The objective of this study was to adapt a nonlinear model (Wang and Engel - WE) for simulating the phenology of maize (Zea mays L.), and to evaluate this model and a linear one (thermal time), in order to predict developmental stages of a field-grown maize variety. A field experiment, during 2005/2006 and 2006/2007 was conducted in Santa Maria, RS, Brazil, in two growing seasons, with seven sowing dates each. Dates of emergence, silking, and physiological maturity of the maize variety BRS Missões were recorded in six replications in each sowing date. Data collected in 2005/2006 growing season were used to estimate the coefficients of the two models, and data collected in the 2006/2007 growing season were used as independent data set for model evaluations. The nonlinear WE model accurately predicted the date of silking and physiological maturity, and had a lower root mean square error (RMSE) than the linear (thermal time) model. The overall RMSE for silking and physiological maturity was 2.7 and 4.8 days with WE model, and 5.6 and 8.3 days with thermal time model, respectively.

Cassava [Manihot esculenta (L.) Crantz] plays an important role as staple food in the tropics. The GUMCAS model is a process-based dynamic simulation model for cassava that has been adapted to the Cropping System Model (CSM) framework of DSSAT (DSSAT-CSM). The objective of this study was to calibrate and evaluate the original GUMCAS model, a modified version of the GUMCAS model, and the current cassava model in DSSAT under potential conditions in the subtropical environment of Rio Grande do Sul State, Brazil. The modified original GUMCAS model consisted of three modifications in the code: we included a third independent "clock" in the cassava development for the onset of starch accumulation, we replaced the rate of leaf appearance submodel with the Wang and Engel model, and we modified the leaf senescence submodel. Model calibration was with a field experiment for cultivar Fepagro-RS 13 during the 2011/2012 growing season in Santa Maria, Brazil. Independent data from 16 experiments conducted at four sites in Rio Grande do Sul State were used for testing the performance of the three versions of the cassava model. The original GUMCAS model had the poorest performance, and the modified GUMCAS model slightly improved the predictions of stem and storage root yield compared with the current DSSAT cassava model. The modified GUMCAS model greatly improved the predictions of developmental stages, leaf development, and leaf area growth dynamics compared with the current DSSAT cassava model. Results from this study contribute to our understanding on how a cassava system functions in the subtropics.

IIIDesenvolvimento vegetativo e reprodutivo em gladíolo Vegetative 'Peter Pears', 'Sunset', 'T704', 'Traderhorn', 'Rose Supreme' and 'Jester', and another

RESUMO O objetivo deste trabalho foi estimar a temperatura base para aparecimento de folhas e o filocrono em uma

Resumo -O objetivo deste trabalho foi verificar a associação da variabilidade interdecadal da chuva em Santa Maria, RS, com a Oscilação Decadal do Pacífico. Parte da variabilidade interanual da precipitação pluvial é explicada pelo fenômeno El Niño Oscilação Sul (ENOS), que acontece no Oceano Pacífico. Na segunda metade da década de 1990, foi relatada outra oscilação na temperatura do Oceano Pacífico, de duração maior que o ENOS, denominada Oscilação Decadal do Pacífico (ODP). Foram usados os dados mensais acumulados de precipitação do período 1912-2008, da Estação Climatológica principal de Santa Maria, e os valores mensais do índice ODP do mesmo período. A análise foi realizada em nível anual, semestral (primeiro e segundo semestre), sazonal (verão, outono, inverno e primavera) e mensal. Existe associação entre a chuva e a ODP, de modo que décadas com chuvas acima da normal são associadas à fase quente da ODP, intercaladas com décadas com chuva abaixo da normal associadas à fase fria da ODP, o que indica oscilações periódicas de médio e longo prazo na precipitação pluvial em Santa Maria, RS.Termos para indexação: chuva, clima, El Niño, La Niña, temperatura da superfície do mar. Linking rainfall variability in Santa Maria with the Pacific Decadal OscillationAbstract -The objective of this work was to verify the association of the interdecadal variability of rainfall in Santa Maria, Rio Grande do Sul state, Brazil, with the Pacific Decadal Oscillation. Part of the interannual variation in rainfall is explained by the El Niño Southern Oscillation (ENSO) in the Pacific Ocean. In the second half of the 1990s, another oscillation in the surface temperature of the Pacific Ocean was reported, with greater duration than ENSO, named the Pacific Decadal Oscillation (PDO). Monthly precipitation data collected at the Meteorological Station of Santa Maria of the 1912-2008 period and monthly PDO indices of the same period were used. The analyses were performed on an annual, semestral (first and second semester), seasonal (Summer, Fall, Winter, and Spring), and monthly basis. There is a link between rainfall and PDO, because decades with precipitation higher than normal are associated with a warm phase of PDO, followed by decades with below-normal rainfall associated with a cool phase of PDO, which indicate mid and long-term periodic oscillations of rainfall in Santa Maria.