Análise de desempenho de um modelo fenológico para a cultura do arroz irrigado no Estado do Rio Grande do Sul

O arroz tem o segundo maior volume de produção em grãos do mundo, sendo o Brasil, o nono maior produtor. O Estado do Rio Grande do Sul, é responsável por aproximadamente 70% de toda a produção nacional de arroz, fato que apresenta grande relevância socioeconômica para o Estado e para o país, uma vez que a agricultura está diretamente ligada a economia. Diversas variáveis meteorológicas exercem influência direta no desenvolvimento da cultura no Estado, como radiação solar, precipitação pluvial e principalmente temperatura. Portanto, o conhecimento de como a cultura responde as diferentes variações meteorológicas no desenvolvimento fenológico é de extrema importância e tem a modelagem como aliada. O objetivo deste trabalho foi avaliar um software computacional que auxilia a determinação das temperaturas cardinais do modelo fenológico utilizado pelo modelo ORYZA2000, auxiliando a calibração dos coeficientes para caracterização das cultivares de arroz irrigado. Pode-se constatar, através dos resultados, que as cultivares analisadas apresentam valores de temperaturas cardinais similares ao longo dos estádios de desenvolvimento abordados e que por vezes subestimam e superestimam as faixas de temperaturas propostas pela literatura. Concluiu-se, que o programa desenvolvido foi capaz de simular corretamente os processos fenológicos existentes na cultura do arroz irrigado e precisar as temperaturas cardinais ideais para duas diferentes cultivares de arroz irrigado, comumente utilizadas na lavoura gaúcha

Variáveis meteorológicas e crescimento de arroz irrigado

A cultura orizícola é de extrema importância para a economia da região sul do Brasil, principalmente para o estado do Rio Grande do Sul/RS, que é o maior produtor nacional de arroz irrigado. Análises durante o desenvolvimento fenológico dos componentes de crescimento das plantas (fontes) de diferentes cultivares e suas interações (feedback) com as variáveis meteorológicas, vem se tornando cada vez mais importantes, pois proporcionam ajustes mais acurados para a indicação ideal da(s) a(s) época(s) de semeadura das culturas em diversos ambientes. O objetivo do trabalho foi analisar o desenvolvimento dos diferentes estádios fenológicos de três cultivares de arroz irrigado: BRS Querência, BRS Pampeira e BRS Pampa CL. Foi conduzido um experimento de campo com três diferentes cultivares e em três épocas de semeaduras, na Estação Experimental da Embrapa Terras Baixas, município de Capão do Leão, RS. As avaliações foram realizadas com amostras de folhas verdes, folhas mortas, colmos e panículas em quatro épocas de coleta, sendo estas, realizadas em um metro linear com quatro repetições e baseadas nos estádios fenológicos de cada cultivar. Pode-se concluir que o predomínio de desenvolvimento das cultivares foi variável e dependente do estádio fenológico em que eram analisadas, as variáveis meteorológicas apresentaram-se favoráveis ao desenvolvimento dos três diferentes tipos de arroz irrigado analisados

Growth and yield of Brazilian potato cultivars

The analysis of plant growth of cultivars is useful for understanding the dynamics of accumulation and partition of photoassimilates during the crop cycle, and this information is important for the crop management of each cultivar. The objective of this study was to evaluate potato cultivars BRS Ana, BRSIPR Bel, BRS Clara, BRS F63 (Camila) and Macaca for growth and yield, under subtropical climatic conditions of Southern Brazil. Plant samples were collected every 20 days, beginning 40 days after planting (DAP), totaling five collections, and physiological growth indexes and the dry mass partitioning to plant organs were estimated. ‘BRSIPR Bel’ showed the fastest development of assimilatory system. ‘BRS Ana’ had the most vigorous plants and the largest leaf area, reaching the leaf area index 4.0 at 70 DAP. ‘BRSIPR Bel’ e ‘BRS Ana’ had the highest dry mass yield, 214 g and 206 g of dry mass plant-1, respectively. ‘BRS F63’ (Camila) and ‘BRSIPR Bel’ presented earlier tuberization and were the most efficient cultivars in the partitioning of dry mass to tubers, with the highest coefficient of dry mass partitioning to tubers estimated between 40 and 64 DAP. These two cultivars also showed the highest yield of marketable tubers.The analysis of plant growth of cultivars is useful for understanding the dynamics of accumulation and partition of photoassimilates during the crop cycle, and this information is important for the crop management of each cultivar. The objective of this study was to evaluate potato cultivars BRS Ana, BRSIPR Bel, BRS Clara, BRS F63 (Camila) and Macaca for growth and yield, under subtropical climatic conditions of Southern Brazil. Plant samples were collected every 20 days, beginning 40 days after planting (DAP), totaling five collections, and physiological growth indexes and the dry mass partitioning to plant organs were estimated. ‘BRSIPR Bel’ showed the fastest development of assimilatory system. ‘BRS Ana’ had the most vigorous plants and the largest leaf area, reaching the leaf area index 4.0 at 70 DAP. ‘BRSIPR Bel’ e ‘BRS Ana’ had the highest dry mass yield, 214 g and 206 g of dry mass plant-1, respectively. ‘BRS F63’ (Camila) and ‘BRSIPR Bel’ presented earlier tuberization and were the most efficient cultivars in the partitioning of dry mass to tubers, with the highest coefficient of dry mass partitioning to tubers estimated between 40 and 64 DAP. These two cultivars also showed the highest yield of marketable tubers

A biophysical sugarcane growth model for global studies

Previsões apontam uma expansão das terras cultivadas ao longo das próximas décadas devido a uma combinação do aumento da população global, com consequente necessidade de aumento da produção de alimentos, e do recente crescimento exponencial da produção de biocombustíveis baseados em cultura agrícolas. As alterações resultantes do uso da terra podem, por sua vez, impactar significativamente os ciclos biogeoquímicos e biogeofísicos ao longo do globo. Portanto, a representação de culturas agrícolas para produção de biocombustíveis, como a cana-de-açúcar, devem ser integradas em modelos de processos superficiais terrestres, possibilitando considerar nas simulações numéricas os feedbacks bidirecionais entre a superfície e a atmosfera. Neste estudo, nós apresentamos um novo modelo mecanicista de crescimento da cultura da cana-de-açúcar, incluído como um módulo dentro do modelo dinâmico de agro-ecossistema Agro-IBIS, que pode ser aplicado em múltiplas escalas espaciais (do local ao global). O modelo pode ser acoplado a um modelo atmosférico, permitindo a simulação das interações bidirecionais entre a atmosfera e o sistema de cultivo de cana. Esse novo módulo inclui uma série de equações e parâmetros de manejo agrícola que diferem das formulações para as culturas anuais pré-existentes. O modelo é avaliado contra observações micro-meteorológicas e de biomassa, obtidas para um ciclo da cultura (391 dias), no norte do Estado de São Paulo (Brasil), e para a produtividade agrícola em diferentes escalas espaciais. Os resultados da validação micro-meteorológica indicam que o modelo produz robustamente as flutuações sazonais e diárias do albedo, biomassa seca, e as relações entre troca líquida do ecossistema (NEE) e das variáveis atmosféricas (temperatura e umidade relativa do ar). Ao nível local, o modelo simulou com precisão a intensidade e a variabilidade diária da evapotranspiração (ET) durante dois ciclos consecutivos da cana-de-açúcar em um sítio experimental na localidade Kalamia, nordeste da Austrália. O modelo simulou com exatidão a média da produtividade da cana-de-açúcar para as quatro maiores mesorregiões produtoras (aglomerados de municípios) do estado de São Paulo (Brasil), durante um período de 16 anos, com viés relativo entre -0,68% e +1,08%. Finalmente, a simulação da produtividade média anual de cana para o Estado de Louisiana (EUA) produziu um viés relativo (-2,67%) baixo, mas apresentou menor variabilidade interanual do que a série de produtividade estimada. Considerando os resultados de todas as validações, podemos concluir que o novo modelo é capaz de capturar a relação entre a produção de biomassa e variabilidade do clima (temperatura e precipitação), indicando que o módulo pode ser utilizado com sucesso para prever alterações nos sistemas de cultivo de cana e as respectivas interações com o clima.Global agricultural lands are predicted to expand over the next few decades due to a combination of increasing global population, the need for increased food production, and exponential growth in crop-based biofuels production. The resultant changes in land use could, in turn, greatly impact biogeochemical and biogeophysical cycles across the globe. Therefore, representation of biofuel crops such as sugarcane should be integrated into the latest models to ensure that accurate simulations of the bidirectional feedbacks between the land surface and atmosphere take place. In this study, we present a new process-based sugarcane model, included as a module within the Agro- IBIS dynamic agro-ecosystem model, that can be applied at multiple spatial scales (from site to global). The model may be coupled to an atmospheric model, allowing the simulation of the bi-directional interactions between atmosphere and the sugarcane cropping system. It includes a series of equations and crop management parameters that differ from the standard formulations for annual crops. The model is evaluated against micrometeorological and biomass observations, obtained for one crop cycle (391 days) in northern São Paulo state (Brazil), and yield at a range of spatial scales. The results of the micro-meteorological validation suggest that the model produces robust simulations of seasonal and daily albedo fluctuations, dry biomass, and relationships between net ecosystem exchange (NEE) and atmospheric variables (temperature and relative humidity). At the site level, the model accurately simulated the intensity and variability of daily evapotranspiration (ET) for two consecutive crop cycles at an experimental site at Kalamia estate, northeast Australia. The model also accurately simulated the average yield for the four largest mesoregions (clusters of municipalities) in the state of São Paulo (Brazil), over a period of 16 years, with a relative bias of -0.68% to 1.08%. Finally, a simulation of the annual average sugarcane yield over 31 years for the State of Louisiana (U.S.) produced a low relative bias (-2.67%) but exhibited lower yiled interannual variability than the estimated yields. Considering the results of all validations, we conclude that the new model is able to accurately capture the relationship between yield and climate variability (temperature and precipitation), indicating that the module may be successfully used to forecast changes in sugarcane cropping systems and associated climate interactions.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Atmospheric patterns associates to dry and wet periods over South and Southeast of Brazil during the austral summer: analysis of climatic simulations

The present work investigates circulation patterns associated to the extremes of intraseasonal precipitation over the South and Southeast of Brazil as simulated by regional climate model RegCM3 (Regional Climate Model). We analyzed ten austral summer simulations, from 1989 to 1998, that were initiated and driven by NCEP reanalysis. The quantis technique was applied in the simulated daily precipitation to identify dry and wet extremes periods. Composites for wet periods over South and Southeast of Brazil show a dipole pattern in the precipitation anomalies between the two regions. During wet periods over Southeast, the anomalies of moisture fluxes present anticiclonic circulation over central Brazil and the transport of heat and moisture from Amazon basin is directed to southeast of Brazil. This circulation is inverted during the wet periods over the South, when there is an intensification of moisture and heat transport to this region. These composites show that RegCM3 simulated the circulations pattern, associated to wet periods, similar to those obtained in several observational studies. Composites of dry periods over the South also present intense precipitation over Southeast, although, there are differences in the circulation pattern compared to wet periods over Southeast. The moisture flux and transient of the divergence of moisture flux in the atmosphere were compared to investigate the differences in the circulation. The dry periods over the South indicates intense transient activity over the Southeast, which suggests the presence of transients systems (as cold fronts). On the other hand, the composites of wet periods over Southeast present characteristics of stationary systems, which is an indicative of the contribution of the South Atlantic Convergence Zone (SACZ). Composites of the circulation during dry periods over the Southeast are very similar to the wet periods over the South Brazil.Pages: 1005-100

Precipitation and temperature variability over South America from 1860 to 2100

The objective of this work is to determine the main modes of precipitation variability over South America in different frequency bands (interannual, interdecadal, intraseasonal and synoptic) and their variation in many periods of time. A detailed verification about modes variability from 1860 to 2100 will be presented to show differences between current and past climate, the main changes observed and what would be the main climate expected. Moreover, it was also determined if the number of extreme precipitation events (drier or wetter) experienced significant changes. To this analysis the principal component (PCA) of 30-years moving periods (1860-1890, 1870-1900, ..., 2070-2100) was calculated. Precipitation data from the coupled atmosphere-ocean general circulation model (HadCM3) developed at the Hadley Centre was used. This data has a resolution of 2.5° (latitude) x 3.75° (longitude), producing a global grid of 96 x 73 grid cells, with a equivalent resolution of 417 km x 278 km at the Equator, reducing to 295 km x 278 km at 45° of latitude (comparable to a spectral resolution of T42).Pages: 1527-153

Effects of RegCM3 parameterizations on simulated rainy season over South America

The impacts of change in the Grell convective scheme and biosphere−atmosphere transfer scheme (BATS) in RegCM3 are described. Three numerical experiments (RegZhang, RegClaris and RegArain) are conducted to reduce the RegCM3-Grell rainfall underestimation over tropical South America. The simulation referred to as RegZhang follows modifications made by Zhang et al. (2008) in the BATS. The RegClaris combines the RegZhang BATS parameters with a reduction of water drainage at the bottom of the subsoil layer in the regions covered by the tropical rain forest and a shorter convective time period for the Grell scheme. The RegArain considers this same modification in the Grell scheme, but uses a deeper total soil column and a deeper root system in the BATS. After the first year of simulation, the soil water content in RegZhang is progressively drained out of the soil column resulting in a deficit of rainfall in the Amazon. The RegClaris and RegArain, on the other hand, simulate a similar rainfall annual cycle in the Amazon, showing substantial improvement not only in phase but also in intensity. This improvement is partially related to an increase in evapotranspiration due to a larger availability of water in the soil column. A remote effect is also noted over the La Plata Basin region, where the larger summer rainfall rate may be related to the increase in moisture transport from the Amazon. Wind- and rainfall-based indices are applied to identify South American monsoon (SAM) timing. The RegClaris rainfall rates are adequate to identify the onset and the demise of SAM according to the observed data, whereas the rainfall deficit in RegZhang is associated with a delay in the onset and an early demise of the SAM