CALIBRAÇÃO DE UM SENSOR CAPACITIVO PARA ESTIMATIVA DA UMIDADE EM TRÊS CLASSES DE SOLOS SAMUEL COLA PIZETTA1; ROGÉRIO RANGEL RODRIGUES2; GERALDO MAGELA PEREIRA3; FABIÁN ENRIQUE DÍAZ PACHECO4, MARCELO RIBEIRO VIOLA5 E LUIZ ANTÔNIO LIMA6 1Doutorando em Recursos Hídricos em Sistemas Agrícolas pela Universidade Federal de Lavras (UFLA)- Campus Universitário, Departamento de Engenharia, C.P. 3037- CEP 37200-000, Lavras-MG, Brasil. scpizetta@hotmail.com;2 Doutor em Recursos Hídricos em Sistemas Agrícolas pela Universidade Federal de Lavras (UFLA)- Campus Universitário, Departamento de Engenharia, C.P. 3037- CEP 37200-000, Lavras-MG, Brasil., técnico no IFMA, Campus Santarém, Brasil. rogeriorr7@hotmail.com;3 Professor Titular da Universidade Federal de Lavras (UFLA) - Campus Universitário, Departamento de Engenharia, C.P. 3037- CEP 37200-000, Lavras-MG, Brasil. geraldop@deg.ufla.br;4 4 Engenheiro Agrícola pela Universidad de Sucre (Unisucre)- Calle 25 # 39-61, Las Margaritas, Sincelejo-Sucre. Colômbia. fabian_18 hotmail.com;5 Professor Adjunto da Universidade Federal de Lavras (UFLA) – Cam pus Universitário, Departamento de Engenharia, C.P. 3037- CEP 37200-000, Lavras-MG, Brasil.. marcelo.viola@deg.ufla.br;6 Professor Associado da Universidade Federal de Lavras (UFLA) - Campus Universitário, Departamento de Engenharia, C.P. 3037- CEP 37200-000, Lavras-MG, Brasil.. lalima@deg.ufla.br 1 RESUMO Um dos maiores desafios de domínio agrícola atualmente é a mensuração prática, rápida e precisa do teor de água no solo. Dessa forma, o conhecimento acerca dos equipamentos que estimem essa umidade é de fundamental importância. Nesse contexto, objetivou-se com este estudo, efetuar a calibração dos sensores de capacitância Eletrodex por meio do método padrão de estufa em três classes de solo, sendo o Argissolo, Latossolo e Nitossolo. Os solos foram coletados no Campus da Universidade Federal de Lavras (UFLA) e o experimento foi realizado no Laboratório de Hidráulica, no município de Lavras, estado de Minas Gerais. Para a calibração foram utilizados sete níveis de umidade que compreenderam diferentes valores de porcentagens da disponibilidade total de água no solo (DTA). Os resultados demonstraram que a utilização desse sensor não permitiu estimar, de forma satisfatória, a umidade volumétrica do solo, nos intervalos de umidade testados, em nenhum dos solos submetidos à calibração, uma vez que não foi possível obter equações que apresentassem coeficientes de determinação adequados. Palavras-chave: instrumentação, constante dielétrica, teor de água, sensor FDR. PIZETTA, S. C.; RODRIGUES, R. R.; PEREIRA, G. M. PACHECO, F. E. D; VIOLA, M. R.; LIMA, L. A.CALIBRATION OF A CAPACITANCE SENSOR FOR MOISTURE ESTIMATION IN THREE SOIL CLASSES 2 ABSTRACT One of the largest agricultural challenges has been the practical, quick and precise measurement of water content at soils, thus requiring satisfactory equipment to perform such task. This research investigated capacitive soil moisture sensors defined by the manufacturer as Eletrodex, comparing its measurements to dry oven techniques for soil moisture determination at three soil classes: Argisol, Oxisol, and Nitosol. Soils were collected at the Campus of the Federal University of Lavras (UFLA), and the experiment was carried out at the Hydraulics Laboratory in Lavras, state of Minas Gerais. For calibration, seven moisture levels were used, which comprised different percentages of total available moisture (TAM). Results lead to the conclusion that the sensor does not satisfactorily estimate the volumetric water content for any soil class tested. Such conclusion is based on the fact that no adequate coefficients of determination could be obtained at calibration curves. Keywords: instrumentation, dielectric constant, content of water, FDR sensor.
One of the main environmental stresses that affect the agriculture is the water deficit. There is a constant scientific search to understand the behavior of plants under conditions of drought, aiming to improve the yield of the agricultural species under the effects of this stress. The objective of this study was to determinate the adequate water availability at each stage of the phenological cycle of Crambe abyssinica Hochst, aiming to assist the establishment of irrigation managements with rational water use for this crop. The experiment was conducted in greenhouse to study the influence of levels of water availability along the phenological stages of plants on crambe. A set of growth parameters were measured using a split plot scheme in time (four phenological stages and five levels of available water in the soil) in a completely randomized design and with four replications. The levels of water availability in the soil promoted alterations of growth rate, and the faster growth of Crambe abyssinica were observed with hydric regimen able of provide levels higher than 45% of available water in the soil; overall, these levels promoted better development of the plants throughout the entire phenological cycle. Increasing the water availability in soil above 45% was fundamental to obtain higher harvest indexes, with maximum index obtained at 63% of water available.
The reference evapotranspiration (ET 0 ) can be estimated by different methods, the method of Penman-Monteith-FAO 56 is considered the standard method of reference. The aim of this study was to compare the performance of the following methods to estimate evapotranspiration Radiation-FAO 24, Blaney-Criddle-FAO 24, Hargreaves & Samani, Camargo and Irrigâmetro, compared with the standard method proposed by the FAO Penman-Monteith-FAO 56 at intervals of one, three, five and seven days, in the southern Espírito Santo climatic conditions. The method of Irrigâmetro showed the best estimates of ET 0 in relation to the standard method, regardless of the range studied, overestimating the ET 0 on 1,58; 1,59; 1,61 and 1,61% for intervals of 1; 3; 5 and 7 days respectively. The methods of Camargo and Blaney-Criddle-FAO 24 underestimated the values of ET 0 . The methods of the Radiation-FAO 24 and Hargreaves & Samani overestimated the evapotranspiration in relation to the standard method, regardless of the interval analyzed.
Different substrates and containers influence the production of coffee seedlings, which can reduce production costs, both with alternative substrates and with containers of smaller volumes of substrates. The aim the present study was to evaluate the viability of alternative substrates in different containers for production of Conilon coffee (Coffea canephora Pierre ex Froehner) seedlings in the nursery of the Federal Institute of Espírito Santo -Campus of Alegre, ES, Brazil. The experimental design was a randomized complete block design with three replications, in split-plot with three plots and four subplots. The plots consisted of three containers (120 cm³ tube, 280 cm³ tube and 615 cm³ bag), and the subplots of four substrates (S1 -Conventional, S2 -Legume compost, S3 -Grass compost, S4 -Vermicompost). At 165 days after sowing, the evaluated variables were shoot and root dry mass, number of leaves, shoot height, leaf area, Dickson quality index, shoot/root ratio, root length, nitrogen and total crude protein. The alternative substrates (Legume compost, Grass compost and Vermicompost) were efficient for production of Conilon coffee seedlings and can replace the conventional substrate at this development stage, providing good quality seedlings. The major developments were observed in the containers with the highest volume (280 cm³ tube and 615 cm³ bag) and reflected directly on the quality of seedlings.
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