Luana Fernandes Gabriel

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.

Associação da variabilidade da precipitação pluvial em Santa Maria com a Oscilação Decadal do Pacífico

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 Nino 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.

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

Modelagem matemática do desenvolvimento foliar em mandioca

O objetivo deste trabalho foi simular a emissao do numero de folhas com dois modelos matematicos, um que considera o efeito linear e outro que considera o efeito nao linear da temperatura do ar sobre o aparecimento de folhas em mandioca, e considerando duas versoes de cada modelo, uma versao com a temperatura media diaria do ar e outra com a temperatura minima e maxima diaria do ar, e validar o modelo de Wang; Engel para a mandioca. O modelo linear e o modelo do filocrono e o nao linear e o modelo de Wang; Engel. Para estimar os coeficientes dos modelos foi usado um conjunto de dados de numero de folhas na haste principal e na ramificacao simpodial de primeira e segunda ordem da variedade de mandioca Fepagro RS 13, coletados em experimentos conduzidos durante os anos agricolas 2005/2006 e 2007/2008. A avaliacao dos modelos foi realizada com dados independentes coletados nos anos agricolas de 2006/2007, 2008/2009, 2009/2010 e 2010/2011. O modelo Wang; Engel proporcionou melhor estimativa para o numero de folhas em mandioca, com menor valor de raiz do quadrado medio do erro, comparado com o modelo do filocrono.

Estimativa das temperaturas cardinais e modelagem do desenvolvimento vegetativo em batata-doce

The objective of this study was to determine the cardinal temperatures of sweet potato and to compare the simulation of node appearance with the plastochron model (linear) and with Wang and Engel model (nonlinear) and the best way to input air temperature in the models. Model calibration and test were conducted with data of number of nodes on the main stem of sweet potato, cultivar Princesa, collected in experiments carried out in Santa Maria, RS, Brazil, at seven planting dates in 2010, 2011 and 2012 growing seasons. Better model predictions were obtained using the cardinal temperatures of 12, 30 and 40 oC. The plastochron and Wang and Engel models showed similar performance. The version of the models that uses mean temperature as input was superior to the version with the minimum and maximum temperatures as input. Both models can be used to simulate the development of sweet potatoes when it is cultivated in the recommended period. Outside this period it is suggested to use the Wang e Engel model.

Variabilidade interdecadal na série secular de temperatura do ar em Santa Maria, RS

The objective of this work was to verify possible associations between the interdecadal variability of minimum (Tmin) and maximum (Tmax) daily air temperatures and daily thermal range (DTR) in Santa Maria, RS, Brazil, with the Pacific Decadal Oscillation (PDO). Daily Tmin and Tmax values, from January 1912 to December 2009, and the monthly values of the PDO index during the same period were used. There is association between the interdecadal variability of Tmin, Tmax, and DTR with the PDO in this location. There was a decrease in Tmin and Tmax, during the 1947-1976 cold phase of the PDO. In the two PDOs warm phases, 1925-1946 and 1977-1998, there was an increase in Tmin during the first period and in Tmax during the second period. There was a reduction in DTR during the 1947-1976 cold phase of the PDO, due to a reduction of average Tmax and maximum Tmax. There was an increase in DTR in the first semester during the current (1999-2009) cold phase of the PDO, due to a decrease in average Tmin. These warming and cooling cycles, on the decadal time scale, may help in defining adaptation and mitigating strategies in agriculture through plant breeding and the development of cultivars tolerant to such temperature oscillations.

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.

Mudança climática e seus efeitos na cultura da mandioca

The objective of this review is to ensemble information from the literature on the response of cassava to climate change. The growth rate of the most plants increases at elevated CO2 because it is the substrate for photosynthesis, however, the increase in temperature may offset the benefits of CO2 on crop productivity due to a shortening of the cycle and increase in respiration of maintenance. Results from greenhouse, field and numerical experiments indicate that the response of cassava crop to elevated CO2 is positive, i.e. the increase in atmospheric CO2 results in increase of storage root yield of cassava. The increase in temperature projected in future climate scenarios in general should not decrease storage root yield of cassava, mainly in Africa, where this crop has an important role on food security. Further studies should be made using the current knowledge in order to confirm previous studies on the response of cassava to elevated CO2 and temperature in regions where few studies have been conducted, like in Brazil.

Efeito do espaçamento de plantio no crescimento, desenvolvimento e produtividade da mandioca em ambiente subtropical

The objective of this study was to analyze the effect of different planting spacings on the growth, development and stems and roots yield in a subtropical environment of Rio Grande do Sul, Brazil. Treatments consisted of four spacings: 0.8x0.8 m, 1.0x1.0 m, 1.2x1.2 m, 1.5x1.5 m, corresponding to densities of 15,625 plants ha -1 -1 , respectively. The cultivar used was Fepagro - RS 13. The variables of growth and development analyzed were green leaf area, plant height, number of senesced leaves, internode lenght, final leaf (FLN), number of lateral shoots, final size of leaves, phyllochron and stem and root fresh and dry weight yield. The maximum leaf area index and phyllochron increases as plant density increases. The final leaf size and number of lateral shoots increases as plant density decreases. The FLN differed only for the second sympodial branching, with the largest number of leaves in the 1.5x1.5m plant spacing. The stems yield of cultivar Fepagro - RS 13 does not vary with the planting spacing, but tuber root yield per area is higher at higher densities, while yield per plant and per root is higher in lower densities.

Relationship between panicle differentiation and main stem leaf number in rice genotypes and red rice biotypes

Panicle differentiation (DP) is a key developmental stage in rice (Oryza sativa L.) because at this stage plant switches from vegetative to reproductive development and source-sink relation changes to allocate part of the photoassimilates for growing spikelets and kernels. The objective of this study was to determine the main stem Haun Stage (HS) and the number of leaves that still have to emerge until flag leaf at PD in several cultivated rice genotypes and red rice biotypes in different sowing dates. A two-year field experiment was conducted in Santa Maria, Rio Grande do Sul State, Brazil, during the 2005-2006 and 2006-2007 growing seasons, and three sowing dates each year. Nine cultivated rice genotypes and two red rice biotypes were used. PD was identified as the R1 stage of the COUNCE scale, by sampling four plants from each genotype on a daily basis. When 50% of the sampled plants were at R1, the main stem HS was measured in 20 plants per genotype. The main stem final leaf number (FLN) was measured in these 20 plants when the collar of the flag leaf was visible. HS at PD is related to FLN in many cultivated rice genotypes and red rice biotypes, and that at PD, the number of leaves still to emerge until flag leaf is not constant for all the rice genotypes. These findings are not in agreement with reports in the literature.