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- Valor agronómico de compostados à base de folhas de lúpuloPublication . Afonso, Sandra; Arrobas, Margarida; Pereira, Ermelinda; Rodrigues, M.A.Atualmente, o principal destino do lúpulo cultivado no mundo é a produção de cerveja. Não obstante, desde a antiguidade que inúmeros usos se conhecem ao lúpulo, nomeadamente na medicina natural para tratar diversas enfermidades, como planta ornamental, na alimentação humana e também como forragem e nas camas do gado. O lúpulo é uma planta trepadeira que chega a ultrapassar sete metros de altura, produzindo uma elevada quantidade de biomassa que origina elevada exportação de nutrientes. Os cones (inflorescências femininas) destinados à produção de cerveja representam uma pequena parte da biomassa produzida. No final da ripagem dos cones remanescem grandes quantidades de caules e folhas. Alternativas de aproveitamento destes recursos deverão ser equacionadas numa ótica de economia circular. Sendo uma planta de elevada exportação as folhas deverão ter um teor de nutrientes interessante para efeitos de compostagem. A presente investigação teve por objetivo avaliar o potencial de aproveitamento da biomassa produzida nos campos de lúpulo, nomeadamente das folhas, através de compostagem. O ensaio consistiu na compostagem de folhas de lúpulo com palha e com estrume em sete combinações diferentes: C1 (folhas/estrume,1/5); C2 (folhas/estrume,1/1); C3 (folhas/estrume,1/3); C4 (folhas/palha,1/2); C5 (folhas/palha,1/1); C6 (folhas/palha,1/0.5); C7 (folhas/palha/cinza, 1/1/0,004). Posteriormente os compostos obtidos foram utilizados como fertilizante orgânico no crescimento de alfaces, em vasos, utilizando três doses D0, D1 e D2 (0, 20 e 40 t /ha de matéria seca). Verificou-se que os compostados C6 e C7 apresentaram concentrações de N nos tecidos mais elevadas e mais baixas, respetivamente. Os teores mais elevados de nitratos e de amónia nos tecidos registaram-se com os compostados C2 e C5, respetivamente. A maior e a menor produção de biomassa registou-se para a dose D2, respetivamente para os compostados C6 e C4. As análises microbiológicas efetuadas aos solos, após a colheita das alfaces, indicaram uma variação significativa entre tratamentos na quantidade média de fungos e actinomicetas, com valores mais elevados a registarem-se nos solos com os compostados C4 (dose D2) e C6 (dose D1 e D2). A respiração basal monitorizada ao longo de 10 dias registou valores cumulativos significativamente diferentes, na sequência C1D1 > C4D2 > C6D2.
- Sufficiency ranges and crop nutrient removals for peppermint (Mentha X piperita L.) established from field and pot fertilizer experimentsPublication . Arrobas, Margarida; Ferreira, Isabel Q.; Afonso, Sandra; Rodrigues, M.A.Peppermint is an important aromatic and medicinal plant used across the world in pharmaceutical, cosmetic and food industries. However, there is a lack of agronomic research on this crop which hinders the implementation of best agricultural practice at farm level. Plant analysis, for instance, cannot be used as a tool to implement a suitable fertilizer recommendation program, since sufficiency ranges and crop nutrient removals have not yet been established. Thus, the main objectives of the present work were to assess the response of peppermint to varying nitrogen(N),phosphorus(P),potassium(K)and boron(B)rates,to establish sufficiency ranges from macro, micronutrients and SPAD-readings and to estimate crop nutrient removals in the above ground biomass.Field trials and pot experiments were conducted from 2013 to 2015 in a wide range of conditions involving 12 N, P, K or B fertilizer trials and a total of 48 cuts of biomass. Nitrogen fertilization increased dry matter yield of peppermint on the vast majority of sampling dates. In contrast, P, K, or B did not produce a significant effect on dry matter yield in any of the experiments. The sufficiency ranges set for macronutrients N, P, K, Ca and Mg are respectively 32.0 – 42.0, 1.2 – 4.5, 10.0 – 30.0, 7.0 – 23.0, and 4.0 – 10.0 g kg−1. Those for micronutrients B, copper (Cu), iron (Fe), zinc (Zn), and manganese (Mn) are respectively 20 – 200, 5 – 25, 100–600,25–300,and30–200mgkg−1.Sufficiency range for SPAD-readings is 45 – 50 SPAD units. All these ranges were established for the commercial harvesting date. The amounts of N, P, K, calcium (Ca), and magnesium (Mg) removed in above ground biomass are respectively 22.7,1.6,26.4,16.4 and 4.8kg Mg−1 of dry biomass.
- 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.
- Índices de suficiência para interpretação de análise foliar de ervas aromáticasPublication . Rodrigues, M.A.; Afonso, Sandra; Arrobas, MargaridaNo Centro de Investigação de Montanha do Instituto Politécnico ele Bragança foi realizado um trabalho de investigação com vista a elaborar normas de interpretação de resultados para a análise foliar de algumas das principais plantas aromáticas e medicinais cultivadas atualmente em Portuga!: erva-cidreira (Melissa officinalis L.), hortelã-pimenta (Mentha x piperita L.) e limonete (Aloysia citrodora Paláu).
- 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.
- Resposta da lúcia-lima, erva-cidreira e hortelã-pimenta à aplicação de adubos orgânicos líquidos autorizados para agricultura biológicaPublication . Arrobas, Margarida; Ferreira, Isabel Q.; Afonso, Sandra; Pinheiro, Clara; Rodrigues, M.A.Grande parte dos produtores nacionais de plantas aromáticas e medicinais (PAM) está a produzir em modo biológico. Um dos grandes desafios que este modo de produção coloca aos produtores é o fornecimento de azoto às plantas. As PAM não têm necessariamente menores necessidades em azoto que as outras espécies cultivadas. A sua biomassa é igualmente composta de azoto, fósforo, potássio e outros nutrientes. Neste trabalho apresentam-se resultados de ensaios em vasos conduzidos com lúcia lima (Aioysio citrodoro Palàu), erva-cidreira (Me/isso officinalis L.) e hortelã-pimenta (Mentha x piperita L.) em que se aplicaram doses de azoto equivalentes a O (NO), 30 (N30), 60 (N60) e 90 (N90) kg/ha, admitindo uma densidade de plantação de 110 000 plantas/ha. Após três cortes, a produção média de biomassa acumulada aumentou da modalidade NO para a modalidade N90 nas três espécies cultivadas. Os valores médios variaram de 6,9 a 8,6 g/vaso, 10,9 a 17,0 g/vaso, 8,3 a 12,0 g/vaso, respetivamente para lúcia-lima, erva-cidreira e hortelã-pimenta. Os teores de azoto nas folhas decresceram ao longo da estação de crescimento, mas mantiveram-se significativamente mais elevados nas modalidades que receberam as doses mais elevadas de azoto como fertilizante. Os valores de clorofila-SPAD, determinados com o medidor de clorofila SPAD-502 Plus, tiveram um comportamento idêntico à concentração de azoto nas folhas, decrescendo ao longo da estação de crescimento e sendo mais elevados nas modalidades fertilizadas com doses mais elevadas de azoto. Um índice de vegetação NDVI (Normalized Difference Vegetation Index), baseado na radiação refletida pela canópia, determinada com o aparelho portátil FieldScout CM1000, mostrou valores mais elevados nas modalidades fertilizada s, sobretudo nas fases mais avançadas do ciclo. Assim, em modo de produção biológico as plantas respondem fortemente à aplicação de azoto, tal como em modo convencional, refletindo-se a falta de nutriente na redução da produção de biomassa. A grande dificuldade está em encontra r fertilizantes azotados autorizados neste modo de produção a preços aceitáveis. Deve referir-se que o fertilizante utilizado neste estudo tem um custo por unidade de azoto 50 vezes superior ao do nitrato de amónio dos fertilizantes comerciais. Resta aos produtores encontrar formas naturais de introduzir azoto no solo, como seja o uso de leguminosas de cobertura em ciclos assincrónicos com as PAM ou como sideração, explorando o ciclo de rotação das culturas.
- Compostaje de hojas de lúpulo ricas en nutrientes con paja de trigo y estiércol de vaca en mezclas adecuadasPublication . Afonso, Sandra; Arrobas, Margarida; Pereira, Ermelinda; Rodrigues, M.A.La cosecha de lúpulo (Humulus lupulus L.) genera grandes cantidades de hojas ricas en nutrientes que se pueden aprovechar en mezclas de compostaje para agregar valor a otros recursos orgánicos de las explotaciones. En este estudio, se mezclaron hojas de lúpulo con estiércol de vaca y paja de trigo en varias combinaciones con el objetivo de establecer orientaciones sobre cómo los agricultores pueden manejar las materias primas y utilizar mejor estos valiosos recursos orgánicos. Se monitoreó el proceso de compostaje y se evaluó la calidad de los compuestos en relación con los efectos sobre la lechuga (Lactuca sativa L.) cultivada en macetas durante dos ciclos consecutivos. La mezcla de hojas de lúpulo con estiércol de vaca produjo un compost estable después de nueve meses de compostaje que se puede utilizar en cultivos hortícolas, independientemente de la proporción de materias primas, debido a sus proporciones de carbono (C)/nitrógeno (N) bajas y similares. Sin embargo, cuando se utilizaron mezclas de hojas y paja en proporciones menores a 2:1, los compuestos no maduraron adecuadamente, mostrando altas proporciones C/N. Su aplicación al suelo condujo a una fuerte reducción de las concentraciones de N en los tejidos vegetales, debido a la inmovilización biológica de N, que redujo significativamente la producción de materia seca de la lechuga. Por lo tanto, para reducir el tiempo de compostaje y aumentar la calidad del compuesto, la proporción hojas/paja debe ser lo más alta posible, al menos 2:1. Alternativamente, el proceso de compostaje debería tomar más tiempo, o el compost mal madurado debe aplicarse mucho antes de sembrar un cultivo para que los procesos biológicos complementarios puedan tener lugar en el suelo, como se registró en el segundo ciclo de la lechuga. La ceniza de los tallos de lúpulo no benefició el proceso de compostaje y demostró que no valía la pena usarla en mezclas.
- Diagnosing the nutritional condition of chestnut groves by soil and leaf analysesPublication . Arrobas, Margarida; Afonso, Sandra; Rodrigues, M.A.Chestnuts have always been a marginal fruit crop, and the trees seldom fertilized as a result. Few studies have been devoted to the management of soil fertility and the nutritional status of this crop. This work reports results of soil and plant analyses of a population of respectively 1041 and 198 soil and leaf samples taken across nine municipalities in the district of Bragança, NE Portugal. A second population of 80 soil, leaf and fruit (only 64) samples were taken across the three most productive municipalities in the district of Bragança, from the same orchards, to allow the establishment of relationships between soil fertility parameters and the nutritional status of the trees. The results of the two soil populations showed high soil acidity, low organic matter content, low phosphorus and high potassium content. A high percentage of leaf samples showed concentrations of nutrients below the lower limit of the sufficiency range in both the first and second sample populations, for nitrogen (respectively 63 and 47%), phosphorus (18 and 15%), potassium (34 and 31%), calcium (19 and 52%), magnesium (21 and 13%) and boron (40 and 43%). In the case of boron, 6 and 8% of leaf samples of the first and second populations displayed values within the excessive concentration range. The results of this work also revealed absence or poor relationships between soil properties and/or soil available nutrients and leaf concentration of nutrients. In this crop, therefore, it seems necessary to start applying regular fertilization programs, mainly based on regular evaluation of the nutritional status of trees through leaf analysis.
- The phenolic composition of hops (Humulus lupulus L.) was highly influenced by cultivar and year and little by soil liming or foliar spray rich in nutrients or algaePublication . Afonso, Sandra; Dias, Maria Inês; Ferreira, Isabel C.F.R.; Arrobas, Margarida; Cunha, Mário; Barros, Lillian; Rodrigues, M.A.The interest in expanding the production of hops outside the traditional cultivation regions, mainly motivated by the growth of the craft brewery business, justifies the intensification of studies into its adaptation to local growing conditions. In this study, four field trials were undertaken on a twenty-year-old hop garden, over periods of up to three years to assess the effect of important agro-environmental variation factors on hop phenol and phenolic composition and to establish its relationship with the elemental composition of hop cones. All the field trials were arranged as factorial designs exploring the combined effect of: (1) plots of different vigour plants year; (2) plots of different plant vigor algae- and nutrient-rich foliar sprays year; (3) plot liming year; and (4) cultivars (Nugget, Cascade, Columbus) year. Total phenols in hops, were significantly influenced by most of the experimental factors. Foliar spraying and liming were the factors that least influenced the measured variables. The year had the greatest effect on the accumulation of total phenols in hop cones in the different trials and may have contributed to interactions that often occurred between the factors under study. The year average for total phenol concentrations in hop cones ranged from 11.9 mg g1 to 21.2 mg g1. Significant differences in quantity and composition of phenolic compounds in hop cones were also found between cultivars. The phenolic compounds identified were mainly flavonols (quercetin and kaempferol glycosides) and phenolic carboxylic acids (p-coumaric and caffeic acids).
- Results from a long-term study on groundcover management in rainfed olive orchardsPublication . Rodrigues, M.A.; Afonso, Sandra; Ferreira, Isabel Q.; Arrobas, MargaridaIn this work, results of a soil management experiment carried out in a rainfed olive orchard were presented. The treatments were: conventional tillage; herbicide application (glyphosate, a non‐selective post‐emergence herbicide) in spring; and sheep walking. The results showed better soil fertility parameters in the treatment consisting of natural vegetation managed by grazing (sheep walking). However, this treatment led to the worst results regarding tree nutritional status and olive yields. After 10 years, the accumulated olive yields were 187.2, 142.9 and 89.5 kg tree‐1 respectively in herbicide, tillage and sheep walking treatments. When the differences among the treatments became dramatically high, and no doubt remained about the effect of the treatments, we decided to change the experimental design. The plot previously grazed began to be managed with glyphosate and vice‐versa. The plot managed by tillage was kept the same. After four years assessing the three nutritional status and olive yields, it was found that the cumulated production (average 4 years) was already slightly higher in the new plot managed with glyphosate (85.4 kg tree‐1), followed by sheep walking (80.3 kg tree‐1) and tillage plot (71.0 kg tree‐1). The result revealed that in rainfed orchards we could not be overly tolerant to herbaceous vegetation since the excessive competition for water in the spring may reduce productivity. Cover cropping is a sensitive strategy in these agroecosystems.