Isabel Lago

Estimativa do plastocrono em meloeiro (Cucumis melo L.) cultivado em estufa plástica em diferentes épocas do ano

Muskmelon (Cucumis melo L.) is a high-value horticultural crop. The prediction of node appearance is an important part of simulation models of crops with decumbent growth like muskmelon and other cucurbits. One way to predict node appearance is by using the concept of plastochron, defined as the time interval between the appearance of successive nodes on a stem or vine. Time can be expressed as thermal time, and in this case, the plastochron has units of °C day node-1. Previous studies have demonstrated that the plastochron in muskmelon varies with genotype and planting date. The objective of this study was to estimate the plastochron in muskmelon grown inside a plastic greenhouse at different transplanting dates. Twelve planting dates were performed inside a 10m X 25m greenhouse covered with polyethylene in Santa Maria, RS, Brazil. The HY-MARK hybrid was used. Twelve plants in each planting date were tagged with colored wire. The number of visible nodes (NN) on the main vine of the tagged plants was measured twice a week. Daily degree-days (DDD, °C day) were calculated, with cardinal temperatures for node appearance in muskmelon (10, 34, and 45°C). Accumulated thermal time (TT, °C day) from transplanting was calculated by accumulating DDD. The NN was linearly regressed against TT. The plastochron was estimated by the inverse of the angular coefficient of the linear regression. Plastochron varied among planting dates, from 13.4 to 21.8°C day node-1, with an average of 18.6 (±2.3)°C day node-1. This difference in plastochron values among planting dates may represent several calendar days when NN is used to estimate the date of developmental stages in muskmelon such as flowering of the first male and hermaphrodite flowers.

Simulating maize phenology as a function of air temperature with a linear and a nonlinear model

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 Missoes 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.

Simulação do desenvolvimento da batata cultivar asterix em cinco cenários de mudanças climáticas em Santa Maria, RS

SIMULATION OF POTATO CULTIVAR ASTERIX DEVELOPMENT UNDER FIVE CLIMATE CHANGE SCENARIOS IN SANTA MARIA In studies of the impact of climate change on agroecosystems, it is important to quantify the effect of global warming on crop development. The objective of this study was to simulate the impact of increasing air temperature scenarios on the potato (Solanum tuberosum L.) development in Santa Maria,

Temperatura base para aparecimento de folhas e filocrono da variedade de milho BRS Missões

The objective of this study was to estimate the base temperature for leaf appearance and the phyllochron of a maize variety in several sowing dates and two growing seasons. A field experiment was conducted in Santa Maria, RS, with seven sowing dates using the BRS Missoes variety in two growing seasons (2005-06 and 2006-07). The experimental design was a completely randomized blocks, with six replications. Plots were three 5 m rows in a 0.8m x 0.21m spacing. Three plants in the central row of each plot were randomly tagged, and the number of fully expanded leaves (NFE) and the number of leaf tips (NFT) were counted once a week on the tagged plants. The base temperature varied with sowing date from 4.5 to 12°C and an average of about 8°C was used to calculate thermal time. Phyllochron was higher when calculated on an NFE basis than on a NFT basis, and varied with sowing date from 50.0 to 69.9°C day leaf -1

Estimativa do plastocrono em cultivares de soja

A parameter widely used in development simulation models of dicot species is the time interval between the appearance of two successive nodes on a stem, known as plastochron, with units of oC day node-1. The objective of this study was to estimate the plastochron in some soybean (Glycine max (L.) Merrill) cultivars recommended for Southern Brazil. Two experiments were carried out at Santa Maria, RS, Brazil, one during the 2004/2005 and another during the 2005/2006 growing season. Six cultivars (BRS 66, CD 201, CD 203, CD 205, FT 9, FUNDACEP 39) were used in 2004/2005 and five cultivars (CD 205, CD 209, CD 213 RR, CD 214 RR, CD 219 RR) in 2005/2006, in a complete randomized block design, with two replications (average of five plants) in 2004/2005 and three replications (average of six plants) in 2005/2006. The plastochron was estimated by the inverse of the slope of the linear regression of the number of visible nodes on the main stem against the accumulated daily thermal time (base temperature of 10 oC and an optimum threshold temperature of 30 oC) from emergence. Many cultivars (CD 201, FT 9 and CD 205 in 2004/2005, and CD 219 RR, CD 205 and CD 214 RR in 2005/2006) had similar plastochron values. Considering all cultivars, the average and variation (lowest and greatest) value of plastochron were 55.9 (49.6 - 60.3) oC day node -1 in 2004/2005 (a dry year), and 50.7 (48.1 - 53.9) oC day node-1 in 2005/2006 (a wet year), respectively. These results and the fact that the plastochron of the CD 205 cultivar, used in both years, was also greater in the driest year indicate environmental (soil water deficit) effect on the plastochron.

Improving predictions of leaf appearance in field grown potato

The calculation of leaf appearance rate (LAR) and number of accumulated or emerged leaves (NL) on the main stem are part of many crop simulation models. The purpose of this study was to adapt and evaluate a model (WE model) for simulating the main stem LAR and NL in potato (Solanum tuberosum L.). The WE model is a non-linear multiplicative model that takes into account the effect of genotype and environmental factors on LAR. A linear model (Phyllochron model) was also used as a comparison with the WE model. A series of field experiments with 14 planting dates over two years (2003 and 2004) was carried out in Santa Maria, RS, Brazil, using the cultivar Asterix. Coefficients of the WE model and the phyllochron model were estimated with data from four planting dates in 2003, and the models were validated with data from the other ten plantings, which are independent data. The statistics used to quantify model performance was the root mean square error (RMSE). The WE model was a better predictor of NL (RMSE=2.0 leaves) than the phyllochron model (RMSE=3.7 leaves). The WE model has coefficients with biological meaning and a non-linear temperature response function, which renders generality and robustness to this LAR model.

Desenvolvimento de cultivares de soja em função do grupo de maturação e tipo de crescimento em terras altas e terras baixas

O objetivo deste trabalho foi caracterizar o desenvolvimento de cultivares de soja com diferentes grupos de maturacao e tipos de crescimento em terras altas e terras baixas no Rio Grande do Sul. Foram conduzidas nove epocas de semeadura em Santa Maria (ambiente de terras altas) e uma epoca de semeadura em Capao do Leao (ambiente de terras baixas) durante os anos agricolas 2010/2011, 2011/2012 e 2012/2013, com 11 cultivares de soja. O delineamento experimental em todos os experimentos foi blocos ao acaso, em parcelas subdivididas. Foi quantificada a duracao, em oC dia, do ciclo de desenvolvimento, da fase vegetativa e reprodutiva, e do periodo entre a data que ocorreu o inicio do florescimento e o numero final de nos para todas as epocas e locais de semeadura. Houve reducao da duracao da fase reprodutiva, do ciclo total de desenvolvimento (exceto algumas cultivares semeadas em setembro), com o atraso da data de semeadura independentemente do grupo de maturacao e tipo de crescimento. As semeaduras de setembro, janeiro e fevereiro promovem uma reducao da fase vegetativa na maioria das cultivares quando comparadas com a epoca recomendada (novembro e dezembro). Cultivares indeterminadas apresentam um maior periodo de sobreposicao das fases vegetativa e reprodutiva do que as cultivares determinadas em todas as epocas e locais de cultivo. O desenvolvimento da soja e similar quando cultivada em terras altas e terras baixas.

Aquecimento global: efeitos no crescimento, no desenvolvimento e na produtividade de batata

The concentration of atmospheric greenhouse gases, mainly the CO2, has increased in the last decades due to anthropogenic activities. The atmospheric CO2 concentration has increased from about 280 parts per million per volume (ppmv) in the pre-industrial period to the currently 380ppmv concentration. There are reports that during the XX century global average temperature increased 0.6±(0.2)°C and projections indicate a possible 1.1 to 6.4°C increase in temperature by the end of the XXI century, depending upon each region. The increase in atmospheric CO2 concentration and air temperature directly affect plant physiological processes, such as photosynthesis and respiration, which may affect crops performance, including potato. The objective of this review was to assemble information from the literature on the possible effects of increasing atmospheric CO2 concentration and air temperature on growth, development and yield of potato. In general, the increase in CO2 concentration followed by an increase in air temperature will result in lower growth, reduction in the duration of the developmental cycle, lower yield and increase of potato diseases. A strategy to minimize the effects of a possible global warming on potato would be to develop cultivars that are tolerant to high temperatures, adapt planting time in each location, change management practices and even, expand growing areas to colder regions.

Comparing two versions of a non-linear model for simulating leaf number and developmental stages in maize based on air temperature

The Wang and Engel (WE) model simulates crop development considering the non-linear response of plant development to temperature. Daily air temperature is the input for the temperature response function [f(T)] in the WE model, and because there are several approaches for computing daily temperatures, there are several ways to calculate the f(T). The objective of this study was to compare two versions of the WE model for simulating leaf number and developmental stages in maize, considering two approaches for imputing daily air temperature (daily mean air temperature and daily minimum/maximum air temperature). A two-year field experiment with the maize variety BRS Missoes sown in several sowing dates was conducted in Santa Maria, Rio Grande do Sul State, Brazil, during the 2005-2006 and 2006-2007 growing seasons. The f(T) in the WE model was calculated using daily mean air temperature calculated as the arithmetic average of daily minimum (TN) and maximum (TX) air temperatures (WETmean), and calculating an f(T) using TN and an f(T) using TX and then averaging the two f(T)s (WETmm). Ligule and tip leaf number, and silking and physiological maturity developmental stages measured in the 2005-2006 growing season were used to estimate model coefficients and the ones measured in the 2006-2007 growing season were used as independent data sets to evaluate models. Predictions of ligule and tip leaf number, silking and physiological maturity of the maize variety BRS Missoes were better with the WETmm model than with the WETmean model.

O fenômeno El Niño Oscilação Sul e a variabilidade interanual da evaporação do tanque Classe A e da umidade relativa do ar em Santa Maria, RS

The objective of this study was to associate the interannual variability of Pan evaporation and air relative humidity with the El Nino Southern Oscilation (ENSO) phenomenon in Santa Maria, RS, Brazil. Daily data records of Pan evaporation (PAN, mm day-1) and mean daily relative humidity (RH, %) measured in Santa Maria, RS, were used. PAN was measured from 1973 to 2006 and RH was measured from 1969 to 2006. Years were grouped into El Nino (EN) years, La Nina (LN) years, and Neutral (N) years, from July 1st of the year to June 30th of the following year. Results showed that PAN is lower in EN years and greater in LN years. On the other hand, RH was greater in EN years and lower in LN years. The effect of ENSO on PAN is greater in November, December, January, and May, whereas RH is affected by ENSO in October, November, December and May.