96 research outputs found
EFEITO DA FERTILIZAÇÃO AZOTADA NA DINÂMICA DE
RESUMO
Este trabalho teve como objectivo estudar
a influência da aplicação de diferentes
quantidades de azoto, repartidas por quatro
aplicações, na disponibilidade de azoto nítrico
no solo, no comprimento radical, na
concentração de azoto nas folhas e na produção
comercial de cebola de dias médios
(cv. Gilmar) no Alentejo. O ensaio decorreu
na Centro de estudos e experimentação da
Mitra da Universidade de Évora e foi delineado
em blocos casualizados com quatro
repetições. Os tratamentos consistiram em 4
níveis de adubação azotada (0, 37, 74 e 111
kg N ha-1), repartidos por quatro aplicações.
A disponibilidade de azoto nítrico no solo,
o comprimento radical e a concentração de
azoto nas folhas foram avaliados aos 33, 57,
96 e 127 dias após a plantação. A densidade
radical (cm cm-3) sob o bolbo e a 4 cm da
linha de cultura, nas diferentes datas e profundidades
de amostragem, não foi afectada
pelos níveis de azoto. Ao longo ciclo, 65 a
100 % das raízes, em termos de comprimento
radical, concentraram-se sob o bolbo e a
densidade radical máxima alcançada foi de
1,88 cm cm-3. A profundidade máxima de
enraizamento situou-se entre os 20 e 30 cm,
não ultrapassando os 10 cm de profundidade
até aos 32 dias após a plantação. Nas condições
do ensaio, os resultados indicam como
recomendável uma aplicação de 30 kg ha– 1
de azoto à plantação e um aumento da quantidade
de azoto aplicado (16,2% do total de
N aplicado), no início da formação do bolbo.
A produção comercial aumentou com o nível
de azoto, mas as produções obtidas com a
aplicação de 74 kg ha-1 (5,12 kg m-2) e de 111
Kg N ha-1 (6,59 kg m-2) não diferiram significativamente.
Palavras-chave: Allium cepa L, azoto nítr
O Desafio dos Recursos Hídricos em Cabo Verde
É paradoxal que localizando-se o arquipélago de Cabo Verde no meio do oceano, a sua população sofra de
carência de água.
Na verdade, essa carência é de água de qualidade, com baixo teor em sais, adequada para o consumo humano e
agricultura. Ao longo dos séculos o engenho dos habitantes, aliado ao trabalho duro, tem permitido às
populações locais lutar com as condições climáticas adversas e produzir o seu sustento recorrendo a poços,
galerias e furos.
Este trabalho pretende retratar a situação atual e os recursos disponíveis em Cabo Verde, bem como as formas
encontradas para exponenciar os escassos recursos hídricos existentes e garantir a sustentabilidade da
população crescente do país.
Pode dizer-se que a dependência centenária das águas subterrâneas está a diminuir gradualmente, à medida
que diminuem as suas disponibilidade e se vai degradando a sua qualidade. Situação esta que levou a que se
tenha recorrido a novas formas de obter da água, caso da dessalinização da água do mar e se tenha
intensificado a captação das águas superficiais.
A dessalinização é atualmente indispensável para abastecer os grande centros populacionais, apesar do elevado
consumo energético que lhe está associado e da manifesta insuficiência e reduzida eficiência das redes de
distribuição existentes. No entanto, o investimento em infra-estruturas de abastecimento de água em zonas
rurais é uma ferramenta demográfica importante e deve ser utilizado para evitar o êxodo rural.
O atual investimento do estado em barragens e grandes diques é uma aposta correta para satisfazer as
necessidades agrícolas. No entanto, a experiência do passado tem demonstrado a necessidade de construção
simultânea de obras de correção fluvial e de um conjunto significativo de pequenos diques nas bacias de
captação para evitar o assoreamento rápido das novas barragens
Hargreaves and other reduced-set methods for calculating evapotranspiration
This edition of Evapotranspiration - Remote Sensing and Modeling contains 23 chapters related to the modeling and simulation of evapotranspiration (ET) and remote sensing-based energy balance determination of ET. These areas are at the forefront of technologies that quantify the highly spatial ET from the Earth's surface. The topics describe mechanics of ET simulation from partially vegetated surfaces and stomatal conductance behavior of natural and agricultural ecosystems. Estimation methods that use weather based methods, soil water balance, the Complementary Relationship, the Hargreaves and other temperature-radiation based methods, and Fuzzy-Probabilistic calculations are described. A critical review describes methods used in hydrological models. Applications describe ET patterns in alpine catchments, under water shortage, for irrigated systems, under climate change, and for grasslands and pastures. Remote sensing based approaches include Landsat and MODIS satellite-based energy balance, and the common process models SEBAL, METRIC and S-SEBS. Recommended guidelines for applying operational satellite-based energy balance models and for overcoming common challenges are made
Influence of Soil and Irrigation Management on the Quality of Seedless Crimson Table Grapes
The market for table grapes is moving into mass production of specialty seed-less
grapes in covered areas, aiming at obtaining premium prices with early or late
production of high quality products. Production of quality seedless grapes is not
straightforward since it is requires the correct combination of various independent
characteristics, such as color, sugars, size and quantity at the right moment for
successful harvesting and marketing. The present study was carried out at the two
largest Portuguese producers located in Alentejo, and has the objective of studying the
effect of irrigation management strategies and two different soils on the various
relevant parameters for successful production and marketing. The management
strategies were the application of ten day stress at the end of the cycle, in order to
promote early maturing of the grapes.
Three different timings of the stress were applied. Soil moisture, sap flow, bark
thickness, as well as leaf water potential, stomatal conductance and chlorophyll content
were measured regularly during the production season. The results indicate that the
roots explore a rather large soil volume and the plants can successfully withstand
reasonable periods of drought without significant changes to the plant physiology.
Additionally late rains can mask the effect of any farmer applied drought and invalidate
any farmer induced stress to the plants. Water-logged soils tend to cause early onset of
maturity, but cause the ripening stage to extend over a longer period of time, and thus,
in effect result in a delay in the harvest date. Topography also has some effect on the
ripening, since hot air tends to accumulate under the plastic at the higher areas of the
field.
This work is funded by PRODER, 4.1, within the scope of project MORECRIMSO
Desenvolvimento dum sistema de rega automático, autónomo e adaptativo – estudo comparativo de cinco métodos para o cálculo da ETo
Para efeitos de desenvolvimento dum sistema de rega automático, são estudados e calibrados cinco métodos de cálculo de Evapotranspiração de referência (Priestley-Taylor, Makkink, Hargreaves, Turc, Jensen-Haise) utilizando apenas os parâmetros climáticos temperatura, T, e radiação solar, Rs. O estudo envolve o cálculo da Evapotranspiração para todos os dias do ano hidrológico 2005/06 e a sua comparação com o método de Penman-Monteith. A estação escolhida para o estudo é a estação de Divor.
Nas condições do estudo (Sul da Península Ibérica) os melhores resultados são obtidos com os métodos de Priestley-Taylor e Jensen-Haise. São apresentados os coeficientes de calibração para todos os cinco métodos para a zona do estudo, por forma a aproximar ao máximo os resultados aos obtidos pelo método de referência.In order to develop an automatic irrigation system, a set of five different methods for calculating reference evapotranspiration are studied and calibrated (Priestley-Taylor, Makkink, Hargreaves, Turc, Jensen-Haise). These methods use temperature, T, and solar radiation, Rs, to calculate evapotranspiration. Evapotranspiration is calculated for all the days of the 2005/06 hidrological year at the Divor meteorological station. The results are compared to, and calibrated against, the Penman-Monteith method.
The best results are obtained by the Priestley-Taylor and Jensen-Haise methods. Calibration coefficients are also calculated for all five methods, so that the results can be as close as possible to those produced by the Penman-Monteith method
Utilização da equação de Hargreaves Samani para o cálculo da ETo em estufas
PosterA equação de Hargreaves Samani, HS, tem sido utilizada com sucesso para o cálculo da Evapotranspiração,
Eto, ao ar livre. Os resultados indicam uma boa correlação entre a Eto obtida por este método e a obtida
pelo método de Penman-Monteith, PM, que exige um conjunto maior de parâmetros. Até a data pouco se
sabe sobre a aplicabilidade da equação de HS em agricultura protegida. Neste ensaio foram instalados minilisimetros
numa estufa na Herdade de Mitra, Évora. A cultura utilizada foi a relva, por forma a eliminar a
necessidade de determinação exacta do coeficiente cultural. Foram medidos em intervalos de 15 minutos a
Temperatura do ar, radiação, Humidade Relativa e o vento no interior e exterior da estufa. A equação de
HS foi calibrada com base nos valores dos lisimetros e com base na equação de PM. Os resultados indicam
que no interior da estufa há uma diminuição da radiação em 44%, e o aumento da temperatura máxima em
2,4ºC e da temperatura mínima em 3,7ºC. A utilização da estufa permitiu uma poupança de água de 42% A
equação de HS resulta em boas estimativas de Eto, desde que seja devidamente calibrada para a radiação no
interior da estufa. A inclusão da radiação no cálculo da Eto pela equação de HS não melhora os resultados--------------------------ABSTRACT----The Hargreaves Samani equation, HS, has been used successfully for calculating Evapotranspiration, Eto,
in open air. The results indicate a good correlation between Eto obtained with this method and that obtained
through the Penman- Monteith, PM, method, which requires a larger number of parameters. Until now,
little is known about the use of the HS equation in greenhouses. In this work, mini-lysimeters were installed
in a greenhouse at the Mitra Experimental Farm, in Évora. Lawn was used as the crop, in order to eliminate
the need for the exact determination of the crop coefficient. Air temperature, radiation, relative humidity
and wind were measured at 15 minute intervals inside and outside of the greenhouse. The HS equation was
calibrated based on the values from the lysimeters and the PM equation. The results indicate that inside the
greenhouse the radiation decreases by 44%, maximum temperature increases by 2.4ºC and the minimum
temperature by 3,7ºC. The use of greenhouse resulted in a water saving of 42%. The HS equation results in
good estimates of Eto once it has been calibrated for the radiation intensity inside the greenhouse. The
inclusion of the radiation in the calculation of Eto by the HS equation did not improve the results
Drip irrigation using a PLC based adaptive irrigation system
Most of the water used by man goes to irrigation. A major part of this water is used to irrigate small plots where it is not feasible to implement full-scale Evapotranspiration based irrigation controllers. During the growth season crop water needs do not remain constant and varies depending on the canopy, growth stage and climate conditions such as temperature, wind, relative humidity and solar radiation. Thus, it is necessary to find an economic irrigation controller that can adapt the daily water application to the plant needs. The dramatic development of Programmable Logic Controllers, PLCs, and their rather affordable price has made it possible to use them as stand-alone irrigation controllers. In this paper a PLC is used to adapt the daily irrigation amount to actual ETc, using a Hargreaves-Samani type equation. This equation only requires temperature values to calculate Evapotranspiration. Once the ETc is calculated, then the PLC manages the irrigation according to the characteristics of the field, the irrigation equipment and the growth stage of the crop. First year results are very encouraging and indicate a 12% saving in irrigation water. It was also found that heat flux form the soil can influence canopy temperature.The development of this study was funded by the Fundação para a Ciência e a Tecnologia (FCT) research project PTDC/AGR-AAM/81271/2006: “Desenvolvimento dum controlador de rega adaptativo, autónomo e automático”
Optimizing rain harvesting for Mediterranean climate
Most of the urban landscaped areas are watered with drinking water from the city utility. This
represents a waste of energy used to pump the water all the way into urban areas, as well as a waste of
chemicals and energy used to purify the water for human consumption. This paper analysis the feasibility of
harvesting rainwater over buildings in Mediterranean climate, and storing them, for use in irrigation. The
results indicate that a typical house can annually save between 3000 and 11000 l of water through rain
harvesting. A simulation model is elaborated that can calculate optimize the relation between catchment area,
irrigated area and tank size, based on daily rainfall and evapotranspiration of a five year period
Water saving with a PLC based adaptive irrigation system
Irrigation is presently the main user of world´s fresh water. Most of it goes to irrigating small plots
where it is not feasible to implement full-scale Evapotranspiration based irrigation controllers. The dramatic
development of Programmable Logic Controllers, PLCs, and their rather affordable price has made it possible to
use them as stand-alone irrigation controllers. In this paper a PLC is used to adapt the daily irrigation amount to
actual ETc, using a Hargreaves-Samani type equation. Once the ETc is calculated, then the PLC manages the
irrigation according to the specifications given by the farmer. First year results indicate an 8% saving in
irrigation water
Screening of candidate G-quadruplex ligands for the human c-KIT promotorial region and their effects in multiple in-vitro models
Stabilization of G-quadruplex (G4) structures in promoters is a novel promising
strategy to regulate gene expression at transcriptional and translational levels. c-KIT
proto-oncogene encodes for a tyrosine kinase receptor. It is involved in several
physiological processes, but it is also dysregulated in many diseases, including cancer.
Two G-rich sequences able to fold into G4, have been identified in c-KIT proximal
promoter, thus representing suitable targets for anticancer intervention. Herein, we
screened an \u201cin house\u201d library of compounds for the recognition of these G4 elements
and we identified three promising ligands. Their G4-binding properties were analyzed
and related to their antiproliferative, transcriptional and post-transcriptional effects
in MCF7 and HGC27 cell lines. Besides c-KIT, the transcriptional analysis covered a
panel of oncogenes known to possess G4 in their promoters.
From these studies, an anthraquinone derivative (AQ1) was found to efficiently
downregulate c-KIT mRNA and protein in both cell lines. The targeted activity of AQ1
was confirmed using c-KIT\u2013dependent cell lines that present either c-KIT mutations
or promoter engineered (i.e., \u3b1155, HMC1.2 and ROSA cells).
Present results indicate AQ1 as a promising compound for the target therapy
of c-KIT-dependent tumors, worth of further and in depth molecular investigations
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