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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.

Studies aimed at mitigating environmental impacts have received attention in recent years. The use of biochar obtained from the pyrolysis is an alternative for the recovery of organic materials that usually are directly discarded in the environment. Biochar has the potential to recover nutrients from wastewater, and in the latter case, the reuse or recycling of biochar as a controlled-release fertilizer could be an option. However, the adsorption characteristics of the ions into different biochars have not been known. The aim of this study was to evaluate the ions adsorption in biochar derived from discarded potatoes, as well as to make physical and chemical characterization of the produced materials. The biochar derived from discarded potatoes was produced by pyrolysis at 450 °C under an N2 atmosphere. In order to define its ionic profile, the adsorption of HnPO4(3–n)–, Ca2+, Mg2+, and Al3+ was tested in pure biochar, as well as adsorption of HnPO4(3–n)–in biochar after it was doped with Al3+. The desorption of these ions was tested by washing with deionized water, and the KCl (1.0 mol·L–1) and Mehlich-1 extractors. In absolute values, the adsorption order of the ions was Al3+ (in acid pH value) = Ca2+ > Al3+ > HnPO4(3–n)–(biochar doped with Al3+) > Mg2+ > HnPO4(3–n)– (biochar without doping). The adsorption of HnPO4(3–n)– was positively influenced by the doping of biochar with Al3+. The biochar has preferential characteristics for cations adsorption, and the doping process can aid in adsorption of anions.

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...

Eucalyptus stands can be managed by coppicing, however, in several Brazilian regions reduced yield has been observed with harvesting successions. This reduction can be attributed to reduced nutrient availability, among other factors. This study aimed to: to assess the nutritional demand of the Eucalyptus stand under a coppice regime, the effect of fertilization on the production of wood, distribution and compartmentalization of nutrients in eucalyptus stands managed by coppice, the effect of the height and number of shoots, on the occasion of the sprouting, in the production of eucalyptus managed by coppice and to compare the productivity of high eucalyptus wood with coppice management regime. The trial was conducted for clone GG157 (Eucalyptus urophylla hybrid), in Latossolo Vermelho-Amarelo (Oxisol), of the Cerrado region in Minas Gerais State, Brazil. Trees were originally planted at the 3.8 &times, 2.4 m spacing and, after the first harvesting, at age 84 months, the stand was managed by coppicing. Treatments consisted of: (a) fertilization or not, (b) one, two or four poles per stump, and (c) selection of 1-, 2- or 4-m-high poles and repeated three times. Sixty months after treatment application, plots of 80 trees were used for the assessments. The gain in trunk yield with fertilization and the combination between the height of poles at the time of pole selection and number of poles left varies between 140.2% for thinning when the pole is 2 m high and maintains 1 pole per strain and 128.6% when the plants are 1 m high and maintain 1 pole per strain. Not supplying nutrients in the coppicing system leads to lower accumulation of nutrients in the tree and reductions in both wood and trunk yields. Trees in the coppicing system use nutrients for trunk production more efficiently than those in high forest. Earlier pole selection enables the best use of growth resources, resulting in increased yield. Adequate nutritional management of coppiced stands results in the maintenance or increase of yield compared to the first rotation.

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.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais O nitrogênio é um dos nutrientes mais demandados pelas espécies vegetais, sua presença no solo, sob formas orgânicas ou minerais disponíveis para as plantas, está vinculada à qualidade e quantidade dos resíduos vegetais aportados ao solo. O estudo teve o objetivo de avaliar a influência do cultivo do eucalipto e da acácia na composição das formas orgânicas e inorgânicas de N e, na abundância natural de 15N em um Argissolo Amarelo. Para isso, foram coletadas amostras de solo e serapilheira em monocultivos do Eucalyptus urograndis (clone do Eucalyptus urophylla S. T. Blake x Eucalyptus grandis W. Hill ex Spreng) de ciclo curto (sete anos), sistemas de cultivo de rotação de acácia (Acacia mangium Willd.) após monocultivo de eucalipto, monocultivo de eucalipto de ciclo longo (24 anos) e mata nativa (Mata Atlântica) como condição original de solo do litoral Norte do Espírito do Santo. Foram avaliados os teores de C orgânico total, N total, N-NH4+, N-NO3-, relação C/N, fracionamento do N orgânico e abundância natural de 15N no solo e serapilheira. Das formas de N-orgânico hidrolisado, o N- amino foi a fração que apresentou maior contribuição (39%), seguida pela fração de N- não identificado (27%), da fração N-amida (18%) e N-hexosamina (15%). O povoamento de acácia promoveu menor abundância natural de 15N e maiores teores de N total e C orgânico no solo e aumentou as formas orgânicas de N-hidrolisado, quando comparado àqueles de eucalipto de ciclo curto. Isto indica o aumento de formas lábeis de N orgânico no solo para as plantas e redução da humificação da matéria orgânica do solo (MOS) de acácia. Neste sentido, a rotação de cultivos florestais com acácia após eucalipto de ciclo curto contribuiu para o aumento de formas orgânicas no solo, importantes para a nutrição de plantas, por serem potenciais fontes de nutrientes às plantas em curto período de tempo. The nutrients nitrogen and one of the most demanded by plant species, and its presence in soil under organic or mineral forms available to plants is linked to quality and quatity of plant residues added to the soil. The study aimed to evaluate the influence of cultivation of eucalyptus and acacia in the composition of organic and inorganic N forms and the natural abundance of 15N in an Ultisol. For this, we collected soil and litter samples in continuous short-rotation eucalypt (Eucalyptus urophylla x Eucalyptus grandis hybrid) (seven years) compared to a rotation system including acacia (Acacia mangium Willd.) after short-rotation eucalypt; and long-rotation eucalypt (24 years). A native vegetation (Atlantic Forest) was used as a reference for the original site condition representative for the northern coast of Espírito Santo state. To do so, we evaluated the content of total organic C, total N, N-NH4+, N-NO3-, C/N ratio, fractionation of organic N and 15N natural abundance in soil and litter. Among the forms of organic-N hydrolyzed, the N-amino was the fraction with the highest contribution of organic N (39%), followed by the fraction of N-unidentified (27%), the fraction of N-amide (18%) and N-hexosamine (15%). The acacia plantation presented smaller natural abundance of 15N and higher levels of total N and soil organic C, and increased organic forms of N-hydrolyzed, when compared to the eucalyptus short-rotation soil. This indicates the increase of labile N-organic forms in the soil for the plants and reduction of humification of soil organic matter (SOM) of acacia. Thus, the crops rotation with acacia after eucalyptus contributed to the increase of organic forms in the soil, important for the nutrition of plants, because they are potential sources of nutrients to the plants in a short-time period.Keyword: acid hydrolysis; organic nitrogen; inorganic nitrogen; litter.

O uso da concentração foliar de nitrogênio total como indicador para diagnose nutricional apresenta algumas limitações. O objetivo deste trabalho foi determinar a confiabilidade da concentração de N total como indicador do status do nutriente para clones de eucalipto e compará-la com indicadores alternativos. Conduziu-se um experimento de casa de vegetação em delineamento de blocos ao acaso, em um arranjo fatorial 2 × 6, com mudas de dois clones de eucalipto (140 dias) e seis doses de N em solução nutritiva. Também foi conduzido um experimento de campo em delineamento inteiramente casualizado, em um arranjo fatorial 2 × 2 × 2 × 3, com duas épocas, duas regiões, dois clones jovens (aproximadamente dois anos) e três posições de amostragem das folhas na copa. As áreas de campo (regiões) tinham contrastantes propriedades físicas e químicas do solo e suas concentrações de N total, N-NH+4 e N-NO−3, foram determinadas em cinco camadas do solo, até 1 m de profundidade. Avaliaram-se como indicadores do status de N da planta, em raízes e folhas, concentrações de N total, N-NH+4 e N-NO−3, clorofila, razão N/P e leituras do medidor de clorofila nas folhas. Amônio (raiz) e N-NO−3, (raiz e folha) previram eficientemente os requerimentos de N para as mudas de eucalipto em casa de vegetação. Similarmente, N/P foliar, valores de clorofila e leituras do medidor de clorofila forneceram bons resultados em casa de vegetação. Entretanto, N/P foliar não refletiu o status de N do solo, e o uso do medidor de clorofila não pode ser generalizado para diferentes genótipos. A concentração foliar de N total não é um indicador ideal, mas essa e os níveis de clorofila melhor representam o status de N do solo para os clones jovens de eucalipto em condições de campo. The use of leaf total nitrogen concentration as an indicator for nutritional diagnosis has some limitations. The objective of this study was to determine the reliability of total N concentration as an indicator of N status for eucalyptus clones, and to compare it with alternative indicators. A greenhouse experiment was carried out in a randomized complete block design in a 2 × 6 factorial arrangement with plantlets of two eucalyptus clones (140 days old) and six levels of N in the nutrient solution. In addition, a field experiment was carried out in a completely randomized design in a 2 × 2 × 2 × 3 factorial arrangement, consisting of two seasons, two regions, two young clones (approximately two years old), and three positions of crown leaf sampling. The field areas (regions) had contrasting soil physical and chemical properties, and their soil contents for total N, NH+4-N, and NO−3-N were determined in five soil layers, up to a depth of 1.0 m. We evaluated the following indicators of plant N status in roots and leaves: contents of total N, NH+4-N, NO−3-N, and chlorophyll; N/P ratio; and chlorophyll meter readings on the leaves. Ammonium (root) and NO−3-N (root and leaf) efficiently predicted N requirements for eucalyptus plantlets in the greenhouse. Similarly, leaf N/P, chlorophyll values, and chlorophyll meter readings provided good results in the greenhouse. However, leaf N/P did not reflect the soil N status, and the use of the chlorophyll meter could not be generalized for different genotypes. Leaf total N concentration is not an ideal indicator, but it and the chlorophyll levels best represent the soil N status for young eucalyptus clones under field conditions.

In general, Latosols have low levels of available P, however, the influence of the parent material seems to be decisive in defining the pool and predominant form of P in these soils. This study evaluated P availability by extraction with Mehlich-1 (M-1) and Ion Exchange Resin (IER), from samples of B horizons of Ferric and Perferric Latosols developed from different parent materials. To this end, in addition to the physical and chemical characterization of soils, 10 sequential extractions were performed with M-1 and IER from samples of B horizons (depth between 0.8 and 1.0 m). Total contents of Ca, P, Fe, Al, and Ti were determined after digestion with nitric, hydrofluoric and perchloric acids. The effects of sequential P extractions on Fe oxides were also evaluated from the analyses of dithionite-citrate-bicarbonate and ammonium acid oxalate. The high similarity between contents of P accumulated after sequential extractions with M-1 and IER in soils developed on tuffite indicated a predominance of P-Ca. Higher contents of P after a single IER extraction show greater efficiency in P removal from highly weathered soils, as from the Latosols studied here. The P contents also show the high sensitivity of extractant M-1 in highly buffered soils. Furthermore, a single extraction with extractant M-1 or IER is not sufficient to estimate the amount of labile P in these soils. Os Latossolos apresentam, de modo geral, baixos teores de P disponível; no entanto, a influência do material de origem parece ser decisiva na definição do estoque e da forma de P predominante nesses solos. O objetivo deste trabalho foi avaliar a disponibilidade de P, pelos extratores Mehlich-1 (M-1) e Resina de Troca Iônica (RTI), em amostras de horizontes B de Latossolos Férricos e Perférricos desenvolvidos a partir de diferentes materiais de origem. Para tanto, além da caracterização física e química dos solos, foram realizadas 10 extrações sequenciais com os extratores M-1 e RTI em amostras de horizonte B coletadas entre 0,8 e 1,0 m de profundidade. Os teores totais de Ca, P, Fe, Al e Ti foram determinados após digestão com os ácidos nítrico, fluorídrico e perclórico. Os efeitos das extrações sequenciais de P sobre os óxidos de Fe também foram avaliados a partir das análises com ditionito-citrato-bicarbonato e oxalato ácido de amônio. A maior semelhança observada entre os teores de P acumulado após as extrações sequenciais com M-1 e RTI nos solos desenvolvidos de tufito é indicativo da predominância de P-Ca. Os maiores teores de P extraídos pela RTI após uma única extração relevam sua maior eficiência na remoção de P em solos bastante intemperizados como os Latossolos estudados e, ainda, ressalta a elevada sensibilidade do extrator M-1 em solos altamente tamponados. Além disso, uma única extração com o extrator M-1 ou RTI não é suficiente para estimar o fator quantidade de P lábil nesses solos.

O nitrogênio é requerido em grandes quantidades pelo eucalipto; entretanto, as repostas à aplicação desse nutriente são divergentes. O objetivo deste trabalho foi avaliar o comportamento diferenciado em crescimento, na nutrição mineral e nas trocas gasosas de clones de eucalipto supridos com N. Os tratamentos consistiram de dois clones de eucalipto (VM-01 e I-144) e seis doses de N (0; 0,74; 2,93; 4,39; 5,85; e 8 mmol L^-1 de NH4NO3), dispostos em delineamento de blocos casualizados com cinco repetições. O clone VM-01 foi superior em altura e altura/diâmetro do colo e teve maiores concentrações foliares de todos os macronutrientes e de Cu, Fe, Mo e Zn. Em termos de produção de matéria seca da raiz e total, raiz/parte aérea e diâmetro do colo, bem como em condutância estomática e transpiração, o clone I-144 teve melhor performance. O desempenho dos clones foi claramente diferenciado, e o crescimento do I-144, independetemente de menor concentração foliar de N, foi em geral melhor que do VM-01. Eucalyptus requires large amounts of nitrogen (N); however, it responds in diverse manners to the application of this nutrient. The aim of this study was to evaluate the differential performance in growth, mineral nutrition, and gas exchanges of N-fertilized Eucalyptus clones. The treatments consisted of 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 NH4NO3) arranged in a randomized complete block design with five replications. VM-01 had greater plant height and greater height/collar diameter ratio, as well as higher leaf concentrations of all macronutrients and of Cu, Fe, Mo, and Zn. In terms of total and root dry matter production, root/shoot ratio, and collar diameter, as well as stomatal conductance and transpiration, I-144 performed better. The performance of the clones was clearly differentiated, and the growth of I-144, despite lower leaf N concentration, was in general better than VM-01.

Este trabalho de revisão tem como objetivo apresentar os Hidróxidos Duplos Lamelares (HDL) como nanomateriais para serem aplicados na agricultura, com destaque para a utilização desses como matrizes para o armazenamento e a liberação lenta de nutrientes e agroquímicos para o cultivo de plantas. São abordadas as características estruturais, as principais propriedades e os principais métodos de síntese e de caracterização dos HDL. São também reportados trabalhos da literatura, demonstrando a potencial aplicação desses materiais no armazenamento e na liberação lenta de nitrato , fosfato, agroquímicos, além da utilização como adsorventes. Pretende-se com esta pesquisa expandir, em um futuro próximo, o campo de investigação desses materiais com aplicação na agricultura, aumentando a interface entre a química e a agronomia. The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.

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 ...