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- The effects of the use of organic solid wastes on the growth of citrus treesPublication . Costa, M.; Beltrão, José; De Brito, J. C.; Neves, Alcinda; Correia, Maribela Pestana; Guerrero, CarlosTwo types of organic solid wastes were selected to be applied in a citrus orchard: the sewage sludge (the most common on the settlements) and the manure (the most common on the agricultural fields). The sewage sludge is a residue originated from the wastewater treatment - the solid phase. Its application as an organic fertilizer may represent an alternative to the pollution effects in nature. In an orchard of orange-trees (Citrus sinensis [L.] Osbeck), the application of sludge was compared with the application of manure and with the control in order to observe the growth response of the trees. Biometric methods where used - number of leaves per tree, diameter of the trunk, leaf area, specific leaf areas and leaf chlorophyll content. In general, the citrus plants response to the application of sewage sludge and manure was positive for the plant growth, compared to the control. The application of the manure, and especially the sewage sludge (once this fertilizer / soil amendment is available in larger amounts) may be a profitable alternative application to the use of mineral fertilizers and to other soil amendments. Moreover, as the possible destinations of sewage sludge (sea, deposition in land fields, incineration) provoke environmental problems, its agricultural reuse is essential to avoid those problems, when correctly applied in relation to trace elements and to pathogenic parameters. The reuse of this solid waste may be a clean and a safe technique to preserve the environment contamination.
- 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.
- Lettuce yield response to salinity of sprinkle irrigation waterPublication . Beltrão, José; Trindade, D.; Correia, P. J.The objective of this work is to study the effect of saline water on the yield of lettuce (Lactuca sativa L., var. longifolia Lam., cv. Nevada), under an experimental design known as double sprinkler line source (DLS), in two different soil types. A saline gradient was created, shown by an electrical conductivity from 1 up to 8 dS/m, and a precise distribution of the salt with a minimal experimental area was obtained. Experiments were carried out in the Campus of Gambelas, University of Algarve, Fare, South Portugal. Lettuce yields were expressed in ton/ha and in fresh weight per plant. It is concluded the main several aspects: 1 - A steep yield reduction from 1 up to 2 dS/m; 2 - A slow yield reduction from 2 up to 5 dS/m; 3 - From 5 up to 8 dS/m yield is very low and near constant. Regression curves had r(2) values not lower than 0.80.
- 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.
- Organic compost effects on Stevia rebaudiana weed control and on soil properties in the Mediterranean regionPublication . Coelho, Luísa; Osório, Júlio; Beltrão, José; Reis, MárioStevia rebaudiana Bertoni is a promising crop for semiarid climates, including Algarve region. The objectives of this work were: to compare the feasibility of the eco-friendly stevia weed control strategy with a compost of vegetable residues (grass clippings and pruning’s); to identify the emerged weed species, and to evaluate the effect of compost application on soil properties. Treatments consisted on the application of a 5 cm layer of compost on soil surface or incorporated, and no compost application as control. The trial was set up in six randomized field plots, with four replications. Each plot was divided into three subplots, with one treatment per subplot, in a total of 24 subplots per treatment. Compost application had a distinct effect on weed species. Some species were significantly reduced when compost was applied, namely as mulch. Compost increased soil water content, mainly in area of the trial with lower soil drainage, especially when compost was applied as mulch, as well as other physical and chemical soil properties. Results showed the positive effect of compost on weed control and soil properties during stevia cultivation.
- Effect of irrigation water regimes on yield of Tetragonia tetragonioidesPublication . Bekmirzaev, Gulom; Beltrão, José; Ouddane, BaghdadThe main purpose of this experiment was to study the effect of several irrigation water regimes on Tetragonia tetragonioides (Pall) O. Kuntze in semi-arid regions. During the experiment period, it was measured that several irrigation regimes were affected in terms of growth, biomass production, total yield, mineral composition, and photosynthetic pigments. The experiment was conducted in the greenhouse at the University of Algarve (Portugal). The study lasted from February to April in 2010. Three irrigation treatments were based on replenishing the 0.25-m-deep pots to field capacity when the soil water level was dropped to 70% (T1, wet treatment), 50% (T2, medium treatment), and 30% (T3, dry treatment) of the available water capacity. The obtained results showed that the leaf mineral compositions of chloride and sodium, the main responsible ions for soil salinization and alkalization in arid and semi-arid regions, enhanced with the decrease in soil water content. However, the minimum amounts of chlorophyll, carotenoids, and soluble carbohydrates in the leaf content were obtained in the medium and driest treatments. On the other hand, growth differences among the several irrigation regimes were very low, and the crop yield increased in the dry treatment compared to the medium treatment; thus, the high capacity of salt-removing species suggested an advantage of its cultivation under dry conditions.
- 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.