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Showing 1 - 200 of 746 Journals sorted alphabetically
ABCD. Arquivos Brasileiros de Cirurgia Digestiva     Open Access   (Followers: 3, SJR: 0.207, CiteScore: 1)
ACIMED     Open Access   (Followers: 1)
Acta Agronómica     Open Access  
Acta Amazonica     Open Access   (Followers: 7, SJR: 0.36, CiteScore: 1)
Acta Bioethica     Open Access   (SJR: 0.196, CiteScore: 0)
Acta Botanica Brasilica     Open Access   (Followers: 3, SJR: 0.325, CiteScore: 1)
Acta botánica mexicana     Open Access   (Followers: 1, SJR: 0.212, CiteScore: 0)
Acta Botánica Venezuelica     Open Access   (Followers: 1, SJR: 0.103, CiteScore: 0)
Acta Cirurgica Brasileira     Open Access   (SJR: 0.395, CiteScore: 1)
Acta Limnologica Brasiliensia     Open Access   (Followers: 4, SJR: 0.28, CiteScore: 1)
Acta Literaria     Open Access   (Followers: 5, SJR: 0.1, CiteScore: 0)
Acta Medica Colombiana     Open Access   (Followers: 1)
Acta Médica Costarricense     Open Access   (Followers: 2)
Acta Medica Peruana     Open Access   (Followers: 2)
Acta Neurológica Colombiana     Open Access   (Followers: 2)
Acta Ortopédica Brasileira     Open Access   (Followers: 1, SJR: 0.343, CiteScore: 1)
Acta Paulista de Enfermagem     Open Access   (Followers: 2, SJR: 0.275, CiteScore: 1)
Acta Pediátrica Costarricense     Open Access   (Followers: 1)
Acta Scientiarum. Agronomy     Open Access   (Followers: 6, SJR: 0.431, CiteScore: 1)
Acta Scientiarum. Animal Sciences     Open Access   (Followers: 4, SJR: 0.25, CiteScore: 0)
Acta zoológica mexicana     Open Access  
Actualidades Biológicas     Open Access   (Followers: 1)
African Human Rights Law J.     Open Access   (Followers: 17)
African Natural History     Open Access   (Followers: 4, SJR: 0.198, CiteScore: 1)
Afro-Asia     Open Access  
Ágora - studies in psychoanalytic theory     Open Access   (Followers: 3, SJR: 0.132, CiteScore: 0)
Agricultura Tecnica     Open Access   (Followers: 5)
Agrociencia     Open Access   (Followers: 1, SJR: 0.2, CiteScore: 0)
Agrociencia Uruguay     Open Access  
Agronomía Mesoamericana     Open Access   (Followers: 1)
Aisthesis     Open Access   (Followers: 7, SJR: 0.106, CiteScore: 0)
Ajayu Órgano de Difusión Científica del Departamento de Psicología UCBSP     Open Access  
Alea : Estudos Neolatinos     Open Access   (Followers: 2, SJR: 0.1, CiteScore: 0)
Alfa : Revista de Linguística     Open Access  
Alpha (Osorno)     Open Access   (SJR: 0.138, CiteScore: 0)
Ambiente & sociedade     Open Access   (Followers: 3, SJR: 0.235, CiteScore: 0)
Ambiente & Agua : An Interdisciplinary J. of Applied Science     Open Access   (Followers: 1, SJR: 0.263, CiteScore: 1)
Ambiente Construído     Open Access   (Followers: 1)
América Latina en la historia económica     Open Access   (Followers: 4, SJR: 0.134, CiteScore: 0)
Anais Brasileiros de Dermatologia     Open Access   (Followers: 2, SJR: 0.52, CiteScore: 1)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2, SJR: 0.418, CiteScore: 1)
Anais do Museu Paulista : História e Cultura Material     Open Access  
Anales de Medicina Interna     Open Access   (Followers: 1)
Anales del Instituto de la Patagonia     Open Access  
Anales del Sistema Sanitario de Navarra     Open Access   (Followers: 1, SJR: 0.157, CiteScore: 0)
Análise Psicológica     Open Access   (Followers: 1, SJR: 0.16, CiteScore: 0)
Análise Social     Open Access   (Followers: 3, SJR: 0.16, CiteScore: 0)
Andean geology     Open Access   (Followers: 9, SJR: 0.674, CiteScore: 1)
Annali dell'Istituto Superiore di Sanità     Open Access   (SJR: 0.386, CiteScore: 1)
Antipoda. Revista de Antropología y Arqueología     Open Access   (Followers: 5, SJR: 0.135, CiteScore: 0)
Anuario Colombiano de Historia Social y de la Cultura     Open Access   (SJR: 0.1, CiteScore: 0)
Anuario de Historia Regional y de las Fronteras     Open Access  
Apuntes : Revista de Estudios sobre Patrimonio Cultural - J. of Cultural Heritage Studies     Open Access   (Followers: 7)
Archivos de Medicina Interna     Open Access   (Followers: 1)
Archivos de Medicina Veterinaria     Open Access   (Followers: 1, SJR: 0.194, CiteScore: 0)
Archivos de Neurociencias     Open Access   (Followers: 3, SJR: 0.111, CiteScore: 0)
Archivos de Pediatria del Uruguay     Open Access   (Followers: 3)
Archivos de Zootecnia     Open Access   (Followers: 1, SJR: 0.202, CiteScore: 0)
Archivos Españoles de Urología     Open Access   (SJR: 0.178, CiteScore: 0)
Argos     Open Access   (Followers: 1)
ARQ     Open Access   (Followers: 6, SJR: 0.113, CiteScore: 0)
Arquitectura y Urbanismo     Open Access   (Followers: 4)
Arquivo Brasileiro de Medicina Veterinária e Zootecnia     Open Access   (SJR: 0.248, CiteScore: 0)
Arquivos Brasileiros de Cardiologia     Open Access   (Followers: 1, SJR: 0.381, CiteScore: 1)
Arquivos Brasileiros de Endocrinologia e Metabologia     Open Access  
Arquivos Brasileiros de Oftalmologia     Open Access   (Followers: 1, SJR: 0.518, CiteScore: 1)
Arquivos de Gastroenterologia     Open Access   (Followers: 1, SJR: 0.396, CiteScore: 1)
Arquivos de Medicina     Open Access  
Arquivos de Neuro-Psiquiatria     Open Access   (SJR: 0.448, CiteScore: 1)
Arquivos do Instituto Biológico     Open Access   (Followers: 1)
Arquivos Internacionais de Otorrinolaringologia     Open Access  
ARS     Open Access   (Followers: 4)
Atenea (Concepción)     Open Access   (SJR: 0.112, CiteScore: 0)
Atmósfera     Open Access   (Followers: 2, SJR: 0.449, CiteScore: 1)
Audiology - Communication Research     Open Access   (Followers: 10)
Avaliação : Revista da Avaliação da Educação Superior (Campinas)     Open Access  
Avaliação Psicológica     Open Access   (SJR: 0.164, CiteScore: 0)
Avances en Enfermería     Open Access   (Followers: 2)
Avances en Odontoestomatologia     Open Access   (Followers: 1, SJR: 0.105, CiteScore: 0)
Avances en Periodoncia e Implantología Oral     Open Access   (Followers: 1)
Bakhtiniana : Revista de Estudos do Discurso     Open Access   (SJR: 0.103, CiteScore: 0)
BAR. Brazilian Administration Review     Open Access   (Followers: 2, SJR: 0.137, CiteScore: 0)
Biota Neotropica     Open Access   (SJR: 0.381, CiteScore: 1)
Biotecnología Aplicada     Open Access   (SJR: 0.146, CiteScore: 0)
Biotecnología en el Sector Agropecuario y Agroindustrial     Open Access  
Boletim de Ciências Geodésicas     Open Access   (SJR: 0.188, CiteScore: 0)
Boletim do Museu Paraense Emílio Goeldi. Ciências Humanas     Open Access   (Followers: 1, SJR: 0.238, CiteScore: 0)
Boletin Chileno de Parasitologia     Open Access  
Boletín de Filología     Open Access  
Boletín de la Sociedad Botánica de México     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Boletín de la Sociedad Geológica Mexicana     Open Access   (SJR: 0.291, CiteScore: 1)
Boletín del Museo Chileno de Arte Precolombino     Open Access   (Followers: 1, SJR: 0.233, CiteScore: 0)
Bosque     Open Access   (Followers: 2, SJR: 0.29, CiteScore: 1)
Bragantia     Open Access   (Followers: 2, SJR: 0.555, CiteScore: 1)
Brazilian Archives of Biology and Technology     Open Access   (Followers: 3, SJR: 0.281, CiteScore: 1)
Brazilian Business Review     Open Access  
Brazilian Dental J.     Open Access   (Followers: 3, SJR: 0.476, CiteScore: 1)
Brazilian J. of Biology     Open Access   (Followers: 3, SJR: 0.523, CiteScore: 1)
Brazilian J. of Chemical Engineering     Open Access   (Followers: 5, SJR: 0.395, CiteScore: 1)
Brazilian J. of Food Technology     Open Access   (Followers: 3, SJR: 0.206, CiteScore: 0)
Brazilian J. of Medical and Biological Research     Open Access   (SJR: 0.611, CiteScore: 2)
Brazilian J. of Microbiology     Open Access   (Followers: 5, SJR: 0.63, CiteScore: 2)
Brazilian J. of Oceanography     Open Access   (Followers: 1, SJR: 0.425, CiteScore: 1)
Brazilian J. of Oral Sciences     Open Access   (Followers: 2, SJR: 0.131, CiteScore: 0)
Brazilian J. of Pain (BrJP)     Open Access  
Brazilian J. of Physical Therapy     Open Access   (Followers: 1, SJR: 0.802, CiteScore: 2)
Brazilian J. of Plant Physiology     Open Access   (Followers: 3, SJR: 1.178, CiteScore: 3)
Brazilian J. of Veterinary Research and Animal Science     Open Access   (Followers: 8, SJR: 0.225, CiteScore: 0)
Brazilian Oral Research     Open Access  
Brazilian Political Science Review     Open Access   (Followers: 2)
Bulletin of the World Health Organization     Open Access   (Followers: 19, SJR: 2.532, CiteScore: 3)
Caderno CRH     Open Access   (Followers: 3, SJR: 0.233, CiteScore: 0)
Caderno de Estudos     Open Access  
Cadernos CEDES     Open Access   (Followers: 1, SJR: 0.119, CiteScore: 0)
Cadernos de Pesquisa     Open Access   (Followers: 2, SJR: 0.183, CiteScore: 0)
Cadernos de Saúde Pública     Open Access   (Followers: 1, SJR: 0.568, CiteScore: 1)
Cadernos de Tradução     Open Access  
Cadernos Metrópole     Open Access   (Followers: 1)
Cadernos Nietzsche     Open Access  
Cadernos Pagu     Open Access   (SJR: 0.356, CiteScore: 0)
Cadernos Saúde Coletiva     Open Access   (Followers: 1)
Caldasia     Open Access   (SJR: 0.195, CiteScore: 0)
Calidad en la educación     Open Access   (Followers: 1)
Case Reports     Open Access  
Cerâmica     Open Access   (Followers: 5, SJR: 0.186, CiteScore: 0)
CES Medicina     Open Access  
Chilean J. of Agricultural Research     Open Access   (Followers: 1, SJR: 0.377, CiteScore: 1)
Chungara (Arica) - Revista de Antropologia Chilena     Open Access   (Followers: 1, SJR: 0.565, CiteScore: 1)
Ciência & Saúde Coletiva     Open Access   (Followers: 2, SJR: 0.566, CiteScore: 1)
Ciência & Educação (Bauru)     Open Access  
Ciência Animal Brasileira     Open Access   (Followers: 1, SJR: 0.216, CiteScore: 0)
Ciência da Informação     Open Access   (Followers: 1, SJR: 0.121, CiteScore: 0)
Ciencia del suelo     Open Access   (Followers: 1)
Ciência e Agrotecnologia     Open Access   (SJR: 0.383, CiteScore: 1)
Ciencia e Cultura     Open Access   (Followers: 1)
Ciencia e investigación agraria     Open Access   (Followers: 1, SJR: 0.211, CiteScore: 0)
Ciencia forestal en México     Open Access  
Ciência Rural     Open Access   (Followers: 2, SJR: 0.337, CiteScore: 1)
Ciencia y Enfermeria - Revista Iberoamericana de Investigacion     Open Access   (Followers: 3, SJR: 0.158, CiteScore: 0)
Ciencias Marinas     Open Access   (Followers: 3, SJR: 0.414, CiteScore: 1)
Ciencias Psicológicas     Open Access  
Cirugia Plastica Ibero-Latinoamericana     Open Access   (SJR: 0.166, CiteScore: 0)
CLEI Electronic J.     Open Access  
Clínica y Salud     Open Access   (SJR: 0.173, CiteScore: 0)
Clinics     Open Access   (SJR: 0.536, CiteScore: 1)
CoDAS     Open Access   (SJR: 0.267, CiteScore: 0)
Comuni@cción     Open Access   (Followers: 1)
Comunicación y sociedad     Open Access   (Followers: 2, SJR: 0.327, CiteScore: 0)
Contaduría y Administración     Open Access   (SJR: 0.219, CiteScore: 0)
Contexto Internacional     Open Access  
Convergencia     Open Access   (Followers: 3, SJR: 0.196, CiteScore: 0)
Correo Científico Médico     Open Access  
Corrosão e Protecção de Materiais     Open Access  
Crop Breeding and Applied Biotechnology     Open Access   (Followers: 3, SJR: 0.609, CiteScore: 1)
Cuadernos de Administración (Universidad del Valle)     Open Access   (Followers: 2)
Cuadernos de Economía     Open Access   (SJR: 0.115, CiteScore: 0)
Cuadernos de Economía     Open Access   (Followers: 2)
Cuadernos de Economia - Latin American J. of Economics     Open Access   (Followers: 3)
Cuadernos de Historia     Open Access   (Followers: 2)
Cuadernos de Historia de la Salud Publica     Open Access  
Cuadernos de Medicina Forense     Open Access   (Followers: 2, SJR: 0.1, CiteScore: 0)     Open Access   (SJR: 0.38, CiteScore: 0)
Cubo. A Mathematical J.     Open Access  
Cuicuilco     Open Access   (Followers: 1)
Cultivos Tropicales     Open Access   (Followers: 1)
Culturales     Open Access   (Followers: 3)
Dados - Revista de Ciências Sociais     Open Access   (SJR: 0.37, CiteScore: 0)
De Jure     Open Access   (Followers: 1)
DELTA : Documentação de Estudos em Lingüística Teórica e Aplicada     Open Access   (SJR: 0.133, CiteScore: 0)
Dementia & Neuropsychologia     Open Access   (Followers: 10, SJR: 0.205, CiteScore: 0)
Dental Press J. of Orthodontics     Open Access   (Followers: 4, SJR: 0.489, CiteScore: 1)
Desacatos     Open Access   (Followers: 1)
Desarrollo y Sociedad     Open Access   (Followers: 3, SJR: 0.109, CiteScore: 0)
Diálogo Andino - Revista de Historia, Geografía y Cultura Andina     Open Access   (Followers: 1, SJR: 0.116, CiteScore: 0)
Diánoia     Open Access   (Followers: 1)
Dimensión Empresarial     Open Access  
Dynamis : Acta Hispanica ad Medicinae Scientiarumque Historiam Illustrandam     Open Access   (Followers: 3, SJR: 0.131, CiteScore: 0)
e-J. of Portuguese History     Open Access   (Followers: 2, SJR: 0.101, CiteScore: 0)
Eclética Química     Open Access   (Followers: 1)
Ecología en Bolivia     Open Access  
Economia Aplicada     Open Access   (SJR: 0.208, CiteScore: 0)
Economia e Sociedade     Open Access  
EconoQuantum     Open Access  
Educação & Sociedade     Open Access   (Followers: 3)
Educação e Pesquisa     Open Access   (Followers: 1, SJR: 0.163, CiteScore: 0)
Educação em Revista     Open Access  
Educación Matemática     Open Access  
Educación Médica     Open Access   (Followers: 1, SJR: 0.236, CiteScore: 0)
Educación Médica Superior     Open Access   (Followers: 1, SJR: 0.237, CiteScore: 0)
Educación y Educadores     Open Access  
Educar em Revista     Open Access  
EDUMECENTRO     Open Access  
En-Claves del pensamiento     Open Access   (Followers: 1, SJR: 0.194, CiteScore: 0)
Encuentros     Open Access  
Ene : Revista de Enfermería     Open Access  
Enfermería Global     Open Access   (Followers: 3, SJR: 0.165, CiteScore: 0)
Enfermería Nefrológica     Open Access   (Followers: 1, SJR: 0.198, CiteScore: 0)
Enfoques     Open Access  
Engenharia Agrícola     Open Access   (SJR: 0.305, CiteScore: 1)

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Engenharia Agrícola
Journal Prestige (SJR): 0.305
Citation Impact (citeScore): 1
Number of Followers: 0  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0100-6916
Published by SciELO Homepage  [745 journals]

    • Abstract: ABSTRACT The apparent soil electrical conductivity (ECa) is an attribute commonly used for the characterization of the spatial variability of soil, but its determination by handheld sensors consumes considerable time and labor. The reduction in the number of sampling points allows minimize them but can result in increased uncertainty of interpolated maps. Thus, the goal of this study was to identify the best spacing and number of ECa measurements, to guarantee the quality of maps generated in three vineyards. The ECa values were obtained using a handheld sensor in different sampling grids. The data were submitted to descriptive statistical and geostatistical analyses. The relative deviation and Kappa coefficient of agreement were used to assess the similarity of generated maps. The reduction in the number of points and increase in the size of the sampling grid reduced the quality of maps and this reduction was greater when the spacing increased in the direction of the terrain slope. A minimum limit of 100 sampling points should be considered for the sampling planning to generate ECa spatial distribution maps, with a more conservative approach when regarding the increase in spacing in the direction of the terrain slope.

    • Abstract: ABSTRACT Vegetation indices (VIs) are quantitative measures used to describe the distribution and spatial variability of the vegetation cover of natural or cultivated areas. The aim of this study was to delimit homogeneous zones (HZs) of different VIs using geostatistics and multivariate analysis in order to identify vegetation patterns in Cabernet Franc and Cabernet Sauvignon vineyards. The evaluation was performed in two vineyards in the municipality of Espírito Santo do Pinhal in the state of São Paulo, Brazil. Reflectance (ρ) was measured at three wavelengths of the electromagnetic spectrum (670, 730, and 780 nm) at canopy height in georeferenced points along planting rows using the Crop Circle ACS-430 active sensor. Nine VIs were calculated based on the ratios between the ρ values. Geostatistical data analysis allowed the spatial prediction of VIs by ordinary kriging interpolation. Principal component analysis and fuzzy k-means clustering were applied for HZs delimitation and the optimal number of zones was defined according to cluster validity functions. Despite the variations of the VIs spatial distribution patterns, the multivariate analysis resulted in a representative categorization of the grapevine vegetative vigor and delimitation of HZs for this characteristic. This was validated according to the observed significant differences between VIs.

    • Abstract: ABSTRACT Surface temperature (Ts) is a determining factor to obtain energy balance parameters, being relevant to understand the influence of this variable on the estimation of evapotranspiration. Thus, the objective of this study was to simulate errors in Ts estimation to verify the consequences of actual evapotranspiration (ETa) estimated by the SAFER (Simple Algorithm for Evapotranspiration Retrieving) model. For this, an image of the Landsat-8 satellite was used to induce errors from 0.2K to 10K in the variable Ts, allowing verifying the consequences in the ETa data. After the estimations of Ts and ETa, the quantitative consequences and dynamics of Ts impact on the ETa data were verified along the different land uses in the study area. The results showed that the precise estimation of Ts is essential to obtain ETa accurately. The image of ETa errors presented the highest relative errors on the surface with exposed soils and with high Ts values. However, the highest residuals of ETa images occurred on the surfaces with milder Ts and higher evapotranspiration rates (irrigated surfaces).

    • Abstract: ABSTRACT Active optical sensors have been widely used for the spatial and temporal monitoring of peanut culture because they are accurate, non-destructive methods for rapidly obtaining data. The objective of this study was to determine the optimal stage of crop growth for collecting sensor readings based on correlations between quality indicators. In addition, we compared vegetation indices (Normalized Difference Vegetation Index [NDVI], Normalized Difference Red-Edge Index, [NDRE], and Inverse Ratio Vegetation Index, [IRVI]) by monitoring temporal variability in the peanut crop in order to determine which of them obtained the best reading quality throughout the process. The experiment was performed on the 2016/17 crop in the agricultural area of the municipality of Dumont in the state of São Paulo, Brazil. The experimental design was based on the basic assumptions of statistical quality control and contained 63 sample points in a 30 × 30 m grid. The parameters were evaluated at 30, 45, 60, 75, and 119 days after sowing (DAS) using proximal sensing with GreenSeeker and OptRX sensors. We found that 45 and 60 DAS were the optimal times for monitoring peanut crop variability. For spatiotemporal monitoring of the culture with control charts, NDRE showed the best readings throughout the process when compared to NDVI and IRVI.

    • Abstract: ABSTRACT Tree crops, such as Arabica coffee (Coffea arabica L.), present enormous technical challenges in terms of pesticide application. The correct deposition and distribution of the active ingredient throughout the aerial part of these plants depends on knowledge of the canopy volume, but manually determining this volume is time consuming and imprecise. The objectives of this study were to develop a method to determine the vegetation volume of coffee crops from digital images captured by camera onboard unmanned aerial vehicles and to compare this approach with traditional vegetation volume estimation (tree row volume (TRV) method). Manual measurements of the canopy volume of four coffee cultivation areas were compared with data obtained using the method presented in this paper. It was concluded that the vegetation volume of coffee trees, a highly important variable in defining pesticide application techniques (in addition to other uses), could be determined in a practical and precise way by digitally processing the images captured by unmanned aerial vehicles. The method is fast and permits the assessment of large areas. Furthermore, estimates based on this method and the traditional TRV method were not significantly different.

    • Abstract: ABSTRACT Cacao is a species of great economic and social importance. Expanding the area grown with this crop has been limited by its climatic requirements. Agroclimatic zoning for agricultural sector and creation of land suitability maps by fuzzy logic contribute to such production expansion. In this sense, this study aimed to develop rainfall zoning for cacao in Bahia state using the fuzzy logic method. The used data came from rainfall historical series of 519 meteorological stations distributed throughout the state. Geostatistical analyses were used to quantify the spatial dependence degree of studied variable and kriging was used to develop maps representing mean monthly rainfall. These maps were submitted to continuous classification by fuzzy mapping for identification of high-risk areas for cocoa growing based on rainfall. Based on the fuzzy method, the southern mesoregion of Bahia state presented the highest rainfall uniformity, suggesting that this area is more suitable for cocoa growing.

    • Abstract: ABSTRACT In the study of spatial variability of soil attributes, it is essential to define a sampling plan with adequate sample size. This study aimed to evaluate, through simulated data, the influence of parameters of the geostatistical model and sampling configuration on the optimization process, and resize and reduce the sample size of a sampling configuration of a commercial area composed of 102 points. For this, an optimization process called genetic algorithm (GA) was used to optimize the efficiency of the geostatistical model estimation based on the Fisher information matrix. The simulated data evidenced that the variation of the nugget effect or practical range did not significantly alter the sample size. GA was efficient in reducing the sample size, determining for soil chemical attributes a sample size between 30 and 40 points (29.41 to 39.22% of the initial sampling grid). The presence of spatial dependence was observed for all soil chemical attributes in the two sampling configurations (initial and optimized). The optimized sampling configuration evidenced an increase in trend intensity in the north direction and a more efficient estimation of parameters of the linear spatial regression model.

    • Abstract: ABSTRACT A common agricultural problem in many regions of Brazil is maize lodging, as a consequence of strong winds and rain which impacts on crop growth and yield. However, collecting data using ground-based, manual field measurement methods is inefficient. An emerging tool is the Remotely Piloted Aircraft System (RPAS), capable of delivering spatial data with high resolution and flexible periodicity. In this study, the potential to detect the maize lodging using crop surface models derived from RPAS was assessed. Our RPA-based approach uses a quantitative threshold to determine lodging percentage. The threshold values of plant height, used to detect the occurrence of lodging, were based on fixed and variable values. The validation of percentage lodging was performed using the RGB orthomosaic. The derived lodging estimates showed a very high correlation to the reference data. High correlations were observed for the fixed threshold at 60% (R2 = 0.93, RSME = 8.72%) and the variable thresholds, Jenks natural breaks and iso-clusters (R2 = 0.92, RSME = 8.89% and R2= 0.92, RSME = 9%, respectively). This study demonstrated the potential of the use of this technique, reducing the subjectivity of ground-based evaluation and the laborious traditional technique of lodging inference.

    • Abstract: ABSTRACT Variation in the spatial distribution of leaf chlorophyll content associated with the progression of the phenological cycle of crops may occur in cultivated areas as a result of the variability of environmental conditions and of the intrinsic properties of the plants. The objective of the present study was to model the trend in variation and assess the temporal stability of index of chlorophyll a, b, and total chlorophyll (Chla, Chlb, and Chlt, respectively), and to characterize the spatial distribution of Chlt index in grapevine cv. ‘Chardonnay’. The assessments consisted of in situ measurements made with a portable meter in a commercial vineyard located in the municipality of Espírito Santo do Pinhal, state of São Paulo, Brazil, in the period between flowering and fruit maturation. Descriptive statistics were applied to the indices and regression models were fitted to ascertain the relationship of their mean variation with time. The temporal stability of Chlt index was estimated using Spearman's rank correlation analysis and thematic maps were created using geostatistical analysis and spatial estimation by ordinary kriging. The Chlb and Chlt indices were non-linearly associated with cycle progression and their decrease after the start of maturation was estimated. The temporal stability of the Chlt index was low and variation in its spatial distribution was observed over the assessed period.

    • Abstract: ABSTRACT Data interpolation is widely required in precision agriculture. However, its effectiveness is a function of the characteristics of the dataset, being necessary for the evaluation of several parameters. This study aimed to identify how the spatial interpolators, Kriging, and Inverse Distance Weighting, are influenced by the degree of spatial dependence of the variables analyzed and the number of neighbors considered in the interpolation process (sampling neighborhood). Soil samples were collected from three sugarcane fields. By the optimization process, we verified that the sampling neighborhood influences the accuracy of interpolations, but there is not a standard recommendation to follow. Thus, the best sampling neighborhood must ever be optimized for each case when preparing fertilizer prescription maps. Evaluating the performance of interpolations is always important to infer the reliability of the prescription maps, since no index that measures the degree of spatial dependence is effective. Because high prediction errors can occur when spatial dependence is poorly modeled, one cannot expect crop response with the continuous application of fertilizers in variable rates. Thus, work with homogeneous soil zones can be an interesting palliative approach. This study guides precision agriculture practitioners on some points that should be carefully considered in the data interpolation process for generating fertilizer prescription maps.

    • Abstract: ABSTRACT The application of nitrogen (N) fertilizer is complex and expensive, so its correct management has financial and environmental benefits. The use of optical proximity sensors is a promising technique. However, the movement of the agricultural machinery or of the person carrying the sensor will result in height differences and/or different tilt and twist angles with respect to the canopy. We considered whether these variations would affect the reflectance measurement. In this study, we took normalized difference vegetation index (NDVI) readings of a wheat canopy, to which 90 kg ha-1 of urea had been applied in stage 5, and observed the NDVI in stages 6, 8 and 10.5. We also tested soybeans, to which 90 kg ha-1 of urea had been applied in stage R1, and took NDVI readings in stages R2 and R5. Our goal was to study the effects of the position of an active reflectance sensor (GreenSeeker) on the NDVI index at different heights and at different angles to the canopy. We observed that the height of the sensor affected the NDVI depending on the stage of the plant and that angles up to 15° of the sensor did not directly affect the readings.

    • Abstract: ABSTRACT Spatial variability evaluation of qualitative attributes can be used as an excellent strategy to design forms of intervention that result in better crop profitability for some agricultural crops, for example, sugarcane. Based on the assumption that qualitative attributes of sugarcane present spatial variability and their distributions along the stems are uniform in different varieties, this study aimed to evaluate the distributions of the qualitative parameters of different sugarcane varieties and the spatial variability of these attributes in a commercial field. Samples of nine varieties were collected for laboratory quality analysis, and the Brix parameter was analyzed by a digital refractometer. The analysis of variance, the Tukey test, and geoestatistcs were the statistical analyses applied to the dataset. The maps were generated using 91 sample results from the laboratory analysis of the 16.6 ha field. It was found that, in the harvest period, there was no significant difference in Brix content along the sugarcane stems. Therefore, we can conclude that the Brix content along the sugarcane stems does not change in the harvesting period, and the ideal sampling size to better represent the factors affecting sugarcane qualitative attributes is six points per hectare.

    • Abstract: ABSTRACT The use of new technologies to meet the demands of the agricultural market is increasing; however, technical information on application is scarce for some areas of knowledge, including irrigation management. The objective of this study is to evaluate an automatic irrigation system with capacitance sensors connected to a local wireless network for the semiautomatic management of irrigation in tomato crops compared with a manual control system based on time-domain reflectometry (TDR)-type sensors. The experiments were carried out in a protected environment, and the seedlings were transplanted following surface drip lines. The study adopted a completely randomized block design consisting of two treatments and 12 repetitions, totaling 24 subplots. The evaluated treatments were an irrigation management system with TDR sensors and a manually-programmed controller, and an irrigation management system with capacitance sensors and a semiautomatically-programmed controller connected to a digital assistant. Quantitative and qualitative parameters as well as the green and dry matter production were evaluated in each treatment. The results indicated that both sensors were effective in managing irrigation in tomato crops. Furthermore, both systems were accurate, and the Alexa® digital assistant was efficient in programming the GreenIQ® semiautomatic system by voice commands.

    • Abstract: ABSTRACT Soil fertility attributes have different scales and forms of spatial and temporal variations in agricultural fields. Adequate spatiotemporal characterization of these attributes is fundamental to the successful development of strategies for variable rate application of fertilizers, enabling the classic benefits of precision agriculture (PA). Studies on Brazilian soil have shown that at least 1 sample ha-1 is required for the reliable mapping of key fertility attributes. However, this sampling density is difficult owing to the operational challenges of sample collection and the cost of laboratory analyses. Given this limitation, soil sensors have emerged as a practical and complementary technique for obtaining information on soil attributes, at high spatial density, without the production of chemical residues and at a reduced cost. Scientists worldwide have devoted their attention to the development and application of sensor systems for this purpose. The concept of proximal soil sensing (PSS) was established in 2011 and involves the application of soil sensors directly on the field. PSS techniques involve different disciplines, such as instrumentation, data science, geostatistics, and predictive modeling. The integration of these different disciplines has allowed successful sensor application for the spatial diagnosis of soil fertility attributes. The present work aimed to present a bibliographic review of the concepts involved and main techniques used in soil sensing to predict fertility attributes. We sought to present a broad view of the challenges, advances, and perspectives of sensor application in Brazilian tropical soils in the context of PA.
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
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