Method To Evaluate The Efficiency Of Manual Overhead Irrigation In Citrus Rootstock Liner Production

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Brazil produces grafted citrus seedlings in closed screen houses to reduce pest and disease incidence. Irrigation is usually performed by hand using either breaker nozzles or drilled polyvinyl chloride (PVC) pipe wands on garden hoses. Rootstocks are produced in cone-shaped containers filled with soilless potting mix. Since the containers have a small upper diameter, nutrient solution capture is reduced with the potential to cause environmental contamination from inefficient fertigation. This study provides a method to assess the efficiency of manual overhead irrigation systems used in liner production. The method consists of determining both the volume of water applied and volume lost (i.e., directly and by percolation) in order to obtain an estimate of the percentage of water loss, irrigation efficiency, and the drainage fraction. The method was tested in a commercial facility under standard production practices. The method's attributes included simplicity, quick sampling and data collection, and accuracy. The evaluated nursery was found to have low irrigation efficiency (27.14%) and excessive nutrient solution losses (72.86%). Considering an average production of 300,000 liners per year on 20,000 m(2), we determined an annual solution loss of 221.8 m(3) with an average environmental release of 158.9 kg of fertilizer. Therefore, more efficient irrigation systems are necessary for sustainable citrus rootstock liners production.364724735National Council of Technological and Scientific Development (CNPq) [479,394/2006-7, 479,665/2009-5]CAPES (Ministry of Education, Brazil)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Method to evaluate the efficiency of manual overhead irrigation in citrus rootstock liner production

Brazil produces grafted citrus seedlings in closed screen houses to reduce pest and disease incidence. Irrigation is usually performed by hand using either breaker nozzles or drilled polyvinyl chloride (PVC) pipe wands on garden hoses. Rootstocks are produced in cone-shaped containers filled with soilless potting mix. Since the containers have a small upper diameter, nutrient solution capture is reduced with the potential to cause environmental contamination from inefficient fertigation. This study provides a method to assess the efficiency of manual overhead irrigation systems used in liner production. The method consists of determining both the volume of water applied and volume lost (i.e., directly and by percolation) in order to obtain an estimate of the percentage of water loss, irrigation efficiency, and the drainage fraction. The method was tested in a commercial facility under standard production practices. The method's attributes included simplicity, quick sampling and data collection, and accuracy. The evaluated nursery was found to have low irrigation efficiency (27.14%) and excessive nutrient solution losses (72.86%). Considering an average production of 300,000 liners per year on 20,000 m(2), we determined an annual solution loss of 221.8 m(3) with an average environmental release of 158.9 kg of fertilizer. Therefore, more efficient irrigation systems are necessary for sustainable citrus rootstock liners production.364724735CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES479,394/2006-7; 479,665/2009-5Sem informaçã

VLT/NACO adaptive optics imaging of the TY CrA system - A fourth stellar component candidate detected

We report the detection of a possible subsolar mass companion to the triple young system TY CrA using the NACO instrument at the VLT UT4 during its commissioning. Assuming for TY CrA a distance similar to that of the close binary system HD 176386, the photometric spectral type of this fourth stellar component candidate is consistent with an ~M4 star. We discuss the dynamical stability of this possible quadruple system as well as the possible location of dusty particles inside or outside the system.Comment: 4 pages, 2 figures postscrip

Kalman-filter control schemes for fringe tracking. Development and application to VLTI/GRAVITY

The implementation of fringe tracking for optical interferometers is inevitable when optimal exploitation of the instrumental capacities is desired. Fringe tracking allows continuous fringe observation, considerably increasing the sensitivity of the interferometric system. In addition to the correction of atmospheric path-length differences, a decent control algorithm should correct for disturbances introduced by instrumental vibrations, and deal with other errors propagating in the optical trains. We attempt to construct control schemes based on Kalman filters. Kalman filtering is an optimal data processing algorithm for tracking and correcting a system on which observations are performed. As a direct application, control schemes are designed for GRAVITY, a future four-telescope near-infrared beam combiner for the Very Large Telescope Interferometer (VLTI). We base our study on recent work in adaptive-optics control. The technique is to describe perturbations of fringe phases in terms of an a priori model. The model allows us to optimize the tracking of fringes, in that it is adapted to the prevailing perturbations. Since the model is of a parametric nature, a parameter identification needs to be included. Different possibilities exist to generalize to the four-telescope fringe tracking that is useful for GRAVITY. On the basis of a two-telescope Kalman-filtering control algorithm, a set of two properly working control algorithms for four-telescope fringe tracking is constructed. The control schemes are designed to take into account flux problems and low-signal baselines. First simulations of the fringe-tracking process indicate that the defined schemes meet the requirements for GRAVITY and allow us to distinguish in performance. In a future paper, we will compare the performances of classical fringe tracking to our Kalman-filter control.Comment: 17 pages, 8 figures, accepted for publication in A&

Decadal-centennial scale monsoon variations in the Arabian Sea during the Early Holocene

An essential prerequisite for the prediction of future climate change due to anthropogenic input is an understanding of the natural processes that control Earth's climate on timescales comparable to human-lifespan. The Early Holocene period was chosen to study the natural climate variability in a warm interval when solar insolation was at its maximum. The monsoonal system of the Tropics is highly sensitive to seasonal variations in solar insolation, and consequently marine sediments from the region are a potential monitor of past climate change. Here we show that during the Early Holocene period rapid

The FALCON concept: multi-object spectroscopy combined with MCAO in near-IR

A large fraction of the present-day stellar mass was formed between z=0.5 and z~3 and our understanding of the formation mechanisms at work at these epochs requires both high spatial and high spectral resolution: one shall simultaneously} obtain images of objects with typical sizes as small as 1-2kpc(~0''.1), while achieving 20-50 km/s (R >= 5000) spectral resolution. The obvious instrumental solution to adopt in order to tackle the science goal is therefore a combination of multi-object 3D spectrograph with multi-conjugate adaptive optics in large fields. A partial, but still competitive correction shall be prefered, over a much wider field of view. This can be done by estimating the turbulent volume from sets of natural guide stars, by optimizing the correction to several and discrete small areas of few arcsec2 selected in a large field (Nasmyth field of 25 arcmin) and by correcting up to the 6th, and eventually, up to the 60th Zernike modes. Simulations on real extragalactic fields, show that for most sources (>80%), the recovered resolution could reach 0".15-0".25 in the J and H bands. Detection of point-like objects is improved by factors from 3 to >10, when compared with an instrument without adaptive correction. The proposed instrument concept, FALCON, is equiped with deployable mini-integral field units (IFUs), achieving spectral resolutions between R=5000 and 20000. Its multiplex capability, combined with high spatial and spectral resolution characteristics, is a natural ground based complement to the next generation of space telescopes.Comment: ESO Workshop Proceedings: Scientific Drivers for ESO Future VLT/VLTI Instrumentation, 10 pages and 5 figure

Quantum Cryptography

Quantum cryptography is a new method for secret communications offering the ultimate security assurance of the inviolability of a Law of Nature. In this paper we shall describe the theory of quantum cryptography, its potential relevance and the development of a prototype system at Los Alamos, which utilises the phenomenon of single-photon interference to perform quantum cryptography over an optical fiber communications link.Comment: 36 pages in compressed PostScript format, 10 PostScript figures compressed tar fil

Galactic Centre science with an ELT.

10m-class telescopes such as the VLT and the Keck Telescope have allowed tremendous progress on the understanding of environment of Sgr A*, the supermassive black hole at the Galactic Centre. However, these telescopes and associated instrumentation are reaching limitations which can only be overcome with larger apertures. We will summarise the most recent results in this area: star and gas dynamics, the origin of massive stars in the central parsec, the detection of stars on almost relativistic orbits. We will then anticipate the results that two E-ELT projects, MICADO and EAGLE, are expected to allow

Dynamics of matric potential on substrates of pine and coconut under the action of capillarity

O tamanho médio de partículas e a porosidade dos substratos condicionam as propriedades matriciais, interferindo na capacidade de retenção e de transmissão da água no meio. O conhecimento desses atributos é fundamental em processos de irrigação por capilaridade, para que o molhamento atinja as camadas superiores dos recipientes com níveis de tensão de água facilmente disponível. O presente trabalho teve como objetivo estudar a ascensão de água por capilaridade para determinar a posição mais apropriada do nível de saturação na ascensão capilar em recipientes com substratos de coco e pinus, de textura grossa e fina. Foram efetuados experimentos avaliando a ascensão de água por capilaridade em colunas segmentadas preenchidas com os substratos. Os valores de umidade em cada segmento foram calculados gravimetricamente e relacionados aos de tensão estimados pela curva de tensão dos substratos. Os substratos com textura fina apresentaram melhor elevação de água por capilaridade, com melhor elevação da umidade em níveis de tensão de água disponível. O substrato de coco fino apresentou água disponível em todo o perfil do recipiente, enquanto o de pinus apresentou as camadas superiores do recipiente com água retida em tensões abaixo do ponto de murcha permanente. O substrato fino de coco apresentou os melhores resultados para aplicação na irrigação por capilaridade, permitindo recomendar o seu uso com o nível de saturação posicionado a cinco centímetros do fundo do recipiente por quinze minutos

Dynamics of matric potential on substrates of pine and coconut under the action of capillarity

The average particle size and porosity of substrates affects the matrix properties of root growth media, interfering in water holding and water conductivity capacity through substrates. The knowledge of these attributes is essential in capillary irrigation processes to allow the wetting front reaches upper layers under easily available water tension. The present work had the objective to study the water rise by capillary processes to determine the most favorable position of the saturation level for contained plants for two substrates: coconut fiber and pine bark, with two grain particle sizes: fine and coarse textures. Water rise trails were carried out in segmented columns filled with substrates. The water content in each column segment was estimated in weight basis and related to the values of water tension estimated by the water tension curve for each evaluated substrate. The results showed that fine substrates presented higher water rise with adequate levels of easily available water. The fine coconut substrate presented easily available water in the entire substrate column, unlike pine bark substrate that showed the upper layer with moisture below the wilting point. The fine coconut substrate showed the best results for capillary application, allowing to recommend irrigation schedule using the saturation level at 5 cm during 15 minutes.O tamanho médio de partículas e a porosidade dos substratos condicionam as propriedades matriciais, interferindo na capacidade de retenção e de transmissão da água no meio. O conhecimento desses atributos é fundamental em processos de irrigação por capilaridade, para que o molhamento atinja as camadas superiores dos recipientes com níveis de tensão de água facilmente disponível. O presente trabalho teve como objetivo estudar a ascensão de água por capilaridade para determinar a posição mais apropriada do nível de saturação na ascensão capilar em recipientes com substratos de coco e pinus, de textura grossa e fina. Foram efetuados experimentos avaliando a ascensão de água por capilaridade em colunas segmentadas preenchidas com os substratos. Os valores de umidade em cada segmento foram calculados gravimetricamente e relacionados aos de tensão estimados pela curva de tensão dos substratos. Os substratos com textura fina apresentaram melhor elevação de água por capilaridade, com melhor elevação da umidade em níveis de tensão de água disponível. O substrato de coco fino apresentou água disponível em todo o perfil do recipiente, enquanto o de pinus apresentou as camadas superiores do recipiente com água retida em tensões abaixo do ponto de murcha permanente. O substrato fino de coco apresentou os melhores resultados para aplicação na irrigação por capilaridade, permitindo recomendar o seu uso com o nível de saturação posicionado a cinco centímetros do fundo do recipiente por quinze minutos.2631Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq