890 research outputs found
VINHOS QUE PENSAM - parte III|III GESTÃO NUTRICIONAL DA VINHA: SENSORES MULTIESPECTRAIS ATIVOS PRÓXIMOS
Os objetivos do presente
trabalho:
• caracterizar a concentração de N,
P, K, Ca, Mg, Zn, Mn, e Fe da copa
da vinha, baseada em observações
multiespectrais e análises de
plantas;
• avaliar a possibilidade de utilização
de sensores multiespectrais
ativos próximos na gestão nutricional
da vinha
VINHOS QUE PENSAM - parte II/III UTILIZAÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE DO SOLO NA INSTALAÇÃO E GESTÃO DAS CULTURAS: EXEMPLIFICAÇÃO NA VINHA
o principal objetivo
deste trabalho passou por verificar:
• a relação entre a CEa do solo e os
indicadores de textura;
• se a CEa do solo poderá ser um
parâmetro importante na instalação
e gestão de parcelas de vinha
ou outro tipo de culturas
Green manure legumes affect seasonal soil and leaf CO2 exchange rates in an olive rainfed orchard
Management methods that decrease requirement for agricultural chemicals are needed
to reduce adverse environmental impacts. Moreover, they can play an important role in
atmospheric C02 emission and fixation. We propose green manure legumes to reduce
erosion, soil compaction and nitrate pollution, to improve biodiversity, soil carbon sink
and fertility, to save fossil fuels and to increase yield and the nutritional value of food
products. The research was carried out near Mirandela, Northeast Portugal, on a 15-
year commercial olive orchard (Olea europaea L. cv. Cobrançosa), grown under
rainfed conditions
Sustainable management of olive rainfed orchards by the introduction of leguminous cover crops
The olive sector has a crucial economic, social, cultural and ecological relevance in the
Mediterranean region, where tillage and herbicides application are still generalized practices.
However, these practices oppose the recommendations of UE Common Agricultural Policy and thus,
management methods that decrease requirement for agricultural chemicals are needed to reduce
adverse environmental impacts. Moreover, they can play an important role in atmospheric C01
emission and fixation. We propose green manure legumes to reduce erosion, soil compaction and
nih·ate pollution, to improve biodiversity, soil carbon sink and fertility, to save fossil fuels and to
increase yield and the safety and nutritional value of food products. The 3-yearfield study carried out
in Northeast Portugal revealed that self-reseeding annual legumes is a promising strategy since
increase the summer soil water content, the vegetative growth and the physiological tree pe1jormance,
that was reflected in a 38% higher cumulative yield then tillage techniques.PTDC-AGR-AAM/098326/200
Sequestro de carbono no olival: mito ou realidade?
O homem, através de diversas atividades econom1cas, tem contribuído para o
aumento da concentração de dióxido de carbono (C02) na atmosfera. A queima de
combustíveis fósseis, o fabrico de cimento a partir de carbonatos e a desflorestação com
expansão da área agrícola são as principais atividades humanas associadas à emissão de C02
para a atmosfera . O C02 é um gás com efeito de estufa, capaz de reter radiação térmica,
contribuindo para o aquecimento global. Para mitiga r o aquecimento global têm vindo a ser
promovidos mecanismos que retirem carbono (C) da atmosfera e o fixem em formas inertes
nos ecossistemas terrestres. O sequestro de carbono ocorre principalmente através da
fotossíntese em que organismos fotossintéticos como as plantas fixam carbono e libertam
oxigénio para a atmosfera. A vegetação terrestre e os solos podem, assim, constituir-se
como importantes reservatórios de carbono e contrariar a tendência de aumento da
concentração de C02 na atmosfera.
Atendendo a que os apoios comunitários na nova PAC serão sobretudo concedidos
em função dos serviços ecossistémicos que os diferentes setores prestarem à sociedade e
que o sequestro de carbono é um dos principais serviços ecossistémicos que a agricultura
pode prestar, apresenta-se uma estimativa do carbono que um olival tradicional de sequeiro
(árvores mais solo) pode fixar nos primeiros 10 anos de vida a seguir à instalação. Foi tido
em conta a quantidade de folhas, raminhos, casca e lenho de cada um dos diversos
componentes da árvore, a percentagem de matéria orgânica e o teor de carbono na matéria
orgânica de cada um daqueles componentes. No solo, foi tido em conta o potencial de
acumulação de carbono no solo estimado a partir de uma situação inicial de solo mobilizado
passando para uma situação em que se permite o desenvolvimento de vegetação herbácea
no coberto.
Assim, uma árvore bem desenvolvida com 10 anos de idade representa uma
quantidade de carbono de 9, 71 kg árvore·1 [75% na parte aérea (medida) e 25% na parte
radicular (estimada)], o que representa 2,0 t C _ha·1
• No solo, se durante 10 anos forem
implementadas medidas que promovam o acréscimo em 1% no teor de matéria orgânica do
solo (profundidade 0-20 cm) relativamente à massa total do solo, serão fixadas 14 t C ha-1
Managing soils for mitigation and adaptation of rainfed olive trees to climate change
The olive sector has an important economic, social, cultural and ecological relevance in the
Mediterranean region, where tillage still is a generalized practice, although the
recommendations of UE policy for a more sustainable agriculture. In fact, tillage has negative
side-effects, including increased soil erosion and high labor and fuel requirements, and relevant
changes on soil quality indicators, as bulk density, porosity, water-holding capacity, organic
matter content and microbial activity. The study conducted in two different rainfed orchards (cv.
Cobrançosa) of Northeast Portugal revealed that cover crops with self-reseeding legumes of
short-cycle, with mulch of dead vegetation during the dry season, and a permanent sward
grazed with a flock of sheep, are better options for soil management in olive tree rainfed
orchards. Both practices influence positively the olive tree water status during the drought
season, as well the nutritional status, contributing to greater physiological performance during
the summer, as evidenced by higher net photosynthetic rate, mainly due to inferior stomatal
limitations, and enhanced yield. Moreover, these less disruptive agronomic practices increased
the levels of total and easily extractable glomalin, a thermostable hydrophobic glycoprotein
produced by arbuscular mycorrhizal fungi, that play an important role in the stability of soil
aggregates and in the sequestration of nitrogen and carbon. These results indicate that these
practices should be included in the portfolio of management strategies against climate change,
contributing to the sustainability of rainfed orchards under a changing environment.This work was funded by the INTERACT project – “Integrative Research in
Environment, Agro-Chains and Technology”, no. NORTE-01-0145-FEDER-000017, in its lines
of research entitled ISAC, co-financed by the European Regional Development Fund (ERDF)
through NORTE 2020 (North Regional Operational Program 2014/2020).info:eu-repo/semantics/publishedVersio
Comparing N recovery from legumes grown as green manures in olive orchards
Green manuring is probably the only option for extending on a great scale the acreage of organic
fanning in the perennial crops of the Mediterranean basin such as olive groves. Olive growers, in
general, do not have animals so the availability of organic manures is not sufficient to maintain soil
fertility. In addition, the organic composts approved for organic farming on the market have high
prices and are sometimes speculative, in relation to their fertiliser value (Rodrigues et al., 2006). In
NE Portugal there is a long tradition in the cultivation of white lupin (Lupinus a/bus) as a means of
improving soil fertility. However, little is known about the dry matter yield and N fixation potential
of lupin in these agrosystems, and also of the transfer of fixed N to the trees. In this work the results
of dry matter yield and N recovery by lupin, vetch (Vicia villosa) and a mixture of self-reseeding
annual legumes are presented. The trial also included plots of oats (Avena saliva) and natural
vegetation
Battery-like behavior of Ni-ceria based systems: synthesis, surface defects and electrochemical assessment
NiO, CeO2 and respective composites are extensively used in energy storage devices due to mostly their high electrochemical activity. However, the assessment of battery-like behavior of Ni-ceria based systems comprising (Ni or Gd)-doped ceria combined with NiO seems to be neglected in the literature. In this work, NiO and ceria-based solid solutions composite powders were obtained by a co-precipitation synthesis method. The structure and particle size of the calcined powders were investigated by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM), respectively. Oxidative states of composites were inspected by X-ray photoelectron spectroscopy (XPS). The electrochemical performance of powders was evaluated by cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy. Refinement of the XRD patterns showed that powders have nanosized crystallites and mean size of particles within 20 – 70 nm were revealed by FESEM. The improved specific capacity of the NiO-CeO2 electrode material (about 2.5 times higher than that of NiO-CGO at 5 mV s−1) is due to an increase in Faradic reactions taken place on its surface with a higher fraction of defects (namely Ni3+, Ce3+ and oxygen vacancies), as determined by XPS. The superior electrochemical performance of the NiO-CeO2 electrode is also confirmed by electrochemical impedance spectroscopy.publishe
On a class of 4D Kahler bases and AdS_5 supersymmetric Black Holes
We construct a class of toric Kahler manifolds, M_4, of real dimension four,
a subset of which corresponds to the Kahler bases of all known 5D
asymptotically AdS_5 supersymmetric black-holes. In a certain limit, these
Kahler spaces take the form of cones over Sasaki spaces, which, in turn, are
fibrations over toric manifolds of real dimension two. The metric on M_4 is
completely determined by a single function H(x), which is the conformal factor
of the two dimensional space. We study the solutions of minimal five
dimensional gauged supergravity having this class of Kahler spaces as base and
show that in order to generate a five dimensional solution H(x) must obey a
simple sixth order differential equation. We discuss the solutions in detail,
which include all known asymptotically AdS_5 black holes as well as other
spacetimes with non-compact horizons. Moreover we find an infinite number of
supersymmetric deformations of these spacetimes with less spatial isometries
than the base space. These deformations vanish at the horizon, but become
relevant asymptotically.Comment: 34 pages, 3 figures. v2: formula (8.35) and other minor typos
corrected; references added; accepted for publication in JHE
Use of kaolin as a reflective clay improves olive tree physiological and yield responses under different environmental conditions
Olive tree (Olea europaea L.) growing area is threatened by the current and predicted adverse environmental
conditions, affecting negatively plant performance and yield. Thus, agronomic strategies to offset those negative effects
and improve olive orchards sustainability need to be implemented. In this regard, we propose the use of kaolin particle
film, a natural heat and irradiance reflecting clay. To achieve a more comprehensive response about kaolin (5%)
action, during two consecutive years we performed two different experiments, in different geographical locations of
Portugal north-west with “Cobrançosa” cultivar: established olive trees under conventional rainfed conditions and
under deficit irrigation (27.5% of ETc). Generally, during the summer period, kaolin was effective in improving water
status and photosynthetic response, by reducing both stomatal and non-stomatal limitations. Moreover, improved leaf
gas exchange restauration after the first rains persists during the winter months in rainfed conditions. Kaolin also
reduces leaf sclerophylly, inducing shade-related leaf characteristics. As a result of better physiological performance
achieved with kaolin application, yield increased 97% and 54.6% in rainfed and deficit irrigation conditions,
respectively. Overall, the results of the present investigation revealed a cost-effective strategy to attenuate the negative
effects of summer stress in olive trees, while allows to save water. Ultimately, this practice might contribute to increase
the sustainability and competitiveness of this sector and anticipate solutions to the negative effects of climate change.This work was funded by the INTERACT project – “Integrative Research in Environment, Agro-Chains and Technology”, no. NORTE-01-0145-FEDER-000017, in its line of research entitled ISAC, co-financed by
the European Regional Development Fund (ERDF) through NORTE 2020 (North Regional Operational Program
2014/2020).info:eu-repo/semantics/publishedVersio
- …