Scielo RSS <![CDATA[Bragantia]]> http://www.scielo.br/rss.php?pid=0006-870520160001&lang=en vol. 75 num. 1 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Endophytic bacteria affect sugarcane physiology without changing plant growth]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100001&lng=en&nrm=iso&tlng=en ABSTRACT The aim of this study was to evaluate if endophytic bacteria inoculants would be beneficial to the sugarcane varieties IACSP94-2094 and IACSP95-5000, promoting changes in photosynthesis and plant growth. The plants, obtained from mini stalks with one bud, were treated with two bacteria mixtures (inoculum I or II) or did not receive any inoculum (control plants). The inocula did not affect shoot and root dry matter accumulation as compared to the control condition (plants with native endophytic bacteria). However, photosynthesis and electron transport rate (ETR) increased in IACSP94-2094 treated with the inoculum II, whereas the inoculum I enhanced photosynthesis and stomatal conductance in IACSP95-5000. The inoculum II caused increase in leaf sucrose concentration of IACSP94-2094 and decrease in IACSP95-5000 leaves. Leaf nitrogen concentration was not affected by treatments, but bacteria inoculation increased nitrate reductase activity in IACSP95-5000, and the highest activity was found in plants treated with the inoculum II. We can conclude that bacteria inoculation changed sugarcane physiology, improving photosynthesis and nitrate reduction in a genotype-dependent manner, without promoting plant growth under non-limiting conditions. <![CDATA[Morphological and chemical characterization of the fruits of cambuci fruit tree]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100010&lng=en&nrm=iso&tlng=en RESUMO O cambucizeiro (Campomanesia phaea), pertencente à família Myrtaceae, é uma planta nativa da Mata Atlântica brasileira. A descrição das características dos frutos de cambucizeiro é importante para subsidiar novos trabalhos de melhoramento genético e sua exploração comercial, principalmente no que tange ao processamento dos frutos. O presente trabalho teve como objetivo realizar a caracterização morfológica e química de frutos de cambucizeiro. Cinquenta e oito acessos, oriundos de diferentes locais da Mata Atlântica e Serra do Mar paulista, foram coletados, propagados por sementes e um exemplar de cada acesso encontra-se no Núcleo de Produção de Mudas de São Bento do Sapucaí (SP). Quarenta frutos de cada acesso foram coletados no mês de maio e submetidos às seguintes análises: diâmetro longitudinal e transversal, massa fresca total dos frutos, número e massa das sementes, sólidos solúveis totais, % ácido cítrico, ratio, firmeza, vitamina C e coloração. A conformidade dos frutos varia intensamente entre os acessos. O número de sementes não é um bom indicativo para a relação com a massa do fruto, mas sim a massa de mil sementes. Alguns acessos possuem elevado teor de sólidos solúveis, mas, por outro lado, a grande maioria possui frutos com elevada acidez. Cambuci é uma excelente fonte de vitamina C. Os frutos dos acessos são de coloração verde, persistindo uma tonalidade opaca quando maduros.<hr/>ABSTRACT The cambuci fruit tree (Campomanesia phaea), belonging to the Myrtaceae family, is a native tree from the Atlantic Forests. The description of the fruits of cambuci fruit tree is important to support new plant breeding researches and trades exploitation, especially regarding the fruit processing. This study aimed to carry out the morphological and chemical characterization of the fruits of cambuci fruit tree. Fifty-eight accessions, from different places of Atlantic Forests and Serra do Mar, were collected and propagated by seed. A sample of each accession is maintained at Núcleo de Produção de Mudas de São Bento do Sapucaí (SP). Forty fruits of each accession were collected in May and submitted to the following analysis: longitudinal and transverse diameters, total fruit fresh mass, number and mass of the seeds, total soluble solids, % of citric acid, ratio, firmness, vitamin C and color. The similarity of fruits is highly variable between all accessions. The number of seeds is not a good indicator to the ratio with fruit mass; however, the mass of thousand seeds is a good indicator. Some accessions have high content of soluble solids, but most of the fruits showed high acidity. The cambuci fruit is an excellent source of vitamin C. The accession fruits have green color, persisting an opaque hue in ripe fruits. <![CDATA[Effects of aluminum on the elongation and external morphology of root tips in two maize genotypes]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100019&lng=en&nrm=iso&tlng=en ABSTRACT The objective of this study was to evaluate the effects of toxic levels of aluminum (Al) on the growth and external morphology of root tips in two maize genotypes with differential Al tolerance. The maize genotypes UFVM-100 (Al-sensitive) and UFVM-200 (Al-tolerant) were treated with 0 and 50 mM Al in a 0.5 mM CaCl2 solution at pH 4.5; root elongation, Al content and the external morphology of the root tips were evaluated. Chemical analysis, hematoxylin staining and energy dispersive X-ray spectrometry (EDS) showed greater Al accumulation in the root tips of the UFVM-200 genotype. The inhibition of root elongation in the UFVM-100 genotype, however, was much stronger than in the UFVM-200 genotype. Both maize genotypes exhibited visible and intense alterations in external micromorphology of the root tip, especially the Al-sensitive UFVM-100 genotype. Scanning electron micrographs showed intense cell disorganization and transverse ruptures of the protodermic and outer cortex layers of the cells in both genotypes. The ruptures were deeper and wider and reached the inner cortex layers in the UFVM-100 genotype. The EDS analysis showed that, in addition to Al accumulation, there was a proportional increase in the P concentration in the root tips of the UFVM-200 genotype. This is indicative of possible precipitation and/or immobilization of Al in the root tip apoplast of this genotype, which contributes to symplastic detoxification. <![CDATA[Establishment of growth medium and quantification of pollen grains of olive cultivars in Brazil's subtropical areas]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100026&lng=en&nrm=iso&tlng=en ABSTRACT Pollen grain germination in vitro indicates viability and consequently provides information related to fruit set. It also assists in the development of hybrids. Along with a suitable species, a standard culture medium is essential for evaluating pollen viability. It should contain a gelling agent consisting of carbohydrates and enhancer elements as well as have the correct pH, temperature, and incubation time. The objective of this study was to optimise the culture medium, determine the pollen germination capacity, and quantify the number of pollen grains per flower of certain olive tree cultivars. A basic sequential culture medium for pollen grain germination was determined, always utilizing the best result from the previous experiment to continue the sequence.The factorial treatment arrangement was: 1) agar versus boric acid; 2) pH versus sucrose; 3) calcium nitrate versus magnesium sulfate. After determining the culture medium components, two experiments were conducted evaluating temperature and incubation time. Another experiment evaluated both the germination percentage and the number of flower pollen grains of 28 cultivars. The culture medium should be composed of 4 g∙L-1 of agar, 90 g∙L-1 of sucrose, and 400 mg∙L-1 of boric acid with a pH adjusted to 5.79 and an incubation time of 60 h at 28 °C. The Manzanilla 215 cultivar had the highest germination rate while Ascolano 315 presented the highest number of pollen grains per flower. <![CDATA[Plant growth-promoting bacteria associated with nitrogen fertilization at topdressing in popcorn agronomic performance]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100033&lng=en&nrm=iso&tlng=en ABSTRACT The use of plant growth-promoting bacteria is a promising alternative with low environmental impact to increase the efficiency of use of chemical fertilizers, ensuring high yield with better cost-effective ratio. In maize crops, several studies have demonstrated an increased yield when Azospirillum-based inoculants are used. In the case of popcorn, there are no available studies related to use of inoculation and its response on yield parameters. Thus, the aim of this study was to evaluate the field performance of popcorn when inoculated with the commercial product Masterfix L (A. brasilense Ab-V5 and A. brasilense Ab-V6) and the non-commercial inoculant UEL (A. brasilense Ab-V5 + Rhizobium sp. 53GRM1) associated with nitrogen fertilization. The trials were conducted in Londrina and Maringá, Paraná State, Brazil, in a randomized block design with four replications, in a split plot design with the inoculation treatments located in the plots (uninoculated, Masterfix L, and UEL) and the different N rates located in the subplots where ammonium sulphate was applied in the topdressing at the V6 stage (0, 50, 100, and 150 kg∙ha–1). The variance analysis showed significant effects (p &lt; 0.05) of inoculation (Londrina environment) and N rates (both environments) only for grain yield. There was no inoculation effect in the grain yield when inoculants were applied together with N-fertilization at topdressing. In the absence of N-fertilization at topdressing, the inoculants Masterfix L. and UEL promoted higher grain yield as compared to the uninoculated plants, with resulting increases of 13.21 and 26.61% in yield, respectively.<hr/>RESUMO A utilização de bactérias promotoras de crescimento vegetal é uma alternativa promissora e de baixo impacto ambiental para aumentar a eficiência de uso de fertilizantes químicos, garantindo elevadas produtividades com melhor relação custo-benefício. Na cultura do milho, diversos trabalhos vêm demonstrando o aumento de rendimento de grãos quando inoculados com Azospirillum spp. No caso do milho pipoca, trabalhos relacionados ao uso da inoculação sobre a produtividade da cultura são inexistentes. Dessa forma, o objetivo do trabalho foi avaliar o efeito da inoculação do produto comercial Masterfix L. (A. brasilense Ab-V5 e A. brasilense Ab-V6) e da formulação experimental UEL (A. brasilense Ab-V5 e Rhizobium sp. 53GRM1), associada à adubação nitrogenada, sobre o desempenho agronômico de milho pipoca. Os experimentos foram conduzidos em Londrina e Maringá (PR), sob o delineamento de blocos casualizados, com quatro repetições, em esquema de parcela subdividida, sendo locados nas parcelas os inoculantes (sem inoculante, Masterfix L e UEL) e, nas subparcelas, doses de N em cobertura no estádio V6, utilizando-se o sulfato de amônio (0, 50, 100 e 150 kg∙ha–1). Pela análise de variância, houve efeitos significativos (p &lt; 0,05) da inoculação (ambiente Londrina) e doses de N (ambos os ambientes) apenas para rendimento de grãos. Não foram observados efeitos da inoculação na produtividade do milho quando realizados conjuntamente com as adubações de cobertura. Na ausência da adubação de cobertura, os inoculantes Masterfix L. e UEL foram superiories ao não inoculado, com incrementos médios na produtividade de 13,21 e 26,61%, respectivamente. <![CDATA[Identification of variability for agronomically important traits in rice mutant families]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100041&lng=en&nrm=iso&tlng=en ABSTRACT The increase of yield potential in new rice (Oryza sativa L.) varieties has been a major challenge for genetic improvement. The generation of mutants, followed by their characterization, constitutes a great possibility to isolate and select genes and genotypes that present agronomic traits of interest. This study aimed to evaluate the effect of chemical mutagen ethyl methane sulphonate (EMS) on agronomic traits in 340 M3 families of rice derived from BRS Querência cultivar. Seeds from each family and the original genotype BRS Querência were sown in the experimental field, and the characters main panicle length, main panicle weight, main panicle grain weight, flag leaf width and plant height were evaluated. Data were subjected to analysis of variance (p ≤ 0.05), and a comparison of means was carried out by Dunnett's test at 5% significance. The results show that there is genetic variability among the mutant families, suggesting that the mutagen EMS at 1.5% is effective for generating mutants for all assessed traits. Among the characters, plant height was the most affected by the mutagen, which provided an increase in the character. For the main panicle length character, seven families showed means above the control; for main panicle weight and grain weight, four and six mutant families were observed, respectively, with a superior performance in comparison to the control.<hr/>ABSTRACT O incremento do potencial produtivo nas novas variedades de arroz (Oryza sativa L.) tem sido um dos principais desafios para o melhoramento genético. A geração de mutantes, seguida da sua caracterização, constitui-se em uma ótima possibilidade para isolar e selecionar genes e genótipos que apresentem caracteres agronômicos de interesse. Este trabalho teve como objetivo avaliar o efeito do mutagênico químico etilmetanossulfonato (EMS) sobre caracteres agronômicos em 340 famílias M3 de arroz, derivadas da cultivar BRS Querência. As sementes de cada família e da testemunha BRS Querência foram semeadas a campo e posteriormente avaliadas para os caracteres comprimento da panícula principal, peso da panícula principal, massa de grãos da panícula principal, largura da folha bandeira e estatura de planta. Os dados foram submetidos à análise de variância (p ≤ 0,05), e a comparação entre as médias foi realizada pelo teste de Dunnett a 5% de significância. Os resultados obtidos mostram que existe variabilidade genética entre as famílias mutantes de arroz e que a indução de mutação com EMS a 1,5% é eficiente na geração de mutantes de arroz para todos os caracteres avaliados. Dentre esses, a estatura das plantas foi a mais afetada pelo agente mutagênico, o qual proporcionou o incremento do caráter. Para o caráter comprimento da panícula principal, sete famílias obtiveram médias superiores à testemunha; já para os caracteres peso e massa de grãos da panícula principal, foram observadas quatro e seis famílias mutantes, respectivamente, com desempenho superior ao da testemunha. <![CDATA[Contribution of agronomic traits for grain yield in physic nut]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100051&lng=en&nrm=iso&tlng=en RESUMO O conhecimento da associação entre os caracteres que compõem a produtividade é importante para a seleção de plantas superiores, principalmente para garantir que o ganho genético ocorra para os diversos caracteres favoráveis. No pinhão-manso, a produtividade de grãos é o principal alvo do programa de melhoramento, porém existem outros caracteres importantes que impactam na produção. Diante desse contexto, o objetivo deste trabalho foi estimar, por meio de análise de trilha, os efeitos diretos e indiretos de caracteres vegetativos sobre a produtividade de grãos de pinhão-manso. Aos 18 meses após o plantio, foram mensurados os caracteres altura de plantas, diâmetro do caule, número de ramos por planta, projeção da copa na linha, projeção da copa na entrelinha e produtividade de grãos. Foram estimadas as correlações fenotípicas entre os caracteres avaliados, sendo essas correlações desdobradas, por meio da análise de trilha, em efeitos diretos e indiretos, considerando-se o caráter produtividade de grãos como a variável dependente principal. Observou-se que 76% da variação em produtividade foi explicada pelas variáveis explicativas, valor este superior ao observado em outros estudos e adequado para explorar os ganhos com a seleção direta e indireta em pinhão-manso. Os caracteres diâmetro do caule, massa de cem sementes e projeção da copa na entrelinha influenciam diretamente a produtividade de grãos, sendo indicados para seleção direta, assim como para a seleção indireta de progênies superiores de pinhão-manso para produtividade de grãos.<hr/>ABSTRACT The knowledge of the association between traits of production is important for selecting superior plants and mainly to ensure that the genetic gain occurs for many favorable traits. In physic nut, grain yield is the main goal of the breeding program, but there are other important traits that have an impact on production. On such background, the aim of this study was to estimate, using path analysis, direct and indirect effects of vegetative traits on the grain yield of physic nut. At 18 months after planting, the traits plant height, stem diameter, number of branches per plant, plant canopy projection on the line, plant canopy projection between rows and grain yield were measured. Phenotypic correlations among traits were estimated and unfolded in direct and indirect effects through path analysis, considering the grain yield as the main dependent variable. It was observed that 76% of the variation in yield was explained by the explanatory variables; this value is higher than those observed in other studies and appropriate to explore the gains from direct and indirect selection on physic nut. Stem diameter, weight of 100 seeds and canopy projection between rows directly influence the grain yield, being suitable for direct as well as indirect selection of physic nut superior progenies for grain yield. <![CDATA[Pruning management of Chardonnay grapevines at high altitude in Brazilian southeast]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100057&lng=en&nrm=iso&tlng=en ABSTRACT The agronomical responses of Chardonnay, a variety indicated for sparkling wine production, is influenced by the vineyard management and the edaphoclimatic conditions of the region. The objective of this study was to evaluate the effects of two pruning types (Royat and double Guyot) on vegetative and reproductive development of Chardonnay vine growing at high altitude in the Brazilian southeastern region. The experiment was carried out in a commercial vineyard located at 1,280 m of altitude in Divinolândia, São Paulo State, Brazil. The Chardonnay vines (clone 96), grafted onto 1103 Paulsen rootstock and trained in a vertical shoot positioning trellis system, were assessed. Vegetative vigor, bud fruitfulness, production and physicochemical composition of grapes were evaluated during 2014 and 2015 growing seasons. The Royat pruning induced higher vegetative vigor and increased the bud fruitfulness, the cluster number and the productivity of Chardonnay vine when compared to Guyot pruning. Even though the increase on yield was observed, there was no effect of pruning type on grape final quality. Therefore, the choice of pruning method in function of variety genetic characteristics and their interaction with environment can optimize the vineyard profitability. In the Brazilian southeast, the Royat system is the most suitable one to grow Chardonnay for sparkling wines production.<hr/>ABSTRACT O comportamento agronômico da videira Chardonnay, indicada para a produção de vinhos espumantes, está relacionado ao manejo do vinhedo e às condições edafoclimáticas da região de cultivo. O objetivo deste trabalho foi avaliar dois tipos de poda (Cordão Royat e Guyot Duplo) no desenvolvimento vegetativo e produtivo da videira Chardonnay, em região de elevada altitude no Sudeste Brasileiro. Foi utilizado o clone 96 da cultivar Chardonnay, enxertado sobre o porta-enxerto 1103 Paulsen, e sustentado em espaldeira, em um vinhedo comercial localizado a 1.280 m de altitude em Divinolândia (SP). Durante os ciclos de produção de 2014 e 2015, foram avaliados vigor vegetativo, fertilidade de gemas, produção e composição físico-química das bagas. A poda do tipo Royat induziu maior vigor vegetativo e aumentou a fertilidade das gemas, o número de cachos e a produtividade da videira Chardonnay quando comparada à poda Guyot. Apesar do aumento de produtividade, não houve efeito do tipo de poda na qualidade final da uva. Portanto, a escolha do sistema de poda em função das características genéticas da cultivar e sua interação com o ambiente pode proporcionar maior rentabilidade ao vinhedo. Para o cultivo da Chardonnay no Sudeste Brasileiro, com a finalidade de se obterem vinhos espumantes, o sistema Royat é o mais indicado. <![CDATA[Planting spacing and NK fertilizing on physiological indexes and fruit production of papaya under semiarid climate]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100063&lng=en&nrm=iso&tlng=en ABSTRACT The nutritional requirements of papaya (Carica papaya L.) increase continuously throughout the crop cycle, especially for potassium and nitrogen, which are the most required nutrients and act on plant vital functions such as photosynthetic activity, respiration, transpiration and stomatal regulation. An experiment was conducted from November 2010 to December 2012 to evaluate physiological indexes and fruit production of papaya cv. Caliman-01 as a function of planting spacing and NK fertilizing. The experimental design consisted of randomized blocks, with treatments distributed in a factorial arrangement (2 × 4 × 4), using 2 planting spacing [simple rows (3.8 × 2.0 m) and double rows (3.8 × 2.0 × 1.8 m)], 4 nitrogen doses (320, 400, 480 and 560 g of N per plant-1) and 4 potassium doses (380, 475, 570 and 665 g of K2O per plant-1) with 4 replications of 3 plants each. The following variables were evaluated: leaf area index (LAI), leaf chlorophyll index (a, b and total index), intercepted photosynthetically active radiation (Int.PAR, in µmol∙m-2∙s-1), efficiency use of photosynthetically active radiation (Ef.PAR) and fruit yield. The fruit production and physiological characteristics of papaya cv. Caliman-01 depend on planting spacing. Under the soil, climate and plant conditions of this study, 665 g of K2O and 320 g of N per plant under double spacing could be recommended for the production of papaya cv. Caliman-01. <![CDATA[Citrus cultivars performance grafted on trifoliate 'Flying Dragon' and 'Rangpur' lime during the orchard young phase]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100070&lng=en&nrm=iso&tlng=en Resumo A redução de porte que o porta-enxerto Poncirus trifoliata var. monstrosa 'Flying dragon' confere às plantas sobre ele enxertadas pode facilitar os tratos culturais, permitir o adensamento de plantio e aumentar a eficiência produtiva, dependendo da cultivar e condições de cultivo. Para cultivares de laranjeiras, há pouca informação sobre o uso do 'Flying dragon' como porta-enxerto, principalmente no Estado do Rio de Janeiro. Assim, um experimento foi conduzido com o objetivo de avaliar o desempenho de laranjeiras doces e da limeira ácida 'Tahiti' enxertadas sobre o porta-enxerto 'Flying dragon', durante a fase de formação do pomar, tendo o limoeiro 'Cravo' como padrão de comparação. O experimento foi conduzido em sistema de cultivo irrigado, nas condições edafoclimáticas do Norte Fluminense. O delineamento experimental utilizado foi em blocos casualizados, em esquema fatorial 2 × 5, sendo avaliados os 2 porta-enxertos citados e 5 cultivares de copas. As cultivares de copas avaliadas foram a limeira ácida 'Tahiti' e as laranjeiras doces 'Natal', 'Bahia', 'Lima Sorocaba' e 'Pera'. Foram feitas avaliações biométricas para estimar o índice de vigor vegetativo (IVV), o volume de copa e as taxas de cobertura nas linhas e entrelinhas de cultivo, atingidas aos 36 meses após o plantio. Nas condições deste experimento, verificou-se que o porta-enxerto 'Flying dragon' reduziu a altura, o IVV, as taxas de cobertura na linha e na entrelinha e o volume de copa das plantas sobre ele enxertadas, quando comparado ao limoeiro 'Cravo', mas a intensidade de redução foi dependente da cultivar-copa.<hr/>ABSTRACT The size reduction that the rootstock Poncirus trifoliata var. monstrosa 'Flying dragon' gives the plants grafted on it can facilitate the cultivation, allow the planting density and increase production efficiency, depending on the cultivar and growing conditions. For orange cultivars, there is information scarcity about the use of 'Flying dragon' as rootstock, mainly in the State of Rio de Janeiro. Thus, an experiment was conducted in order to evaluate the performance of sweet oranges and acid lime 'Tahiti' grafted on the rootstock 'Flying dragon' during the young phase of the orchard, using the 'Rangpur' lime as a standard for comparison. The experiment was conducted on irrigated cropping systems, in edaphoclimatic conditions of the northern Rio de Janeiro. The experimental design was a randomized block, in a 2 × 5 factorial, being evaluated the 2 mentioned rootstocks and 5 canopies cultivars. The evaluated canopies cultivars were the acid lime 'Tahiti' and the sweet oranges 'Natal', 'Bahia', 'Lima Sorocaba' and 'Pera'. Biometric evaluations were made to estimate the vegetative vigor index (VVI), the canopy volume and coverage rates in the lines and rows of cultivation, reached 36 months after planting. Under the conditions of this experiment, it was found that the rootstock 'Flying dragon' reduced height, VVI, the coverage rates in the lines and rows, and the canopy volume of plants grafted on it, when it was compared to 'Rangpur' lime, but the reduction capacity was dependent of the canopy cultivar. <![CDATA[<em>Spilocaea pyracanthae</em> causing leaf scab on loquat in Pakistan]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100076&lng=en&nrm=iso&tlng=en ABSTRACT Loquat is attacked by many phytopathogenic fungi. Among these Spilocaea pyracanthae is of economic importance. The fungus received no attention in Pakistan and some other parts of the world. The current study is focused on the symptomatology of this disease and the etiology of the fungus. During extensive surveys of loquat orchards in 2013 heavy infestations of this disease were observed. The leaf symptoms were observed as olive brown, opaque necrotic sub-circular spots, with light brown coloration in the center. Two or more spots coalesced in severe infections covering large leaf areas. The fungus was identified as Spilocaea pyracanthae on the basis of conidia and morphological characters. The pathogenicity of the fungus was confirmed on healthy plants under greenhouse conditions by following Koch's postulates. The fungus produced characteristic leaf scab symptoms on young leaves. This is the first report of Spilocaea pyracanthae causing leafscab of loquat in Pakistan. <![CDATA[Activity of soil microbial biomass altered by land use in the southwestern Amazon]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100079&lng=en&nrm=iso&tlng=en ABSTRACT The increasing demand for food creates environmental problems, mainly due to the removal of native vegetation cover for agriculture expansion in Brazil. These changes in land use lead to changes in the soil organic matter dynamics. Microorganisms represent the most biological and physiological diversity in soil, as well as are responsible for more than 95% of the decomposition and nutrient cycling processes. The objective in this research was to check if there is difference of patterns in activity of soil microbial biomass under varied natural vegetation, pastures in use and agricultural systems recently established. The area covered by this study corresponds to the states of Rondônia and Mato Grosso. Canonical variate analysis was used in physical, chemical and microbiological factors in each ecoregion and land use, looking for patterns and variables that can differentiate them. The native areas showed distinct patterns in the dynamics of microbiological attributes mainly related to the amount of litter in each biome studied. For the disturbed areas, there were similar results between pastures and native areas, significantly different from the results obtained in agricultural areas, which, due to differences in management and kind of cultures analyzed, showed a great variability in the final result. The results support the recommendation for use of microbiological attributes as indicators of land use change, combined with chemical and physical factors of the soil.<hr/>RESUMO A demanda crescente de alimentos gera problemas ambientais, principalmente devido à remoção das coberturas vegetais nativas para a expansão da agricultura no Brasil. Essas alterações no uso da terra acarretam mudanças na dinâmica da matéria orgânica do solo. Os micro-organismos representam a maior diversidade biológica e fisiológica do solo, além de serem responsáveis por mais de 95% dos processos de decomposição e ciclagem de nutrientes. O objetivo deste trabalho foi verificar se há diferenciação dos padrões de atividade da biomassa microbiana dos solos sob as diferentes vegetações naturais, pastagens em uso e sistemas agrícolas recém-implantados. A área de abrangência desta pesquisa corresponde aos Estados de Rondônia e Mato Grosso. Foi realizada a análise de variável canônica de atributos físicos, químicos e microbiológicos de cada ecorregião e uso da terra, buscando evidenciar os padrões e as variáveis que os diferenciam. As áreas nativas apresentaram padrões distintos na dinâmica dos atributos microbiológicos relacionados principalmente à quantidade de serapilheira em cada bioma estudado. Em relação às áreas antropizadas, observaram-se resultados similares entre pastagens e áreas nativas, significativamente diferentes dos resultados obtidos em áreas agrícolas, que, devido à diferença de manejo e diversidade de culturas analisadas, apresentaram uma grande variabilidade no seu resultado final. Os resultados obtidos mostram que os atributos microbiológicos devem ser utilizados como indicadores de mudança de uso da terra quando associados a fatores químicos e físicos do solo. <![CDATA[Nitrogen fertilization in top dressing for corn crop with high yield potential under a long-term no-till system]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100087&lng=en&nrm=iso&tlng=en RESUMO A intensificação da produção para elevar a produtividade de milho tem aumentado a demanda por fertilizantes nitrogenados. Com o objetivo de avaliar a acidificação do solo e definir as doses de máxima eficiência técnica (MET) e econômica (MEE) de N-ureia em cobertura para obtenção de alta produtividade de milho, realizou-se um experimento no município de Candói (PR), em um Latossolo Vermelho de textura argilosa sob plantio direto de longa duração (30 anos). Os tratamentos, dispostos em blocos ao acaso com 4 repetições, constaram de 5 doses de nitrogênio (N), na forma de ureia: 0, 90, 180, 270 e 360 kg∙ha-1, aplicadas em cobertura no estádio de desenvolvimento V4. O milho, híbrido P1630, foi cultivado após aveia-preta, em 2012, com 65 kg N∙ha-1 na semeadura. A aplicação de N, na forma de ureia, reduziu o pHCaCl2, os teores de Ca2+ + Mg2+ trocáveis, a capacidade de troca de cátions (CTC) efetiva e a saturação por bases do solo. Os teores de N nas folhas e nos grãos, a altura das plantas e da inserção da espiga, o número de grãos por fileira, a massa de grãos por espiga, a massa de 1.000 grãos e a exportação de N pelos grãos de milho aumentaram linearmente com as doses de N em cobertura. A produtividade de milho aumentou com as doses de N, de acordo com o modelo Linear Response Plateau. A MET e a MEE seriam obtidas com a dose de 209 kg N∙ha-1 em cobertura para produtividade de 19,6 t∙ha-1 de milho.<hr/>ABSTRACT Agricultural intensification to increase corn yield has increased the demand for nitrogen fertilizers. A field experiment was carried out in Candói, Paraná State, Brazil, on a clayey Typic Hapludox (Oxisol) under a long-term continuous no-till (30 years) to evaluate the effects of nitrogen (N) fertilization as urea in top dressing on soil acidification and determine the N-urea rates of maximum technical yield (MTY) and maximum economic yield (MEY) for obtaining high corn yield. A randomized complete block design was used, with four replications. The treatments consisted of N-urea application in top dressing at the rates of 0, 90, 180, 270, and 360 kg∙ha-1. Urea was applied in the V4 stage of the crop corn. Corn, hybrid P1630, was cultivated after black oat in 2012, with 65 kg N∙ha-1 at sowing. The N application as urea decreased the soil pHCaCl2, the exchangeable Ca2+ + Mg2+ levels, the effective cation-exchange capacity (CEC) and the soil base saturation. The N content in leaves and grains, the plant and ear height, the number of grains per row, the mass of grains per ear, the 1,000-grain mass, and the N export by grain of corn increased linearly with increasing N rate applied in top dressing. Corn yield increased with N rates as the Linear Response Plateau model and stabilized at 19.6 t∙ha-1. The MTY and MEY would be obtained at a rate of 209 kg N∙ha-1 in top dressing. <![CDATA[Impacts of fertigation via surface and subsurface drip irrigation on growth rate, yield and flower quality of <em>Zinnia elegans</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100096&lng=en&nrm=iso&tlng=en ABSTRACT Drip irrigation combined with split application of fertilizer nitrogen (N) dissolved in the irrigation water (i.e. drip fertigation) is commonly considered best management practice for water and nutrient efficiency. This research was conducted to study the influence of drip fertigation in combination with or without N fertilizers on vegetative growth, flowering quality, nutrients concentration in plants and soil fertility after the harvest of zinnia ( Zinnia elegans). A field experiment was conducted using a randomized complete block split plot design with two systems of drip irrigation (surface and subsurface drip irrigation) and 4 nitrogen rates (0, 30, 60, and 120 kg∙ha–1) as the main and split plots, respectively. The results revealed that vegetative growth rate, flowering characteristics , plant chemical contents, plant uptake and available soil from N, P, K, Fe, Mn, and Zn of zinnia increased significantly with increasing N level up to 120 kg∙ha–1. A similar trend was also found in the post-harvest soil fertility and nutrient uptake that approved the importance of drip fertigation with N fertilizers. Subsurface drip irrigation system was found to be more efficient than surface drip irrigation system to obtain maximum yield accompanied by the highest nutrients concentration in zinnia plants and soil fertility after harvest. <![CDATA[Impact of nitrification inhibitor with organic manure and urea on nitrogen dynamics and N<sub>2</sub>O emission in acid sulphate soil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100108&lng=en&nrm=iso&tlng=en ABSTRACT The accurate prediction of N transformation is an important requisite for optimizing N use efficiency in cropping systems. An incubation study was conducted to verify the impacts of nitrification inhibitor (NI) with organic manure (OM) and urea on N dynamics and N2O emission in acid sulphate soil. The conducted experiment was two-level factorial with 4 N sources (N1 = 100% of N from urea, N2 = 75% of N from urea + 25% N from rice straw, N3 = 75% of N from urea + 25% of N from cow dung and N4 = 75% of N from urea + 25% of N from poultry dung) and two levels of NI (with and without DCD). The NI (Dicyandiamide - DCD) with OM + urea enhanced mineral N contents and it was the highest (255.07 µg∙g-1) for urea with DCD applications. The highest net N-mineralization (213.07 µg∙g-1) was recorded for the application of urea with DCD and net nitrification (16.26 µg∙g-1) was recorded for the application of urea alone, but the highest cumulative N2O emission (5.46 µg∙g-1) was in urea + poultry dung (PD). In addition, DCD most effectively inhibited net nitrification (28.78%) and N2O emission (32.40%) from cow dung (CD) and urea in the tested soils. The combination of DCD with CD and urea was more effective in reducing N2O emissions (43.69%). These results suggest that the DCD with CD and urea may be the most potential combination to reduce nitrification and N2O emission as well as N loss from acid sulphate soil. <![CDATA[Variation in the sugar yield in response to drying-off of sugarcane before harvest and the occurrence of low air temperatures]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052016000100118&lng=en&nrm=iso&tlng=en ABSTRACT The need to irrigate sugarcane in the Brazilian Savanna is due to the lack of rain from April to September. For efficient sugar accumulation, the crop needs water stress or heat stress at the maturation stage. However, when the water deficit is intense at this stage, it occurs the reduction in crop production. The objective of this study was: (i) to assess the quality of the raw material of sugarcane in different drying-off seasons before harvest; (ii) to evaluate the influence of heat stress on the culture. The experiment was conducted in Santo Antônio de Goiás (GO), Brazil, in Oxisol, with CTC4 variety in cane-plant cycle. A randomized block design in a split-plot array in time was used. The treatments of the plots were five drying-off times (90, 60, 30, 15 and 0 days before harvest) and, in the subplots, five seasons of the yield evaluation. Irrigation was carried out by surface drip method, which provided 50% of crop water requirement. The best results for sugar yield occurred 30 days before harvest, period in which the crop irrigation could be interrupted. The water deficit of 37.76 mm appears to be the critical limit of water shortage in the soil, from which the sugarcane yield starts to be reduced. The sugar concentration in the stalk was more influenced by low air temperatures than sugarcane yield.<hr/>ABSTRACT A necessidade de irrigar a cana-de-açúcar no Cerrado deve-se à escassez de chuvas durante o período de abril a setembro. Para o acúmulo eficiente de açúcar, a cultura necessita de estresse hídrico ou térmico na fase da maturação. Porém, quando o déficit hídrico é intenso nessa fase, ocorre a redução na produção da cultura. Assim, o objetivo do presente trabalho foi: (i) avaliar a qualidade da matériaprima da cana-de-açúcar em diferentes épocas de interrupção da irrigação antes da colheita; (ii) avaliar a influência do estresse térmico sobre a cultura. O experimento foi conduzido em Santo Antônio de Goiás (GO), Brasil, em Latossolo Vermelho-Amarelo, com a variedade CTC4 no ciclo de cana-planta. Utilizou-se o delineamento de parcelas subdividas no tempo. Os tratamentos das parcelas foram cinco épocas de interrupção da irrigação (90, 60, 30, 15 e 0 dias antes da colheita) e, nas subparcelas, cinco épocas de avaliação da produção. A irrigação foi feita por gotejamento superficial, com déficit de 50%. Os melhores resultados da qualidade da matéria-prima ocorreram aos 30 dias antes da colheita, período em que a irrigação poderia ser interrompida. O déficit hídrico de 37,76 mm parece ser o limite crítico da falta de água no solo, a partir do qual a produtividade de colmos começa a ser reduzida. A concentração de açúcar no colmo foi mais influenciada pelas baixas temperaturas do ar que a produtividade de colmos.