Teor de clorofila e produtividade do feijoeiro em razão da adubação nitrogenada

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Drought tolerance is associated with rooting depth and stomatal control of water use in clones of Coffea canephora

center dot Background and Aims Drought is a major environmental constraint affecting growth and production of Coffea canephora. Selection of C. canephora clones has been largely empirical as little is known about how clones respond physiologically to drought. Using clones previously shown to differ in drought tolerance, this study aimed to identify the extent of variation of water use and the mechanisms responsible, particularly those associated morphological traits.center dot Methods Clones (14 and 120, drought-tolerant; 46 and 109A, drought-sensitive, based on their abilities to yield under drought) were grown in 120-L pots until they were 12-months old, when an irrigation and a drought treatment were applied; plants were droughted until the pressure potential (Psi(x)) before dawn (pre-dawn) reached -3.0 MPa. Throughout the drought period, Psi(x) and stomatal conductance (g(s)) were measured. At the end of the experiment, carbon isotope ratio and parameters from pressure-volume curves were estimated. Morphological traits were also assessed.center dot Key Results and Conclusions With irrigation, plant hydraulic conductance (K-L), midday Psi(x) and total biomass were all greater in clones 109A and 120 than in the other clones. Root mass to leaf area ratio was larger in clone 109A than in the others, whereas rooting depth was greater in drought-tolerant than in drought-sensitive clones. Predawn Psi(x) of -3.0 MPa was reached fastest by 109A, followed progressively by clones 46, 120 and 14. Decreases in g(s) with declining Psi(x), or increasing evaporative demand, were similar for clones 14, 46, and 120, but lower in 109A. Carbon isotope ratio increased under drought; however, it was lower in 109A than in other clones. For all clones, Psi(x), g(s) and KL recovered rapidly following re-watering. Differences in root depth, KL and stomatal control of water use, but not osmotic or elastic adjustments, largely explained the differences in relative tolerance to drought stress of clones 14 and 120 compared with clones 46 and 109A.

Nitrogênio em cobertura e molibdênio via foliar no feijoeiro irrigado cultivado em solo de cerrado

O nitrogênio é o nutriente exigido em maior quantidade pelo feijoeiro e, mesmo quando suprida adequadamente desse nutriente, a planta de feijão pode ter sua produtividade limitada pela deficiência de molibdênio, pela participação deste no metabolismo do nitrogênio. O objetivo deste trabalho foi avaliar a resposta do feijoeiro (Phaseolus vulgaris L.), cultivar 'BRS Pontal', irrigado, à aplicação de nitrogênio em cobertura e molibdênio via foliar, quando cultivado em Neossolo Quartzarênico, no município de Cassilândia, MS. O delineamento experimental foi o de blocos ao acaso, no esquema fatorial 4x2, com quatro repetições. Os tratamentos foram constituídos de quatro doses de nitrogênio (0, 30, 60 e 120 kg ha-1) aplicados em cobertura, utilizando como fonte a ureia, e pela aplicação ou não de molibdênio (80 g ha-1) via foliar, na forma de molibdato de amônio. O índice relativo de clorofila nas folhas do feijoeiro foi aumentado pela aplicação de nitrogênio em cobertura e molibdênio via foliar. A aplicação de nitrogênio em cobertura proporcionou aumento na produtividade de grãos do feijoeiro apenas quando combinado com o fornecimento de molibdênio via foliar. O fornecimento de 80 g ha-1 de molibdênio via foliar aumentou a eficiência de utilização do nitrogênio pelo feijoeiro.

Eficiência de absorção, transporte e utilização de macronutrientes por porta-enxertos de caramboleira, cultivados em soluções nutritivas

O estado nutricional de plantas cultivadas em solução nutritiva pode ser influenciado pelo tipo de solução utilizada, afetando desta forma seu adequado crescimento. Com este trabalho, objetivou-se avaliar a exigência nutricional de porta-enxertos de caramboleira, cultivados em quatro diferentes soluções nutritivas. O delineamento experimental empregado foi inteiramente casualizado, com três repetições, tendo como tratamentos as quatro soluções. Como solução padrão foi utilizada a de Hoagland & Arnon, comparada à outras três soluções. O experimento foi conduzido em condições de casa-de-vegetação, em recipientes plásticos com 8 L de capacidade. Após 150 dias do transplantio, foram determinados a matéria seca e o teor de nutrientes, inferindo-se o conteúdo dos macronutrientes na planta. Com esses resultados calculou-se os índices: eficiência de absorção; eficiência de transporte e eficiência de utilização dos nutrientes. As soluções nutritivas de Sarruge, de Castellane & Araújo e de Furlani foram semelhantes na produção de matéria seca das plantas de caramboleira. O uso da solução nutritiva de Hoagland & Arnon resultou em menor produção de matéria seca das caramboleiras, e, também, menor eficiência de utilização de Ca e Mg pelas plantas. A eficiência de transporte dos nutrientes foi a mais afetada pelas soluções nutritivas utilizadas, enquanto a eficiência de utilização dos nutrientes sofreu pouca variação em função das soluções empregadas.

Nitrogen management in maize cover crop rotations

Winter cover crops can affect N nutrition of the following maize crop. Although legumes have been recommend for maize rotations, in tropical areas grasses may be more interesting because they provide a longer protection of soil surface. Legumes can add N to the system and grasses can compete with maize for the available nutrient. An experiment was conducted in Botucatu, São Paulo State, Brazil, to study N dynamics in the soil surface straw-maize system as affected by N fertilization management and species included in the no-till rotation. Treatments were fallow, black oat (Avena strigosa), pearl millet (Pennisetum glaucum), white lupins (Lupinus albus), black oat fertilized with N. and pearl millet fertilized with N. Maize was grown afterwards in the same plots, receiving 0.0, 60.0 and 120.0 kg ha(-1) of N sidedressed 30 days after plant emergence. Soil, straw and maize samples were taken periodically. The highest corn yields were observed when it was cropped after pearl millet fertilized with N. Nitrogen side dressed application up to 120 kg ha(-1) was not able to avoid corn yield decrease caused by black oat. Grasses can be recommended in maize rotations in tropical areas, provided they receive nitrogen fertilizer and show no allelopathy. Due to its higher ON ratio and dry matter yield they are better than legumes, protecting the soil surface for a longer period. Pearl millet is particularly interesting because it enhances N use efficiency by the following maize crop. For a better N availability/demand synchronism, the cover crops should be desiccated right before maize planting.

Growth parameters and nutrient content in four multipurpose tree species with potential characteristics for agroforestry systems in a Cerrado region in Botucatu, São Paulo State, Brazil

In order to evaluate growth characteristics, adaptability, biomass production, nutrient recycling, nutrient distribution and the ability to regenerate degraded land, a trial using four multipurpose tree species (Leucaena leucocephala, Leucaena diversifolia, Acacia melanoxylon and Mimosa scabrella) was undertaken over two years in a distrophic red yellow latosol (oxisol) following a randomized block experimental design with four replications. At the age of two years, A. melanoxylon and L. diversifolia were the tallest species (5.25 and 4.97 m, respectively) and A. melanoxylon and M. scabrella had the largest diameters at 20 cm from tree base. Mimosa scabrella and A. melanoxylon had the highest dry matter production and quantity of nutrients in the above ground biomass. In all species, the highest nutrient contents were found in the leaves, followed by branches and stems. From all species, the highest Nutrient Utilization Efficiency Indexes were obtained for sulphur, phosphorous, and magnesium; L. diversifolia was the most efficient for nitrogen, potassium, calcium, sulphur, and manganese, while A. melanoxylon was the most efficient for phosphorus, magnesium, boron, iron, and zinc. Litter production levels over a three month period were as follows: M. scabrella > A. melanoxylon > L. diversifolia > L. leucocephala. Litter nutrient content was higher in M. scabrella than in the other species.

Phosphorus and potassium budget in the soil-plant system in crop rotations under no-till

Soil management and crop rotations can affect P and K budget in soil, decreasing losses, and increasing fertilizer use efficiency. The P and K budget in the soil-plant system at depths up to 60. cm was studied for different soil managements and crop rotations under no-till for three years in Botucatu, São Paulo, Brazil. The investigated crop rotations were: triticale (X Triticosecale) and sunflower (Helianthus annuus) cropped in autumn-winter; pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor), and Sunn hemp (Crotalaria juncea) were grown in the spring, as well as an additional treatment with chiseling followed by a fallow period; and soybean (Glycini max, L., Merril) was cropped in the summer. Each year triticale and sunflower were grown in plots and pearl millet, forage sorghum, Sunn hemp and of chisel/fallow in sub-plots. The triticale/millet rotation led to the largest decrease in available P within the 0-0.60. m layer of the soil profile and the largest K increase within the 0-0.05. m layer. Potassium mobility in the soil profile and the increases in the available K content in the 0.40-0.60. m layer were independent of the management system. Crop rotations with or without chiseling are not effective in preventing soil P losses. There is considerable K leaching below 0.60. m, but chiseling and the use of high K accumulating plants as triticale results in lower K losses. © 2012 Elsevier B.V.

Eficiência de utilização de nutrientes por cultivares de batata

The use of cultivars efficient in nutrient use is essential to increase yield and reduce production costs. The objective of this study was to evaluate absorption and nutrients use efficiency on five potato cultivars. The experiment was conduced in Itaí, São Paulo State, Brazil, in winter cropping season of 2008 on Oxisol. The experimental design was randomized blocks with split-plots and four replications. Plots comprised the five potato cultivars and subplots were established by sampling times, performed at planting and every seven days after emergence. At 97 DAP was calculated the nutrients use efficiency for dry matter production and at 122 DAP were calculated the nutrients use efficiency for fresh tuber and tuber dry matter yield. Mondial and Asterix cultivars showed greater dry matter production, higher fresh tubers yield and nutrients accumulation. Nutrients use efficiency for total dry matter and tubers dry matter, was similar among cultivars, but Ágata was more efficient in nutrients use efficiency for fresh tubers yield.

Trocas gasosas, índices fisiológicos e acúmulo iônico em plantas jovens de Annona emarginata (Schltdl.) H. Rainer em solução nutritiva

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Seasonal variation in leaf traits between congeneric savanna and forest trees in Central Brazil: Implications for forest expansion into savanna

The ecology of forest and savanna trees species will largely determine the structure and dynamics of the forest-savanna boundaries, but little is known about the constraints to leaf trait variation imposed by selective forces and evolutionary history during the process of savanna invasion by forest species. We compared seasonal patterns in leaf traits related to leaf structure, carbon assimilation, water, and nutrient relations in 10 congeneric species pairs, each containing one savanna species and one forest species. All individuals were growing in dystrophic oxisols in a fire-protected savanna of Central Brazil. We tested the hypothesis that forest species would be more constrained by seasonal drought and nutrient-poor soils than their savanna congeners. We also hypothesized that habitat, rather than phylogeny, would explain more of the interspecific variance in leaf traits of the studied species. We found that throughout the year forest trees had higher specific leaf area (SLA) but lower integrated water use efficiency than savanna trees. Forest and savanna species maintained similar values of predawn and midday leaf water potential along the year. Lower values were measured in the dry season. However, this was achieved by a stronger regulation of stomatal conductance and of CO2 assimilation on an area basis (A area) in forest trees, particularly toward the end of the dry season. Relative to savanna trees, forest trees maintained similar (P, K, Ca, and Mg) or slightly higher (N) leaf nutrient concentrations. For the majority of traits, more variance was explained by phylogeny, than by habitat of origin, with the exception of SLA, leaf N concentration, and A area, which were apparently subjected to different selective pressures in the savanna and forest environments. In conclusion, water shortage during extended droughts would be more limiting for forest trees than nutrient-poor soils. © 2013 Springer-Verlag Berlin Heidelberg.

Cinética de absorção de silício por cultivares de cana-de-açúcar e de arroz

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Manejo da adubação nitrogenada e utilização do nitrogênio (15N) pelo milho sob plantio direto com diferentes plantas de entressafra

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Eficiência de utilização de nutrientes em híbridos interespecíficos de eucalipto

Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

Níveis de carboidratos em dietas extrusadas para tilápias-do-nilo revertidas ou não sexualmente

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Adubação fosfatada em cultivares de batata (Solanum tuberosum L.)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)