Soil tillage is an agricultural practice that directly affects the global carbon cycle. Our study sought to assess the implications of adopting sunn hemp cover crops with different tillage practices on CO2 emissions for two soil types (clayey and sandy soil) cultivated with sugarcane in Brazil. The experimental design was a split‐plot with randomized blocks, with the main plots being with cover crop or fallow and sub‐plots being under conventional or minimum tillage. Our results indicate that during the first 50 days after soil tillage, the variation in soil CO2 emissions was stimulated by cover crop and soil tillage, while after that, it became dominated by the root respiration of sugarcane plants. We also found that over the first 97 days after the tillage, the clayey soil showed differences between minimum tillage with cover crop and fallow. Conversely, for sandy soil over the first 50 days following, there were differences between the tillage systems under cover cropping. Emissions from sugarcane rows were found to be greater than those from inter‐row positions. We concluded that soils under different textural classes had distinct patterns in terms of soil CO2 emissions. The correct quantification of CO2 emissions during the sugarcane renovation period should prioritize having a short assessment period (~50 days after soil tillage) as well as including measurements at row and inter‐row positions.
ABSTRACT:The use of data mining is a promising alternative to predict soil respiration from correlated variables. Our objective was to build a model using variable selection and decision tree induction to predict different levels of soil respiration, taking into account physical, chemical and microbiological variables of soil as well as precipitation in renewal of sugarcane areas. The original dataset was composed of 19 variables (18 independent variables and one dependent (or response) variable). The variable-target refers to soil respiration as the target classification.Due to a large number of variables, a procedure for variable selection was conducted to remove those with low correlation with the variable-target. For that purpose, four approaches of variable selection were evaluated: no variable selection, correlation-based feature selection (CFS), chisquare method (χ 2 ) and Wrapper. To classify soil respiration, we used the decision tree induction technique available in the Weka software package. Our results showed that data mining techniques allow the development of a model for soil respiration classification with accuracy of 81 %, resulting in a knowledge base composed of 27 rules for prediction of soil respiration. In particular, the wrapper method for variable selection identified a subset of only five variables out of 18 available in the original dataset, and they had the following order of influence in determining soil respiration: soil temperature > precipitation > macroporosity > soil moisture > potential acidity.
No turismo, o marketing possui relevante importância, e a promoção, inserida nesse contexto, tem por objetivo comunicar e promover produtos para um mercado-alvo. A contribuição da evolução tecnológica para a atividade é expressiva e uma possível aplicação para o uso dela é o ambiente de imersão digital, no qual o usuário pode ter acesso a imagens panorâmicas de atrativos e a vídeos interativos de destinos turísticos. Objetivou-se com esta pesquisa estudar o ambiente de imersão digital como ferramenta de promoção turística, compreender as ações de promoção de alguns destinos turísticos e verificar a receptividade e a aceitabilidade da ferramenta. Para tal, realizaram-se pesquisa bibliográfica, com base em autores que abordam o tema estudado, e estudo exploratório, por meio de entrevistas, com instituições representativas da atividade turística. Constatou-se que há uma homogeneização das ferramentas de promoção utilizadas pelas instituições; além disso, observou-se que a receptividade e a aceitabilidade do ambiente de imersão digital, pelos entrevistados, foram, em geral, positivas. Palavras-chave: ambientes de imersão digital, marketing turístico, promoção de destinos turísticos, instituições de turismo.
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