Abstract Activated biochars were prepared from residues of medium density fiberboard (MDF) produced by the furniture industry. Biomass residue was pre-treated with FeCl3 in two different FeCl3:biomass ratios (0.5:1 and 1:1, w/w) aiming to produce a matrix embedded with iron oxide. The pyrolysis process produced maghemite on the biochar surface and its magnetic properties were confirmed by its attraction to a hand magnet and its magnetic susceptibility. Samples were also characterized using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), surface area by BET-N2, Fourier transform infrared (FTIR), X-ray diffraction, magnetic susceptibility, and cation exchange capacity (CEC). Magnetic biochar exhibited up to twelve-fold higher surface area than the non-magnetic biochar, which varies according the maghemite particles content. Iron oxide on biochar surface also contributed for increasing CEC around ten-fold compared to non-magnetic biochars. Phosphorus adsorption isotherms showed that these magnetic biochars have high capacity to sorb oxyanions like phosphate, especially at lower pH. Thus, these magnetic biochars could be used to clean water bodies contaminated with oxyanions in acidic conditions.

Resumo: O objetivo deste trabalho foi avaliar os efeitos da aplicação parcelada e combinada de zinco foliar (ZnF) + Zn no solo (ZnS) sobre o teor de Zn dos grãos (TZnG) do feijão-comum (Phaseolus vulgaris). Dois experimentos foram realizados em casa de vegetação durante dois períodos. No primeiro experimento, duas cultivares de feijão-comum receberam seis doses de ZnF (0, 120, 240, 480, 720, ou 1.200 g ha-1), com aplicações parceladas nos estágios da planta R5, R7 e R8, ou R7 e R8, ou R8. No segundo experimento, uma cultivar recebeu três doses de ZnS (0, 5 ou 10 kg ha-1) combinadas com doses de ZnF (0, 1, 1,5, 3, 6 ou 10 kg ha-1). No primeiro experimento, com o incremento do ZnF, o TZnG aumentou linearmente de 15,3 para 20,7 mg kg-1. O parcelamento do ZnF não afetou o TZnG. No segundo experimento, o ZnF sem o ZnS não afetou o TZnG. O ZnS dobrou o TZnG em comparação ao tratamento sem aplicação de ZnS. Com 5 kg ha-1 de ZnS, o mais alto TZnG (67,5 mg kg-1) foi obtido com 7,8 kg ha-1 de ZnF. Com 10 kg ha-1, o mais alto TZnG (66,0 mg kg-1) foi obtido com 4,9 kg ha-1 de ZnF. O parcelamento do ZnF não é vantajoso em relação à aplicação única, e a combinação ZnF e ZnS aumenta o TZnG do feijão-comum em casa de vegetação.

Abstract: The objective of this work was to evaluate the effects of the split and combinated application of foliar zinc (ZnF) + soil Zn (ZnS) on Zn concentration in the grains (ZnCG) of common bean (Phaseolus vulgaris). Two experiments were carried out in a greenhouse during two seasons. In the first experiment, two common bean cultivars received six ZnF rates (0, 120, 240, 480, 720, or 1,200 g ha-1), with split applications at the R5, R7, and R8, or R7 and R8, or R8 plant stages. In the second experiment, one cultivar received three ZnS rates (0, 5, or 10 kg ha-1) combined with ZnF rates (0, 1, 1.5, 3, 6, or 10 kg ha-1). In the first experiment, with the ZnF increment, ZnCG increased linearly from 15.3 to 20.7 mg kg-1. ZnF splitting did not affect ZnCG. In the second experiment, ZnF without ZnS did not affect ZnCG. ZnS doubled ZnCG in comparison with the treatment without ZnS application. At 5 kg ha-1 ZnS, the highest ZnCG (67.5 mg kg-1) was obtained with 7.8 kg ha-1 ZnF. At 10 kg ha-1, the highest ZnCG (66 mg kg-1) was obtained with 4.9 kg ha-1 ZnF. ZnF splitting is not advantageous over a single application, and the combination of ZnF and ZnS increases ZnCG in common bean, in greenhouse conditions.

RESUMO O uso de fertilizantes com alguma proteção aos íons fosfato pode diminuir sua adsorção pelo solo e aumentar a absorção pela cultura, o que aumenta a eficiência da adubação. O objetivo deste trabalho foi avaliar o desempenho de um fertilizante fosfatado associado a biocarvão em um solo com alta capacidade de fixação de P. Os biocarvões foram produzidos a partir de duas fontes de biomassa: bagaço de cana-de-açúcar (BC) e serragem de madeira (SM), as quais foram pirolisadas em duas temperaturas (350 °C e 700 °C). Após a caracterização química e física, os biocarvões foram granulados com superfosfato triplo (TSP) em uma proporção 3:1 (TSP: biocarvão). A avaliação agronômica dos fertilizantes foi realizada por dois cultivos sucessivos de milho (Zea mays L.) em casa de vegetação em Latossolo argiloso em esquema fatorial (5x3) em delineamento de blocos inteiramente casualizados com 4 repetições. Os tratamentos consistiram de cinco fertilizantes (TSP-SM350, TSP-SM700, TSP-BC350, TSP-BC700 and TSP) e três doses de P (100, 200 e 400 mg dm-³ de P). Foram avaliados a produção de massa de matéria seca, acúmulo de P no milho, além do P disponível no solo após os cultivos. A produção de matéria seca, conteúdo de P na planta e P disponível no solo apresentou resultados superiores em ambos os cultivos na dose de 400 mg dm-3, já a taxa de recuperação aumentou de forma inversa em relação as doses. A simples associação de biocarvão com fertilizante fosfatado solúvel não aumentou a eficiência de uso de P pelo milho, mas aumentou o P disponível no solo após dois cultivos sucessivos.

ABSTRACT The use of fertilizers with some degree of protection of the phosphate ions can reduce soil adsorption and increase the absorption by plants, increasing the efficiency of phosphorus (P) fertilization. This study aimed to evaluate the performance of a phosphate fertilizer associated with biochar in granules in a P-fixing soil in a greenhouse experiment. Biochars were produced from two sources of biomass: sugarcane bagasse (SB) and wood sawdust (WS), which were pyrolysed at two temperatures (350 °C and 700 °C). After chemical and physical characterization, the biochar samples were granulated with triple superphosphate (TSP) in a 3:1 ratio (TSP: biochar). The agronomic evaluation of the fertilizers was carried out by two successive maize crops (Zea mays L.) in the greenhouse, using a factorial scheme of (5x3) in randomized block design with four replicates. The treatments consisted of five fertilizers (TSP-WS350, TSP-WS700, TSP-SB350, TSP-SB700, and TSP) and three P doses (100, 200, and 400 mg dm-3). It was evaluated the dry matter production, P uptake in maize and P available in the soil after cultivation. The results indicate that dry matter production, considering the P uptake by the plant and the P available in the soil when using a dose of 400 mg dm-3, presented higher results in both crop cycles and the recovery rate in both cultivations occurred inversely to the P doses. The simple association of biochar with soluble phosphate fertilizer did not increase the efficiency of P use by maize, but it increased available P in soil.

ABSTRACT: High copper (Cu) and zinc (Zn) contents in soil can cause phytotoxicity to plants and contaminate surface and groundwater, with negative effects on agriculture and the environment. Functionalized charcoal (OCh) has high cation exchange capacity (CEC) and the ability to adsorb Cu and Zn and control their availability in the soil and water. An adsorption study at two pH levels was carried out to evaluate increasing Cu and Zn sorption capacity provided by the functionalization process of a charcoal. In addition, a kinetics study of competitive and non-competitive adsorption-desorption of Cu and Zn in OCh was also evaluated. The results showed that functionalized charcoal (Ch) increased CEC 8.7 times due to an increase in carboxyl and phenolic groups, without changing its specific surface area. The Cu and Zn kinetics study showed higher interaction of Cu with the OCh, with total adsorption capacity of 53.1 mg g−1. From this amount, only 74.9 % was desorbed. However, competitive adsorption with Zn reduced the total amount of Cu adsorbed and decreased the Cu affinity for organic matter. This study shows the potential use of functionalized charcoal for control of Cu and Zn availability in the soil solution.

ABSTRACT Given the increase in crop yields and the expansion of agriculture in low fertility soils, deficiency of micronutrients, such as iron, in plants grown in tropical soils has been observed. The aim of this study was to evaluate Fe availability and Fe uptake by corn (Zea mays L.) plants in 13 different soils, at two depths. Iron was extracted by Mehlich-1, Mehlich-3, and CaCl2 (Fe-CC) and was fractionated in forms related to low (Feo) and high (Fed) crystallinity pedogenic oxyhydroxides, and organic matter (Fep) using ammonium oxalate, dithionite-citrate, and sodium pyrophosphate, respectively. In order to relate Fe availability to soil properties and plant growth, an experiment was carried out in a semi-hydroponic system in which part of the roots developed in a nutrient solution (without Fe) and part in the soil (the only source of Fe). Forty-five days after seeding, we quantified shoot dry matter and leaf Fe concentration and content. Fed levels were high, from 5 to 132 g kg-1, and Feo and Fe-CC levels were low, indicating the predominance of Fe as crystalline oxyhydroxides and a low content of Fe readily available to plants. The extraction solutions showed significant correlations with various soil properties, many common to both, indicating that they act similarly. The correlation between the Mehlich-1 and Mehlich-3 extraction solutions was highly significant. However, these two extraction methods were inefficient in predicting Fe availability to plants. There was a positive correlation between dry matter and Fe levels in plant shoots, even within the ranges considered adequate in the soil and in the plant. Dry matter production and leaf Fe concentration and content were positively correlated with Fep concentration, indicating that the Fe fraction related to soil organic matter most contributes to Fe availability to plants.

RESUMO Ácidos húmicos (AH) são componentes principais das substâncias húmicas (SH), as quais são encontradas em praticamente todos os solos, sedimentos e corpos d’água. Elas apresentam papel fundamental na maioria, se não todas, as propriedades químicas e físicas do ambiente. Apesar de sua importância, a elevada complexidade dos AH (e das SH, em geral) fazem deles um sistema pouco compreendido. Portanto, compreender as propriedades físico-químicas e as interações dos AH se faz crucial para determinar o papel fundamental dessas substâncias no ambiente e obter detalhes estruturais. Surfactantes catiônicos são conhecidos por interagirem com AH por interações tanto eletrostáticas (cabeça polar) quanto hidrofóbicas (cauda apolar). Como os surfactantes representam um sistema muito bem conhecido e caracterizado, eles representam ótimas escolhas como sondas moleculares para estudar os AH. Avaliou-se a interação entre surfactantes catiônicos com AH pela técnica de titulação calorimétrica isotérmica visando obter informações sobre a estrutura básica dos AH, a natureza dessa interação e se AH de diferentes origens apresentam estruturas básicas diferentes. Ao contrário do que o modelo supramolecular prega, a estrutura dos AH não é fracamente retida, podendo separar-se dependendo das condições do meio ao que forem submetidas. A estrutura dos AH não sofreu nenhuma divisão ou mudança conformacional durante a interação com os surfactantes catiônicos. Parece existir uma estrutura básica dos AH que é mantida virtualmente a mesma apesar das diferentes origens ou composições desses AH.

ABSTRACT Humic acids (HA) are a component of humic substances (HS), which are found in nearly all soils, sediments, and waters. They play a key role in many, if not most, chemical and physical properties in their environment. Despite the importance of HA, their high complexity makes them a poorly understood system. Therefore, understanding the physicochemical properties and interactions of HA is crucial for determining their fundamental role and obtaining structural details. Cationic surfactants are known to interact electrostatically and hydrophobically with HA. Because they are a very well-known and characterized system, they offer a good choice as molecular probes for studying HA. The objective of this study was to evaluate the interaction between cationic surfactants and HA through isothermal titration calorimetry in a thermodynamic manner, aiming to obtain information about the basic structure of HA, the nature of this interaction, and if HA from different origins show different basic structures. Contrary to what the supramolecular model asserts, HA structure is not loosely held, though it may separate depending on the conditions the HA are subjected to in their milieu. It did not show any division or conformational change when interacting with surfactants. The basic structure of the HA remains virtually the same regardless of the different sources and compositions of these HA.

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.

A eutroficação de aquíferos está fortemente ligada à mobilidade de P nos solos. Embora essa mobilidade tenha sido considerada, num passado mais distante, como inexpressiva, estudos mais recentes têm mostrado que o P, tanto na forma orgânica (Po) quanto na inorgânica (Pi), pode se perder por percolação e eluviação de partículas através do perfil de solos, particularmente naqueles menos intemperizados e, ou, arenosos com menor adsorção de P. O objetivo deste trabalho foi verificar perdas por lixiviação e eluviação de formas de P em colunas de solos, constituídas por cinco anéis de PVC sobrepostos, com 5 cm de diâmetro e 10 cm de altura cada, submetidas a fluxos de percolação de água. Foram utilizadas amostras de dois Latossolos Vermelho-Amarelos, texturas argilosa e média. Os solos receberam, previamente, quatro doses de P na forma de KH2PO4, correspondentes a 0; 12,5; 25 e 50 % da capacidade máxima de adsorção de P (CMAP), homogeneizadas com todo o volume de solo das colunas e deixados em incubação por 60 dias. No anel superior, aplicou-se, homogeneamente, cama de aviário nas doses equivalentes a 0, 20, 40, 80 e 160 t ha-1; com base no peso do material seco. O experimento foi constituído pelo esquema fatorial: quatro níveis da CMAP, cinco doses de cama de aviário, dois solos, com três repetições dispostas em blocos casualizados. As colunas foram submetidas a 10 percolações com água deionizada, em duas aplicações semanais, durante 35 dias, de modo que se atingisse um volume aproximado de 1.200 mm. Nos lixiviados de cada coluna, foram determinados: P reativo (Pi) e P não reativo (Po). No final do experimento, o P no solo de cada anel foi extraído com Mehlich-1 e com NaHCO3 0,5 mol L-1; pH 8,5 (Olsen), sendo determinadas, para este último extrator, as formas Pi e Po. Com o aumento das doses aplicadas de cama de aviário, as perdas de P por lixiviação foram, em média, 6,4 vezes maiores na forma de P não reativo (Po) que no P-reativo (Pi). Tanto a fertilização mineral prévia com P quanto a aplicação de doses crescentes de cama de aviário causaram movimentação descendente de P nas colunas de solo, extraído tanto pelo Mehlich-1 quanto pelo NaHCO3 (Olsen). O nível crítico ambiental (NCA), teor de P disponível no solo acima do qual a percolação de P-reativo aumenta exponencialmente, foi de 100 e 150 mg dm-3 para o Mehlich-1 e de 40 e 60 mg dm-3 para o Olsen, para os solos de textura média e argilosa, respectivamente. Em solos intemperizados, com acúmulo de P residual ao longo dos cultivos, as perdas de P por lixiviação no perfil podem ser significativas, de modo particular quando fertilizados com cama de aviário.

The eutrophication of aquifers is strongly linked to the mobility of P in soils. Although P mobility was considered irrelevant in a more distant past, more recent studies have shown that P, both in organic (Po) and inorganic forms (Pi), can be lost by leaching and eluviation through the soil profile, particularly in less weathered and/or sandier soils with low P adsorption capacity. The purpose of this study was to determine losses of P forms by leaching and eluviation from soil columns. Each column consisted of five PVC rings (diameter 5 cm, height 10 cm), filled with two soil types: a clayey Red-Yellow Latosol and a sandy loam Red-Yellow Latosol, which were exposed to water percolation. The soils were previously treated with four P rates (as KH2PO4 ) to reach 0, 12.5, 25.0 and 50 % of the maximum P adsorption capacity (MPAC). The P source was homogenized with the whole soil volume and incubated for 60 days. After this period the soils were placed in the columns; the soil of the top ring was mixed with five poultry litter rates of 0, 20, 40, 80, and 160 t ha-1 (dry weight basis). Treatments consisted of a 4 x 5 x 2 factorial scheme corresponding to four MPAC levels, five poultry litter rates, two soils, with three replications, arranged in a completely randomized block design. Deionized water was percolated through the columns 10 times in 35 days to simulate about 1,200 mm rainfall. In the leachate of each column the inorganic P (reactive P, Pi) and organic P forms (unreactive P, Po) were determined. At the end of the experiment, the columns were disassembled and P was extracted with the extractants Mehlich-1 (HCl 0.05 mol L-1 and H2SO4 0.0125 mol L-1) and Olsen (NaHCO3 0.5 mol L-1; pH 8.5) from the soil of each ring. The Pi and Po fractions were measured by the Olsen extractant. It was found that under higher poultry litter rates the losses of unreactive P (Po) were 6.4 times higher than of reactive P (Pi). Both the previous P fertilization and increasing poultry litter rates caused a vertical movement of P down the soil columns, as verified by P concentrations extracted by Mehlich-1 and NaHCO3 (Olsen). The environmental critical level (ECL), i.e., the P soil concentration above which P leaching increases exponentially, was 100 and 150 mg dm-3 by Mehlich-1 and 40 and 60 mg dm-3 by Olsen, for the sandy loam and clay soils, respectively. In highly weathered soils, where residual P is accumulated by successive crops, P leaching through the profile can be significant, particularly when poultry litter is applied as fertilizer.

Com o incremento exponencial da avicultura no Brasil, a disponibilidade de dejetos de aves e de cama de aviário tem aumentado de maneira semelhante. A proibição de uso desses produtos na ração animal tem feito com que eles sejam direcionados para a produção agrícola como fertilizantes. Ainda há na literatura carência de informação sobre lixiviação de bases no perfil do solo em conseqüência do efeito de ânions inorgânicos acompanhantes, como cloreto, nitrato e sulfato, e do efeito complexante de ácidos orgânicos de baixa massa molecular. O objetivo deste trabalho foi estudar o efeito da aplicação de cama de aviário na lixiviação de Ca, Mg, K e Na em solos e sua associação com ânions inorgânicos e ácidos orgânicos de baixa molecular. Amostras de dois Latossolos Vermelho-Amarelos, um de textura média e outro de textura argilosa, foram colocadas em colunas de PVC constituídas de cinco anéis, cada um com 10 cm de altura e 5 cm de diâmetro, ligados entre si com fita adesiva. O solo colocado no anel superior recebeu, homogeneamente, cinco tipos de camas de aviário: casca de café, casca de arroz, sabugo de milho, capim-napier e maravalha, totalizando 160 t ha-1 de material seco, comparado à testemunha (sem a cama de aviário). O experimento constituiu um fatorial 5 x 2, com cinco camas e dois solos, dispostos em blocos casualizados com três repetições. As colunas foram submetidas a 10 percolações com água deionizada, duas vezes por semana, até atingirem o volume de 1.200 mm de chuvas. Nos 10 percolados, foram analisadas as concentrações de Ca, Mg, K e Na, dos ânions Cl-, NO3-e SO4(2-) e de ácidos orgânicos de baixa massa molecular. Houve grande lixiviação de bases nas colunas, principalmente até a terceira percolação. Esse fato foi causado pela adição dessas bases, em doses elevadas, pelas camas de aviário e, aparentemente, também pelo efeito dos ânions acompanhantes Cl-, NO3-e SO4(2-)no solo de textura média, Cl-e NO3-no solo de textura argilosa e, de maneira menos expressiva, pelo efeito acompanhante/complexante dos ácidos orgânicos de baixa massa molecular. No solo argiloso, a percolação de Ca esteve positivamente correlacionada com a concentração dos ácidos málico e oxálico. A concomitante elevada concentração de ácido acético nos percolados de solos tratados com todas as camas sugere que este pode estar favorecendo a lixiviação de bases no solo, provavelmente como ânion acompanhante.

The exponential growth in poultry farming in Brazil has led to a parallel increase in the production of manure and poultry litter. The litter generated in this activity used to be largely employed as cattle feed. However, the enactment of a law that bans the use of poultry litter as animal feed intensified its use as organic fertilizer in agriculture. Despite its importance, there are gaps in our knowledge on an adequate use to obtain high plant yields without threatening the environment. One of these gaps is base-leaching in the soil profile as a result of the presence of accompanying anions such as chloride, nitrate and sulphate, and the complexing effect of low molecular mass organic acids. Samples of two Oxisols (a clayey and a sandy loam Red-Yellow Latosol) were placed in PVC columns. Each column consisted of five PVC rings (5 cm diameter, 10 cm height) fixed to each other with scotch tape. Five types of poultry litter (coffee husks, ground corn cob, rice husk, napier grass and wood shavings) were homogenously applied to the soil in the top ring in a dose equivalent to 160 t ha-1 (dry weight basis). The treatments consisted of a 5 x 2 + 1 factorial combination, corresponding to five poultry litter types, two soils with distinct textures, and a control treatment with no poultry litter application, with five repetitions, arranged in a complete randomized block design. Deionized water was applied on top of the columns twice a week, in a total volume corresponding to 1.200 mm, totaling 10 applications. Leachates were analyzed for cations (Ca, Mg, K and Na), anions (Cl-, NO3-and SO4(2-)) and low molecular mass organic acids by ion chromatography. Results indicate substantial base-leaching through the soil columns, particularly up to the third percolation. This was most likely a result of the presence of bases contained in the high poultry litter doses and the presence of accompanying anions (Cl-, NO3-and SO4(2-)in the sandy loam soil and Cl-and NO3-in the clayey soil). Ca leaching was positively correlated with the malic and oxalic acid concentrations in the clayey soil. High acetic acid concentration in leachates of poultry litter-treated soils suggest that it may have favored base-leaching in the soil profile as a result of its action as an ion pair.