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Projeto de investigação
As leguminosas na gestão do azoto e do fósforo em agricultura sustentável
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Publicações
Reduced Effect of Commercial Leonardite and Seaweed Extract on Lettuce Growth under Mineral, Organic, and No Fertilization Regimes
Publication . Aguiar, Peltier; Corrêa, Gediane Maria Garcia; Rodrigues, M.A.; Arrobas, Margarida
In this study, two commercial products based on the main groups of contemporary biostimulants—a commercial leonardite and a seaweed extract—were tested with the objective of assessing the conditions under which they can enhance lettuce (Lactuca sativa L.) performance, particularly to determine if synergies with conventional fertilization methods can be observed. The experimental protocol was arranged as a factorial design with two factors: organic or mineral fertilization × plant biostimulant. The organic or mineral fertilization factor included five levels: two rates of a nitrogen (N) fertilizer (40 (Nmin40) and 80 (Nmin80) kg ha−1 of N), the same N rates applied as an organic amendment (Norg40 and Norg80), and an unfertilized control (N0). The plant biostimulants used were a commercial leonardite (leonardite) for soil application before planting, a commercial seaweed extract (algae) for foliar application during the growing season, and a control without plant biostimulant. Leonardite significantly increased lettuce dry matter yield (DMY) compared to the control only in the first growing cycle (11.5 and 13.5 g plant−1) and showed no significant interaction with conventional fertilization. It also consistently increased phosphorus (P) levels in the plant tissues. The seaweed extract did not show any effect on the plant, nor did it have any interactions with conventional fertilization regarding DMY. In contrast, with mineral fertilization, lettuce DMY increased from 8.0 and 4.0 g plant−1 (N0) to 22.2 and 12.0 g plant−1 (Nmin80) in the first and second growing cycles, respectively. The response to organic fertilization was lower, yet DMY still increased from 4.0 to 8.1 g plant−1 in the second growing cycle. Generally, this type of plant biostimulant is tested under some form of environmental stress, where it often yields positive results. In this study, the optimal cultivation conditions maintained for the lettuce in the pots likely explain the limited response to the biostimulants. This study suggests that the product labels should more clearly indicate whether they are recommended for general cultivation conditions or specifically for situations where a particular environmental stress can be anticipated.
Different Species and Cultivars of Broad Beans, Lupins, and Clovers Demonstrated Varying Environmental Adaptability and Nitrogen Fixation Potential When Cultivated as Green Manures in Northeastern Portugal
Publication . Aguiar, Peltier; Arrobas, Margarida; Nharreluga, Ézar Alfredo; Rodrigues, M.A.
The success of growing legumes as green manure depends on their spatial and temporal
integration within agroecosystems, which minimizes competition with cash crops, and on their
nitrogen (N) fixation potential. This study evaluated seven legume species for biomass production,
N fixation, and suitability for use in cropping systems in northern Portugal. Oats (Avena sativa L.)
were grown to estimate the N fixation using the difference method, as a non-legume reference crop is
required for this purpose, and oats are widely grown in the region. The study was conducted over
four cropping cycles (2021–2024) in two climate zones across four land plots. The results indicated
that the biomass production and N fixation varied by the species/cultivar and cropping cycle, which
was significantly influenced by spring precipitation. Broad beans (Vicia faba L.) failed to develop
in one cycle on highly acidic soil (pH 4.9), showing negative N fixation values when calculated
by the difference method. Conversely, the lupins maintained a relatively high level of N fixation
across all the conditions, demonstrating strong environmental adaptability. Thus, the N fixation
values across the four cycles ranged from −5.4 to 419.4 kg ha−1 for broad bean (cv. Favel), while
yellow lupin (Lupinus luteus L.) exhibited average values between 204.0 and 274.0 kg ha−1. The
percentage of N derived from the atmosphere (%Ndfa) ranged from −13.3 to 91.6, −39.4 to 85.8, 83.8
to 94.7, 74.9 to 94.3, 72.8 to 92.2, 23.1 to 75.8, and 11.7 to 21.7 for these species/cultivars. Due to their
environmental adaptability, biomass production, and N fixation capacity, these legumes could be
used as green manure in inter-rows of woody crops or in summer annual crops like tomatoes and
maize, grown in winter as an alternative to fallow land. The lupins showed strong promise due to
their environmental resilience.
Contributions to accelerating a numerical simulation of free flow parallel to a porous plane
Publication . Schepke, Claudio; Spigolon, Roberta A.; Rufino, José; Cristaldo, Cesar F. Da C.; Pizzolato, Glener L.
Flow models over flat p orous surfaces have applications in natural processes, such as material, food, chemical processing, or mountain mudflow simulations. The development
of simplified a nalytical or numerical models can predict characteristics such as velocity, pressure, deviation length, and even temperature of such flows for geophysical and engineering purposes. In this context, there is considerable interest in theoretical and experimental models. Mathematical models to represent such phenomena for fluid mechanics have continuously been developed and implemented. Given this, we propose a mathematical and simulation model to describe a free-flowing flow pa rallel toa
porous material and its transition zone. The objective of the application is to analyze the influence o f t he p orous matrix on the flow u nder d ifferent m atrix p roperties. W e i mplement a Computational Fluid Dynamics scheme using the Finite Volume Method to simulate and calculate the numerical solutions for case studies. However, computational applications of this type demand high performance, requiring parallel execution techniques. Due to this, it is necessary to modify the sequential version of the code. So, we propose a methodology describing the steps required to adapt and improve the code. This approach decreases 5.3% the execution time of the sequential version of the code. Next,
we adopt OpenMP for parallel versions and instantiate parallel code flows and executions on multi-core. We get a speedup of 10.4 by using 12 threads. The paper provides simulations that offer the correct understanding, modeling, and construction of abrupt transitions between free flow a nd porous media. The process presented here could expand to the simulations of other porous media problems. Furthermore, customized simulations require little processing time, thanks to parallel processing.
Liming alone is not enough: The role of phosphorus and boron in supporting legume pasture growth
Publication . Aguiar, Peltier; Arrobas, Margarida; Aguiar, Carlos; Rodrigues, Nuno; Jongen, Marjan; Teixeira, R.F.M.; Domingos; Tiago; Rodrigues, Manuel Ângelo; Rodrigues
Soil 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.
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Fundação para a Ciência e a Tecnologia
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Número da atribuição
PRT/BD/154361/2023