http://repositorio.ufc.br/handle/riufc/41 2026-06-19T20:14:10Z http://repositorio.ufc.br/handle/riufc/86124 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 2024-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86835 Título: Interação entre lâminas de água e densidade populacional de cultivares eretas e decumbentes de caupi (Vigna unguiculata (L.) Walp.) Autor(es): Silva, João José Mendes Abstract: Field study was carried out aiming to analyze responses of erect and decumbent oowpea (Vigna unguiculata (L) Walp ) cultivars to three plant densities and three water tables. [...] Tipo: Dissertação 1990-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86833 Título: Caracterização física, físico-química e valor nutricional de três novas variedades de milho (Zea mays, L.) adaptadas às condições do Ceará Autor(es): Thé, Patrícia Maria Pontes Abstract: The maize (Zea mays, L.) is one of the world's most important cultivated plants. It is broadly grown and used in Brazil in many different ways, as food and feed. [...] Tipo: Dissertação 1990-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86827 Título: Capacidade de recuperação e desempenho das culturas alimentares no MATOPIBA: Impactos e desafios. Autor(es): Frota, Marisa Guilherme da; Lemos, José de Jesus de Sousa; Ozaki, Vitor Augusto; Duarte, Gislaine Vieira Abstract: This study sought to evaluate the recovery capacity of food crops (rice, beans, cassava, and corn) in the MATOPIBA region. The cultivation of rice, beans, and cassava largely originates from family farming, which plays a crucial role in feeding the population and supplying the local market. Additionally, it is essential for job creation, income generation, and, most importantly, maintaining food security. To assess the recovery capacity of these crops, an Agricultural Resilience Index was con-structed for each crop and state during the period from 2002 to 2021. The results show that the states of Maranhão and Bahia exhibited a downward trend in resilience for the cultivation of rice, beans, and cassava. The state of Tocantins stands out as the only state showing an upward trend in recovery capacity for all crops. Regarding corn and soybean cultivation across the four states, a growing trend in recovery capacity was observed. Tipo: Artigo de Periódico 2026-01-01T00:00:00Z