cm de diâmetro x 10 cm de profundidade) sobre as semidiagonais de cinco hexágonos delimitados sobre cada uma das áreas selecionadas para amostragem (PD, PCAA e PCDA). Os hexágonos de amostragem apresentavam 2 m de lado e, em cada uma das seis semidiagonais dos mesmos, foram coletadas dez amostras simples de solo (55 por hexágono) nas seguintes distâncias, a partir de uma amostra simples central, medidas até o centro do orifício de coleta: 12,5; 25,0; 37,5; 50,0; 75,0; 100,0; 112,5; 150,0 e 200,0 cm, sendo a amostra simples central comum às seis semidiagonais. Foram determinados o pH (H2O), os teores de P e K disponíveis e de Ca2+ e Mg2+, H + Al, P-rem e a matéria orgânica. As amostras simples foram agrupadas sucessivamente a partir do centro do hexágono, formando nove unidades de amostra: A (até 18,75), B (até 31,25), C (até 43,75), D (até 56,25), E (até 81,25), F (até 106,25), G (até 118,75), H (até 156,25) e I (até 206,25 cm). Foi realizada análise de regressão das médias e dos desvios-padrão das características avaliadas, considerando possíveis dimensões da unidade de amostra de solo. A partir dos resultados obtidos, pôde-se concluir que: para a caracterização do indivíduo solo (unidade de amostra), devem-se coletar 25 amostras simples, necessárias à formação de uma amostra composta representativa, num hexágono de 68,75 cm de lado e área de 1,228 m2. A population consists of individuals and a correct sampling of the individuals estimates population characteristics adequately. However, to evaluate soil fertility, what would be the soil individual (sample units), and of what size? The objective of this study was to determine the dimension of the individual soil component of a particular population, in three sampling areas: under no-till or under conventional tillage before or after plowing, and to evaluate soil fertility and develop a soil sampling method, determining the number of single samples required to form a composite sample that would characterize a soil individual (sample unit). Single soil samples (5.4 cm diameter x 10 cm deep) were collected along the semi-diagonals of five hexagons outlined on the selected sampling areas. The sampling hexagons had 2 m long sides and from each of the six semi-diagonals, 10 single soil samples (55 per hexagon) were collected at the distances 12.5; 25.0; 37.5; 50.0; 75.0; 100.0; 112.5; 150.0 and 200.0 cm, measured from a simple central sample, to the center of the sampling spot. The single central sample was the same for the six semi-diagonals. Soil pH (H2O), available P and K, Ca2+ and Mg2+ concentrations and H + Al, equilibrium-P and organic matter were determined. The single samples were grouped successively from the hexagon center and formed nine sampling units: A (up to 18.75), B (up to 31.25), C (up to 43.75), D (up to 56.25), E (up to 81.25), F (up to 106.25), G (up to 118.75), H (up to 156.25) and I (up to 206.25 cm). Regression analysis of the means and standard deviations of the evaluated characteristics was performed considering the possible dimensions of the soil sample unit. Based on the results, the conclusion was drawn that 25 simple samples must be collected to characterize a soil individual (sample unit), for the formation of a representative composite sample in a 68.75 cm-sided hexagon with an area of 1.228 m2.

Afforestation of degraded pastures can potentially enhance carbon sequestration, but little is known about the effects of eucalyptus plantations on soil organic matter (SOM) fractions. We used density and particle size SOM fractionations to evaluate changes in SOM for a chronosequence of eucalyptus plantations established on degraded pastures in two contrasting regions in southeastern Brazil. Declines in the content of soil C derived from the pasture (C4 photosynthetic pathway) and the accumulation of that derived from the eucalyptus (C3 photosynthetic pathway) were followed through 13C natural abundance of the SOM. The two study areas were in the Rio Doce River Valley, Minas Gerais State, namely: 1, Belo Oriente (BO, a region with lower elevation, higher mean annual temperature, lower forest productivities and dominated by clayey Typic Haplustoxs); 2, Virginopolis (VG, a region of higher elevation, higher forest productivities and dominated by clayey Rhodic Ustoxs). In the BO region the chronosequence included 0, 4.2, 13.2, 22.2, 32.0 and 34.2 years of eucalyptus cultivation and in the VG region soils were cultivated with eucalyptus for 0, 8.2, 19.2, 29.2 and 33.2 years. The accumulated cultivation time corresponds to about five rotations. In both regions the initial soil condition was represented by a site that was still under pasture. Soil samples collected at 0–10 and 10–20 cm depths were analyzed for: total organic carbon (TOC); C in the fulvic (FAF), humic (HAF) and humin (HF) fractions; C in the free (FLF) and occluded (OLF) light fractions; C associated with the heavy fractions, namely, the sand (SF), silt plus clay (S + CF) and clay (CF) fractions; and C in the microbial biomass (MB). Carbon stocks of virtually all SOM fractions were about twice as high in the VG region than in the BO region. Eucalyptus cultivation in the BO region increased C stocks in all SOM fractions, except for the MB fraction that was not altered and the SF fraction that declined with time of eucalyptus cultivation. Increases in TOC, FAF and HF organic C fractions were observed in the VG region. Mean annual accumulations across the entire cultivation period in the 0–10 cm soil layer showed virtually no difference averaging 0.22 Mg C ha−1 year−1 for the BO region and 0.23 Mg C ha−1 year−1 for the VG region. However, gains of TOC peaked by the end of the third rotation in the BO region and the second rotation in the VG region, so the TOC accumulation rate during the respective aggrading periods would correspond to 0.35 and 0.57 Mg C ha−1 year−1. There was no clear evidence that the more labile, fast cycling SOM fractions were more sensitive indicators of the impact of eucalyptus cultivation in the BO region, whereas in the VG region the FLF and OLF were more sensitive to the land use change than TOC.

O objetivo do presente trabalho foi avaliar a mobilidade e a compartimentalização de Zn aplicado via radicular em feijoeiro e cafeeiro. Foram instalados dois experimentos em casa de vegetação, em solução nutritiva, em sistema de vasos geminados, sendo o sistema radicular igualmente dividido nos dois recipientes. Em um dos recipientes geminados, adicionou-se uma solução sem Zn e, no outro, foram aplicadas doses crescentes do elemento (0,0; 0,5; 1,0; 2,0; 3,0; 4,0mmol L-1) na forma de ZnSO4, as quais constituíram os tratamentos no delineamento em blocos ao acaso com quatro repetições. O Zn apresentou mobilidade no floema do feijoeiro, indicando ser retranslocado da parte aérea para o sistema radicular. Já no cafeeiro, o Zn demonstrou praticamente imobilidade no floema. As plantas de feijoeiro apresentaram resposta linear crescente, em função das doses de Zn, para o teor Zn nas diferentes partes analisadas. Plantas de cafeeiro apresentaram mínima alteração no peso da matéria seca e teor de Zn na parte aérea. O caule apresentou-se como um local de concentração de Zn, tanto em cafeeiro como em feijoeiro. Two experiments were conducted aiming at evaluating translocation and compartmentation of zinc applied on roots of bean and coffee seedlings in greenhouse grown in nutrient solution. The plants were grown in geminate containers system and nutrient solution containing 0.0; 0.5; 1.0; 2.0; 3.0; 4.0mmol L-1 of zinc by ZnSO4, which constituted the treatments. The dry matter and total zinc concentration were determined in the stems, roots, upper leaves and lower leaves. Total zinc analysis showed translocation of zinc towards the roots in bean, indicating zinc mobility in phloem of these plants. However, in coffee seedlings zinc showed minimum mobility in phloem. The bean plants presented linear increasing in zinc concentration in the different analyzed parts because of treatments. Coffee seedlings showed minimum alteration in the dry matter and zinc concentration in the aerial part. The stem showed to be a concentration location of zinc, so much in coffee and bean seedlings as weel.

Low-molecular-weight organic acids with one or more carboxylic groups are ubiquitous. In soils, they can originate from leaching of plants, litter decomposition, plant-roots exudation, and microbial activity. Their presence in the soil may favor the formation of soluble organo-metallic complexes that improve the transport of Zn, Cu, Fe, and Mn to plant-root surfaces via diffusion. The current study sought to determine if some of the organic acids (OA) in soils and a cover-crop residue influence the diffusive flux (DF) of Zn, Cu, Mn, and Fe. Two OA were added to two Oxisols (Typic Haplustox): a clayey Dark Red Latosol (DRL) and a sandy-loam Red Yellow Latosol (RYL). Acetic and citric acid were added to achieve concentrations of 0, 250, 500, 1000, and 2000 mmol (m 3 soil) -1 . The effect of adding plant material (pearl millet) on the soil DF of the cationic micronutrients was also determined. Soil diffusive flux was evaluated by incubating positively charged and negatively charged exchange-resin membranes with the soil in PVC diffusion chambers for 15 d. Desorption of Zn, Cu, Fe, Mn, and OA from the resins was performed with 0.5 mol l -1 HCI. The results demonstrated that the DF of the cationic micronutrients increased with the addition of organic acid. The DF of Zn and Mn occurred mostly towards the cationic resin, whereas the diffusive flux of Cu and Fe occurred mostly towards the anionic resin. Apparently, the dissolution of oxides and/or complexation of micronutrients adsorbed to the solid phase or in the soil solution contributed to the obtained results. Citric acid was more efficient than acetic acid in maintaining a larger DF value for Zn, Cu, and Fe. The addition of millet plant material to the soil increased the DF in the following order: Mn > Cu > Fe > Zn; Mn moved towards the cationic resin, and the other micronutrients moved towards the anionic resin. These findings suggest that organic compounds play an important role in the short-distance transport of cationic micronutrients in highly weathered soils.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:45:58Z No. of bitstreams: 1 S0100-06832005000200010.pdf: 170295 bytes, checksum: 7933bb3dcf2115b1bcc10a14a2a46d62 (MD5) Made available in DSpace on 2013-08-22T18:45:58Z (GMT). No. of bitstreams: 1 S0100-06832005000200010.pdf: 170295 bytes, checksum: 7933bb3dcf2115b1bcc10a14a2a46d62 (MD5) Previous issue date: 2005-04-01 Made available in DSpace on 2013-09-30T18:07:34Z (GMT). No. of bitstreams: 2 S0100-06832005000200010.pdf: 170295 bytes, checksum: 7933bb3dcf2115b1bcc10a14a2a46d62 (MD5) S0100-06832005000200010.pdf.txt: 35571 bytes, checksum: 761ef5145fd6eb336874e87784376356 (MD5) Previous issue date: 2005-04-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:25:22Z No. of bitstreams: 2 S0100-06832005000200010.pdf: 170295 bytes, checksum: 7933bb3dcf2115b1bcc10a14a2a46d62 (MD5) S0100-06832005000200010.pdf.txt: 35571 bytes, checksum: 761ef5145fd6eb336874e87784376356 (MD5) Made available in DSpace on 2014-05-20T13:25:22Z (GMT). No. of bitstreams: 2 S0100-06832005000200010.pdf: 170295 bytes, checksum: 7933bb3dcf2115b1bcc10a14a2a46d62 (MD5) S0100-06832005000200010.pdf.txt: 35571 bytes, checksum: 761ef5145fd6eb336874e87784376356 (MD5) Previous issue date: 2005-04-01 Diferenças inter e intra-específicas na habilidade de suportar períodos de estresse nutricional podem dever-se à capacidade de armazenar e liberar íons dos vacúolos, e, ou, à intensidade de retranslocação de nutrientes em tais condições. Neste trabalho, pretendeu-se avaliar diferenças varietais quanto ao tamanho do pool não-metabólico de Pi; velocidade de liberação do Pi previamente armazenado (VLPi), quando o P citoplasmático cai a um valor limite; capacidade de transportar Pi de regiões menos ativas para aquelas mais ativas metabolicamente e definir compartimentos que são preferencialmente fontes e os que são preferencialmente drenos para o Pi, em condições de absorção limitada de P. Avaliaram-se a produção de matéria seca e os teores internos de Pi, orgânico (Po) e total solúvel em ácido (Pts), de diferentes órgãos de plantas dos cultivares de soja (Glycine max L. Merrill) Santa Rosa, Uberaba, IAC8, Doko e UFV1, submetidos a oito dias de omissão do elemento. A VLPi foi estimada como tangente às equações obtidas para Pi como função do perído de omissão no ponto médio do período de omissão em que houve maior decréscimo em Pi (zero a quatro dias de omissão de P), t = dois dias, considerando-se que -deltaPi/deltat expressa a velocidade de liberação de Pi. A capacidade interna de tamponamento de Pi (CTIPi) foi calculada como o inverso da VLPi. O cultivar Santa Rosa apresentou maior capacidade de armazenar Pi, quando o suprimento externo foi alto, liberando-o mais intensamente sob condições de baixo suprimento de P que os cultivares IAC8 e UFV1. O cultivar Uberaba mostrou-se superior ao Doko em sua habilidade de armazenar e utilizar o Pi. Folhas superiores mostraram ser o principal dreno para o Pi armazenado em folhas medianas e inferiores, seguidas por raízes e caules. Raízes comportaram-se como fontes ou drenos para o Pi. Raízes e folhas superiores apresentaram maiores (VLPi) e menores valores de CTIPi que folhas medianas e folhas inferiores, sendo o caule o compartimento com menor VLPi e maior CTIPi. Dentre as variedades, as diferenças foram pequenas, destacando-se a maior VLPi e menor CTIPi do cultivar Santa Rosa. O cultivar Doko apresentou a menor VLPi e maior CTIPi, enquanto Uberaba, IAC8 e UFV1 ocuparam posição intermediária quanto a essas características. Differences among plants in their ability to support nutritional stress periods may be caused by a differential vacuole capacity of ion storage and release and may also depend on the intensity of nutrient re-translocation under such conditions. In five soybean cultivars, submitted to eight days of P deprivation, the dry matter production and the contents of three phosphorus (P) forms - inorganic (Pi), organic (Po), and acid-soluble total (Pts) of different plant organs were determined. Pi release velocity (RSPi) was estimated as the tangent to the equations obtained for Pi f(t) at the point t = 2 days (the mean point in the period of greatest Pi decrease), considering that -deltaPi/deltat expresses the rate of Pi release. The internal Pi buffering capacity (IBCPi) was calculated as the inverse of the RSPi. Cultivars' differences in size of the non-metabolic Pi pool, RSPi, and the ability to transport Pi from less to more actively metabolizing regions were evaluated. The preferential Pi source and sink compartments under limited P absorption conditions were also evaluated. The cultivar Santa Rosa showed the highest Pi storage ability when the external supply was high, and a more intensive release under low P supply conditions than IAC8 and UFV1. The cultivar Uberaba was superior to Doko in its ability to store and use Pi. In all cultivars, upper leaves and roots were the main sink of Pi stored in the middle and lower leaves. Roots and upper leaves showed larger RSPi and lower IBCPi values than middle and lower leaves. Universidade Federal de Viçosa (UFV) Departamento de Fitotecnia Universidade Federal de Viçosa (UFV) Departamento de Solos Universidade Estadual Norte Fluminense Laboratório de Ciência do Solo Universidade Estadual Paulista Julio de Mesquita Filho Faculdade de Ciências Farmacêuticas Departamento de Toxicologia Universidade Estadual Paulista Julio de Mesquita Filho Faculdade de Ciências Farmacêuticas Departamento de Toxicologia

Aluminum (Al) tolerance mechanisms in crop plants have been extensively researched, but our understanding of the physiological mechanisms underlying Al tolerance in trees is still limited. To investigate Al tolerance in eucalypts, seedlings of six species (Eucalyptus globulus Labill., Eucalyptus urophylla S.T. Blake, Eucalyptus dunnii Maiden, Eucalyptus saligna Sm., Eucalyptus cloeziana F. J. Muell. and Eucalyptus grandis w. Hill ex Maiden) and seedlings of six clones of Eucalyptus species were grown for 10 days in nutrient solutions containing Al concentrations varying from 0 to 2.5 microM (0 to 648 microM Al3+ activities). Root elongation of most species was inhibited only by high Al3+ activities. Low to intermediate Al3+ activities were beneficial to root elongation of all species and clones. Among the species tested, E. globulus and E. urophylla were more tolerant to Al toxicity, whereas E. grandis and E. cloeziana were more susceptible to Al-induced damage. Although E. globulus seedlings were tolerant to Al toxicity, they were highly sensitive to lanthanum (La), indicating that the tolerance mechanism is specific for Al. Fine roots accumulated more Al and their elongation was inhibited more than that of thick roots. In E. globulus, accumulation of Al in root tips increased linearly with increasing Al concentration in the nutrient solution. The majority of Al taken up was retained in the root system, and the small amounts of Al translocated to the shoot system were found mainly in older leaves. No more than 60% of the Al in the thick root tip was in an exchangeable form in the apoplast that could be removed by sequential citrate rinses. Gas chromatography/mass spectrometry and ion chromatography analyses indicated that root exposure to Al led to a greater than 200% increase in malic acid concentration in the root tips of all eucalypt species. The increase in malate concentration in response to Al treatment correlated with the degree of Al tolerance of the species. A small increase in citric acid concentration was also observed in all species, but there were no consistent changes in the concentrations of other organic acids in response to Al treatment. In all eucalypt species, Al treatment induced the secretion of citric and malic acid in root exudates, but no trend with respect to Al tolerance was observed. Thus, although malate and citrate exudation by roots may partially account for the overall high Al tolerance of these eucalypt species, it appears that tolerance is mainly derived from the internal detoxification of Al by complexation with malic acid.

During the industrial processing of kaolin, the ore material is submitted to bleaching treatments with sulfuric and phosphoric acids and metallic zinc, in order to remove colored iron-rich minerals. The effluent waste is initially strongly acidic, and is chemically neutralized with calcium oxide and left to dry in open pits dug out in the terrain surrounding the industrial plant. The dried residue is then accumulated in deposits so as to produce the “solid reject”. The Fe in these reject deposits precipitates as poorly crystalline iron-bearing compounds, which are difficult to identify by conventional X-ray diffraction techniques, and must be further characterized by complementary 57Fe Mossbauer analysis. 298 and 80 K Mossbauer spectra of the whole sample collected from the solid reject deposit of the Caolim Azzi industrial plant, in the city of Mar de Espanha, MG, Brazil, revealed that Fe3+ is mainly in octahedral sites of silicates. After treating this whole sample with NaOH, the Mossbauer parameters at 298 and 80 K indicated mainly the presence of iron oxide (hematite; ideal formula, αFe2O3) and oxyhydroxides, such as lepidocrocite (γFeOOH), goethite (αFeOOH) and iron hydroxysulphate, as jarosite (MFe3(SO4)2(OH)6; M = mono or divalent cation).

Eucalyptus shoot blight in the Rio Doce Valley (ESBVRD) is a physiological anomaly that has been related to hypoxic environment and Mn excess. This study had the objective of understanding the mechanisms involved in the differential tolerance of eucalyptus clones to ESBVRD. Two experiments were carried out: (I) two clones, a sensitive and a ESBVRD tolerant, two O2 concentrations (normal and hypoxic) and five concentrations of Mn (0, 5, to 90 mg L-1); (II) same two eucalyptus clones, two O2 concentrations (normal and mild hypoxic) and two Mn concentrations (30 and 300 mg L-1). The hypoxic condition reduced the plant dry weight and increased the production of ethylene in the two clones, both more strikingly in the sensitive clone. The O2 deficiency was the first factor predisposing the clones to ESBVRD, in contrast to Mn excess, that appeared to act over a longer period for the expression of the symptoms.

A compactação do solo por tráfico de veículos pesados altera a disponibilidade de nutrientes para as plantas, interfere no crescimento radicular e nos processos de fluxo de massa e de difusão, constituindo um problema no manejo florestal, no qual têm sido utilizadas máquinas de maior capacidade de carga. O objetivo deste trabalho foi avaliar a influência da compactação de solos e doses de K no crescimento e nutrição potássica de mudas de Eucalyptus camaldulensis. Utilizaram-se amostras de dois solos com texturas diferentes, em vasos sob condição de casa de vegetação, sendo os tratamentos dispostos num esquema fatorial 3 x 4 (densidades de solo e doses de K) para cada solo, em delineamento inteiramente casualizado, com três repetições. Amostras de dois solos, um Latossolo Vermelho argiloso (LVarg) e um Latossolo Vermelho-Amarelo franco-arenoso (LVAfar), foram acondicionadas em vasos de PVC com 2 dm3 de solo e compactadas com o auxílio de uma prensa hidráulica. Para o solo argiloso, foram testadas as densidades de 0,9; 1,1 e 1,3 g cm-3 e, para o solo franco-arenoso, de 1,3; 1,5 e 1,7 g cm-3. As doses de potássio foram 0, 50, 100 e 150 mg kg-1 para os dois solos. O experimento foi colhido 100 dias após a emergência, tendo sido realizadas a quantificação da matéria seca, a mensuração de raízes (comprimento, diâmetro médio e superfície radicular) e as análises químicas, com vistas em determinar os teores de K no tecido vegetal e no solo. Constatou-se que, com a compactação do solo, de modo geral, o crescimento de raízes e a eficiência de utilização de K diminuíram e aumentou o diâmetro médio radicular. As doses de K elevaram o teor de K no tecido vegetal e proporcionaram aumento da matéria seca apenas nos tratamentos em que o solo foi mais compactado. Conclui-se que a aplicação de K em solos compactados é fundamental para o crescimento de plantas de eucalipto e que a compactação reduz o crescimento radicular e a eficiência da adubação potássica. Traffic of heavy machinery during forest harvesting causes soil compaction and alters the nutrient availability for plants, affects root growth, and the mass flow and diffusion processes, thus representing a problem for forest management. The objective of this study was to evaluate the influence of soil compaction and potassium application on growth and K nutrition of Eucalyptus camaldulensis. The study was carried out in pots under greenhouse conditions, using a completely randomized design with treatments in a 3 x 4 factorial arrangement (compaction levels and K rates) for each soil, with three replicates. Samples of two soils, a clayey Red-Latosol (LVarg) and a sandy Red Yellow-Latosol (LVAfar), were placed in 2.0 dm3 pots of PVC pipe and compacted to densities of 0.9, 1.1 and 1.3 g cm-3 for the LVarg, and 1.3, 1.5 and 1.7 g cm-3 for the LVAfar, using a hydraulic press. Potassium rates were 0, 50, 100 and 150 mg kg-1, for both soils. One hundred days after seedling emergence, the plant shoots were harvested and the dry weight, K contents in plant and soil, and root measurements (length, surface area, and mean diameter) assessed. Increasing soil compaction reduced both root and shoot growth and the K utilization efficiency, but increased the mean root diameter. Potassium application increased the plant nutrient content, but had no effect on shoot growth at low compaction levels. This study indicated that K application in compacted soils is essential for eucalypt growth; and that soil compaction reduces root growth and the efficiency of K acquisition by roots.

The total contents of potassium (K) and magnesium (Mg) in selected Brazilian soils (Oxisols, Ultisols, Inceptsols, and Alfisols) developed from different parent materials were investigated to estimate the contribution of clay minerals to K and Mg reserves. Total K and Mg contents in the Na-saturated clay were determined by HF total digestion. The contribution of each mineral species to the total contents of K and Mg, was estimated by a sequential mineral extraction procedure, following the order: Na-saturated clay—1) amorphous aluminum and iron oxides (ammonium oxalate); 2) crystalline iron oxides (dithionite–citrate–bicarbonate); 3) amorphous aluminosilicate and gibbsite (0.5 M NaOH); 4) kaolinite (5 M NaOH); 5) mica (NaHSO4), and 6) feldspar (HF total digestion). In order to monitor mineralogical changes, after each extraction, the samples were studied by x-ray diffraction (XRD), analytical transmission electron microscopy (ATEM), differential thermal analysis and thermo-gravimetric analysis. Total amou...

The use of a commercial bleach solution (CB) for in vitro propagation of orchids has proven to be an efficient technique and an alternative to the use of the autoclave and laminar flow chamber (LFC). The aim of this study was to evaluate the use of CB in disinfestation of culture media (CM) for seeding and for re-cultivation of orchid plantlets and its effect in different types of flasks and on the nutritional state of the plantlets. In the seeding experiment , seeds of Laelia tenebrosa Rolfe were used, with evaluation of three types of flasks; five concentrations of CB applied to the CM of 2, 5, 10, 20 and 40 mL L -1 and the control treatment. In the re-cultivation experiment , Cattleya kerri Brieger & Bicalho plantlets were used. The rates of CB added to the CM were 2, 5, 10, 20, 30, 35 and 38 mL L -1 in polypropylene containers, and the rates sprayed on the plantlets at re-cultivation were 5, 12.5, 25, 50, 75, 87.5 and 95 mL L -1 . The proportion of germinated seeds and the dry matter weight of the protocorms were greater in the control treatment. The increasing rates of CB added to the CM had worse results for germination in glass flasks. In re-cultivation, there was no significant difference in the growth of the plantlets between the autoclaved flasks and those disinfested in CB. Keymessage: Both orchid seeding and re-cultivation of seedlings can be carried out entirely and efficiently without the use of an autoclave and laminar flow chamber, using chemical disinfection with commercial bleach.

Highly weathered kaolinitic soils in Brazil often have adequate levels of K and Mg to support plant growth. The source of K and Mg in these soils and their relationship with the dominant mineral, kaolinite, is addressed in this article. Crystallographic, chemical, and morphological properties of kaolinite, from selected highly weathered Brazilian soils, were investigated by x-ray diffraction (XRD), analytical electron microscopy (AEM), chemical, and thermal methods. Kaolinite properties showed significant variations such as d(001) spacing ranging between 0.713 to 0.728 nm, width at half height (WHH) between 0.30 to 0.97 °20, and dehydroxylation temperature between 489 to 518°C. Kaolinite in the clay fraction has relatively poor crystal order with a mean crystallinity index value(CI) of 12.7. The dominant forms of the clay-fraction kaolinite were elongated and rounded, with relatively lower proportions of hexagonal particles. The silt-fraction kaolinite showed a tendency to form subspherical large aggregates with high stability. The average Fe 2 O 3 level in the kaolinite of the clay fraction (19.1 g kg -1 ) was higher than that obtained for the silt fraction (6.6 g kg -1 ). The smaller kaolinite particles of the clay fraction showed a lower degree of crystal order, higher K and Mg levels, and lower dehydroxylation temperatures. From the strong relationship between the asymmetry index (AI) of the (001) diffraction line and the level of K in kaolinite from the younger soils, we believe that both K and Mg in kaolinite are part of residual micaceous layers interleaved in kaolinite crystals.

In the greenhouse growth of two coffee-tree varieties, Catuai (sensitive) and Icatu (tolerant) to aluminum, was evaluated in surface-fertilized and limed soil following subsurface treatment with seven lime levels (0.0; 0.49; 1.7; 2.9; 4.1; 6.6 and 9.3 t/ha). Plants were grown for 6.5 months in soils in PVC columns, subdivided into two horizons. In the lower 12 – 34 cm depth horizon, soil Al saturation varied between 93 and 0%. For both varieties evaluated, shoot dry weight and leaf area remained unchanged following limestone application. This fact shows that surface layer correction permitted normal shoot growth. High Al saturation resulted in decrease of root dry weight percent, root length percent and root surface percent in the 12–34 cm horizon, which were compensated by higher percentages of these properties in the upper 0–12 cm horizon. The ratio between root surface – root dry matter (cm2/g) of Catuai variety was increased by limestone application to the lower soil horizons, indicating that roots turn longer and thinner, when Al soil saturation decreased. This also shows a great sensitivity to Al of the Catuai variety. In contrast, in the Icatu variety, all root characteristics remained stable at all levels of Al tested.

Plant root exposure to soil aluminum (Al) depends on the soil solution Al concentration and transport to the root by diffusion. Changes in Al diffusive flux for two Oxisols was measured under laboratory conditions as a function of pH, water matric potential, and applications of gypsum, potassium chloride, and calcium phosphate. Double‐faced cation exchange resin sheets served as sinks for Al transported during 10‐day incubations through chambers containing 314 cm3 of soil. Across a range of soil pH values from 4.5 to 5.5, maximum diffusive flux of Al occurred at pH values of 4.7–4.8 in both soils and corresponded to increases of 2.2–3.0% relative to the unlimed treatment. Between pH values of 4.7–4.8 and 5.4, diffusive flux of Al decreased by 38 and 46% in the two Oxisols. Diffusive flux of Al decreased by 16–20% for the two Oxisols as soil water potentials decreased from ‐10 to ‐200 kPa. Magnitude of the reductions in diffusive flux of Al with decreasing soil water potential were less than those...

Os solos mais intemperizados, desenvolvidos nos trópicos úmidos, apresentam baixa reserva de nutrientes nas frações mais grosseiras. Para avaliar a presença de potássio e magnésio nos minerais, amostras das frações areia e silte de solos desenvolvidos de diferentes materiais de origem e estádios de intemperismo dos estados de MG, ES, RS e RR foram estudadas por difratometria de raios-X (DRX), análise termodiferencial, análise termogravimétrica diferencial e microscopia eletrônica. Os teores totais de elementos da TFSA e das frações do solo foram determinados por digestão fluorídrica das amostras. A fração silte também foi submetida a extrações seqüenciais e seletivas dos minerais para estimar a contribuição das espécies minerais nos teores totais de K e Mg. A fração areia dos solos mais intemperizados é muito pobre em nutrientes, com predomínio de quartzo, indicando limitada reserva de K e Mg. Para os solos mais jovens, esta fração apresenta os maiores teores totais de K e Mg, superando as frações mais finas do solo, com presença de minerais primários, como mica, feldspato e anfibólio. Partículas de mica e agregados de caulinita foram as principais fontes de K e Mg totais para as frações areia e silte dos solos mais intemperizados. Os minerais micáceos nestes solos, identificados e analisados por microscopia eletrônica, apresentaram teores de K2O variando de 33,3 a 62,8 e 27,4 a 98,1 g kg^-1 e de MgO de 76,5 a 116,8 e 19,7 a 68 g kg^-1 para as frações areia e silte, respectivamente. Devido aos baixos teores de mica na fração silte dos solos mais intemperizados (menor que 1%) e a alta proporção de quartzo, mesmo após a extração de caulinita, a concentração da amostra não foi suficiente para detecção de minerais micáceos por DRX. Apenas para o LV de Barroso (MG), verificou-se o aparecimento de discreta reflexão de mica. The highly weathered soils developed in the humid tropics have low nutrient reserve in the coarse fractions. To evaluate K and Mg total contents in minerals in the sand and silt fractions, soil samples developed from different parent materials and weathering degree from MG, ES, RS and RR states, Brazil, were selected to be analyzed by X-ray diffraction (XRD), differential thermal analysis, thermogravimetry and electron microscopy. The total contents of K and Mg of the whole soil and its fractions were determined by HF extraction. To estimate the mineral contribution in the total contents of K and Mg, the silt fraction was submitted to mineral selective extractions. The sand fraction of the more weathered soils has very low K and Mg contents, with predominance of quartz. For the younger soils, this fraction showed higher K and Mg levels in the presence of primary minerals, such as mica, feldspar and amphibole. Mica particles and kaolinite flakes were the main sources of K and Mg for the sand and silt fractions of the highly weathered soils. The mica minerals were analyzed by electron microscopy, with K2O contents ranging from 33.3 to 62.8 and 27.4 to 98.1 g kg^-1 and MgO contents from 76.5 to 116.8 and 19.7 to 68 g kg^-1 for sand and silt fractions, respectively. Because of low mica content in the silt fraction of the more weathered soils (less than 1%), and the high quartz level, even after kaolinite extraction, the mica was not detected by XRD. Only one soil showed a small mica peak.

This work evaluated the effect of different placement and rates of two phosphorus (P) fertilizers on P‐availability by three methods of extraction, nine years after application to a Brazilian Oxisol cultivated with Eucalyptus camaldulensis. The treatments were applied to 24x18 m plots and 96 seedlings of E. camaldulensis were planted (3.0x1.5 m) in each plot. Single superphosphate (SSP) and rock phosphate (RP) were tested in three rates (100, 200, and 400 kg ha‐1 of P2O5). Each fertilizer was either (1) surface‐applied in bands (0.6 m either side of the rows of trees) and incorporated before planting or (2) incorporated into furrows (0.2 m deep in the tree rows) before planting. As additional treatments, the combination of RP (96 kg ha‐1 of P2O5 applied in broadcast, or bands, or in furrows) + SSP (54 kg ha‐1 of P2O5 localized in the planting hole before planting) were tested. Twelve soil subsamples from two layers (0–15 and 25–40 cm) were taken from each plot (from the planting rows or between t...