DSpace Communidade:

Desenvolvimento de equipamento óptico para avaliação nutricional em plantas: aplicação na cultura do milho

Mon, 01 Jan 2024 00:00:00 GMT

Título: Desenvolvimento de equipamento óptico para avaliação nutricional em plantas: aplicação na cultura do milho Autor(es): Nogueira, Felipe Hermínio Meireles Abstract: The search for technologies that promote more sustainable and efficient practices is an increasingly important priority on the global agricultural scene. With this in mind, the use of spectroradiometry techniques to assess nitrogen concentration in maize crops has proved to be a promising alternative for conducting precision agriculture practices. In addition, the development of new instruments with optical sensors for agricultural applications has become increasingly important given the challenges of maintaining the sustainability of production systems. With this in mind, this work sought to improve elements of the use of MSPAT (Multispectral Soil Plant Analysis Tools) to determine reflectance. The improvements involved the development of a reference plate with sintered barium sulphate, new approaches using programming techniques, electronics and 3D printing. In addition, the performance of the optical instruments used to estimate leaf nitrogen in the maize crop was also assessed. With this in mind, an experiment was carried out in the experimental area of the Agricultural Electronics and Mechanisation Laboratory (LEMA), located at the Federal University of Ceará (UFC), with AG-1051 maize planted under treatments N0, N60, N90, N120, N150 and N180 (0, 60, 90, 120, 150 and 180 kg.ha-1 of N, respectively) with four replications, in two crop cycles and a Completely Randomized Design (CRD). The assessments took place during the V5, V10 and R2 phenological stages and were carried out using the MSPAT, SPAD and FieldSpec PRO FR 3 equipment. The spectroradiometer was used under the conditions provided by the dark-room of the UFC Geoprocessing Laboratory. The samples were then prepared for nitrogen (N) determination according to the methodology proposed by Kjeldah. In addition to leaf nitrogen, morphological parameters were also assessed throughout plant development, production, biomass and dry matter. The spectral indices (NRI, Normalise Ratio Index) were then correlated with the leaf N data and the individual bands were evaluated using Pearson's coefficient (r). Linear regression was then carried out (p-value < 0.01) with the NRI's to select the models, by optical instrument, that showed the best coefficient of determination (R²) with the leaf N data sets: i) at each stage of development, for the two crop cycles and ii) with the entire data set. Cross-validation (k-fold) was then carried out to assess the error parameters RMSE, MAE and adjusted coefficient of determination (R²adj.). The results for the best predictive models reveal different patterns for the selected bands between the data sets, as well as low generalisation capacity. However, it was possible to validate relevant models with MSPAT, SPAD and FieldSpec, which showed an R²adj. of 0.7871; 0.6959; 0.7199 and RMSE of 0.0425; 4.47; 0.0214 g.kg-1; respectively. From the model that showed the best performance with MSPAT, when using the NRI with the 900 and 560nm bands, the application in an agricultural area provided an RMSE of 2.73 g.kg-1 and MAE of 2.47 g.kg-1. However, it is clear that the use of new technologies has great potential for assessing leaf N in maize crops. Tipo: Dissertação

Manejo da adubação nitrogenada em capim-marandu sob pastejo: respostas da planta e do animal e dinâmica de carbono e nitrogênio no solo

Wed, 01 Jan 2025 00:00:00 GMT

Título: Manejo da adubação nitrogenada em capim-marandu sob pastejo: respostas da planta e do animal e dinâmica de carbono e nitrogênio no solo Autor(es): Freitas, Roberta Santos de Abstract: Approximately 50 to 70 percent of Brazilian pastures are in a state of degradation, which requires technological alternatives to improve forage quality and productivity. This study aimed to evaluate the effects of different nitrogen sources and application strategies on the agronomic characteristics of Marandu grass, cattle performance, and soil carbon (C) and nitrogen (N) stocks. The experiment was conducted at Tocantins Federal University (UFT) over two experimental years (2022-2023), with an 84-day experimental period per year, divided into three 28-day cycles. Urea (UR) and ammonium nitrate + calcium (NA) were tested under two application methods, single application (AU) and split applications (AP), in a 2×2 factorial design with three replicates. In the first year, 150 kg N ha⁻¹ was applied, and in the second year, 75 kg N ha⁻¹. Male cattle were used, with an average weight of 349.26 kg in the first year and 287.17 kg in the second year, distributed across 12 experimental paddocks of 0.33 ha each, with two animals per paddock. Animal performance was evaluated by weighing at each cycle, and forage samples were collected for agronomic and chemical and bromatological analyses. Litter was collected and analyzed for biomass, total nitrogen, organic matter (OM), and total carbon (TC). Carbon and nitrogen assessments were performed to estimate the soil C and N stocks by dry combustion. The use of NA fertilizer resulted in greater plant height (41.53 cm), higher organic matter content (923.6 g kg⁻¹), and litter carbon (567.01 g kg⁻¹) in the second year, compared to urea (34.85 cm; 877.40 and 545.71 g kg⁻¹, respectively). In the first year, the URAU fertilization reduced the crude protein content of the forage from 13% to 8%. In the second year, urea promoted higher leaf production in the first cycle but reduced it in the following cycles. Split fertilizer application resulted in a higher leaf blade/stem ratio in both years and greater animal productivity gains in the first year (TPG = 66.25 kg animal⁻¹; ADG = 0.789 kg animal⁻¹; TPA = 401.52 kg ha⁻¹; CY = 13.38 @ ha⁻¹). The use of NA resulted in higher C stocks up to 40 cm (32.82 and 20.61 Mg ha⁻¹) and higher N stocks in the 0–20 cm layer (2.02 Mg ha⁻¹), while split fertilization increased nitrogen content and stock in the 60–80 and 80–100 cm layers (0.600 and 0.370 Mg ha⁻¹, respectively). The use of NA as a nitrogen fertilizer increases the proportion of leaves with higher crude protein content and enhances soil C and N stocks in the upper layers. Split nitrogen fertilization, regardless of fertilizer source, is a promising management strategy, as it improves animal productivity, forage and litter quality, and nitrogen stocks in deeper soil layers. Tipo: Tese

Análise de risco da produção de café sombreado no maciço de Baturité, Ceará

Thu, 01 Jan 2026 00:00:00 GMT

Título: Análise de risco da produção de café sombreado no maciço de Baturité, Ceará Autor(es): Lima, Vitória Figueiredo; Campos, Kilmer Coelho; Campos, Robério Telmo; Braga, Francisco Laercio Pereira Abstract: Coffee is one of the most traded commodities in the international market, with prominence to the production of specialty coffees. Within this context, coffee in the state of Ceará is particularly relevant for its high quality, as the Baturité Massif regionaccounts for 70% of the state's income, generating employment and local income. The objective is to analyze the profitability of shaded coffee producers in the Baturité Massif, state of Ceará, under deterministic and risk conditions in 2023. The analysis methods are: the analysis of profitability indicators based on parameters of gross income and production costs, and the risk analysis by the Monte Carlo method to estimate the probabilistic distribution of each profitability indicator. The results showed that production has a positive average gross margin, allowing producers to remain in the activity in the short term. The risk analysis showed low risk, and this production is very profitable, as there is a 94% probability that the profit will be higher thanthe sample average. Tipo: Artigo de Periódico

Reconhecimento facial na segurança pública dos estádios de futebol: estudo de caso da Arena Castelão e o desafio do viés algorítmico

Wed, 01 Jan 2025 00:00:00 GMT

Título: Reconhecimento facial na segurança pública dos estádios de futebol: estudo de caso da Arena Castelão e o desafio do viés algorítmico Autor(es): Abreu Neto, Renato Torres de Abstract: This study analyzes the challenges inherent in implementing facial recognition technologies in Brazilian public security, from the perspective of structural racism, personal data protection, and existing legal gaps. Beginning with a historical contextualization of public surveillance policies and the rise of the Surveillance State, the concept of technological racism is discussed, illustrated by algorithmic failures and problematic use cases of these tools in Brazil and abroad, which highlight risks and perpetuate inequalities. The issue of algorithmic bias in artificial intelligence and machine learning systems is investigated, contrasting it with the inadequacy of the current legal framework and draft legislation under discussion at various legislative levels. The study places particular emphasis on the obstacles to applying the General Personal Data Protection Law (LGPD) to facial biometric monitoring in football stadiums, addressing the processing of sensitive data, the complex definition of legal bases, the delicate balance between privacy and the public interest in security, the absence of specific regulation from the National Data Protection Authority (ANPD), and observed deficiencies in terms of governance, transparency, control, and accountability. To deepen the empirical analysis of the issues raised, a detailed case study is developed concerning the use of this technology at Arena Castelão, in Fortaleza/Ceará. Finally, it is argued that, despite the potential benefits for security, the indiscriminate adoption of such technologies entails significant risks of discrimination and violation of fundamental rights, demanding a qualified public debate, greater social control, and the development of specific and robust legislation to ensure its ethical, transparent, and responsible use. Tipo: Dissertação