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| Registros recuperados: 5.225 | |
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| Christoforo,André L.; Couto,Natalia G.; Almeida,João P. B.; Aquino,Vinicius B. de M.; Lahr,Francisco A. R.. |
| ABSTRACT The use of new wood species in construction requires knowledge of their properties for safer and more economical structural sizing. In Brazil, structural projects are carried out according to the standard document ABNT NBR 7190:1997. Tests required by this standard for the complete characterization of species require large machines with high costs, which are present only in large research centers. Considering the lack of experimental determination, this study aimed, with the help of analysis of variance of regression models, to investigate the possibility of estimating, through apparent density, wood properties obtained in tests where failure is considered fragile, allowing the estimation of properties of species still little used. Ten wood... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Hardwoods; Fragile failure; Regression models; Analysis of variance. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000100105 |
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| Al-Janobi,Abdulrahman; Al-Hamed,Saad; Aboukarima,Abdulwahed; Almajhadi,Yousef. |
| ABSTRACT Draft and energy requirements are the most important factors in the activities of farm machinery management owing to their role in matching the tractor with implements for different tillage operations. This study's aim was to model the draft and energy requirements of a moldboard plow based on two novel variables. The first was the soil texture index (STI), which was formed from the clay, sand, and silt contents with a range of 0.03–0.84. The second variable was the field working index (FWI), formed by combining the plow width, plowing speed, soil bulk density, soil moisture content, plowing depth, and tractor power into one dimensionless variable, which had a range of 7.17–82.45. The coefficient of determination (R2) values obtained using a... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Soil texture index; Field working index; Artificial neural network; Prediction; Tillage. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000300363 |
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| Goneli,André L. D.; Corrêa,Paulo C.; Figueiredo Neto,Acácio; Kirsch,Michele R. H.; Botelho,Fernando M.. |
| ABSTRACT Knowledge regarding the static pressure drop in granular layers is of fundamental importance in the development of efficient drying and aeration projects of agricultural products. Thus, the objective of this study was to evaluate the effects of impurity contents on the static pressure drop in different bed depth of castor bean grains, as well as modify the mathematical models per the obtained experimental data and select the model that best represents this phenomenon. First, impurities in castor bean grains of the Guarani variety were eliminated and 6% of the moisture content (dry basis) was retained. The coarse impurity contents were obtained with 2%, 4%, and 6% of mass addition. The pressure drop in different bed depth of clean and impure castor... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Bulk density; Load loss; Porosity; Ricinus communis L.; Moisture content. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000200184 |
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| Cordeiro Júnior,José J. F.; Cavalcanti,Sávio D. L.; Souza,Rayanne T. de A.; Batista,Pedro H. D.; Guiselini,Cristiane. |
| ABSTRACT Sugarcane has a great economic interest in Brazil, so it needs technologies to increase its yield strength, especially for seedling production. This study aimed to ascertain the influence of shading nets on early growth and development of pre-sprouted sugarcane seedlings. An experiment was conducted in a protected environment, in the Rural Federal University of Pernambuco (UFRPE), in Recife-PE, Brazil. The protected environments were covered with anti-UV low-density polyethylene plastic plus: Solpack® red ultranet net, Solpack® white net, Solpack® freshnet net, and without shade net, and five replications each. The experiment was carried out in a completely randomized design, and multivariate principal component analysis (PCA) was used to verify... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Protected environment; Shade nets; Solar radiation; Saccharum officinarum. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000100010 |
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| Arcoverde,Sálvio N. S.; Souza,Cristiano M. A. de; Rafull,Leidy Z. L.; Cortez,Jorge W.; Orlando,Roberto C.. |
| ABSTRACT Machinery traffic intensification has been recurrent in intensive agriculture in annual crops, which may lead to structural soil degradation and, consequently, a reduction of its productive capacity. Therefore, this study aimed to assess the influence of tractor traffic intensification on soil physical attributes and soybean yield components. The study was performed in an Oxisol under no-tillage for 10 years, using a randomized block design with five tractor traffic intensities (0, 2, 4, 6, 8, and 12 passes) and five replications. Density, porosity, macroporosity, microporosity, and penetration resistance were assessed in the soil and stem diameter, number of pods per plant, number of grains per pod, grain weight per plant, thousand-grain weight,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Soil compaction; Yield components; Shoot; Soil penetration resistance; Machinery traffic. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000100113 |
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| Fruehwirth,Marcelo; Sbizzaro,Mariana; Rosa,Danielle M.; Sampaio,Silvio C.; Reis,Ralpho R. dos. |
| ABSTRACT Atrazine is a herbicide widely used in agriculture; however, because of its toxicity, alternatives are needed to remove this compound from the environment. In this study, we investigated the adsorption process and the atrazine-adsorbing ability of three biochars produced at different pyrolysis temperatures from byproducts of the wood industry. The biochars were characterized by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and their physical characteristics were evaluated by Brunauer-Emmett-Teller (BET) analysis. The biochar pyrolyzed at 350 °C (BM350) adsorbed 26.04% of the herbicide, showing the best performance among the three biochars tested, even though it had the lowest specific surface area (1.467 m2... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Water contamination; Isotherm; Functional groups; Kinetics models. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000600769 |
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| Silva,Bruna de O.; Santos,Gustavo A. de A.; Santos,Miquéias G. dos; Morais Filho,Luiz F. F.; Faria,Rogério T. de. |
| ABSTRACT Brazil stands out worldwide for its high grain production in areas of direct sowing. The objective of this study was to simulate and assess the relationship of soil organic carbon content and nitrogen, crop yield, and biomass of two crop sequences under the no-tillage system in a subtropical region of São Paulo, Brazil, using CSM-CROPGRO-Soybean and CSM-CERES-Maize models. The modeling was carried out considering the meteorological conditions of Jaboticabal, SP, Brazil. The treatments consisted of combining two summer crops (maize and soybean) with maize cultivation as a winter crop. The average biomass and productivity for corn were 15594 kg ha−1 and 5996 kg ha−1, respectively, and for soybeans they were 5905 kg ha−1 and 3441 kg ha−1,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: CSM-CROPGRO; CSM-CERES-Maize; Conservationist tillage; Greenhouse gas emission. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000400536 |
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| Feitosa,Carlos E. L.; Costa,Pedro H. dos S.; Meneses,Kamila C. de; Oliveira,Ulisses C. de; Farias,Maryzélia F. de. |
| ABSTRACT Soil compaction in agricultural areas has greatly increased in recent decades due to intensive farming practices, including short-cycle crops and machinery intensification. This study aimed to evaluate the impacts of management systems on the physical quality of a dystrophic Yellow Oxisol, in the Cerrado region of Brazil. Treatments consisted of five soil management systems, with five replications (native forest [control], slash-and-burn agriculture, pasture, no-tillage, and conventional tillage). Data analysis was performed using a completely randomized experimental design. All systems were analyzed for soil density, macroporosity, microporosity, total porosity, hydraulic conductivity, infiltration, water retention curve, penetration resistance,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: S index; Land cover change; Physical properties; Infiltration; Soil compaction. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000500609 |
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| Alvino,Francisco C. G.; Aleman,Catariny C.; Filgueiras,Roberto; Althoff,Daniel; da Cunha,Fernando F.. |
| ABSTRACT Monitoring of large agricultural lands is often hampered by data collection logistics at field level. To solve such a problem, remote sensing techniques have been used to estimate vegetation indices, which can subsidize crop management decision-making. Therefore, this study aimed to select vegetation indices to detect variability in irrigated corn crops. Data were collected in São Desidério, Bahia State (Brazil), using an OLI sensor (Operational Land Imager) embedded to a Landsat-8 satellite platform. Five corn growing plots under central pivot irrigation were assessed. The following vegetation indices were tested: NDVI (Normalized Difference Vegetation Index), EVI (Enhanced Vegetation Index), SAVI (Soil Adjusted Vegetation Index), GNDVI (Green... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Vegetation cover; Decision-making; Remote sensing. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000300322 |
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| Ribeiro,Felipe O.; Fernandes,Antonio R.; Matos,Gilson S. B. de; Lindolfo,Marcelo M.; Guedes,Rafael S.; Rodrigues,Graziele R.. |
| ABSTRACT This study aimed to define management zones (MZs) for fertirrigated açaí cultivation, based on spatial variability of the foliar nutrients and productivity data. The work was carried out in an area of 5.75 ha of a 7-year crop, with 80 georeferenced sample points. Fresh fruit productivity and nutrient (N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn) contents were determined. The average contents of macronutrients were considered adequate for adult açaí plants, and their spatial dependence associated with fruit productivity allowed the representation of their distributions through maps of variability. Through multivariate analysis, three main components were highlighted. These components explained 51.5 % of the total variability of the data, where PC1... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Amazon; Management zones; Multivariate analysis; Nutrient contents; Precision agriculture. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000600800 |
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| Savi,Daniel; Kmiecik,Leonardo L.; Strapasson Neto,Lauro; Silva,Thiago X. da; Jasper,Samir P.. |
| ABSTRACT Studies on the longitudinal distribution of seeds in the sowing row seek to improve crop homogeneity, thus generating high productivity. In this context, seed tubes must be analyzed for their angular curvature. Thus, this study aimed to evaluate the influence of the seed tube curvature on the longitudinal distribution of corn and soybean seeds at different speeds. Two experiments were conducted completely randomized in a double factorial design. The first factor consisted of the seed tube curvature (straight and curved) and the second factor consisted of sowing speeds (1.11, 1.39, and 1.67 m s−1 for corn and 1.39, 1.67, 1.94, and 2.22 m s−1 for soybean), with five replications. The parameters analyzed to measure the longitudinal distribution were... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Sowing uniformity; Productivity; Seed drill; Performance monitoring; Bench experiment. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000600732 |
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| Araújo,Edcássio D.; Santos,Dionei L.; Alvino,Francisco C. G.; Ferreira,Lucas B.; Cunha,Fernando F. da. |
| ABSTRACT Correct determinations of distribution (Ed) and application (EA) efficiencies allow adequate estimations of the gross irrigation depth. This study aimed: i) to determine the distribution efficiency using the Christiansen uniformity coefficient (CUC) in a sprinkler irrigation system under different weather conditions and working pressures; ii) to compare the mean, median, and cumulative CUC values; and iii) to evaluate the predictive capacity of four EA estimation models. CUC values were determined from 80 assessments, as well as the mean, median, and cumulative. The precipitated water depth accumulated in each collector was considered for the accumulated CUC. More uniform evaluations were used for EA (working pressure of 196 kPa), resulting in 20... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Uniformity coefficient; Irrigation efficiency; Evaporation and wind drift. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000100024 |
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| Martins,Murilo B.; Ruiz,Daniel. |
| ABSTRACT Operational conditions of mechanized harvesting can affect the quality of harvested sugarcane. Therefore, the aim of this study was to assess the influence of the displacement speed and cutting height on the quality of the raw material during the mechanized harvest of sugarcane. Vegetable losses were accounted for in the field by manual collection of the fractions left after harvest. Vegetable and mineral impurities were determined at the processing stage in the laboratory. Both the displacement speed and cutting height did not affect vegetable losses. However, the increase in vegetal impurities occurred at higher displacement speeds, whereas lower cutting heights resulted in higher amounts of mineral impurities. |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Agricultural mechanization; Harvest; Quality; Saccharum spp. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000300352 |
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| Alves,Guilherme E.; Borém,Flávio M.; Andrade,Ednilton T.; Isquierdo,Éder P.; Siqueira,Valdiney C.; Dias,Camila de A.. |
| ABSTRACT This study aimed to evaluate drying kinetics for natural and pulped coffee, using different temperatures and drying airflows. For the conduction of the experiment, coffee fruits (Coffea arabica L. cv. Topázio) were harvested manually, selecting only ripe fruits and subsequent to the hydraulic separation. For drying the coffee, use a mechanical dryer with two temperatures (40 and 45°C) and four drying air streams (24; 60; 96 and 132 m3.min-1.m-2). Twelve models for employees to describe the drying kinetics of coffees. Among the models used to describe the drying process of natural coffee and pulped coffee, according to the results of the coefficient of determination, relative mean error, standard deviation of estimates and distribution of waste... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Coffea arabica L.; Mathematical modeling; Drying rate. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000200192 |
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| Mendonça,Thaís G.; Silva,Marília B. da; Pires,Regina C. de M.; Souza,Claudinei F.. |
| ABSTRACT Agriculture is one of the segments that most uses water and developments have been made to save irrigation water. Deficit irrigation is a technique that can contribute to production and water saving in agriculture. This study aimed to evaluate the viability of deficit irrigation in tomato production irrigated by subsurface drip in a greenhouse and estimate water saving. The experiment was conducted at the CCA/UFSCar, in Araras, São Paulo, Brazil, with grape tomato cultivation. It consisted of three treatments, 100 % water depth and deficit irrigation (75 and 50 % of water depth), with a randomized block design. Irrigation management was performed using mean soil moisture data collected through TDR probes installed in each treatment. Tomato plants... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: TDR; Water resources; Irrigation management; Water content. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162020000400453 |
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| Registros recuperados: 5.225 | |
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