Early yield prediction of a maize crop is important for planning and policy decisions. Many countries, including South Africa use the conventional techniques of data collection for maize crop monitoring and yield estimation which are based on ground-based visits and reports. These methods are subjective, very costly and time consuming. Empirical models have been developed using weather data. These are also associated with a number of problems due to the limited spatial distribution of weather stations. Efforts are being made to improve the accuracy and timeliness of yield prediction methods. With the launching of satellites, satellite data are being used for maize crop monitoring and yield prediction. Many studies have revealed that there is a correlation between remotely sensed data (vegetation indices) and crop yields. The satellite based approaches are less expensive, save time, data acquisition covers large areas and can be used to estimate maize grain yields before harvest. This study applied Landsat 8 satellite based vegetation indices, Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI) and Moisture Stress Index (MSI) to predict maize crop yield. These vegetation indices were derived at different growth stages. The investigation was carried out in the Kopanong Local Municipality of the Free State Province, South Africa. Ground-based data (actual harvested maize yields) was collected from Department of Agriculture, Forestry and Fisheries (DAFF). Satellite images were acquired from Geoterra Image (Pty) Ltd and weather data was from the South African Weather Service (SAWS). Multilinear regression approaches were used to relate yields to the remotely sensed indices and meteorological data was used during the development of yield estimation models. The results showed that there are significant correlations between remotely sensed vegetation indices and maize grain yield; up to 63 percent maize yield was predicted from vegetation indices. The study also revealed that NDVI and SAVI are better yield predictors at reproductive growth stages of maize and MSI is a better index to estimate maize yield at both vegetative and reproductive growth stages. The results obtained in this study indicated that maize grain yields can be estimated using satellite indices at different maize growth stages.

Orientador: Regiane Cristina O. de Bueno / Coorientador: Marcelo de Almeida Silva / Banca: Carlos Gilberto Raetano / Banca: Denise Tourino Rezende de Cerqueira / Resumo: A arquitetura das plantas pode ser modificada pelas práticas de condução da cultura influenciando assim aspectos fitossanitários e a produtividade. Diante disso, este trabalho teve como objetivo verificar a influência de diferentes arranjos de plantio na população de pragas e nas características morfofisiológicas na cultura da soja. O experimento foi composto por oito tratamentos, sendo quatro sistemas de plantio com diferentes espaçamentos entre linhas e duas cultivares de soja, uma de hábito de crescimento determinado e outra indeterminado e quatro repetições com parcelas de 12 x 07 m. Foram avaliados utilizando a população de insetos-praga, os danos de percevejos, os parâmetros morfofisiológicos, e ao final do ciclo as variáveis agronômicas e produtividade. Em relação à população de insetos-praga os sistemas de plantio convencional e fileira dupla foram os que tiveram maior ocorrência de lagartas desfolhadoras. Quanto à população de percevejos e inimigos naturais não houve diferença entre os tratamentos. No teste de tetrazólio houve maior quantidade de danos nos grãos no sistema de fileira dupla. A condição fisiológica das plantas de soja se manteve melhor nos sistemas de plantio convencional e fileira dupla, porém para os parâmetros de razão da área foliar (RAF) e área foliar específica (AFE) não houve diferença. O sistema de plantio reduzido apresentou maior quantidade de ramificações e consequentemente maior quantidade de vagens e grãos, entretanto este incremento não refletiu na produção, pois os tratamentos não diferiram entre si quanto à produtividade. / Abstract: The architecture of the plants can be modified by the driving practices of culture influencing plant health and productivity. Thus, this study aimed to investigate the influence of different planting arrangements in the pest population and the morphophysiological traits in soybean. The experiment consisted of eight treatments, four tillage systems with different row spacings and two soybean cultivars, one of determinate growth habit and other indeterminate and four replications with plots of 12 x 07 m. Were evaluated using the population of insect pests, stink bug damage, the morphophysiological parameters , and at the end of the cycle variables agronomic and productivity. In relation to the population of insect pests conventional tillage systems and double row were those who had a higher incidence of defoliating caterpillars. As the population of bed bugs and natural enemies there was no difference between treatments. In tetrazolium test a higher amount of damage to grain in double row system. The physiological condition of the soybean plants kept in the best of conventional and double row planting systems, but for the parameters of leaf area ratio (RAF) and specific leaf area (AFE) there was no difference. The system of reduced tillage had greater amount of branching and hence larger amount of beans and grains, however this increase was not reflected in production because the treatments did not differ in terms of productivity. / Mestre

Made available in DSpace on 2014-06-11T19:28:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-18Bitstream added on 2014-06-13T18:35:04Z : No. of bitstreams: 1 000754448.pdf: 1348251 bytes, checksum: 8fde2d8307ee7de4fcd2c5fe29feb1e8 (MD5) / A arquitetura das plantas pode ser modificada pelas práticas de condução da cultura influenciando assim aspectos fitossanitários e a produtividade. Diante disso, este trabalho teve como objetivo verificar a influência de diferentes arranjos de plantio na população de pragas e nas características morfofisiológicas na cultura da soja. O experimento foi composto por oito tratamentos, sendo quatro sistemas de plantio com diferentes espaçamentos entre linhas e duas cultivares de soja, uma de hábito de crescimento determinado e outra indeterminado e quatro repetições com parcelas de 12 x 07 m. Foram avaliados utilizando a população de insetos-praga, os danos de percevejos, os parâmetros morfofisiológicos, e ao final do ciclo as variáveis agronômicas e produtividade. Em relação à população de insetos-praga os sistemas de plantio convencional e fileira dupla foram os que tiveram maior ocorrência de lagartas desfolhadoras. Quanto à população de percevejos e inimigos naturais não houve diferença entre os tratamentos. No teste de tetrazólio houve maior quantidade de danos nos grãos no sistema de fileira dupla. A condição fisiológica das plantas de soja se manteve melhor nos sistemas de plantio convencional e fileira dupla, porém para os parâmetros de razão da área foliar (RAF) e área foliar específica (AFE) não houve diferença. O sistema de plantio reduzido apresentou maior quantidade de ramificações e consequentemente maior quantidade de vagens e grãos, entretanto este incremento não refletiu na produção, pois os tratamentos não diferiram entre si quanto à produtividade. / The architecture of the plants can be modified by the driving practices of culture influencing plant health and productivity. Thus, this study aimed to investigate the influence of different planting arrangements in the pest population and the morphophysiological traits in soybean. The experiment consisted of eight treatments, four tillage systems with different row spacings and two soybean cultivars, one of determinate growth habit and other indeterminate and four replications with plots of 12 x 07 m. Were evaluated using the population of insect pests, stink bug damage, the morphophysiological parameters , and at the end of the cycle variables agronomic and productivity. In relation to the population of insect pests conventional tillage systems and double row were those who had a higher incidence of defoliating caterpillars. As the population of bed bugs and natural enemies there was no difference between treatments. In tetrazolium test a higher amount of damage to grain in double row system. The physiological condition of the soybean plants kept in the best of conventional and double row planting systems, but for the parameters of leaf area ratio (RAF) and specific leaf area (AFE) there was no difference. The system of reduced tillage had greater amount of branching and hence larger amount of beans and grains, however this increase was not reflected in production because the treatments did not differ in terms of productivity.