Percorrer por autor "Rodrigues, Manuel Ângelo"
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- Assessing the Role of Phosphorus, Starter Nitrogen and Boron in Subterranean Clover and Annual Ryegrass Grown in Acidic Soils Under Mediterranean Conditions in PortugalPublication . Sawimbo, Almeida; Aguiar, Peltier; Arrobas, Margarida; Aguiar, Carlos; Rodrigues, Nuno; Jongen, Marjan; Teixeira, Ricardo F. M.; Domingos, Tiago; Rodrigues, Manuel ÂngeloIn Mediterranean pasture systems, maintaining legume persistence and productivity is often constrained by phosphorus (P) deficiency in acidic soils. Although small doses of starter nitrogen (N) are commonly used in pulse crops to support early growth before N fixation begins, this practice has not been widely tested in legume-grass mixtures. In addition, boron (B), a micronutrient particularly important for dicot species, may also influence legume performance under these conditions. Thus, this study investigated the effects of P application on dry matter yield (DMY) and nutrient uptake in subterranean clover (Trifolium subterraneum L., cv. Denmark), annual ryegrass (Lolium multiflorum Lam., cv. Falladino) and their mixture, using a pot experiment with acidic soils from two distinct locations in Portugal. The study also evaluated the impact of a small N starter dose and B application. Although Soil 2 had higher acidity (pH 5.0) than Soil 1 (pH 5.4), it supported greater biomass production, likely due to its higher organic carbon (C) content (50.8 g kg-1), which may have buffered soil acidity. P application significantly increased P uptake, DMY and N accumulation in legumes, suggesting a critical role in nodulation and/or nodule function. The N starter had no significant effect, likely because sufficient N was released from soil organic matter prior to the onset of biological N fixation. While the B application increased tissue B concentrations, it did not affect DMY, possibly because B was adequately available from organic matter. These findings highlight the importance of P in legume management in pasture systems and suggest that, in soils with sufficient organic matter, the application of starter N and B may not be necessary.
- 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.
- Chemical evaluation of agro-industrial wastes for composting water hyacinthPublication . Oliveira, Verónica; Rodrigues, Manuel Ângelo; Arrobas, Margarida; Rodrigues, Edite; Simões, P.; Miguens, Filomena; Santos, DanielaWater hyacinth (WH) waste removed from watercourses can be valued through composting. In this study it was determined the elemental composition of WH waste and other local organic residues to prepare suitable mixtures for composting. Rice husk, straw and woodchip showed high C/N ratios (> 80). In turn, farmyard manures and vegetables displayed low C/N ratios (< 20). WH tissues showed increased C/N ratios with the aging process (from 17.4 to 37.1). WH tissues had low P (< 2 g kg-1) and high Fe (>5000 mg kg-1) and Mn (2476.7-- 12885.8 mg kg-1) concentrations. Fe and Mn levels were particularly high in the roots (31706.8 and 38335.2 mg kg-1, respectively). Such high levels of Mn and Fe may impair the composting process and restrict the agricultural use of compost. Thus, the composting piles must be prepared from an optimized combination of organic materials that avoids either of those problems.
- 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.
- Evaluating soil phosphorus tests and nutrient limitations in Mediterranean pasturesPublication . Arrobas, Margarida; Raimundo, Soraia; Sawimbo, Almeida; Rodrigues, Nuno; Jongen, Marjan; Teixeira, Ricardo F.M.; Domingos, Tiago; Rodrigues, Manuel ÂngeloReliable phosphorus (P) fertilization guidelines for Mediterranean pastures remain uncertain due to inconsistent soil testing methods, the complexity of mixed-species systems, and the neglect of other limiting nutrients. This study primarily aimed to identify reliable soil P tests and secondarily to explore potential nutrient limitations by assessing seven acidic Portuguese soils under Mediterranean conditions using subterranean clover (Trifolium subterraneum) and ryegrass (Lolium multiflorum) as model species. Five P extraction methods (Egner-Riehm, Olsen, Bray II, Mehlich I, and anion exchange resin) were compared alongside a pot experiment with clover, ryegrass, and their mixture. Biomass production, plant nutritional status, and soil-plant relationships were used to assess nutrient availability and plant response. The Egner-Riehm method proved the most reliable, showing linear correlation with the resin method (R2 = 0.89), widely regarded as the best indicator of soil P bioavailability. P availability was therefore not a limiting factor for biomass production. The lowest soil P content (54 mg kg-1 P2O5, Egner-Riehm) was close to the medium threshold (50-100 mg kg-1), yet plant growth indicated adequacy. In contrast, nitrogen (N) emerged as the main growth constraint, and boron (B) deficiency further restricted clover performance, confirming additional nutritional imbalances. A linear relationship between soil and tissue B supported its association with DMY, and tissue B levels were below sufficiency thresholds. Overall, in acidic Portuguese soils under Mediterranean conditions, soil P was adequate, whereas N and B acted as key constraints to productivity. These findings support more accurate and efficient fertilization strategies for Mediterranean pastures.
- 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.
- Liming alone is not enough: The role of phosphorus and boron in supporting legume pasture growthPublication . Aguiar, Peltier; Arrobas, Margarida; Aguiar, Carlos; Rodrigues, Nuno; Jongen, Marjan; Teixeira, R.F.M.; Domingos; Tiago; Rodrigues, Manuel ÂngeloSoil fertility management is a critical factor for ensuring the persistence of the legume component in improved pastures in Mediterranean regions. To promote legume growth, the most common practices include the application of lime to correct Soil acidity and phosphate fertilizers to address phosphorus (P) deficiencies. This study examined two acidic soils and evaluated the need for P and boron (B) supplementation following liming. A factorial pot experiment (Soil type × vegetation type × fertilizer treatment) was conducted using subterranean clover (Trifolium subterraneum L.), annual ryegrass (Lolium multiflorum Lam.), and their mixture. Results revealed significantly higher dry matter yield (DMY) for the legume (18.1 g pot⁻¹) compared to the grass (5.9 g pot⁻¹), due to the legume's ability to access atmospheric nitrogen (N). Soil 2, which had higher initial P availability than Soil 1, and P fertilization both enhanced N accumulation in legume tissues, the percentage of N derived from the atmosphere (%Ndfa), and DMY. These outcomes indicate that liming alone was insufficient to increase P availability and eliminate the need for P fertilization. For instance, DMY increased from 15.0 g pot⁻¹ with liming alone to 19.4 g pot⁻¹ when P was supplemented. Additionally, B application increased N uptake and %Ndfa in the legume, with the latter rising from 48.9% in the liming-only control to 77.5% with B supplementation. These results suggest that liming, by increasing Soil pH, may reduce B bioavailability, highlighting the need for B supplementation following lime application.
- 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.