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- Um olhar sobre a gestão do solo em olival face ao aquecimento globalPublication . Rodrigues, M.A.; Raimundo, Soraia; Arrobas, MargaridaAs previsões para as alterações climáticas para as regiões do território nacional onde a oliveira tem expressão económica traçam um cenário de aumento de temperatura, com vagas de calor mais frequentes, e menor precipitação, em particular no período estival, com riscos de secas mais prolongadas. O que há de novo, então, neste cenário? Significa que o pior do clima mediterrânico, isto é, o que mais restringe atualmente a produtividade primária se está a agravar.
- Photosynthesis, yield, nutrient availability and soil properties after biochar, zeolites or mycorrhizal inoculum application to a mature rainfed olive orchardPublication . Lopes, João Ilídio; Arrobas, Margarida; Raimundo, Soraia; Gonçalves, Alexandre; Brito, Cátia; Martins, Sandra; Pinto, Luís; Moutinho-Pereira, José; Correia, Carlos M.; Rodrigues, M.A.Soil conditioners and beneficial microorganisms are important tools that can be used to increase the sustainability of agro-systems. However, the high diversity of conditions where they can be applied may influence the results, which requires extensive field research. In this study, a field trial of four years was conducted in olive (Olea europaea L.) to assess the effect of biochar, zeolites and a commercial mycorrhizal inoculum in the photosynthetic performance, nutritional status of trees, olive yield and soil properties. The experimental design also included a fertilizer treatment with nitrogen (N), phosphorus (P), potassium (K) and boron (B), which nutrients were applied at 50 kg ha1 of N, P2O5 and K2O and 2 kg ha1 of B, and an untreated control. The mineral fertilizer treatment increased significantly the dry mass of pruning wood and the average olive yield by 21% over the control treatment. The mineral treatment increased plant N nutritional status, the most likely reason why the trees of this treatment performed better. Overall, the soil treatments had net photosynthetic rates similar to each other and higher than the control treatment, from the second year onwards. Biochar increased soil organic matter, as a result of the carbon (C) contained in the amendment itself, and probably by stimulating soil biological activity. Biochar and zeolites did not improve the productive performances of the tress, but increased the soil cation exchange capacity (CEC), which can benefit the system in the long-term. Mycorrhizal fungi did not show any benefit for soil or plants, which could mean that mycorrhization was not established, or their effect was not better than that of native microorganisms. In the conditions of this study, the interest of using commercial mycorrhizal fungi in a mature olive orchard seems to be low.
- Lettuce response to the application of two commercial leonardites and their effect on soil properties in a growing medium with nitrogen as the main limiting factorPublication . Arrobas, Margarida; Andrade, Monica; Raimundo, Soraia; Mazaro, Sergio Miguel; Rodrigues, M.A.The aim of the study was to compare the effect of two leonardites (Humitec & REG; and Humic Gold & REG;) and an organic compost (Nutrimais & REG;) with an untreated control on lettuce. The pot experiment was carried out in NE Portugal, in autumn 2019 and spring 2020. Humitec, Humic Gold and Nutrimais were applied alone or as a supplement to nitrogen (N), phosphorus (P) and potassium (K). The experiment was arranged as a three-factor experimental design (organic amendment, NPK addition and growing season). The growing season significantly influenced lettuce dry matter yield (DMY), the spring cycle being the highest yielding (10.6 to 6.5 g plant(-1)). NPK fertilization also significantly increased lettuce DMY (11.2 to 5.9 g plant(-1)). The organic amendment significantly influenced the concentration of some nutrients in plant tissues and some soil properties, but it did not influence lettuce DMY. In respect of growing season, Nutrimais increased lettuce DMY in the first one. In relation to the absence or otherwise of NPK fertilization, Nutrimais increased lettuce DMY in the pots not receiving NPK. Leonardites did not influence soil properties, tissue nutrient concentration or lettuce DMY. The positive effect on the lettuce DMY of organic compost was probably due to the supply of N, apparently the plants' most significant limiting factor. The non-positive results of leonardites were due to the fact that they neither provided N, nor enhanced its bioavailability from the soil. Thus, NPK fertilizer and Nutrimais, a compost of low C/N ratio, providing some N had the greatest effect on lettuce DMY.
- A controlled-release fertilizer improved soil fertility but not olive tree performancePublication . Silva, Ermelinda; Arrobas, Margarida; Gonçalves, Alexandre; Martins, Sandra; Raimundo, Soraia; Pinto, Luís; Brito, Cátia; Moutinho-Pereira, José; Correia, Carlos M.; Rodrigues, M.A.The use of a controlled-release fertilizer (CRF) was studied in a traditional rainfed olive grove in a Mediterranean climate where precipitation is very irregular, particularly in the spring. The objective of the study was to assess whether a CRF can improve the olive tree's performance compared to a conventional nitrogen (N) fertilizer (CF), by supplying N gradually and reducing the risk of potential N loss from leaching. The fertilized treatments showed better plant N nutritional status, which resulted in enhanced net photosynthesis and higher leaf concentrations of total soluble sugars, chlorophylls and soluble proteins which, in turn, increased olive yield by 43% in comparison to the unfertilized control. However, in general, no significant differences were found between fertilized treatments in the performance parameters of the trees evaluated, including olive yield. Somewhat unexpectedly, CRF consistently increased the soil organic carbon (C) (29%), kjeldahl-N (75%) and easily extractable glomalin-related soil proteins (EE-GRSP) (60%) and total GRSP (T-GRSP) (122%) compared to the CF. The result was ascribed to a stimulus on the development of herbaceous vegetation and eventually on the activity of the roots of the trees due to the higher soil inorganic-N availability in the autumn. Thus, some soil inorganic-N in the autumn seems to comprise a low risk of leaching, since weeds act as a catch crop and convert this inorganic N into an organic substrate, with potential benefits in the long-term for the agro-system.
- Omitting the Application of Nitrogen or Potassium Reduced the Growth of Young Chestnut (Castanea sativa) Trees, While a Lack of Boron Decreased Fruit YieldPublication . Arrobas, Margarida; Raimundo, Soraia; Correia, Carlos M.; Rodrigues, M.A.The chestnut tree (Castanea sativa Mill.) is gaining importance in the mountainous regions of southern Europe due to the high value of its fruits. It is essential to establish effective cultivation protocols, considering that this species is still relatively understudied. In this study, we present the outcomes of the initial establishment of a chestnut orchard conducted through a nutrient omission trial for four years. The treatments included a fertilization plan with nitrogen, phosphorus, potassium, and boron (NPKB), the control, and four other treatments corresponding to the omission of each nutrient (-NPKB, N-PKB, NP-KB, NPK-B). The -NPKB and NP-KB treatments showed significantly lower trunk circumferences and canopy volumes compared to the other treatments. The NPKB treatment resulted in the lowest fruit production, with a total accumulated yield (2020–2022) of 0.56 kg tree–1, a value significantly lower than that of NPKB (1.12 kg tree–1) and N-PKB (1.19 kg tree–1). The assessment of nutrient concentrations in the leaves revealed plants with deficient levels of B and K in treatments that did not receive these nutrients. Conversely, N levels in the leaves in the -NPKB treatment fell within the sufficiency range (20 to 28 g kg–1). This suggests that the sufficiency range should be adjusted to higher values, given the treatment’s effect on tree growth. It was also observed that the -NPKB treatment led to lower soil organic matter compared to the other treatments, likely due to reduced herbaceous vegetation development under the canopy, leading to decreased organic substrate deposition in the soil. The main findings of this study are that N and K were crucial elements for the optimal growth of chestnut trees, while B played a significant role in fruit production.
- Large chestnut trees (Castanea sativa) respond poorly to liming and fertilizer applicationPublication . Rodrigues, M.A.; Raimundo, Soraia; Pereira, Abel; Arrobas, MargaridaEstablishing a fertilization plan for large trees is particularly difficult due to the high soil volume that the roots exploit and the buffer effect of the perennial woody structure on the concentration of nutrients in the leaves. This work evaluates the response of chestnut, a very large tree, to different fertilizer solutions. The study was conducted in two chestnut orchards planted in acid soils that were subjected to the application of lime plus phosphorus (Lime+P), lime plus a compound NPK fertilizer (Lime+NPK), and an unfertilized control (Control). The effects of the treatments on soil properties, nutritional status and photosynthetic performance of the trees, and nut production, were assessed from field and laboratory analyses. Liming significantly increased soil pH and exchangeable calcium (Ca). Treatments did not significantly influence leaf P and K levels, although leaf N concentrations were significantly higher in the Lime+NPK treatment on two of the three sampling dates. In one of the trials, the average accumulated nut yield was higher in the Lime+NPK (71.7 kg tree−1) treatment compared with the control (59.6 kg tree−1) and the Lime+P (51.7 kg tree−1) treatments, although without significant differences at P < 0.05. Overall, the results show the chestnut tree to be a species tolerant of soil acidity. The results also show that the buffer capacity of the plant in regulating the nutrient concentration in the leaves seems to be higher for P than for N, and therefore, concentrations of N in the leaves require the regular application of the nutrient as a fertilizer.
- Leonardites ricas em ácidos húmicos e fúlvicos tiveram um efeito reduzido na composição dos tecidos e na produção de matéria seca de jovens plantas de oliveira cultivadas em vasosPublication . Arrobas, Margarida; Raimundo, Soraia; Rodrigues, M.A.O uso de substâncias húmicas na agricultura tem aumentado nos últimos anos, e as leonardites têm sido uma importante matéria-prima no fabrico de produtos comerciais ricos em ácidos húmicos e fúlvicos. Produtos à base de leonardite têm sido usados para melhorar as propriedades do solo e ajudar as plantas a suportar melhor stresses abióticos e bióticos. Neste estudo, os efeitos de duas leonardites comerciais (Humitec® e Humic gold® e de um resíduo sólido urbano comercial (Nutrimais®) autorizados para agricultura biológica, e de uma modalidade testemunha não fertilizada nas propriedades do solo e na produção de matéria seca e composição dos tecidos, foram avaliados num ensaio em vasos com jovens plantas de oliveira cultivadas durante catorze meses. Os trêsprodutos orgânicos foram aplicados em duas doses (simples e dupla) mas dentro das gamas recomendadas nos folhetos comerciais. O estudo foi organizado em duas experiências: uma contendo os sete tratamentos mencionados anteriormente; e outra tendo os mesmos tratamentos suplementados com adubo mineral NPK (este não autorizado para agricultura biológica). No geral, o resíduo sólido urbano aumentou o carbono orgânico do solo em ~8% relativamente à testemunha. Na experiência sem suplementação de NPK, as concentrações de azoto na parte aérea e de fósforo nas raízes foram mais elevadas com a aplicação de resíduo sólido urbano em relação à testemunha (mais 12% de azoto nas folhas e mais 32% de fósforo nas raízes), enquanto na experiência com suplementação NPK não foram observadas diferenças significativas entre tratamentos. A produção de matéria seca total foi ~10% mais elevada no conjunto de tratamentos com NPK em comparação com os tratamentos sem NPK. As leonardites não influenciaram significativamente nenhuma das variáveis medidas em comparação com a testemunha. Neste estudo, uma boa gestão da maioria de variáveis ambientais que afetam o crescimento das plantas (por ser uma experiência em vasos), pode ter reduzido a possibilidade de obtenção de um efeito positivo no estado nutricional e no crescimento das plantas com o uso de leonardites comerciais. As leonardites parecem ter tido um ligeiro efeito na imobilização biológica de azoto. Isto não é necessariamente uma vantagem ou uma desvantagem, é antes uma característica que deve ser compreendida para ajudar os agricultores a tirarem melhor partido do uso desses produtos.
- Nitrogen Use Efficiency and Crop Yield in Four Successive Crops Following Application of Biochar and ZeolitesPublication . Rodrigues, M.A.; Torres, Luiza do Nascimento Dias; Damo, Letícia; Raimundo, Soraia; Sartor, Laércio; Cassol, Luís César; Arrobas, MargaridaTwo soil amendments, biochar and zeolites, were evaluated in their potential for increasing crop productivity and agro-system sustainability. The effect of biochar and zeolites, in combination with four nitrogen (N) rates [0 (N0), 50 (N50), 100 (N100), and 200 (N200) kg ha−1], on crop yield, N use efficiency, and soil properties was evaluated in a cropping system of irrigated forage maize (Zea mays L.) grown in summer and oats (Avena sativa L.) grown in winter as a catch crop. Biochar increased soil organic carbon (C), pH, cation exchange capacity (CEC), and extractable phosphorus (P), but strongly reduced N recovery in the set of the four cropping cycles. In biochar-amended plots, N50 had a negative apparent N recovery (− 21%), indicating that less N was recovered by the plants than in the N0 treatment without biochar. Biochar reduced maize dry matter (DM) yield by 15.6% in comparison to the untreated control, indicating N immobilization by biochar at low N rates (N0 and N50). Zeolites did not influence crop productivity or soil properties, except for the increase in extractable K, probably the result of its initial K content. N application to maize significantly increased the productivity of both crops, including that of the non-fertilized oats. Under the conditions of this experiment, biochar and zeolites did not prove to be useful soil amendments to increase crop DM yield in the short-term. The use of biochar increased soil organic C, which associated to a high N rate can enable the dual objective of maintaining productivity and the sustainability of the agro-system. The results stressed also the important role of oats as a cover crop to reduce the risk of nitrate leaching and denitrification during winter.
- Produtividade de uma pastagem submetida a regimes de fertilização anual com azoto, fósforo, potássio ou boroPublication . Raimundo, Soraia; Arrobas, Margarida; Felix, Alberto; Vergueira, Ana; Martins, Carolina; Ribeiro, Emanuel; Faria, Inácio; Silva, Jessica Lana Menezes; Teixeira, João; Amorim, José; Queirós, José; Gonçalves, Luís; Amorim, Manuel; Cardoso, Nilton; Carneiro, Pedro; Martins, Ricardo; Pires, Jaime; Rodrigues, M.A.Este estudo tem como objetivo avaliar o efeito de longo prazo da fertilização de um lameiro na recuperação dos nutrientes aplicados e na produção de biomassa. Os lameiros são característicos de zonas de montanha, onde existe reduzida experiência da prática de fertilização com fertilizantes minerais. O ensaio está instalado em Bragança desde a primavera de 2013. Os regimes de fertilização em estudo são aplicação anual 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), e uma modalidade testemunha. Anualmente é feita a avaliação de biomassa, usando caixas de exclusão de 0,50 x 0,50 m, em dois cortes, um no fim do inverno e outro no fim da Primavera. O corte de fim de inverno simula a produção de biomassa na fase de pastoreio e o corte de fim de primavera simula a biomassa produzida na fase de produção de feno. Após 11 cortes de vegetação, a aplicação de azoto aumentou de forma significativa a produção de biomassa sobre os restantes tratamentos. As restantes modalidades fertilizadas não aumentaram a produção de biomassa relativamente à testemunha. Na exportação de nutrientes na biomassa, os valores de cada nutriente tendem a ser mais elevados no talhão correspondente à aplicação desse nutriente e também no talhão fertilizado com azoto. No primeiro caso devido ao aumento da concentração do nutriente na biomassa e no segundo devido ao efeito do azoto no aumento de biomassa.
- Produtividade de uma pastagem submetida a aplicação anual de azoto, fósforo, potássio ou boroPublication . Rodrigues, M.A.; Raimundo, Soraia; Pires, Jaime; Arrobas, MargaridaA fertilização é um dos instrumentos frequentemente utilizados na gestão de pastagens, designadamente para aumentar a produtividade e a qualidade da pastagem e equilibrar as componentes gramínea e leguminosa. Estudos de fertilização são relativamente abundantes em pastagens melhoradas com introdução de espécies semeadas, mas não tanto em pastagens de vegetação espontânea. Em Bragança, na Qta de Sta Apolónia, decorre um ensaio onde, desde 2013, se têm aplicado cinco modalidades de fertilização anual, designadamente aplicação de azoto, de fósforo, de potássio ou de boro, de forma isolada, e uma modalidade testemunha sem fertilização. A produção de biomassa aumentou de forma significativa apenas na modalidade fertilizada com azoto, tendo correspondido a 122% da obtida na modalidade testemunha (efeito acumulado de 5 anos). A biomassa surge mais rica em proteína na modalidade fertilizada com azoto e, respetivamente, também mais rica em cada talhão nos minerais que se aplicaram como fertilizante.