6,897 research outputs found

    Environment classification for upland rice production region in Brazil.

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    The upland rice (UR) cropped area in Brazil has decreased in the last decade. A portion of this can be attributed to the UR breeding program strategy adopted since the 1980s, according to which direct grain selection is targeted primarily to the most suitable areas. New strategies for an improved breeding under non-optimal conditions for UR require detailed characterization of spatial, inter-annual and sub-seasonal climate variability, particularly in relation to types, intensity and timing of drought events during the cropping cycle. This paper used a process-based crop model to support the Brazilian UR breeding program in efforts to adopt a new strategy that accounts for the varying range of environments where UR is currently cultivated

    Gayatri Chakravorty Spivak and adult education : rearranging desires at both ends of the spectrum

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    As Gayatri Chakravorty Spivak identifies deeply with her role both as an educator and a teacher, she writes and talks extensively about her teaching at Columbia University and her teaching activities with adults in the rural areas of India and some African countries. I discuss in this article some of her valuable thoughts, observations, and insights gained over a number of years, which can be inspiring for adult education. After a short introduction to Spivak’s working context and her approach to education, some of her most important concepts will be presented in a concise overview: ‘The importance of aesthetic education’; ‘the necessity to teach at two ends of the spectrum’; and ‘the task to rearrange desires and to change epistemologies’. The article ends with a short insight into the current contexts and discourses of adult education, including an example of how some of these concepts can be applied in research projects in the context of ‘adult education and migration’.peer-reviewe

    A Weakly nonlinear theory for spiral density waves excited by accretion disc turbulence

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    We develop an analytic theory to describe spiral density waves propagating in a shearing disc in the weakly nonlinear regime. Such waves are generically found to be excited in simulations of turbulent accretion disks, in particular if said turbulence arises from the magneto-rotational instability (MRI). We derive a modified Burgers equation governing their dynamics, which includes the effects of nonlinear steepening, dispersion, and a bulk viscosity to support shocks. We solve this equation approximately to obtain nonlinear sawtooth solutions that are asymptotically valid at late times. In this limit, the presence of shocks is found to cause the wave amplitude to decrease with time as 1/t^2. The validity of the analytic description is confirmed by direct numerical solution of the full nonlinear equations of motion. The asymptotic forms of the wave profiles of the state variables are also found to occur in MRI simulations indicating that dissipation due to shocks plays a significant role apart from any effects arising from direct coupling to the turbulence

    Environmental group identification for upland rice production in central Brazil.

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    Upland rice (Oryza sativa L.) production is basically concentrated in four central Brazilian States, Mato Grosso, Goiás, Rondônia and Tocantins. To reduce the genotype and environment (G × E) interactions, the classification of environment groups was proposed. The goal of this study explores possibilities to adjust the upland rice regional breeding systems to optimally fit to the range of environments they are targeting, based on a historical yield data set of the Brazilian Geographic and Statistics Institute (IBGE, www.ibge.gov.br/home/) from 54 microregions. The specific objectives of this study were: (i) to identify and classify environmental groups in the Brazilian upland rice production area; (ii) to validate these environmental groups using yield data set from the upland rice multi-trial experiments (MTEs); (iii) and to identify the most representative site for each environmental group. For this the historical upland rice yield data from 54 microregions were detrented from the effects of technological advances and adjusted to the reference year, 2006. The adjusted yield data were used to build a matrix, which was submitted to a cluster analysis allowing the identification of three different environmental groups. These groups were classified as: highly favorable environment (HFE); favorable environment (FE); and less favorable environment (LFE). The HFE is less affected by inter-annual rainfall variability than the other two groups. The upland rice breeding programs must take into account the differences among the environmental groups to conduct their trials and suggest genotypes for the upland production area

    Environmental characterisation to guide breeding decisions in a changing climate

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    Substantial evidence now exists suggesting that agricultural yields will have to increase significantly in order to meet food needs during the 21st century. One such way of increasing yields is to develop high yielding cultivars through crop improvement. This Working Paper summarises the results of a CCAFS project named Target Population of Environments (TPE). The project aimed at providing actionable information to crop breeders and, therefore, inform breeding decisions. We developed and applied a methodology for classifying crop growing environments, determining stress profiles and, finally, assessing the potential benefit of improved breeding practice. We present two contrasting case studies, one for upland rice in central Brazil and another for common beans in Goiás (Brazil). Analyses are also currently being conducted for lowland irrigated rice in Colombia, and plans to conduct research on rice in sub-Saharan Africa. Results of the TPE project are publicly available in the form of dynamic maps and graphs at http://www.ccafs-tpe.org

    Elaboração de uma base de dados de climáticos para a área de produção do arroz de terras altas.

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    O objetivo desse estudo foi apresentar uma metodologia para organizar os dados climáticos em uma base de dados, fazer a análise da consistência dos mesmos e estimar os dados de precipitação pluvial, temperatura máxima e mínima do ar e radiação solar faltantes, de forma a obter uma série histórica de 30 anos de dados diários para os estados de Goiás, Mato Grosso, Tocantins e Rondônia.Pôster - graduação

    Uso do modelo de simulação Oryza/Apsim 2000 na definição da população de plantas para o arroz de terras altas.

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    Com este trabalho se propôs simular a resposta do arroz de terras altas a diferentes populações de plantas, em várias épocas de semeadura, com o modelo de simulação do crescimento, desenvolvimento e produtividade ORYZA/APSIM 2000, visando maximizar a produtividade dessa cultura. Para tanto, considerou-se as populações de plantas de 100, 150, 250 e 450 plantas m-2, as quais foram combinadas com cinco datas de semeadura: 01/11, 15/11, 01/12, 15/12 e 31/12. A produtividade de grãos simulada do arroz de terras altas apresentou resposta quadrática à população de plantas, com valores máximos sendo alcançados com populações acima de 350 plantas m-2. Contudo, considerando a maior eficiência técnica, as menores populações de plantas testadas são as mais adequadas. Há maior probabilidade de se obter altas produtividades de arroz de terras altas em datas de semeadura precoces, a partir de 01/11.bitstream/item/46422/1/boletimdepesquisa-36.pd

    Identification of mega environments in the Brazilian upland rice production area.

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    The goal of this study explores possibilities to adjust the upland rice regional breeding systems to optimally fit the range of environments they are targeting, based on a historical yield data set of the IBGE. The specific objectives of this study were: to identify and classify environment groups in the Brazilian upland rice (UPR) production area; to validate these environment groups using yield data set from the upland rice multi-trial experiments (MTEs); and to identify the most representative site for each environment group. For that, the historical upland rice yield data from 54 microregions were detrented from the effects of technological advances and adjusted to the reference year, 2006. A matrix was built with the adjusted yield data and submitted to a cluster analysis allowing to identify three different environment groups. These groups were classified as: high favourable environment (HFE); favourable environment (FE); and low favourable environment (LFE). The HFE has as characteristic being less affected by inter-annual rainfall variability than the other two. KEYWORDS: environment classification, cluster analysis, yield
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