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

Dinâmica dos processos evaporativos: variabilidade climática e mitigação de impactos

Thu, 01 Jan 2026 00:00:00 GMT

Título: Dinâmica dos processos evaporativos: variabilidade climática e mitigação de impactos Autor(es): Lima, José Brenno Carneiro de Abstract: Water losses from evaporation and evapotranspiration are considered the main natural sources of water loss in surface reservoirs. In the Brazilian semi-arid region, evaporation could consume up to 50% of the water inflow into reservoirs. Therefore, the study of evaporative processes is of great relevance to water resource management, whether in semi-arid climatic conditions, as is the case in most of the state of Ceará, or in temperate climates. In light of this, this thesis is divided into three chapters, two of which were conducted in the state of Ceará (Brazil) and one in Germany. The first chapter assessed the long-term trend in potential evaporation, as estimated using the Penman method, based on meteorological data measured at eight specialised weather stations in the Jaguaribe River Watershed. The Mann-Kendall test and Sen’s slope were applied to the potential evaporation data and the meteorological variables to determine the statistical significance and magnitude of the temporal variation, with the aim of identifying the factors responsible for the observed changes. In the second chapter, the impact of cloud cover and cloud types on incident solar radiation was assessed. Historical time series of cloud cover, cloud types and midday solar radiation were used, obtained from six meteorological stations across Germany. Incident radiation on clear days and under cloud cover conditions was compared in order to understand the effect of cloud cover and cloud types on radiation. In the third chapter, the effect of installing a floating photovoltaic system (FPS) on the main meteorological variables that govern the evaporation process was assessed, as well as its impact on the water balance of a large reservoir. The influence of the FPS installation on the evaporation process was investigated using a sensitivity analysis of the Penman model, which was parameterised to estimate evaporation taking into account the PFS coverage. The impact of the FPS on the water balance was estimated by extrapolating experimental data to the reservoir scale, enabling the estimation of evaporated flow and the effects on water availability under dynamic hydrological conditions. Based on the findings of this thesis, the main conclusions are: (i) There is statistically significant evidence of a change in the pattern of potential evaporation in the Jaguaribe River catchment, but with non-uniform occurrence (increases and decreases), with increases in air temperature and insolation being responsible for the increase in evaporation, and reductions in wind speed and increases in relative humidity being the causes of the decrease in evaporation. (ii) As the cloud cover fraction increases, a trend towards a reduction in radiation incident on the Earth’s surface is observed. However, for medium and high clouds, it is found that, under conditions of cloud cover between 1 and 2 octas, there is a slight increase in radiation incidencewhen compared to the radiation recorded on clear days. (iii) It was found that global radiation is the meteorological variable to which the model is most sensitive. The presence of the FPS tends to bring the reservoir to a new equilibrium level, with an increase in the flooded area, partially offsetting the reduction in the evaporation rate. The installation of the FPS shows high potential as a strategy for increasing the water availability of reservoirs. Tipo: Tese

Avaliação do sensor de umidade S12 para arduíno no monitoramento automático da umidade do solo

Thu, 01 Jan 2026 00:00:00 GMT

Título: Avaliação do sensor de umidade S12 para arduíno no monitoramento automático da umidade do solo Autor(es): Cavalcante, Ruan Santana Abstract: Water is a fundamental abiotic resource for life on Earth, present in various human activities, especially in agriculture. Population growth has led to an increase in water demand, which has necessitated the implementation of new agricultural technologies focused on controlling and using water in a sustainable and improved way, with the use of water monitoring through soil moisture sensors. Arduino systems have been gaining popularity in the market and in scientific research related to agricultural engineering due to their operational simplicity and low cost, enabling the development of automated sensor systems for soil moisture monitoring. The objective of this study is to evaluate the potential performance of the corrosion-resistant Arduino soil moisture sensor model S12 by analyzing its response time compared to the response time of a properly calibrated neutron probe. The methodology consists of evaluating the response time of the Arduino S12 moisture sensor using a calibrated neutron probe as a comparison for soil moisture measurements. The variation in moisture readings made with the Arduino S12 sensor will be observed relative to those taken with the neutron probe within a tank system with soil, where the moisture and temperature of the soil are kept under constant control. Moisture measurements will be taken from saturation to the lowest moisture limit detected by the sensor, and from these data, the calibration curve and the response time curve of the sensor will be constructed and compared with the neutron probe's response time. The calibration curve of the Arduino sensor showed consistency with its linear behavior and a positive correlation between the measured soil moisture values and time, with a coefficient of determination of 0.98, a value within the acceptable range for the equation. Moreover, the results of the analysis of variance for the variation in soil moisture measured by the sensor and time showed no significant difference between measurements taken from different soil samples, which indicates good precision of the sensor for estimating soil moisture. Tipo: Dissertação

Produtividade e desenvolvimento do sorgo granífero sob diferentes manejos hídricos, adubação nitrogenada e inoculação com Bacillus aryabhattai

Thu, 01 Jan 2026 00:00:00 GMT

Título: Produtividade e desenvolvimento do sorgo granífero sob diferentes manejos hídricos, adubação nitrogenada e inoculação com Bacillus aryabhattai Autor(es): Rocha e Silva, Wevertonn Vasconcelos Abstract: Grain sorghum exhibits high adaptation to water stress conditions, making it a viable crop for semi-arid regions. The objective of two studies was to evaluate the development and yield of grain sorghum (cv. LAS 3004 G) under different water management strategies associated with nitrogen fertilization and inoculation with Bacillus aryabhattai. Growth and yield variables, such as stem diameter, plant height, panicle mass, and panicle length, were analyzed. The experiments were conducted in a greenhouse at the Federal University of Ceará, Fortaleza, Brazil. Two experiments were carried out in a randomized block design: Experiment I followed a 5x2 factorial scheme (five irrigation depths: 40, 60, 80, 100, and 120% of crop evapotranspiration (ETc); and two nitrogen application methods: conventional and fertigation, totaling 40 experimental units); and Experiment II followed a 5x2 factorial scheme (five irrigation frequencies: 1, 2, 3, 4, and 5 days based on daily ETc; with and without inoculation, totaling 40 experimental units). In Experiment I, results indicated that the 80% ETc irrigation depth was the most efficient, promoting growth similar to higher depths with lower overall water consumption. In general, higher irrigation depths reduced the crop cycle, anticipating flowering and harvest. There was no significant difference between nitrogen application methods for yield variables. In Experiment II, inoculation with B. aryabhattai shortened the crop cycle and mitigated the effects of water deficit, increasing panicle mass by 60.76% under the highest water restriction (5-day irrigation frequency) compared to the non-inoculated treatment. Higher irrigation frequencies (F1 and F2) significantly influenced the development and yield of the sorghum crop. The crop cycle was extended under conditions of lower water supply. Inoculation with Bacillus aryabhattai promoted increases in yield variables, especially under higher water stress conditions, indicating a mitigating effect Tipo: Dissertação