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- Efficiency of triple emitter source (TES) for irrigation experiments of horticultural cropsPublication . Beltrão, José; Jesus, S. B.; Silva, V.; Sousa, P. B.; Carvalho, Isabel Saraiva de; Trindade, D.; Rodrigues, M. H.; Machado, A.Triple emitter source TES experimental irrigation was designed. Three trickle laterals were connected together in order to form a triple joint lateral. Two of them and their emitters are connected to two tanks of stock solutions. The third lateral contains only fresh water. The emitters of the two solution lines have different and varying discharges to obtain several mixings of the two stock solutions. The third line is necessary to obtain constant water application rates for each trickling point along the lateral. This method was tested for several experiments involving the study of the combined effects of salinity and fertilizers on the yield function of horticultural crops, namely lettuce and cabbage. As concluding remarks, it was shown the high uniformity of the factor to be evaluated, through the use of Christiansen coefficient of uniformity distribution CUC, which value was always larger than 90%. Main advantage of this experimental design is its smaller experimental plots (reducing pollution and research costs).
- Avaliação do comportamento agronómico de porta-enxertos tolerantes à tristeza dos citrinosPublication . Pinto, J. M.; Duarte, Amílcar; Tomás, J. C.; Candeias, M. F.; Beltrão, JoséA detecção no nosso país de alguns núcleos de plantas infectadas com o citrus tristeza virus (CTV), impôs a necessidade de desenvolver um plano de prevenção, nomeadamente através do incentivo da substituição progressiva dos porta-enxertos susceptíveis por porta-enxertos tolerantes. Com a identificação do seu principal vector (Toxoptera citricidus Kirk.) em finais 2003, nas regiões de Entre-Douro e Minho e de Trás-os-Montes é de prever que a dispersão da doença ocorra mais rapidamente. As novas plantações utilizam na sua maioria as citranjeiras Troyer e Carrizo, que nem sempre se mostram adequadas às condições edafo-climáticas existentes. Considerando esta problemática, a Direcção Regional de Agricultura do Algarve, em colaboração com outras entidades (Universidade do Algarve e Centro de Citricultura), tem vindo a desenvolver estudos conducentes à adaptação de novos porta-enxertos, com o objectivo de diversificar as opções existentes relativamente aos condicionalismos da região. Com este objectivo foi instalado em Tavira, em Maio de 1998, num solo calcário, um ensaio de campo para avaliação do comportamento de 11 clones de porta-enxertos (T. Sunki x P. trifoliata FAO 30590; Citranjeira Troyer B2 FAO 31655; T. Cleopatra x P. trifoliata FAO 30584; T. Cleopatra x C. Carrizo FAO 30575; Laranjeira Gou Tou B7; Citrandarineira 31443; Laranjeira azeda B6C-T1; Tangerineira Changsa; Tangerineira Sunki; Tangerineira Cleópatra; Citranjeira Troyer 4 AS). Durante três anos, as plantas foram submetidas a três níveis de salinidade da água de rega, expressos pela condutividade eléctrica da água de rega ECw – 1; 3 e 6 dS.m-1, obtidos através de um esquema experimental fonte dupla gota-a-gota. Foram medidos vários parâmetros agro-ambientais, como o desenvolvimento vegetativo das plantas e o aumento da condutividade eléctrica do extracto de saturação do solo (medido no extracto aquoso). Os resultados obtidos mostram que os porta-enxertos com maior tolerância à salinidade foram o clone de laranjeira azeda B6C-T1 e a laranjeira Gou Tou.
- The combined effects of salts and calcium on growth and mineral accumulation of Tetragonia tetragonioides - A salt removing speciesPublication . Neves, Alcinda; Miguel, Maria Graça; Marques, C.; Panagopoulos, Thomas; Beltrão, JoséHigh soil salinity levels have drastic effects on the growth and yield of horticultural crops. Salination may be controlled by environmentally safe and clean techniques as the use of salt removing species. Tetragonia tetragonioides, a wild halophytic species has been studied for this purpose. It was studied the effect of high salt concentrations on growth and mineral composition and the influence of high calcium concentration on plant response. Plants were grown in 5 litters in randomized pots and were daily irrigated. The NaCl concentration of the irrigation solution ranged from 0 up to 200 mM. Additionally, the irrigation solution provided plants with two calcium concentrations: 2 and 10 mM of CaCl2. T. tetragonioides present high ability for sodium and chloride leaf accumulation. Besides that, the species provide more advantages: 1) high biomass production potential; 2) several harvests during the year (summer and winter); 3) high content of minerals; 4) horticultural importance, as a leaf vegetable crop; 6) easy multiplication (seed propagation) and easy crop management; 7) tolerance to drought and warm conditions; 8) soil erosion control due to its excellent soil covering. The obtained results suggest that plants supplemented with the high calcium level had longer stems than plants in the low calcium level, accumulated greater amounts of calcium at high salinity levels and present similar leaves dry matter.
- Resposta à salinidade de porta-enxertos tolerantes à tristeza dos citrinosPublication . Pinto, M. J.; Cipriano, A. L.; Duarte, Amílcar; Mariano, J.; Beltrão, JoséA presença em Espanha de forma endémica do vírus da tristeza (CTV) levou nos últimos anos á destruição de milhares de àrvores infectadas. No algarve, a detecção de focos da doença, impôs a necessidade de desenvolver um plano de prevenção, nomeadamente, incentivando a substituição progressiva dos porta-enxertos susceptíves (como a laranjeira azeda) por porta-enxertos tolerantes.
- Combined effects of potassium and wastewater application on the yield and quality of Bermuda grass (Cynodon dactylon) in the Mediterranean regionsPublication . Beltrão, José; Santos, R.; Correia, P. J.The reuse of treated wastewater is considered as an alternative disposable to potable water in the mediterranean agriculture and landscape, namely in golf courses. Bermuda grass (Cynodon dactylon, Peers) is used very often on the fairways, roughs and tees of golf courses of the Mediterranean Basin due to its tolerance to drought, salinity, high temperatures and damages. The objective of this work is to study the response of this cultivar to the combined effects of municipal wastewater and two levels of potassium fertilization, during Spring and Summer. The experimental design known as sprinkle point source was used to simulate the various levels of wastewater application, expressed by the crop coefficient kc. This procedure is characterized by the assumption that a point creates a linear irrigation gradient from the water point source, producing a gradual change in water application, and a high degree of irrigation uniformity must be obtained in parallel isohyets. Chemical analysis of wastewater irrigation water was monitored through all the experimental period (from April to September). Climatic data was also recorded. Yield (aboveground biomass) and the good visual appearance (GVA) of the lawn were assessed in two sampling dates, May and July. Municipal wastewater can be used to irrigate Bermuda grass, without an apparent decrease on grass quality. As concluding remarks, it may be seen that the irrigation water amount is the most pronounced limiting production factor of bermuda grass (Cynodon dactilon, Peers), when compared with potassium fertilization, but it is possible that there is a positive interaction between water and irrigation. This response is modulated by evaporative air conditions since lower yields were obtained in summer. On the other hand, if the potassium fertilization is increased, two situations may occur: 1) with high amounts of water application, leaching problems may occur, mainly on sandy soils, and production may decrease; 2) if potassium fertilization increases, and irrigation water decreases, yield decreases due to the increase of salinity (potassium fertilizers are salts), mainly on salt affected soils.
- Saline stress and cell toxicity evaluation using suspended plant cell cultures of horticultural crops grown in a bioreactorPublication . Lima-Costa, Maria Emília; Ferreira, A. L.; Duarte, Amílcar; Beltrão, JoséCrop salt damage consists, usually, of leaf burn and defoliation, and it is associated with accumulation of toxic levels of sodium and/or chloride in leaf cells (Storey and Walker, 1999). The cell and tissue culture are simple biological systems that offer a direct approach to the metabolic changes. The plant cell growth in a controlled environment, as a bioreactor, is a unique tool for cell ion transport studies. Cell suspension culture of citrus cell line was exposed to a medium containing different sodium chloride concentrations (0mM, 42.7mM and 85.5mM). The growth profile of control cells (absence of NaCl) and 85.5mM cells were similar. The lack of inhibition of biomass accumulation, of all tested saline conditions clearly showed that the level of NaCl concentration used was not toxic for the cell metabolism. Also its ability to resist to 85.5mM NaCl can be on evidence that this suspension cel culture might have salt tolerance characteristics.
- Analysis of spatial interpolation for optimising management of a salinized field cultivated with lettucePublication . Panagopoulos, Thomas; Jesus, J.; Antunes, Maria Dulce; Beltrão, JoséThe lack of randomisation in irrigation experiments is usually a disadvantage. The introduction of spatial variable experimental design offers a convenient tool to help solving this problem. In order to understand the variation of some soil physical and chemical properties in an experimental block and its effect on lettuce (Lactuca sauna L.) production, graphical interpretation of those soil properties was done with the use of geostatistics in a geographic information system (GIS). In this work three techniques of geostatistics were used for the creation of several maps of soil properties in an experimental plot cultivated with lettuce. Lettuces were evaluated for individual weight and diameter at the end of the cropping season. The soil properties studied were: total mineral nitrogen, phosphorus, potassium, pH, electric conductivity and saturated soil hydraulic conductivity. The techniques used were: ordinary kriging, inverse distance and Thiessen polygon. Cross validation used to compare the prediction performances of the three geostatistical interpolation algorithms determined that kriging was the best technique for each soil property. Prior to the creation of the maps, semivariograms were produced for each soil property. The maps resulting from the interpolation techniques were introduced in a GIS and their values reclassified. After that, spatial modelling was used to develop a final overlay map from all the information of the analysed soil properties simulating a "lettuce production capability map". This final map was created with the objective to determine which areas in the plot had optimal conditions for lettuce development. It was concluded that the plot did not had an optimal area for lettuce production. Localized problems with soil properties were found that could be solved with simple geographically restricted amendment treatments. Final lettuce yield had high correlation (r(2) = 0.83) with the lettuce capability map derived. (c) 2005 Elsevier B.V. All rights reserved.