INFLUÊNCIA DO Al3+ EM SOLUÇÃO NUTRITIVA NO CRESCIMENTO DE TRÊS ESPÉCIES FLORESTAIS UTILIZADAS NA RECUPERAÇÃO DE ÁREAS DEGRADADAS

One of the main limiting factors in the performance of agricultural and forest crops in tropical soils is the toxic effect of Al3+ in soils. However, some plant species present adaptive mechanisms that confer tolerance to these conditions. The aim of this study was to evaluate the development of three tree species grown in nutrient solution with different levels of Al3+. Therefore, seedlings of Acacia mangium, Mimosa artemisiana and Enterolobium contortisiliquum were produced in nutrient solution with four concentrations of Al3+ (control, 185, 370 and 555 μmol L-1) during 95 days of cultivation. At the end of the experiment, the plants were targeted and a fraction of the known roots was scanned to estimate root area and length. The stem, leaves and remaining roots were dried in a forced air oven, being determined the biomass and N, P and K in plant tissue. The species showed different patterns of growth due to the increase of the activity of Al3+ in nutrient solution, and Acacia mangium and Enterolobium contortisiliquum were more tolerant to Al3+, demonstrating potential use in the recovery of degraded areas with acid soils. The N concentration in the plant parts were not influenced by Al3+, however the concentration of P increased in the roots of three species with intermediate levels of Al3+, resulting in reduction of P in shoots of Acacia mangium and Mimosa artemisiana. The concentration of K+ in Acacia mangium was reduced only in the lower Al3+, whereas for Mimosa artemisiana was gradually reduced.Um dos principais fatores limitantes no desempenho das culturas agrícolas e florestais na maioria dos solos tropicais é o efeito tóxico do Al3+. No entanto, algumas espécies vegetais apresentam mecanismos de adaptação que lhes conferem tolerância a essas condições. O objetivo deste estudo foi avaliar o desenvolvimento de três espécies florestais cultivadas em solução nutritiva com diferentes níveis de Al3+. Para tanto, mudas de Acacia mangium, Mimosa artemisiana e Enterolobium contortisiliquum foram cultivadas em solução nutritiva com quatro concentrações de Al3+ (controle, 185, 370 e 555 mmol L-1) durante 95 dias. Ao final do experimento, as plantas foram segmentadas e uma fração conhecida das raízes foi digitalizada para estimativa de área e comprimento radicular. O caule, folhas e o restante das raízes foram secos em estufa de ventilação forçada, sendo determinada a biomassa e os teores de N, P e K no tecido vegetal. As espécies apresentaram padrões de crescimento diferenciados em função do aumento do teor de Al3+ na solução nutritiva, sendo que a Acacia mangium e a Enterolobium contortisiliquum foram mais tolerantes ao Al+3, demonstrando potencial de uso na recuperação de áreas degradadas e com solos ácidos. Os teores de N nas partes das plantas não foram influenciados pelo Al3+, no entanto, a concentração de P aumentou nas raízes das três espécies com níveis intermediários de Al3+, resultando em redução de P na parte aérea da Acacia mangium e Mimosa artemisiana. A concentração de K na Acacia mangium foi reduzida somente no menor nível de Al3+, enquanto para Mimosa artemisiana a redução foi gradativa

Nutritional status and physiological and anatomical aspects in maize under cationic micronutrient Omission

Com o objetivo de caracterizar e diagnosticar a deficiência de micronutrientes catiônicos, foram realizados quatro ensaios independentes, cultivando plantas de milho em soluções nutritivas com restrições de ferro, cobre, manganês ou zinco. Foram avaliados aspectos fisiológicos, anatômicos e teores foliares nas plantas em diferentes tempos de omissão desses micronutrientes. No estudo fisiológico foram quantificadas as trocas gasosas e a fluorescência da clorofila. O estudo anatômico foi feito na região mediana da lâmina foliar, montando-se lâminas a partir de material incluído em historresina ou com impressão da epiderme com cola instantânea. Foi evidenciada a produção de amido na bainha do feixe vascular e, como coloração de contraste, foi utilizado o azul-de-toluidina. Foram obtidas imagens digitalizadas por meio de fotomicroscópio, sendo a proporção dos diferentes tecidos quantificada pelo software Image Pro- Plus. O mesmo software foi utilizado para quantificar a produção de amido. Os teores foliares de ferro, cobre, manganês e zinco foram determinados por meio de espectrofotômetro de emissão óptica com plasma acoplado por indução. Todas as características foram avaliadas na segunda folha acima da última com lígula visível. Os sintomas visuais da deficiência nutricional surgiram aos 5, 12 e 16 dias, nos ensaios com ferro, manganês e zinco, respectivamente. No ensaio com cobre não foram observados sintomas visuais de deficiência até o vigésimo segundo dia. A deficiência de ferro, cobre, manganês e zinco promoveu redução na taxa de assimilação de CO 2 e na produção de amido, porém apenas a deficiência de manganês e de zinco afetou o crescimento da planta. A deficiência de ferro afetou etapas iniciais da fase fotoquímica, principalmente a absorção e transferência de energia pelo complexo coletor. O estudo anatômico mostrou que as deficiências de manganês e zinco foram as que promoveram maiores alterações nas proporções dos tecidos, com menor efeito para o ensaio com ferro e cobre. Em todos os ensaios, os teores foliares apresentaram reduções com o tempo de omissão; no entanto, no ensaio com ferro, houve tendência de estabilidade com o tempo de omissão, principalmente após o aparecimento dos sintomas visuais. A indução da deficiência levou à diminuição dos teores foliares na ordem de cobre > zinco ≅ manganês > ferro. O teor de ferro na folha do milho mostrou-se ineficiente no diagnóstico do estado nutricional deste nutriente. Mesmo com reduções acentuadas nos teores de cobre, não foi verificado efeito sobre o crescimento da planta ou estresse nutricional.In order to characterize and diagnose the deficiency of cationic micronutrients, four independent experiments were carried out with maize plants cultivated in nutritive solutions with iron, copper, manganese or zinc omission. Physiological and anatomical aspects and leaf micronutrient content were evaluated at different times of omission of these nutrients. In the physiological study, gaseous exchanges and chlorophyll fluorescence were quantified. The anatomical study was conducted in the median region of the leaf blade, with glass slides being assembled from material embedded in Historesin or epidermis print with instant glue. Starch production was determined in the sheath of the vascular bundle with toluidine blue being used as contrast dye. Digital images were obtained with a photomicroscope, with the proportion of the different tissues being quantified with the software Image Pro-Plus, which xwas also used to estimate starch production. iron, copper, manganese and zinc leaf contents were determined in a optical emission inductive- coupled plasma spectrophotometer (ICP-OES). All the characteristics evaluated were studied in the second leaf above the last with visible ligule. The visual symptoms of nutritional deficiency were observed on days 5, 12 and 16, in the iron, manganese, and zinc experiments, respectively. No visual symptoms of deficiency were observed in the copper experiment until day 22. Iron, copper, manganese and zinc deficiency decreased the CO 2 assimilation rate and starch production, but only manganese and zinc deficiency affected plant growth. Fe deficiency affected the initial stages of the photochemical phase, mainly the absorption and transference of energy. The anatomical study showed that manganese and zinc deficiencies promoted the highest alterations in the tissue proportions, with a smaller effect being observed on the iron and copper experiments. In all the experiments, the leaf content of micronutrient decreased along the omission time; however, in the iron experiment there was a tendency for stabilization with omission time, mainly after the appearance of deficiency symptoms. Induced deficiency led to a decrease in the leaf contents in the following order: copper > zinc ≅ manganese > iron. Iron content in maize leaf was shown to be inefficient in diagnosing the nutritional status of this nutrient. Even with pronounced copper content reductions, no effect on plant growth or nutritional stress was verified.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Transport in soil, absorption and translocation of boron by clones of eucalyptus

Fatores ambientais, como falta ou má distribuição de chuvas, e deficiências nutricionais têm sido importantes redutores da produção de florestas plantadas no Brasil. O boro (B) é, entre os micronutrientes, aquele que mais freqüentemente se apresenta deficiente no solo, o que leva a freqüentes adubações com esse elemento. Para avaliar o transporte no solo, a absorção e a translocação de B por clones de eucalipto, foram realizados três ensaios em casa de vegetação. No primeiro ensaio, a contribuição do fluxo de massa e da difusão para o transporte de B até as raízes de eucalipto, em resposta ao potencial de água do solo e às doses do nutriente, foi determinada utilizando amostras de um Latossolo Vermelho-Amarelo. Os tratamentos corresponderam a dois potenciais de água do solo (-10 e 40 kPa) e seis doses de B (0, 0,5, 1, 2, 3 e 5 mg dm-3 de B). O controle do potencial da água do solo foi efetuado pelo uso de um tensiômetro por vaso e o ajuste, por acréscimo de água destilada. A máxima produção de matéria seca de raízes foi obtida nas doses correspondentes a 0,98 e 2,38 mg dm-3 de B, nos potenciais de água de -10 kPa e -40 kPa, respectivamente. A máxima produção de matéria seca de parte aérea foi obtida nas doses correspondentes a 0,96 e 1,82 mg dm-3 de B, nos potenciais de água de -10 kPa e -40 kPa, respectivamente. Foram observadas relações positivas e significativas entre o B aplicada, o B extraível com água quente, o B na solução do solo e o conteúdo de B na planta, para ambos os potenciais matriciais. O fluxo de massa foi o mecanismo predominante no transporte de B, chegando a suprir 100 % das necessidades das plantas nas doses mais elevadas. A difusão foi um mecanismo complementar importante naquelas condições de baixo teor de B no solo e sob déficit hídrico. No segundo ensaio, oito clones de eucalipto cresceram em soluções nutritivas com 0, 10, 20, 50 e 100 μmol L-1 de B, durante 70 dias. Na finalização do ensaio, foram determinadas características fisiológicas, produção de matéria seca, teor e conteúdo de B. Houve resposta diferenciada dos clones à concentração de B na solução nutritiva, com máxima produção de matéria seca entre 24 e 69 μmol L-1 de B. Os clones apresentaram distinção na eficiência de utilização de B. Sob deficiência, foi observada inversão do gradiente de concentração entre as folhas jovens e maduras, evidenciando redistruição de B no floema do eucalipto. No terceiro ensaio, a translocação de B foi avaliada em dois clones de eucalipto (68 e 129), por meio de aplicação foliar do traçador isotópico 10B, em uma única folha madura de plantas com e sem deficiência de B. Amostras de tecidos jovens (folhas jovens e ápices caulinares), folhas maduras e raízes foram coletadas nos tempos de 0, 1, 5, 12 e 17 dias após a imersão da folha em solução contendo 10B. A razão isotópica 10B:11B foi determinada por meio de espectrômetro de massa de alta resolução com fonte de plasma ativado indutivamente (HR-ICP-MS). Os principais carboidratos solúveis no exsudato xilemático e nas folhas foram avaliados por meio de cromatografia iônica. As plantas que estavam deficientes em B retomaram o crescimento após a aplicação de B. Os resultados da razão isotópica mostraram que houve translocação de B no eucalipto. O clone 129 apresentou maior translocação de B para os tecidos jovens, folhas maduras e raízes do que o clone 68, mostrando ser mais eficiente na translocação do nutriente. As plantas com suprimento adequado de B não apresentaram translocação do elemento, evidenciando que a translocação de B em eucalipto pode ser um mecanismo indutivo. O sorbitol foi o principal poliálcool presente nas folhas do eucalipto.Environmental factors, such as limited rainfall and nutritional deficiencies, have been important drawbacks for forest plantations in Brazil. Among the micronutrients, deficiency of boron (B) is the most frequently encountered in the field, requiring constant application. In order to evaluate the transport in soil, absorption and translocation of B by clones of eucalyptus, three experiments were carried out under greenhouse conditions. In the first one, the contributions of mass flow and diffusion in the transport of B to eucalyptus roots were evaluated in response to water potential and doses of B. The experiment consisted of one soil, one clone of eucalyptus, two water potentials (-10 and -40 kPa) and six application rates of B (0, 0.5, 1, 2, 3 and 5 mg dm-3). The water potential was controlled using a tensiometer in each pot. The maximum root dry weight was attained at 0.98 and 2.38 mg dm-3 of B for potential -10 kPa and -40 kPa, respectively. The maximum shoot dry weight was reached at 0.96 and 1.82 mg dm-3 of B for the -10 kPa and -40 kPa potential, respectively. Positive and significative relationships were observed between B application rate, extractable B, B in soil solution and plant B content for both water potentials. Mass flow was the predominant mechanism for B transport in the soil, reaching 100 % when high doses of B were applied. Diffusion was more important under conditions of low B in soil and under water deficit. In the second experiment, eight clones of eucalyptus were grown in nutrient solutions at B concentrations of 0, 10, 20, 50 and 100 μmol L-1 for 70 days, after which, the physiological variables, dry matter production and B content were determined. There was a differential response of the eucalyptus clones to the concentration of B in nutrient solution, with maximum dry matter production occurring between 24 and 69 μmol L-1 of B in nutrient solution. The genotypes differed in B use efficiency. Under B deficiency, the B concentration gradient between younger leaves and older leaves was reversed in comparison to those under normal B conditions, providing evidence of B mobility. In the third experiment, B translocation was evaluated with two clones (68 and 129) of eucalyptus using the 10B stable isotope as a tracer. 10B was applied once to only one mature leaf of seedlings with and without B deficiency. Samples of young tissue, mature leaves and roots were taken at 0, 1, 5, 12 and 17 days after the 10B application. 10B:11B isotopic ratio was determined with a high resolution-inductively coupled plasma mass spectrometer (HR-ICP-MS). Samples of xylem sap and leaves from seedlings were taken for soluble carbohydrate analyses by ion chromatography. In the deficient plants, new branchs were observed after B application. The results showed that B was translocated from mature leaf to young tissues. The clone 129 translocated more B from the treated leaf to young tissue, other mature leaves and roots than the clone 68. The plants grown under sufficient B supply showed no B translocation, providing evidence that B translocation may be an inductive mechanism. Sorbitol was the main polyol found in the leaves of eucalyptus.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Production and evaluation of potassium fertilizers from silicate rock

Rising price and limited geographical availability of traditional sources of potassium (K) fertilizers have stimulated a search for alternative K sources in different parts of the world. We evaluated mineral transformations and agronomic properties of an alternative source of K produced through thermal and chemical treatment of the verdete rock (VR). Chemical and mineralogical characteristics were evaluated before and after each treatment. Four K sources (verdete rock, KCl, acidified verdete, and calcinated verdete) were applied to a Typic Hapludox at different rates. Eucalyptus and sequentially cropped maize and grass were grown in the treated soils. Ver- dete rock, which contained glauconite and microcline as K crystalline minerals, had very low solubility in water and in citric acid. Thermal and chemical treatments increased the concentration of water soluble K and citric acid soluble K. These treatments also caused crystalline K minerals to collapse and form sylvite and arcanite. Untreated verdete rock was not suitable as a K source for maize (Zea mays L.) and eucalyptus (Eucaliptus urograndis I144). Thermal and chemical treatments increased agronomic performance of VR to be similar to KCl. When K was applied as K-calcined verdete, 82% of the total K was recovered in maize and grass cultivations. Less K was recovered in plant following addition of K-acidified verdete and KCl (72% and 77%, respectively). Potassium recoveries by eucalyptus were about 52, 53, and 60% of the amount applied of calcined verdete, acidified verdete, and KCl, respectively. Both calcination and thermal treatment increased the K uptake and dry matter production for all plant species tested to be similar to KCl suggesting that this silicate rock could be beneficiated to be an effective K fertilizer

Nitrogen release from urea with different coatings

Coatings or urease inhibitors are designed to reduce losses of ammonia [NH 3(g) ] from urea fertilizers. However, nitrogen (N) release and its effects on soil solution have not previously been evaluated under standardized conditions in soils. In this study, the urea fertilizers were incubated in chambers filled with sandy loam soil, adapted for the collection of NH 3(g) and soil solution by centrifugation. In the fast-release N fertilizers, around 93% and 100% of urea-N applied was recovered within the first hours of incubation. In contrast, in the slow-release N fertilizers, less than 40% of urea-N applied, was recovered at 19 days of incubation. The maximum N release from the fertilizers followed the order: UP1 (106%) ≈ UNBPT (102%) ≈ urea (93%) > USP2 (57%) ≈ USP3 (57%) > USP4 (31%) ≈ USP5 (18%). NH 3(g) volatilization accounted for only 3% of the applied N in the slow-release fertilizers, which corresponded to about 88% less than the NH 3(g) loss from prilled urea. This study demonstrated distinct N release patterns, which changed the N dynamics in the soil. Some coatings effectively delayed urea release from granules and reduced NH 3(g) gas losses, while other were not efficient

Nitrogen release from urea with different coatings

Coatings or urease inhibitors are designed to reduce losses of ammonia [NH 3(g) ] from urea fertilizers. However, nitrogen (N) release and its effects on soil solution have not previously been evaluated under standardized conditions in soils. In this study, the urea fertilizers were incubated in chambers filled with sandy loam soil, adapted for the collection of NH 3(g) and soil solution by centrifugation. In the fast-release N fertilizers, around 93% and 100% of urea-N applied was recovered within the first hours of incubation. In contrast, in the slow-release N fertilizers, less than 40% of urea-N applied, was recovered at 19 days of incubation. The maximum N release from the fertilizers followed the order: UP1 (106%) ≈ UNBPT (102%) ≈ urea (93%) > USP2 (57%) ≈ USP3 (57%) > USP4 (31%) ≈ USP5 (18%). NH 3(g) volatilization accounted for only 3% of the applied N in the slow-release fertilizers, which corresponded to about 88% less than the NH 3(g) loss from prilled urea. This study demonstrated distinct N release patterns, which changed the N dynamics in the soil. Some coatings effectively delayed urea release from granules and reduced NH 3(g) gas losses, while other were not efficient

Acid Ammonium Citrate as P Extractor for Fertilizers of Varying Solubility

ABSTRACT: There are several globally accepted methods to chemically characterize P-fertilizers, but not all are suitable to predict the agronomic efficiency of the P sources in terms of plant nutrition. Our aim was to investigate the performance of P extractors for fertilizers, investigating the consistency of different methods for P sources of varying properties and the related plant responses. The experiment was carried out in a greenhouse, using corn as a model plant. Phosphorus values extractable in water, 2 % citric acid, 2 % formic acid, ammonium neutral citrate + water, and acid ammonium citrate were evaluated for eight P fertilizers of varied solubility and correlated with P uptake by corn. The extractors citric acid and formic acid recovered no predictive amounts of P from crystalline apatite sources (Araxá and Patos phosphate rocks, PRs). However, they showed a satisfactory performance for Bayóvar PR and partially acidulated PRs but extracted low amounts of P from soluble P sources such as superphosphates. Neutral ammonium citrate + water extractors could accurately predict the efficiency of soluble P sources but underestimated the performance of Bayóvar (a reactive PR). In contrast, the extractor acid ammonium citrate, AAC, (pH 3) accurately predicted the agronomic efficiency of all P fertilizers. We therefore suggest AAC as an effective predictor of the agronomic effectiveness of any inorganic phosphorus sources

Characterization of verdete rock as a potential source of potassium

Potassium is a nutrient found at low levels in Brazilian soils, requiring large inputs of fertilizers to achieve satisfactory crop yields. Brazil has high external dependence and limited reserves of soluble K mineral, which is traditionally exploited for the production of fertilizers. On the other hand, it is common the occurrence in the country of potassium-rich silicate minerals which are not commercially exploited. This study aimed to characterize mineralogically and chemically samples of verdete rock separated into size fractions and evaluate its potential as potassium fertilizer. The mineral composition of verdete rock is based on glauconite, quartz and feldspar. The total K2O content in verdete rock ranged from 5.18 to 9.0 dag/kg. The K content extracted in water or 2% citric acid was 2.4% below the total of K, indicating low reactivity of verdete rock and limitations for direct use as K source. The processes of physical fractionation and sedimentation in water are inefficient to promote the concentration of K in the different verdete rock fractions. The total K content in some samples are considerable and may enable the use of this rock as raw material for production of more reactive potassium fertilizers

Uso da técnica HRICP-MS na avaliação dos isótopos de boro em eucalipto

The 10B isotope tracer technique is essential to study the B mobility in plants. Factors that can influence the quality of measured B isotope ratios were optimized experimentally using High Resolution Inductively Coupled Plasma Mass Spectrometry (HRICP-MS). An isotopically certified standard (NIST SRM-951) was used. The best combination was obtained using a resolution of 400, a RF power of 1250 W, followed by 15 measurements over a 10-s integration period each (15*10). Utilizing this approach it was possible to obtain a precision of 0.3 % in standard material and 2z % in the experimental samples. The results show the importance of establishing optimized work conditions before carrying out the analytical series

Capacidade de suprimento de potássio em solos de Minas Gerais-Brasil

O potássio está presente em diferentes formas no solo, diferindo na acessibilidade para as plantas e com reversibilidade entre essas formas. A capacidade dos solos no suprimento de K para as plantas é diferenciada e determinante na sustentabilidade da produção agrícola e no manejo da fertilização com este nutriente. Assim, neste trabalho objetivou-se avaliar a capacidade de suprimento de K por solos do Estado de Minas Gerais (Brasil) de diferentes mineralogias, em cultivo sucessivo de milho. O experimento foi conduzido em casa de vegetação, num esquema fatorial 7 x 6 (sete solos e seis doses de K), sendo as unidades experimentais distribuídas em blocos casualizados, com quatro repetições, por sete cultivos sucessivos. As plantas eram colhidas após 45 d para cada cultivo. A disponibilidade de K para as plantas foi avaliada no início e no intervalo de cada cultivo, usando os extratores Mehlich-1 e Mehlich-3. Veri!cou-se expressiva redução dos teores de K no solo, comprometendo a produção de matéria seca do milho em todos os solos estudados. A reserva de K foi maior nos Argissolos, seguido dos Cambissolos e Latossolos. Houve participação de formas não trocáveis de K na nutrição do milho. A disponibilidade de K no solo avaliada pelo extrator Mehlich-1 representou 40% do K absorvido pelas plantas e, 61% do K absorvido quando utilizou-se o extrator Mehlich-3