Browsing by Author "Afonso, Sandra"
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- Adubação com azoto, fósforo, potássio e boro numa pastagem natural (lameiro) em Trás-os-Montes: produção e composição elementar da matéria secaPublication . Rodrigues, M.A.; Ferreira, Isabel Q.; Afonso, Sandra; Röndahl, Eje; Pires, Jaime; Arrobas, MargaridaDesde a Primavera de 2013, uma pastagem natural (lameiro) tem vindo a ser submetida a aplicação anual (2013, 2014, 2015) de azoto (80 kg N ha-1, na forma de nitrato de amónio), fósforo (150 kg P2O5 ha-1, na forma de superfosfato 18%), potássio (100 kg K2O ha-1 na forma de cloreto de potássio) e boro (3 kg B ha-1, na forma de tetraborato de sódio). A experiência contempla ainda uma modalidade testemunha e três repetições por tratamento. O ensaio está instalado na Qta. de Sta. Apolónia em Bragança. A produção de biomassa é avaliada duas vezes ao ano, no início da Primavera (produção de pasto de outono/inverno) e no fim da Primavera (produção de feno de primavera). São utilizadas caixas de exclusão e uma quadrícula de 50x50 cm para delimitar a área correspondente a cada amostra colhida. As amostras de biomassa são secas em estufa de ventilação forçada, regulada a 70 °C, moídas e analisadas para a composição elementar. Nas cinco colheitas entretanto efetuadas, a modalidade fertilizada com azoto produziu 25,5 t matéria seca (MS) ha-1, valor significativamente superior ao dos restantes tratamentos, cujos valores se situaram próximos de 20 t MS ha-1. Nenhum outro tratamento fertilizante exerceu efeito significativo na produção de MS relativamente à testemunha. O azoto (ou proteína) contido na biomassa colhida foi significativamente superior na modalidade de fertilização azotada em comparação com as restantes, devido à maior produção de biomassa e mais elevada concentração de azoto nos tecidos. Também foi exportado mais fósforo, potássio ou boro respetivamente nas modalidades fertilizadas com estes elementos relativamente às restantes modalidades com exceção da modalidade fertilizada com azoto. Nesta última, a maior exportação de P, K ou B deveu-se à maior produção de biomassa enquanto nas modalidades fertilizadas com P, K ou B se deveu à maior concentração dos nutrientes nos tecidos. Nas condições desta experiência apenas a fertilização azotada aumentou a produção e o teor de proteína na MS. Num futuro próximo pretende avaliar-se a alteração da composição florística da pastagem e o valor bromatológico da forragem.
- Aflatoxin Contamination of Various Staple Foods from Angola and MozambiquePublication . Matusse, Cláudio; Lucamba, Zelda; Bila, João; Macuamule, Custódia; Sampaio, Ana; Afonso, Sandra; Venâncio, Armando; Rodrigues, PaulaAflatoxins constitute a significant risk in staple foods produced in African countries. This research aimed to analyze the total aflatoxin (AFT) contamination of various staple foods in Angola and Mozambique. A total of 233 samples of corn, peanuts, beans, rice, and cassava flour collected from farmers or local markets from the province of Cuanza Sul, Angola, and the provinces of Gaza and Inhambane, South Mozambique, were analyzed for the presence of AFT using the lateral flow strip method via AgraStrip® ProWATEX® (Romer). The results showed that, from all matrices, the highest incidence and level of AFT were found in corn produced in Mozambique, with medians ranging from 6.5 to 66.5 μg/kg, with the samples showing values as high as 9200 μg/kg. Levels higher than the maximum admissible levels recommended by the Codex Alimentarius Commission for cereals and pulses (15 μg/kg) were observed in up to 90% of the corn samples, depending on the province. Corn produced in Angola showed lower amounts of AFT, with medians ranging from 1.2 to 7.7 μg/kg. Considering the maximum admissible levels for AFT recommended by the European Commission and the Codex Alimentarius Commission for cereals and pulses, the level of AFT contamination in staple food produced and consumed in the studied provinces is high and constitutes a public health risk for the population. Therefore, risk mitigation strategies are urgently needed.
- Agronomic and chemical evaluation of hop cultivars grown under Mediterranean conditionsPublication . Afonso, Sandra; Arrobas, Margarida; Rodrigues, M.A.Aim of study: Evaluation of the agronomic performance and chemical profile of four hop cultivars grown under Mediterranean conditions. Area of study: The study was undertaken in Bragança, north-eastern Portugal. Material and methods: The newly introduced cultivars (‘Columbus’, ‘Cascade’ and ‘Comet’) were compared with the well-stablished ‘Nugget’. The field experiment was carried out between 2017 and 2019. Dry matter (DM) yield (plant and cones), tissue elemental composition and bitter acid and nitrate (NO3-) concentrations in the cones were assessed. Main results: ‘Comet’ was the most productive cultivar with the highest total DM yield (1,624 to 1,634 g plant-1), cone yield (572 to 633 g plant-1), and dry weight of individual cones (0.28 to 0.79 g cone-1). ‘Cascade’ showed the lowest average total DM yield (723 to 1,045 g plant-1). The year affected the average values of DM yield and the concentration of bitter acids in the cones, with ‘Cascade’ showing the highest sensitivity between cultivars. The concentrations of α and β-acids in the cones were within or close to the normal ranges internationally accepted for all cultivars. ‘Columbus’ exhibited the highest levels of α-acids, ranging between 12.04 % and 12.23%, followed by ‘Nugget’ (10.17–11.90%), ‘Comet’ (9.32–10.69%) and ‘Cascade’ (4.46–8.72%). The nutrient accumulation criteria in cone and leaf tissues seem to be a differentiating factor between cultivars with influence on bitter acid biosynthesis and biomass production. Research highlights: All cultivars showed notable performance in terms of DM yield and bitter acid concentration in the cones when compared to international standards.
- An insight into the Portuguese sector of aromatic and medicinal plantsPublication . Rodrigues, M.A.; Afonso, Sandra; Ferreira, Isabel Q.; Arrobas, MargaridaIn recent years in Portugal, many new farmers began to settle in the medicinal and aromatic plants (MAP) sector. They are mostly young, highly educated, though not always in agronomy. Almost all adopted organic farming practices and put soil screen for protection against weeds. In this work, we provide a diagnosis of the situation of the new producers and give up a guideline to mitigate the situation that has arisen. Shortly after installation, virtually all producers are experiencing great difficulties, because they cannot fertilize their plants and the biomass they produce is very low. The application of solid fertilizer and organic amendments is not possible due to soil screen. They have appeared on the market liquid organic fertilizer which can be used in fertigation, but their costs are prohibitive. Studies for three years with verbena, lemon balm and peppermint have shown that these fertilization solutions give tenuous productivity increases, revealing the plants deep symptoms of nitrogen deficiency very quickly. In the future seems to be no alternative to the removal of the screen and to the introduction into the system of a livestock component or legumes with ability to fix atmospheric nitrogen. Some legumes can be grown during the winter in an asynchronous cycle with the main MAP grown in Portugal. However, these cropping technologies have not yet been tested in Portugal, which can leave the producers vulnerable to error.
- Aplicação de azoto e boro ao solo e foliar em amendoalPublication . Arrobas, Margarida; Rodrigues, M.A.; Barreales, David; Pereira, Ermelinda; Afonso, Sandra; Capelo, Márcio Amaro Bueno Sorrentino; Ribeiro, A.C.Com vista a melhorar o sistema de recomendação de fertilização para a amendoeira, foi instalado um ensaio de campo em Alfândega da Fé (NE Portugal) num pomar com uma densidade de plantação de 6x4 m. O delineamento experimental consistiu na aplicação de 4 doses de N (0, 25, 50 e 100 kg N ha-1) e 4 doses de B (0, 1, 2 e 3 kg B ha-1) ao solo, suplementadas com aplicações foliares de N (3 aplicações de ureia, 0,5%, durante a estação de crescimento) ou B (duas aplicações com 0,3 kg B ha-1). Um delineamento equivalente ao anterior de aplicação de N e B ao solo foi mantido sem adubação foliar. Avaliou-se a produção de fruto e a proporção de semente (amêndoa), endocarpo e mesocarpo. Procedeu-se à determinação da concentração de alguns nutrientes nos diferentes tecidos na data de colheita e ao cálculo da exportação dos nutrientes. A aplicação de N ao solo originou diferenças significativas na produção de fruto. As doses de 0 e 25 kg N ha-1 produziram menos que as doses de 50 e 100 kg N ha-1 (5,75, 8,29, 12,59 e 12,25 kg árvore-1, respetivamente). Em média, o endocarpo representou a fração do fruto com maior massa seca, 47,1%, o mesocarpo 40,1% e a semente 12,8%. O N exportado pelo fruto variou entre 15,0 g N árvore-1 (N0) e 69,7 g N árvore-1 (N100) com diferenças significativas entre doses. A suplementação foliar com N não resultou em acréscimo produtivo significativo. A aplicação de boro ao solo não mostrou efeito significativo na produção, tendo esta variado entre 12,0 kg árvore-1 em B0 e 9,1 kg árvore-1 em B3. O mesocarpo foi responsável pela maior exportação de B. A exportação deste nutriente variou entre 177,6 (B0) e 361,8 (B3) mg árvore-1. O suplemento foliar com B não revelou efeito positivo significativo.
- Assessing the potential use of two portable chlorophyll meters in diagnosing the nutritional status of plantsPublication . Afonso, Sandra; Arrobas, Margarida; Ferreira, Isabel Q.; Rodrigues, M.A.The SPAD-502 and the FieldScout CM 1000 chlorophyll meters were compared in their performance in diagnosing the nutritional status of plants. Leaves of a wide range of greenness were used to push the sensitivity of the tools to their limits. Both devices showed high reproducibility when used by different operators. The SPAD-readings were well-correlated with leaf nitrogen (N) concentrations, since leaves from heavily fertilized plants were not included in the sample population. The FieldScout-readings showed a marked saturation curve with the leaf N concentration, thus it cannot be used as a reliable N nutritional status index. The results also showed that the use of SPAD-502 in the diagnosis of the nutritional status of an orchard requires the establishment of specific critical concentrations for cultivars and sampling dates. The SPAD-502 appeared to have potential in the diagnosis of the nutritional status of the orchard for nutrients other than N.
- Assessing the soil fertility and the tree nutritional status of chestnut groves grown in the region of Bragança, Northeastern of PortugalPublication . Arrobas, Margarida; Afonso, Sandra; Ferreira, Isabel Q.; Röndahl, Eje; Rodrigues, M.A.In the NE of Portugal there is a growing interest in the chestnut tree crop which has led the producers to intensify the cropping system, namely by increasing the use of fertilizers. However, few studies exist on the adaptation of the chestnut trees to soil conditions as well as their response to fertilizer application. The soil testing and plant analysis laboratory of the Polytechnic Institute of Bragança initiated a project aimed to assess the soil fertility of the chestnut groves and the tree nutritional status in order to be able to better advise the producers in their annual fertilization programs. Soil (217) and leaf (84) samples were collected in three counties of NE Portugal (Bragança, Vinhais and Macedo de Cavaleiros). The results show high acidity in soils [pH<4.5 (4%), 4.51< pH<5.5 (68%), 5.51< pH< 6.5 (27%)]. The organic matter content was lower than 3% in 79% of soil samples. More than 50% of soil samples presented P contents classified as very low (25%) or low (32%). Most of the samples revealed K contents classified as high (58%) or very high (29%). Leaf nutrient concentrations varied in the ranges of 14.8‐27.8 (N), 0.8‐3.1 (P), 2.6‐15.9 (K), 2.4‐17.0 (Ca), 0.8‐4.4 (Mg) g kg‐1 and 10‐215 (B) mg kg‐1. However, in spite of the great variability in leaf concentration of each one of the nutrients analyzed, no significant relationships were found between soil properties and the concentration of the nutrients in the leaves. The organic matter content was not correlated with leaf N concentration. The same occurred between extractable soil P and K and the concentration of these nutrients in the leaves. The best linear relationship was found between soil pH and leaf Mg concentration. The results also stressed that little information on tree nutritional status can be drawn from soil testing.
- Assessment of farmer’s knowledge and attitudes toward fungi and mycotoxin contamination in staple crops in southern MozambiquePublication . Bila, João; Macuamule, Custódia; Bombe, Amina; Ribeiro, Maria Isabel; Venâncio, Armando; Afonso, Sandra; Rodrigues, PaulaIn Mozambique, 80% of the population directly depends on agriculture as a source of food and income. However, some of the most produced food crops, such as maize, rice and peanuts, are easily contaminated by fungi and mycotoxins. The naturally high prevalence of mycotoxins can be aggravated by the high vulnerability and lack of knowledge of the farmers. The aims of this study were to assess the knowledge and perceptions of small-size and medium-size farmers in the provinces of Inhambane and Gaza, southern Mozambique, regarding awareness of fungi and mycotoxin contamination of food crops, losses of production and income, and the causes and consequences of this contamination. A survey was conducted with 180 farmers in the two provinces. A multiple linear regression model was used to correlate the level of knowledge with the sociodemographic characteristics of the studied population. Results The results showed that 97.8% of the farmers have an insufficient level of knowledge about fungi and mycotoxins contamination of food crops. While 17.8% showed sufficient or good knowledge of the conditions that promote fungal contamination, only 3.9% knew what measures to apply to mitigate their occurrence. The level of knowledge was lower for the Inhambane farmers. According to the estimated model, province, gender, age (>45 years old), primary and secondary (1st cycle) education, another source of income other than agriculture and experience as a farmer (>10 years) are statistically significant predictors of the level of knowledge of the Mozambican farmers analyzed. These findings highlight the urgent need of tailored interventions to promote good agricultural and storage practices that allow the mitigation of mycotoxin contamination of food.
- Avaliação da situação nutricional dos soutos de castanheiro do distrito de Bragança através de análises de terras e foliaresPublication . Arrobas, Margarida; Afonso, Sandra; Rodrigues, M.A.O castanheiro tem sido uma espécie fruteira cultivada em condições marginais, sendo as árvores raramente fertilizadas. Poucos estudos foram dedicados à gestão da fertilidade do solo e ao estado nutricional desta cultura. Este trabalho apresenta os resultados de análises de populações de 1041 e 198 amostras de solos e folhas, respetivamente colhidas em nove municípios no distrito de Bragança. Uma população suplementar de 80 amostras de solos, folhas e frutos foi ainda colhida nos três municípios mais produtivos do distrito de Bragança, estas nos mesmos pomares, para permitir o estabelecimento de relações entre parâmetros de fertilidade do solo e do estado nutricional das árvores. Os resultados das duas populações de solos mostram elevada acidez, baixo teor de matéria orgânica, baixo teor em fósforo e alto teor em potássio. Uma percentagem elevada de amostras de folhas mostrou concentrações de nutrientes abaixo do limite inferior do intervalo de suficiência, tanto na primeira como na segunda população de amostras, para azoto (respetivamente 63% e 47%), fósforo (18% e 15%), potássio (34% e 31 %), cálcio (19% e 52%), magnésio (21% e 13%) e boro (40% e 43%). No caso do boro, 6% e 8% das amostras de folhas da primeira e segunda populações apresentaram valores dentro do intervalo de concentrações excessivas. Os resultados deste trabalho revelaram ausência ou relações fracas entre propriedades e ou nutrientes disponíveis no solo e a concentração de nutrientes nas folhas. O estado nutricional dos soutos indica que é urgente começar a aplicar programas regulares de fertilização, principalmente com base na avaliação do estado nutricional das árvores através da análise de folhas.
- Biomass production and nutrient concentration on potted Stevia in response to N, P, K or B fertilizationPublication . Afonso, Sandra; Arrobas, Margarida; Rodrigues, M.A.Stevia rebaudiana (Bertoni) is a perennial plant belonging to Asteraceae family, native from Amambay region, between Brazil and Paraguay. It has been used for centuries by Guarani Indians as a sweetener and to treat diabetes. Stevia composition includes glycosides from steviol, the steviosides, natural sweeteners that reduce blood glucose, noncaloric, with a sweetening power much higher than sucrose. Studies also showed a high content of proteins, K, P, Mg, Ca and trace of copper, iron, manganese and zinc. Japan was one of the first countries to commercialize stevia based products and to establish it as a crop, and since then interest has expanded overall. European Union only authorized stevia as a food additive since 2011. Natural and healthy alternatives to sugar are being more preferred by consumers, explaining the great increased of stevia based products, and the perspectives are for stevia consumption to increase even more in the coming years. Also there is a growing scientific interest on stevia. However, agronomic knowledge is still scarce. This investigation aimed to assess the effect of increasing rates of N, P, K or B application on stevia biomass production and nutrient concentration in plant tissues. The effect of fertilizer treatments on stevia was also assessed through the use of the portable chlorophyll meter SPAD-502 plus which estimate leaf chlorophyll content. A pot experiment was installed as a randomized design with four replications. Five rates of each nutrient were applied, namely N (0, 0.75, 1.5, 2.25, 2 g/pot), K (0, 0.25, 0.5, 1, 1.25 g/pot), P (0, 1.25, 2.5, 3.75, 5 g/pot), or B (0, 0.025, 0.05, 0.075, 0.1 g/pot). The data is important to adjust fertilizer rates to crop demands, enabling to maximize production and improve the nutritional value of stevia products. Results showed a significant increase of dry biomass in response to N fertilization, attaining the higher values with a rate of 1.5 g N/ pot. There were not found significant differences in dry matter yield with P, K or B fertilizer rates. SPAD readings showed a slight variation with N fertilization and maximum values were recorded in the 1.5 g N/pot treatment.