Lilian Osmari Uhlmann

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.

Parâmetros quantitativos de hastes florais de gladíolo conforme a data de plantio em ambiente subtropical

The objective of this work was to determine the growing seasons, in a subtropical environment, when it is possible to produce gladiolus ( Gladiolus x grandiflorus ) stems that meet commercial, quantitative standards for cut flowers of the national market. Two field experiments were carried out – one from August 2011 to July 2012, and the other from August 2012 to July 2013 – with three gladiolus cultivars and 12 planting dates for each experiment. Stem total length, rachis length, and stem diameter were evaluated at the harvesting point, when the petal color appears in the first three florets at the stem base. The best months for production of gladiolus stems are July, August, September, February, March, and April, although in the other planting dates the stem quality was never below the minimum standard (except for the periods of frost during heading).

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.

Limite crítico no solo para transpiração e crescimento foliar em mandioca em dois períodos com deficiência hídrica

A cassava crop is often exposed to more than one period of water deficit during the growing season. The objective of this study was to verify if there is a difference in the FTSW (fraction of transpirable soil water) threshold for transpiration and leaf growth in cassava plants subjected to one or two periods of water deficit. Two experiments with cassava (Fepagro RS 13 cultivar) were conducted. Treatments were four soil water regimes subdivided into two periods, period 1 (P1) and period 2 (P2): water regimes WR1 and WR2 (with water deficit in both periods and without water deficit in both periods, respectively), and water regimes WR3 and WR4 (with water deficit only in P1 or P2, respectively). The FTSW approach was used to indicate the threshold for transpiration and leaf growth. The FTSW threshold was 0.35, 0.38, and 0.37 for leaf growth and 0.28, 0.26, and 0.28 for transpiration in P1 of WR2 and WR3 and P2 of WR4, respectively. In P2 of WR2, the FTSW threshold for leaf growth and transpiration was 0.09 and 0.13, respectively. It was concluded that there is a decrease in the FTSW threshold in cassava during the second period compared to the first period of soil water deficit, which can be explained by the smaller leaf area, which allowed a longer leaf turgor period, thus delaying activation of the stomata control mechanisms. The practical implication of these results is that they can be used as parameters for crop irrigation, as well as for selecting cultivars more tolerant to water deficit.

Desempenho de cultivares de mandioca em ambiente subtropical

The objective of this study was to evaluate and compare variables of growth, development and yield components of roots and stems of five cassava cultivars in subtropical environment in Rio Grande do Sul, Brazil. A field experiment was conducted in the 2010-2011 and 2011-2012 growing seasons at Santa Maria, RS, with five cassava cultivars, Fepagro - RS 13, Fepagro - RS 13, Fepagro - RS 14, Estrangeira, Fecula Branca and Cascuda in a randomized block design with four replicates and a two factor scheme. Variables of growth and development such as leaf area, plant height and leaf number and yield components of roots and stems were collected. The cultivars Fepagro - RS 13 and Fepagro - RS 14 have the highest LAI, above-ground biomass and height compared to the cultivars Estrangeira, Fecula Branca and Cascuda, because the former have greater sympodial branching. Cultivars Fepagro – RS13 and Fepagro – RS 14 have high production of both above-ground and tuber roots whereas cultivars Estrangeira, Cascuda and Fecula Branca are adapted for tuber roots production in subtropical environment of Rio Grande do Sul, Brazil.

DESENVOLVIMENTO FOLIAR DE ARROZ CULTIVADO E ARROZ VERMELHO EM CENÁRIOS DE AUMENTO DE TEMPERATURA

The objective of this study was to simulate leaf development of cultivated rice genotypes and weedy red rice biotypes in climate change scenarios at Santa Maria, RS, Brazil. A leaf appearance (LAR) model adapted for rice was used to simulate the accumulated leaf number, represented by the Haun Stage, from crop emergence to flag leaf appearance (EM-FL). Three cultivated rice genotypes and two weedy red rice biotypes in six emergence dates were used. The LAR model was run for each emergence date using 100 years of synthetic daily weather data and six climate scenarios, including current, +1, +2, +3, +4 and +5 oC increase in mean air temperature, with symmetric and asymmetric increase in daily minimum and maximum temperature. The increase in air temperature scenarios decreased the duration of the EM-FL phase in the earlier emergence dates (08/20, 09/20, 10/20) whereas in mid (11/20) and late emergence dates (12/20 and 01/20) the longest EM-FL phase was in the symmetric +5 oC scenario and the shortest duration was in the asymmetric +3 and +4 oC scenarios. The timing of the onset of flooding irrigation and nitrogen dressing may be altered if global warming takes place and weedy red rice has a potential to enhance its competitiveness with cultivated rice in future climates.

CO2-response function of radiation use efficiency in rice for climate change scenarios

The objective of this work was to evaluate a generalized response function to the atmospheric CO2 concentration [f(CO2)] by the radiation use efficiency (RUE) in rice. Experimental data on RUE at different CO2 concentrations were collected from rice trials performed in several locations around the world. RUE data were then normalized, so that all RUE at current CO2 concentration were equal to 1. The response function was obtained by fitting normalized RUE versus CO2 concentration to a Morgan-Mercer-Flodin (MMF) function, and by using Marquardts method to estimate the model coefficients. Goodness of fit was measured by the standard deviation of the estimated coefficients, the coefficient of determination (R2), and the root mean square error (RMSE). The f(CO2) describes a nonlinear sigmoidal response of RUE in rice, in function of the atmospheric CO2 concentration, which has an ecophysiological background, and, therefore, renders a robust function that can be easily coupled to rice simulation models, besides covering the range of CO2 emissions for the next generation of climate scenarios for the 21st century.

Long-term changes in rice development in Southern Brazil, during the last ten decades

The objective of this work was to test long-term trends in the duration of rice development phases in Santa Maria, RS, Brazil. The duration from emergence to V3 (EM-V3), emergence to panicle differentiation (EM-R1), emergence to anthesis (EM-R4), and emergence to all grains with brown hull (EM-R9) was calculated using leaf appearance and developmental models for four rice cultivars (IRGA 421, IRGA 417, EPAGRI 109, and EEA 406), for the period from 1912 to 2011, considering three emergence dates (early, mid, and late). The trend of the time series was tested with the non-parametric Mann-Kendall test, and the magnitude of the trend was estimated with simple linear regression. Rice development has changed over the last ten decades in this location, leading to an anticipation of harvest time of 17 to 31 days, depending on the cultivar maturity group and emergence date, which is related to trends of temperature increase during the growing season. Warmer temperatures over the evaluated time period are responsible for changing rice phenology in this location, since minimum and maximum daily temperature drive the rice developmental models used.