Produção de cebola de dias curtos no Alentejo. Influência da adubação localizada

As baixas temperaturas e o fácil encharcamento da maioria dos solos do Alentejo constituem uma restrição à produção de hortícolas ao ar livre, no Outono-Inverno. A cebola de dias curtos pode constituir uma opção pela sua capacidade para superar estes constrangimentos. Assim, este trabalho teve como objectivo estudar o comportamento de duas cultivares de cebola de dias curtos, plantadas no Outono e a influência da localização da adubação aquando da plantação. O ensaio decorreu na herdade experimental da Mitra da Universidade de Évora e os tratamentos em estudo foram: a cultivar de cebola de dias curtos (“Spring Star” e “Mineutaka”) e o método de aplicação do adubo à plantação (distribuição a lanço e localização do adubo numa faixa a 10 cm ± 2 de profundidade, sob a linha de cultura). A adubação localizada não afectou a densidade radical (cm cm-3) sob a linha de cultura, nem a produção comercial de bolbos a qual foi respectivamente para a “Spring Star” e “Mineutaka” de 8,3 e 9,0 kg m-2. Visto as cultivares estudadas terem apresentado resistência ao excesso de água e às baixas temperaturas que ocorreram durante o ciclo, com produções consideráveis, a cebola de dias curtos apresenta-se como uma cultura com elevado potencial agronómico para o Alentejo. Adicionalmente, dada a época em que é realizada a cultura a água para a rega não será um factor limitante

Prediction of optimal harvest date for processing tomato based on the accumulation of daily heat units over the fruit ripening period.

Author Affiliation: Universidade de Évora, Departamento de Fitotecnia, Mitra 7002-554 Évora, Portugal. Editors: No editors Document Title: Journal of Horticultural Science and Biotechnology Abstract: For maximum yield of processing tomato by once-over mechanical harvesting, an optimum date for harvest has to be selected at the time when the factory-graded fruit yield is at its maximum. By recording the proportion of green, ripe (i.e. turning and red) and rotten (i.e. over-ripe and damaged) fruit over a period of approximately 20 days, the optimal harvest date can be identified. Based on observations taken from crops at 4 sites in the Mediterranean region over 3 years (1997-1999), the proportional change of fruit types (i.e. total fruit weight percentage) was closely related to the accumulation of daily maximum temperature during crop maturation. When the heat units were calculated based on the daily maximum and minimum temperatures by 6 well-known methods, the reduction in green fruit percentage was significantly related to the sum of heat units calculated by all methods. The maximum ripe fruit percentage, approximately 80% of the total fruit weight, occurred soon after the green fruit percentage was equal to the rotten fruit percentage, both approximately 10% of the total fruit weight. Therefore, the heat units required to reduce the green fruit from 25 to 10% of the total fruit weight, calculated by different methods, can be used to accurately predict the optimal harvest date based on the accumulation of ambient temperature. In a range of likely temperature regimes, 7-9 days prediction for optimal harvest date can be made. However, the simplest method based on daily maximum temperature alone is as accurate as all the more complex methods and is likely to find wider application in the processing tomato industry. Publisher: Headley Brothers Ltd., The Invicta Pres

Soil fertility and climate change

Palestra na universidade de Basillicata no ambito do workshop Soil Fertility and climate change

Soil, Water and Nitrates Management in Horticultural Production

The goal of this Special Issue, entitled “Soil Science and Water and Nitrate Management in Horticultural Production”, is to examine recent advances in horticultural practices and strategies that can contribute to maintaining or increasing soil fertility and the efficiency of water and nitrogen use. The decrease in soil fertility, and in the quality and availability of irrigation water, is a reality that is maximized by global warming. On the other hand, nitrogen fertilization may contribute to nitrate leaching and/or the release of gases (carbon dioxide and nitrous oxide), with a great impact on global warming. Therefore, the management of soil, water, and nitrogen is critical to dealing with soil and water degradation, and with climate change. Moreover, such management has a decisive impact on plant growth and the quality of horticultural crops. In this Special Issue, seven scientific contributions were collected that can contribute to an increase in the use of these more sustainable factors. Three papers analyzed the use of organic waste materials as a way to reduce inorganic fertilization, improve soil fertility and plant growth, and promote a circular economy

Chemigation with Micronized Sulfur Rapidly Reduces Soil pH in a New Planting of Northern Highbush Blueberry

Northern highbush blueberry (Vaccinium corymbosum L.) is adapted to acidic soil conditions and often grows poorly when soil pH is greater than 5.5. When soil pH is high, growers will usually mix prilled elemental sulfur (So) into the soil before planting (converted to sulfuric acid by soil bacteria) and, if needed, inject acid into the irrigation water after planting. These practices are effective but often expensive, time consuming, and, in the case of acid, potentially hazardous. Here, we examined the potential of applying micronized So by chemigation through a drip system as an alternative to reduce soil pH in a new planting of ‘Duke’ blueberry. The planting was located in western Oregon and established on raised beds mulched with sawdust in Oct. 2010. The So product was mixed with water and injected weekly for a period of ≈2 months before planting and again for period of ≈2 months in late summer of the second year after planting (to assess its value for reducing soil pH once the field was established), at a total rate of 0, 50, 100, and 150 kg·ha−1 So on both occasions. Each treatment was compared with the conventional practice of incorporating prilled So into the soil before planting (two applications of 750 kg·ha−1 So each in July and Oct. 2010). Within a month of the first application of So, chemigation reduced soil pH (0–10 cm depth) from an average of 6.6 with no So to 6.1 with 50 kg·ha−1 So and 5.8 with 100 or 150 kg·ha−1 So. However, the reductions in pH were short term, and by May of the following year (2011), soil pH averaged 6.7, 6.5, 6.2, and 6.1 with each increasing rate of So chemigation, respectively. Soil pH in the conventional treatment, in comparison, averaged 6.6 a month after the first application and 6.3 by the following May. In July 2012, soil pH ranged from an average of 6.4 with no So to 6.2 with 150 kg·ha−1 So and 5.5 with prilled So. Soil pH declined to as low as 5.9 following postplanting So chemigation and, at lower depths (10–30 cm), was similar between the treatment chemigated with 150 kg·ha−1 So and the conventional treatment. None of the treatments had any effect on winter pruning weight in year 1 or on yield, berry weight, or total dry weight of the plants in year 2. Concentration of P, K, Ca, Mg, S, and Mn in the leaves, on the other hand, was lower with So chemigation than with prilled So during the first year after planting, whereas concentration of N, P, and S in the leaves were lower with So chemigation during the second year. The findings indicate that So chemigation can be used to quickly reduce soil pH after planting and therefore may be a useful practice to correct high pH problems in established northern highbush blueberry fields; however, it was less effective and more time consuming than applying prilled So before plantin

El ocio y el deporte en la época del turismo global

El desarrollo del mercado mundial tiene como consecuencia,  más allá de las crecientes interdependencias económicas, la globalización de las culturas y modos de vida. En cualquiera de estas dimensiones el deporte desempeña un papel importante y contribuye a dicha globalización, como lo muestran las organizaciones internacionales, los eventos mundiales, las comunidades internacionales y las estructuras internacionales basadas en el deporte. Sin embargo el modo en el que se relacionan estas dimensiones en la época del capitalismo desorganizado se basa en la disyunción. Según esta tesis, Appadurai (1996) propone un esquema básico para el análisis de las disyunciones entre las diferentes dimensiones de la globalización, sugiriendo el concepto de paisajes (“scapes”) para subrayar la forma fluida e irregular que caracteriza bien el flujo de capitales, bien las comunicaciones o los estilos de vida. Al enfatizar que la globalización está fuertemente influida por los contextos históricos, lingüísticos y políticos de quienes intervienen en ella, el autor pone el acento en los mundos imaginarios que ayudan a construir dichos paisajes. En este artículo aprovechamos algunas de estas pistas teóricas, analizando tres tipos de paisajes en los contextos del ocio y del deporte, intentando mostrar la relación de disyunción, contribuyendo unos al aumento de la homogeneización y otros a una mayor diferenciación. Analizamos sucesivamente los paisajes mediáticos (deporte como espectáculo global), los paisajes tecnológicos (el papel de los nuevos medios de comunicación y la velocidad con que se crean los mapas cognitivos globales descontextualizados), los paisajes de ideas (el papel de las imágenes y de la estética de las experiencias del ocio deportivo)

Dilemas y paradojas del autogobierno del cuerpo

La contemporaneidad preside el nacimiento de un tiempo cotidiano completamente invadido por una extensa búsqueda de la vida humana: la angustia de la edad, la obsesión por la salud y la forma física, los rituales de mantenimiento y régimen alimenticio, la búsqueda de terapias autónomas y la proliferación de la automedicación son indicadores de la fascinación sin precedentes por el autoconocimiento y la autorrealización. Esta reflexividad social, conocimiento impregnado del saber médico y psicológico típico de la modernidad tardía, no siempre aumenta la capacidad de dominio de la situación externa de los actores. Al contrario, intimida e inhibe, frecuentemente, las posibilidades de elegir. Un mayor conocimiento sobre la vida social no parece equivaler a un mayor control sobre nuestro destino. Tal incapacidad, originada por el exceso de reflexividad, es también la consecuencia de la atmósfera de rigidez e inmovilidad en el nivel social. La sociedad parece inmune a cualquier cambio mientras que las reformas permanentes se desplazan hacia el propio individuo y hacia su cuerpo. En un momento en el que los límites de conocimiento de la sociedad en su conjunto invalidan sus capacidades de cambio, el conocimiento que cada individuo tiene sobre sí mismo y las posibilidades de alteración del recorrido y la arquitectura corporal que parece asegurar se convierten en el último refugio del progreso

Dilemes i paradoxes de l’autogovern del cos

La contemporaneïtat presideix el naixement d’un temps quotidià completament envaït per una extensa recerca de la vida humana: l’angoixa de l’edat, l’obsessió per la salut i la forma física, els rituals de manteniment i règim alimentari, la recerca de teràpies autònomes i la proliferació de l’automedicació són indicadors de la fascinació sense precedents per l’autoconeixement i l’autorealització. Aquesta reflexivitat social, coneixement impregnat del saber mèdic i psicològic típic de la modernitat tardana, no sempre augmenta la capacitat de domini de la situació externa dels actors. Al contrari, intimida i inhibeix, sovint, les possibilitats d’escollir. Un major coneixement sobre la vida social no sembla equivaler a un major control sobre el nostre destí. Aquesta incapacitat, originada per l’excés de reflexivitat, és també la conseqüència de l’atmosfera de rigidesa i immobilitat en el nivell social. La societat sembla immune a qualsevol canvi mentre que les reformes permanents es desplacen cap al mateix individu i cap al seu cos. En un moment en el qual els límits de coneixement de la societat en el seu conjunt invaliden les seves capacitats de canvi, el coneixement que cada individu té sobre ell mateix i les possibilitats d’alteració del recorregut i l’arquitectura corporal que sembla assegurar, es converteixen en l’últim refugi del progrés

Nitrogen Fertigation is Less Efficient but Safer than Granular Fertilizer Application in Newly-Planted Blueberry

Nitrogen fertilizer methods and rates were evaluated in a new field of highbush blueberry (Vaccinium corymbosum L. `Bluecrop"). Treatments included four application methods (split fertigation, continuous fertigation, and two non-fertigated controls) and four rates of N application (0, 50, 100, and 150 kg/ha of N). Fertigation treatments were irrigated by drip and injected with dissolved ammonium sulfate fertilizer; split fertigation was applied as a triple split from April to June while continuous fertigation was applied weekly from leaf emergence to 60 d prior to the end of the season. Non-fertigated controls were fertilized with granular ammonium sulfate and irrigated by drip or microsprays. Canopy cover, which indicates the relative size of young plants, was significantly affected by the rate of N fertilizer application during the first year after planting. The interaction between N application method and rate was also significant. In general, continuous fertigation produced the lowest canopy cover among treatments at 50 kg/ha of N and the highest canopy cover at 150 kg/ha. Apparently, the other methods required less N to produce their canopy but were less responsive than continuous fertigation to additional N fertilizer applications. In fact, up to half the plants died when they were fertilized at 150 kg/ha with granular fertilizer. This occurred whether plants were irrigated by drip or microspray. Alternatively, none of the plants died when they were fertigated continuously. Reduced growth and plant death was associated with high electrical conductivity in the soil solution (>3 dS/cm). The first year results indicate that fertigation is actually less efficient (i.e., less plant growth per unit of N applied) than granular fertilizer application but is also safer (i.e., less plant death) when high amounts of fertilizer is applied

Comparison of tomato root distributions by minirhizotron and destructive sampling

Abstract Calibration of minirhizotron data against root length density (RLD) was carried out in a field trial where three drip irrigation depths: surface (R0) and subsurface, 0.20 m (RI) and 0.40 m depth (RII) and two processing tomato cultivars: `Brigade' (CI) and `H3044' (CII) were imposed. For each treatment three minirhizotron tubes were located at 10, 37.5 and 75 cm of the way from one plant row to the next. Roots intersecting the minirizotrons walls were expressed as root length intensity (L a) and number of roots per unit of minirhizotron wall area (N ra). Root length density (RLD) was calculated from core samples taken for each minirhizotron tube at two locations: near the top of the minirhizotron (BI) and 15 cm apart from it, facing the minirhizotron wall opposite the plant row (BII). Minirhizotron data were regressed against RLD obtained at BI and BII and with their respective means. The results show that for all the situations studied, better correlations were obtained when RLD was regressed with L a than with N ra. Also was evident that the relationship between L a and RLD was strongly influenced by the location of soil coring. RLD was correlated with L a trough linear and cubic equations, having the last ones higher determination coefficients. For instance at 10 cm from the plant row when values from the top layer (0–40 cm) were analysed separately, L a was significantly regressed with RLD measured at BII and described by the equations: RLD = 0.5448 + 0.0071 L a (R 2 = 0.51) and RLD = 0.4823 + 0.0074L a + 8×10–5 L a 2 – 5×10–7 L a 3 (R 2 = 0.61). Under the 40 cm depth the highest coefficients of determination for the linear and cubic equations were respectively 0.47 and 0.88, found when L a was regressed with RLD measured at BI. For minirhizotrons located at 75 cm from the plant row and for location BI it was possible to analyse jointly data from all depths with coefficients of determination of 0.45 and 0.59 for the linear and cubic equations respectively