Michel Rocha da Silva

Crescimento vegetativo e produtivo de duas cultivares de morango sob épocas de plantio em ambiente subtropical

The proper growth of leaves results in an increase in leaf area, which allows for greater interception of solar radiation, and consequently greater photosynthetic activity and better crop productivity for different planting times. The objectives of this work were to obtain equations in order to estimate leaf area from the linear dimensions of the leaf blades, to establish allometric relationships between the leaf area and the number of leaves in the primary crown, and to determine the productivity of fruits for different planting dates of two strawberry cultivars. The experiment was carried out at the experimental area of the Department of Plant Science, at the Federal University of Santa Maria, in Santa Maria, Rio Grande do Sul, with the Araza and Yvapita cultivars. Plants were sown on six dates: 03/04/2008, 07/05/2008, 02/06/2008, 02/02/2009, 02/04/2009 and 02/06/2009. The experimental design used was of randomised blocks with four replications (plots of 30 plants each). In each plot, six plants were tagged for weekly determination of the number and area of leaves in the primary crown, and the fresh weight and number of fruits per plant. The power model satisfactorily characterised the allometric relationship between the development of the leaf area and the number of leaves accumulated in the primary crown. Fruit production was influenced by planting time, so that early planting in the period recommended by EMBRAPA (April) provides greater leaf area at the beginning of flowering, and a higher yield potential, especially in years with high solar radiation in the spring, as happened in 2008.

Base temperature for leaf appearance and phyllochron of selected strawberry cultivars in a subtropical environment

Leaf development is characterized by the appearance of new leaves and is related to crop leaf area index, which affects the interception of solar radiation used for photosynthesis and biomass production and ultimately defines crop yield. The objectives of this paper were to estimate the base temperature for leaf appearance and to determine the phyllochron of two strawberry cultivars considering several planting dates. A two-year field experiment was conducted during 2008 and 2009 in Santa Maria (RS). The cultivars Araza (early) and Yvapita (late) were used at three planting dates in both years. Base tempera- ture (Tb) was estimated using the Mean Square Error (MSE) approach of the regression between accumulated leaf number (LN) and accumulated thermal time (ATT). The phyllochron was calculated as the inverse of the slope of the regression of LN against ATT. Estimated Tb for leaf appearance in both cultivars was 0 °C. Variations in phyllochron were observed among the two cultivars, among planting dates and also during the plant developmental period of each cultivar. Before flowering, the phyllochron was similar in both cultivars and after flowering it was higher in cultivar Araza. Phyllochron was greater for later planting dates and increased at short photoperiods in Fall and Winter. Results showed that both cultivars have a typical long- day plant response because phyllochron decreased as photoperiod increased up to approximately 11.8 hours, and phyllochron was the lowest at longer photoperiod.

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.

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.

Plant development and tuber yield in the potato in a subtropical climate

Os objetivos deste trabalho foram caracterizar desenvolvimento das plantas e determinar a produtividade de tuberculos de clones avancados de batata em duas epocas de cultivo (outono e primavera) em ambiente subtropical do Rio Grande do Sul. Foram avaliados dez clones avancados do Programa de Genetica e Melhoramento de Batata da Universidade Federal de Santa Maria e duas cultivares (Asterix e Macaca). Foram determinados: numero de folhas acumuladas na haste principal, numero final de folhas, filocrono, evolucao do indice de area foliar verde, indice de area foliar maximo, duracao em dias das fases plantio-emergencia, emergencia-inicio de tuberizacao, inicio de tuberizacao-inicio de senescencia e emergencia-inicio da senescencia e a massa fresca e seca de tuberculos. Ocorreu uma variacao do filocrono, numero final de folhas e da evolucao do indice de area foliar em funcao do genotipo, em cada epoca de cultivo. Comparando os cultivos de primavera e outono, e descontando-se a fase plantio-emergencia, a duracao das fases do ciclo de desenvolvimento da batata foram, em geral, menores no cultivo de outono. Verificou-se que a duracao das fases emergencia-inicio de tuberizacao e inicio de tuberizacao-inicio de senescencia determinam a produtividade de tuberculos. Exceto o clone SJSM 03478-37, os clones avancados apresentam elevada producao de tuberculos e boa adaptacao as duas epocas de cultivo em ambiente subtropical do Rio Grande do Sul.

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.

ACOMPANHAMENTO DA SAFRA 2012/2013 DE ARROZ IRRIGADO NO RIO GRANDE DO SUL POR MODELAGEM NUMÉRICA

O objetivo deste trabalho foi realizar o acompanhamento de safra de arroz irrigado durante o ano agricola 2012/2013 para o estado do Rio Grande do Sul. Para o acompanhamento de safra, foi utilizado o modelo SimulArroz. Foi utilizado o grupo de maturacao precoce de cultivares de arroz, com simulacoes nos niveis de tecnologia alto, medio e baixo. A media de produtividade observada foi de 7481,7 kg/ha, enquanto que a media de produtividade simulada com o SimulArroz nos niveis de tecnologia alto, media e baixo foi de 8732,0 kg/ha, 7041,7 kg/ha e 5597,9 kg/ha respectivamente. O modelo demonstrou boa sensibilidade as variacoes meteorologicas entre as regioes do RS, demonstrando maior potencial produtivo de arroz para as regioes da Fronteira Oeste e da Campanha. Portanto, o modelo SimulArroz simulou de forma satisfatoria a produtividade de arroz irrigado para os municipios em que foi testado, podendo ser utilizado no acompanhamento de safra.