Browsing by Author "Rodrigues, Manuel Ângelo"
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- Biomass and nutrient release dynamics of decomposing rolling down legume cover crops in a steep-sloped Mediterranean vineyardPublication . Brito, Cátia; Martins, Sandra; Saraiva, Francisco; Roque, João; Arrobas, Margarida; Rodrigues, Manuel Ângelo; Correia, CarlosWell-managed cover crops are gaining traction as an alternative to conventional tillage, offering a range of agronomic and ecological benefits. This field study, conducted in a commercial vineyard in the Douro region (Portugal) during the 2022/2023 growing season, evaluated the decomposition dynamics and nutrient release from different legume cover crop residues over a period of 183 days after sowing and 114 days after rolling. These mixtures consisted of subterranean clovers (SC), low-growing (LG), and moderately-growing (MG) legumes. MG legumes produced the highest biomass (7.8 t ha-1), followed by LG (7.2 t ha-1) and SC (5.9 kg ha-1). MG residues decomposed more rapidly, potentially meeting early grapevine nutrient demands. SC residues decomposed more slowly, retaining nutrients over longer periods and acting as a sustained source of fertility, while LG legumes provided a balance between rapid and gradual nutrient release. Biomass production peaked before rolling termination, suggesting that the lower canopy foliage might have started decomposing as the crops reached maximum vegetative expansion and early seed formation, reflecting the dry, hot environmental conditions during the study year. The observed nutrient release from cover crop residues, particularly during the first 45 days post-termination, suggested a potential to support grapevine nutrient requirements, although direct uptake by grapevines was not assessed in this study. SC residues retained higher levels of key macronutrients and micronutrients over time. These findings highlight the importance of selecting legume cover crop mixtures aligned with vineyard management goals, whether rapid nutrient supply or sustained soil fertility. The study also underscores the influence of environmental conditions, residue composition and termination timing on nutrient dynamics. Long-term research is recommended to evaluate cover crops' chemical composition, cumulative effects on soil organic carbon (C) and nutrients, microbial activity and effects on grapevine performance across diverse Mediterranean environments.
- The Composting of Water Hyacinth: A Life Cycle Assessment PerspectivePublication . Serafini, Lais Fabiana; Arrobas, Margarida; Rodrigues, Manuel Ângelo; Feliciano, Manuel; Miguens, Filomena; Oliveira, Verónica; Santos, Daniela; Díaz de Tuesta, Jose Luis; Gonçalves, ArturWater hyacinth is an invasive species that causes eutrophication in lentic waters. While mechanical removal is effective, it generates hazardous waste with biological contamination risk. Composting is a safe waste treatment option, inhibiting seeds and yielding agriculturally suitable compost. Life cycle assessment evaluated the environmental impacts of six composting piles using eight different by-products (potato peel, cattle manure, wood chip, rice straw, potato leftovers, olive pomace and biochar), all formulations containing water hyacinth. The worst environmental performances were the M2 pile (water hyacinth + olive pomace + cattle manure + potato leftovers) which achieved the highest AP (47.33 kg SO2 eq.) and EP (10.56 kg PO4³− eq.), while M3 (water hyacinth + olive pomace + rice straw + potato leftovers) had the highest GWP (816.51 kg CO2 eq.) and OLD (2.99E-11 kg R11 eq.). The biological composting process contributed the most to the overall increase in the impact categories for all piles due to air emissions (CH4 and N2O). M3 and M5 (water hyacinth + wood chip) had the worst performance in fossil fuel consumption due to distances travelled from by-products and energy use in the maintenance of composting piles. Concerning packaging, Big Bags with polypropylene had a greater impact than polyethylene bags (50 kg capacity). Evaluating the potential avoidance of mineral fertilisers, M3 compost showed potential for reducing TSP fertiliser production by 46%. Overall, M4, which incorporated a mixture of water hyacinth, olive pomace, wood chips and biochar, was the most favourable option from an environmental point of view.
- Increased uptake and accumulation of phosphorus and other nutrients by legumes enhance their bioavailability for non-legume speciesPublication . Aguiar, Peltier; Arrobas, Margarida; Rodrigues, Manuel ÂngeloLegumes are promoted in agroecosystems for their ability to fix atmospheric nitrogen (N), thereby reducing or eliminating the need for N fertilisation while also contributing N-rich organic residues, which non-legume species can subsequently utilise. In phosphorus (P)-poor soils, certain legumes appear to access less available forms of P, converting them into organic P and facilitating its use by non-legume species. This study evaluated seven legume species/cultivars and one grass species (as a control) in a trial conducted in low-fertility soils under four different growing conditions (location × year). The objective was to investigate the role of legumes in P and other nutrient uptake and accumulation in plant tissues. Some lupins and broad beans accumulated up to 30 kg/ha of P in their biomass, even without accounting for P in the roots. Calcium (Ca) and magnesium (Mg) concentrations in plant tissues were also significantly higher in legumes than in grass. In addition to concentrating certain nutrients in their tissues, legumes produced substantially more biomass due to their access to atmospheric N, resulting in considerably higher nutrient accumulation. Ca and Mg in some legumes exceeded 100 and 40 kg/ha in aboveground biomass, respectively, whereas in grasses, they remained below 4 kg/ha. Thus, when legumes are cultivated as green manure, these nutrients are returned to the soil in organic form, which can subsequently become available to non-legume crops through the mineralisation process of the organic substrate. Therefore, cultivating legumes not only enhances N availability for other species but also improves the cycling of other essential nutrients.
- Regenerative Agriculture: Insights and Challenges in Farmer AdoptionPublication . Moisés, Cristiano; Arrobas, Margarida; Tsitos, Dimitrios; Pinho, Diogo; Rezende, Raiza Figueiredo; Rodrigues, Manuel ÂngeloRegenerative agriculture has emerged as a new organic farming movement, initially difficult to distinguish from similar approaches. Its core concerns, such as ecosystem degradation caused by intensive farming, align with those of many other organic systems. However, regenerative agriculture prioritizes soil health, biodiversity, and social equity, setting itself apart through its scalability and flexibility. Unlike other ecological farming methods, often limited to smaller scales, regenerative agriculture aims to be implemented on large farms, typically major contributors to pollution due to reliance on external inputs like fertilizers and pesticides. Notably, regenerative certification standards are more flexible, allowing the use of industrially synthesized inputs under specific conditions, provided that regenerative principles are upheld. This review systematically examines seven core regenerative practices: no-tillage farming, crop rotation, cover cropping, green manures, intercropping, perennial cover systems, and integrated crop-livestock systems. It outlines the practical advantages and ecological benefits of each, while identifying key adoption challenges, including costs, farm size, and institutional barriers. The paper argues that addressing these issues, particularly concerning scale and socio-economic constraints, is essential for broader adoption. By synthesizing recent evidence, this review clarifies the distinctiveness of regenerative agriculture and highlights pathways for its scalable implementation.
- Resposta do cânhamo (Canabis sativa) à densidade de sementeira e fertilização azotadaPublication . Eje, Röndahl; Arrobas, Margarida; Queijo, Luís; Rocha, João; Rodrigues, Manuel ÂngeloO cânhamo já foi uma cultura muito importante. Durante a época dos Descobrimentos os navios utilizavam até cem toneladas de cordas e têxteis para as velas feitas de cânhamo. Recentemente foram identificados cerca de vinte e cinco mil produtos manufaturados com cânhamo. Os objetivos deste trabalho foram estudar a resposta da densidade da plantação e da fertilização azotada na produtividade de fibra e de semente na cultura do cânhamo. Os ensaios foram conduzidos com irrigação em dois locais no nordeste de Portugal, em Bragança (na Terra Fria) e em Mirandela (na Terra Quente). A cultura foi semeada em três densidades (25, 50 e 100 kg ha-1) e adubada com três doses diferentes de azoto (50, 100 e 200 kg ha-1). Foi também incluída uma modalidade testemunha, sem fertilização azotada, e três repetições de cada tratamento. Os resultados mostraram que ambos os fatores em estudo, densidade de plantação e adubação azotada, tiveram influência na produtividade de uma forma não linear. A maior produção de fibra neste ensaio foi obtida com a cultura semeada na densidade de 25 e 50 kg ha-1 de semente e com uma adubação de 100 kg N ha-1. Com uma adubação superior a 100 kg N ha-1 verifica-se uma diminuição na produtividade que poderá ser justificada por desequilíbrios nutricionais associados ao excesso de azoto. A maior produção de semente neste ensaio foi obtida nos tratamentos com a menor densidade de plantação e nas três menores dosagens de azoto.
- Sewage Sludge Provided Nitrogen To Maize (Zea Mays L.) Very Rapidly, Demonstrating a High Short-Term Net Mineralization RatePublication . Dimande, Paulo; Arrobas, Margarida; Rodrigues, Manuel ÂngeloThis study aims to evaluate the potential of sewage sludge as a sustainable alternative to traditional farmyard manures, considering the limited availability of such resources in many regions specializing in crop production. This study compared the application of sewage sludge (SS) and cow manure (CM) at equivalent nitrogen (N) rates in silage maize (Zea mays L.) cultivation over two growing seasons. Organic amendments were applied at rates of 50 (SS50, CM50), 100 (SS100, CM100), and 200 (SS200, CM200) kg ha(-)(1) of N, alongside an unfertilized control (N0), with three replicates per treatment in a completely randomized design. Dry matter yield (DMY) increased significantly with the applied dose but showed no significant differences between amendments. N availability indices, including the pre-side-dress soil nitrate test, leaf N concentration, and stalk nitrate test, revealed higher N availability from sewage sludge compared to cow manure at equivalent application rates. Apparent N recovery (ANR) by the end of the second growing season was 99.8%, 90.8%, and 74.5% for SS50, SS100, and SS200, respectively, and 76.7%, 75.4%, and 50.5% for CM50, CM100, and CM200, respectively. The rapid mineralization of sewage sludge likely results from its low carbon (C)/N ratio and the absence of lignin and other low-energy organic compounds, which are less metabolically accessible to soil microorganisms. These properties position sewage sludge as an intermediate between conventional organic compost and mineral fertilizers, making it particularly suitable for cropping systems requiring high short-term N availability.
- A Spray Foliar Containing Methylobacterium symbioticum Did Not Increase Nitrogen Concentration in Leaves or Olive Yield Across Three Rainfed Olive OrchardsPublication . Rodrigues, Manuel Ângelo; Lopes, João Ilídio; Martins, Sandra; Brito, Cátia; Correia, Carlos M.; Arrobas, Margarida; Rodrigues, Manuel ÂngeloBiological nitrogen (N) fixation has been advocated in agricultural fields due to being considered a more sustainable way to introduce N into agrosystems than industrial N fertilizers. In this study, a foliar spray inoculant containing the microorganism Methylobacterium symbioticum was applied. This microorganism is known for fixing N in the phyllosphere, regardless of the cultivated species. This study was conducted in three rainfed olive orchards over three years. In two orchards managed according to European Union (EU) integrated production rules, the experiment was organized as a factorial design with inoculant (applied at two levels, yes and no) and N fertilization (applied to the soil at three levels, 0, 40, and 80 kg ha−1 of N). The third trial, managed according to EU organic farming rules, was organized in a completely randomized design with three treatments: with (yes) and without (no) inoculant and with a treatment involving a seaweed extract, also for foliar application. The microbiological inoculant did not consistently influence olive yield or N concentration in leaves across the three trials. Conversely, N application to the soil significantly influenced N concentration in leaves and olive yield. In one of the trials, in the third year of the study, soil N application (80 kg ha−1) resulted in an olive yield of ~eight times higher than the unfertilized control treatment. The seaweed extract also did not lead to significant differences in leaf mineral composition or olive yield compared with the other treatments. These findings from the on-farm research highlight the importance of accurately determining the conditions under which commercial products can deliver effective results. It is crucial to acknowledge that these products involve expenses not only in their acquisition but also in their application.
- White Lupin and Hairy Vetch as Green Manures: Impacts on Yield and Nutrient Cycling in an Organic Almond OrchardPublication . Raimundo, Soraia; Arrobas, Margarida; Ribeiro, António C.; Rodrigues, Manuel ÂngeloOrganic farming systems, which prohibit synthetic fertilizers, often rely on legumes for their ability to fix atmospheric nitrogen (N). In orchards, legumes can be established as cover crops between tree rows to enhance nutrient cycling. This study evaluated the effects of two legume cover crops, white lupin (Lupinus albus L.) and hairy vetch (Vicia villosa Roth), compared to a Control treatment with conventional tillage, which is the most commonly used method of soil management in the region, in an organically managed almond [Prunus dulcis (Mill.) D.A.Webb] orchard compliant with European Union standards, in an experiment arranged as a completely randomized design. In the first year, kernel yield was highest in the Control treatment (404 kg ha-1), while significantly lower yields were recorded for white lupin (246 kg ha-1) and hairy vetch (283 kg ha-1), likely due to competition for resources between cover crops and trees. In the second year, however, the trend reversed, with cover crop treatments yielding significantly more (Lupin: 313 kg ha-1; Vetch: 296 kg ha-1) than the Control (199 kg ha-1). The cover crops accumulated over 150 kg ha-1 of N in their tissues, enhancing soil N availability and increasing N concentrations in almond leaves. In addition to N, cover crops influenced the cycling of other nutrients, increasing potassium (K) and boron (B) concentrations while reducing calcium (Ca) and manganese (Mn) in plant tissues. Despite being derived from a two-year study, these results highlight the complexity of interpreting cover crop effects, underscoring the need for further long-term research to provide more comprehensive guidance to growers.