RESUMO O conhecimento das demandas nutricionais dos diferentes genótipos de batata é necessário para o desenvolvimento de recomendações de fertilização. Objetivou-se determinar e comparar as curvas de acúmulo de macronutrientes nos genótipos de batata Agata, Asterix, BRSIPR Bel e F183-08-01, visando subsidiar o parcelamento de adubação que atenda as demandas específicas de cada genótipo. O delineamento foi em blocos casualizados, com os tratamentos (genótipos × estádios de planta) dispostos em esquema de parcelas subdivididas, com três repetições. Os genótipos foram cultivados em parcelas contendo 75 plantas cada. As subparcelas dentro de uma parcela continham quatro plantas cada e corresponderam ao número de dias após o plantio, quando amostras destrutivas de plantas inteiras foram coletadas. As plantas das subparcelas foram colhidas aos 24, 38, 52, 66 e 80 dias após o plantio, para estimar a massa seca acumulada por diferentes partes da planta (parte aérea + raízes, tubérculos e plantas inteiras) e para determinar as curvas de acúmulo de macronutrientes. F183-08-01 apresentou o maior acúmulo total de N, Ca, Mg e S (141,37; 29,21; 25,16; e 22,36 kg ha-1, respectivamente). As maiores taxas de acúmulo de macronutrientes para todos os genótipos de batata ocorreram aos 24 dias após o plantio, coincidindo com o início da formação dos tubérculos.

ABSTRACT Knowledge on the nutritional demands of different potato genotypes is necessary for the development of fertilizing recommendations. This study aimed to determine and compare the macronutrient accumulation curves in the Agata, Asterix, BRSIPR Bel and F183-08-01 potato genotypes, in order to subsidize the split fertilization that could meet the specific demands of each genotype. A randomized block design was used, with the treatments (genotypes × plant stages) arranged in a split-plot scheme, with three replications. The genotypes were grown in plots containing 75 plants each. The subplots within a plot contained four plants each and corresponded to the number of days after planting, when destructive samples of whole plants were collected. The plants from the subplots were harvested at 24, 38, 52, 66 and 80 days after planting, to estimate the dry mass accumulated by different parts of the plant (shoots + roots, tubers and whole plants), as well as to determine the macronutrient accumulation curves. F183-08-01 presented the highest total accumulation of N, Ca, Mg and S (141.37, 29.21, 25.16 and 22.36 kg ha-1, respectively). The highest rates of macronutrient accumulation for all the potato genotypes occurred at 24 days after planting, coinciding with the beginning of the tubers formation.

Resumo A couve de folhas é um alimento com alto teor de vitaminas e minerais, que são fundamentais para a dieta humana. Contudo, informações sobre a influência dos fatores extrínsecos e intrínsecos, durante o seu cultivo, em sua composição são escassas. O objetivo deste trabalho foi quantificar os seguintes minerais em folhas de couves produzidas no Distrito Federal (DF): cálcio, magnésio, potássio, fósforo, zinco, manganês, sódio e ferro, correlacionando os teores verificados com os teores presentes no solo. As amostras de folhas e solo foram coletadas em 16 diferentes propriedades rurais no DF, quando também foram aplicados questionários aos produtores sobre as práticas culturais adotadas durante a produção. Os resultados obtidos de teores médios foliares (base em folhas frescas) por 100 g de alimento foram: cálcio, 222,8 mg; ferro, 1,3 mg; magnésio, 37,6 mg, e zinco, 0,6 mg. Esta composição atende a 28% das necessidades diárias de cálcio em crianças de 4 a 8 anos, sendo também supridos 13% de ferro, 29% de magnésio e 13% de zinco, com base no consumo de 100 g de folhas frescas de couve. Foi verificada correlação negativa para teores de magnésio no solo e na folha, com R = -0,69. Para os outros minerais analisados não se verificou correlação significativa. O conteúdo de fósforo e de potássio nos solos foi considerado alto, enquanto que, contrariamente, foram determinadas concentrações baixas de teores de magnésio. O teor de micronutrientes na couve foi considerado baixo e aventa para um manejo inadequado da adubação, fator corroborado pelas respostas dos questionários sobre práticas culturais. Práticas de manejo que levam ao equilíbrio de nutrientes no solo refletem diretamente na interação solo-planta. Recomendações regionais atualizadas de adubação e correção dos solos poderiam auxiliar agricultores e técnicos, refletindo diretamente na obtenção de teores mais equilibrados de micro e macronutrientes em alimentos de origem vegetal.

Abstract Collard is a food with a high content of vitamins and minerals, fundamental for the human diet. However, information on the influence of extrinsic and intrinsic factors in its composition during cultivation is still scarce. The objective of this work was to quantify the minerals in collard leaves produced in the Federal District (DF), Brazil: calcium, magnesium, potassium, phosphorus, zinc, manganese, sodium and iron, correlating with the present soil contents. Leaf and soil samples were collected in 16 different rural properties in the Federal District, in which questionnaires were also applied on the cultural practices adopted during plant growing. The average foliar contents per 100 g of fresh leaves were: calcium, 222.8 mg; iron, 1.3 mg; magnesium, 37.6 mg; and zinc, 0.6 mg. This composition meets 28% of daily calcium requirements in children aged from 4 to 8 years: 13% iron, 29% magnesium and 13% zinc, based on the consumption of 100 g of fresh collard leaves. Negative correlation was verified for magnesium contents in soil and leaf, with R = -0.69. A significant correlation was not verified for the other analyzed minerals. Phosphorus and potassium contents in soils were considered high while, contradictorily, low concentrations of magnesium were found. The foliar micronutrients contents were considered low and suggests for an inadequate management of the fertilization, factor corroborated by the answers of the cultural practices questionnaires. Management practices that lead to nutrient balance in soil reflect directly on soil-plant interaction. Up-to-date regional recommendations on soil fertilization and correction could assist farmers and technicians, directly reflecting the achievement of more balanced levels of micro and macro nutrients in vegetables.

ABSTRACT Wastewater treatment is a challenging problem faced by the mining industry, especially when mine effluents include acid mine drainage with elevated arsenic levels. Iron (hydr)oxides are known to be effective in removal of As from wastewater, and although the resulting compounds are relatively unstable, the presence of structural Al enhances their stability, particularly under reducing conditions. The purpose of this study was to assess the effectiveness of Al-Fe (hydr)oxide co-precipitates for the removal of As from wastewater and to assess the chemical stability of the products. Different Al-Fe (hydr)oxides were synthesized at room temperature from ferrous and aluminum salts using three different Fe:Al molar ratios (1:0.0, 1:0.3, and 1:0.7) and aged for 90 days (sulfate experiments) or 120 days (chloride experiments) in the presence of arsenic. At the end of the aging periods, the precipitated sludges were dried and characterized in order to evaluate their stability and therefore potential As mobility. All treatments were effective in reducing As levels in the water to below 10 µg L-1, but the presence of Al impaired the effectiveness of the treatment. Aluminum decreased the chemical stability of the precipitated sludge and hence its ability to retain As under natural environmental conditions.

ABSTRACT The intensive nature of soil use in vegetable production areas has led to a marked decrease in soil quality. The objective of this study was to evaluate the effects of adoption of soil management systems on vegetable production with regards to the chemical properties of a Rhodic Ferralsol after five years and to evaluate the use of the Principal Component Analysis (PCA) statistical tool in discriminating the different treatments. The experiment was conducted under field conditions in central Brazil in a randomized block design with four replications and a 3 × 2 factorial arrangement (three soil management systems × two cover crops). The soil management systems used were NT (no-tillage), RT (reduced tillage), and CT (conventional tillage). The cover crops used were corn (Zea mays) alone and corn intercropped with the gray velvet bean (Stizolobium niveum). Reduced tillage showed the highest values of sum of bases, cation exchange capacity (T), and total organic carbon contents in the 0.00-0.05 m layer. In the same layer, RT and CT showed higher values of pH and K content. No-tillage and RT showed the highest P and Ca2+ contents and H+Al and T values. In the 0.05-0.10 m layer, RT had higher a pH value and Mg2+ contents. No-tillage and CT had higher potential acidity in this layer. The management systems (0.10-0.30 m) and the cover plants (all layers) had no effect on the properties analyzed. The use of PCA determined that the two principal components explained the following percentage of the data variance: 90.8 % (0.0-0.05 m), 79.8 % (0.05-0.10 m), and 83.1 % (0.10-0.30 m). Analysis of the eigenvectors and the grouping of treatments in PCA also showed that RT was most effective in improving soil fertility properties. Reduced tillage was most effective in increasing soil fertility after five years. The PCA is recommended as a useful tool and it allowed the identification of patterns not revealed by traditional tools.

Resumo: O objetivo deste trabalho foi avaliar os teores de carbono orgânico total (COT) e das frações granulométricas da matéria orgânica de um Latossolo Vermelho cultivado com hortaliças, sob diferentes sistemas de manejo e de cultivo de plantas de cobertura. O experimento foi realizado por seis anos, em delineamento de blocos ao caso, em arranjo fatorial 3x2, com três sistemas de manejo do solo - plantio direto (SPD), preparo reduzido (PPR) e preparo convencional (SPC) - e dois cultivos de cobertura, um de milho solteiro e outro de milho consorciado com mucuna-cinza (Stizolobium niveum) (MM), com quatro repetições. Os teores de COT, estimados para a camada 0,00-0,30 m, foram maiores em SPD e PPR. Independentemente da profundidade avaliada, o consórcio MM promoveu os maiores teores de carbono orgânico particulado (COP), que foram fortemente influenciados pela incorporação da palhada. Em todas as camadas, observaram-se correlações negativas entre os teores de COP e os de carbono orgânico associado a minerais (COAM), indício de ocorrência do efeito "priming". Os teores de COT correlacionaram-se positivamente aos de COAM, o que destaca a importância de mecanismos de estabilização da matéria orgânica no incremento dos teores de COT no solo.

Abstract: The objective of this work was to evaluate the contents of total organic carbon (COT) and of the organic matter fractions in an Oxisol cultivated with vegetables under different soil management systems and with different cover crops. The experiment was carried out for six years in a randomized block design, in a 3x2 factorial arrangement with three soil management systems - no-tillage (SPD), minimum tillage (PPR), and conventional system (SPC) -, and two cover crops, one of maize and the other of maize intercropped with Stizolobium niveum (MM), with four replicates. COT levels, estimated for 0.00-0.30-m, soil depth were higher in SPD and PPR. Regardless of the evaluated soil depth, MM intercropped system promoted higher contents of particulate organic carbon (COP), which were strongly affected by straw incorporation. In all soil depths, negative correlations were observed between the contents of COP and those of carbon associated to minerals (COAM), which indicate the occurrence of priming effect. COT contents were positively correlated to those of COAM, stressing the importance of soil organic matter stabilization mechanisms for improving COT contents in the soil.

Os adubos orgânicos fornecem nutrientes, melhoram as condições do solo e também apresentam bioatividade, ou seja, efeitos estimulantes nas plantas. Efeitos como indução de crescimento e melhora na qualidade nutricional vêm justificando a crescente comercialização de bioestimulantes e fertilizantes de base orgânica. Neste trabalho, a bioatividade é discutida com base na fisiologia vegetal. A literatura disponível comprova ações fisiológicas destas substâncias, principalmente no crescimento de raízes e aumento na absorção de nutrientes. Contudo, as abordagens das pesquisas têm focado nos aspectos básicos relacionados às frações extraídas em laboratório, que não representam necessariamente a realidade da matéria orgânica em seu estado natural no solo e sua bioatividade. Por outro lado, conhece-se muito pouco do mecanismo de ação dos produtos comerciais utilizados a campo. Assim, é importante que as pesquisas passem a incluir também aspectos como: (1) indicação de fontes mais promissoras para extração de matéria orgânica; (2) métodos simplificados tanto de extração das frações e da matéria orgânica como para avaliações da sua bioatividade e; (3) experimentos de campo com avaliação da produtividade das culturas associada aos possíveis mecanismos de ação. A utilização criteriosa de novas tecnologias para o aumento da eficiência da adubação dos solos em áreas de cultivo de hortaliças é importante tanto do ponto de vista econômico quanto ambiental.

Organic manure supplies nutrients, improves soil conditions and also exhibits bioactivity, ie stimulating effects in plants. Effects such as growth enhancement and plant nutrient status improvement comes justifying the increasing commercialization of organic-based biostimulants and fertilizers. In this work, bioactivity is discussed focusing on the physiology of vegetables. The available literature confirms such physiological actions, particularly in the growth of roots and nutrient uptake increase. However, research approaches have been more focused on the basic aspects of fractions isolated in laboratory, which does not necessarily represent the reality of the natural organic matter in soil and its bioactivity. On the other hand, little is known on the mechanism of action of commercial products, which have been used in the field. Therefore, it is important that research initiatives also include aspects such as: (1) indicating the most promising sources for the extraction of organic matter, (2) both simplified methods of' extraction of organic matter fractions as for the evaluation of their bioactivity and (3) field experiments evaluating crops productivity associated to the possible mechanism of action. The judicious use of new technologies to increase the efficiency of fertilization of soils in growing vegetables areas is important both from an economic as environmental sense.