Flávio Miguel Schneider

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.

Transmissividade a radiação solar do polietileno de baixa densidade utilizado em estufas

The transmissivity of the solar radiation by polyethylene cover used in plastic greenhouses was evaluated in the Central Region of the Rio Grande do Sul State, Brazil. The study was carried out inside a 10m x 25m greenhouse covered with low density transparent polyethylene with 100µm thickness, located at Federal University of Santa Maria. Incoming global solar radiation inside and outside was measured daily dunng July, 1991 to January, 1992. The effect of polyethylene cover on diffuse solar radiation was determined dunng 1993 year. The average transmissivity of global solar radiation was 56.2% early in the moming and 81.3% at near noonday. Diffuse solar radiation proportion was higher inside than outside the greenhouse and enhanced when water condenses on the inner surface of the film.

Comparação do crescimento e desenvolvimento da alface (Lactuca sativa L.) no interior e no exterior de uma estufa de polietileno em Santa Maria, RS

Growth and development of lettuce cultivar Brasil- 202, White Boston and Regina inside and outside of a polyethylene greenhouse were compared in Santa Maria, RS. During a winter period of 50 days the greenhouse caused an increase in about 256 degree-days in the temperature values above the base temperature for growth (estimated in 10°C). Mean soil temperature was also 5.3°C higher inside the greenhouse. The growth patterns of plants cultivated inside the greenhouse were similar to those cultivated outside. Growth parameters of leaf surface, shoot fresh weight, dry weight of leaves. stem and roots and the shoot/root ratio were lower outside the greenhouse. The number of leaves per plant was similar in both conditions. Brasil-202 showed earlier growth and higher dry matter accumulation. Protection of plants with polyethylene greenhouses is an efficient technique to improve lettuce crop production in winter.

Effect of polyethylene mulches on soil temperature and tomato yield in plastic greenhouse

Este experimento foi conduzido para avaliar o efeito da cobertura do solo com polietileno transparente, preto, branco e co-extruzado branco-preto sobre a temperatura do solo e produtividade do tomateiro no interior de uma estufa plastica, em Santa Maria, Rio Grande do Sul, Brasil. O periodo experimental foi de 21 de agosto a 02 de dezembro de 1994. Observou-se que a temperatura maxima e media diaria do solo foi maior sob polietileno transparente. A amplitude maxima da onda diaria de temperatura do solo foi maior nos materiais opacos em relacao ao transparente. Nao houve diferenca estatistica na produtividade do tomateiro entre os tratamentos, mas a produtividade media foi maior com plasticos opacos do que com o plastico transparente. Entre os plasticos opacos, a maior produtividade foi obtida nos plasticos brancos, que refletem maior fracao da radiacao solar global incidente do que o plastico preto.

Soil heating by solarization inside plastic greenhouse in Santa Maria, Rio Grande do Sul, Brazil

Abstract Solar heating of soil by mulching with transparent polyethylene (known as soil solarization) is a physical method of soil disinfestation. The increase in soil temperature by solarization inside a plastic greenhouse in Santa Maria, Rio Grande do Sul State, Brazil, was measured. It was estimated the time which soil temperature exceeded some thermal levels in solarized soil, During the 1992/1993 and 1993/1994 summers, experiments were carried out in a 10 m × 25 m plastic greenhouse. Soil temperature was measured at 2 cm, 5 cm, 10 cm, and 20 cm depths in one solarized and uncovered plot. An increase of 10°C or more was observed in solarized soil at 2 cm and 5 cm depths in comparison to the bare soil. Soil temperature exceeded 50°C or more several days during 1993/1994 up to the 10 cm depth. The estimated exposure time at several thermal levels in solarized soil allow to conclude that solarization presents potential in the region.

ALTERAÇÕES MICROMETEOROLÓGICAS CAUSADAS POR TÚNEIS BAIXOS DE TELA PLÁSTICA PRETA CULTIVADOS COM ALFACE

SUMMARY Micrometeorological afterations caused by low tunnels of black plastic screen with 18, 30, and 50% of solar radiation reduction in central region of the Rio Grande do Sul state, Brazil, was investigated during the summer. The experiment was carried out in the Federal University of Santa Maria, where four plots were cultivated with lettuce. Three plots were covered by low tunnels of black plastic screen and one was left uncovered as a control. The study was conducted in 3 periods: 11/30/90 to 01/17/91, 02/06/91 to 03/25/91, and 12/10/91 to 03/01/92. Soil and air temperature, and soil water consumption decreased with solar radiation reduction. However, air minimum temperature and relative humidity were similar inside and outside, and aiso among different leveis of reduction caused by plastic screen.

MODIFICAÇÃO AMBIENTAL CAUSADA POR TÚNEIS BAIXOS DE POLIETILENO TRANSPARENTE PERFURADO CULTIVADOS COM ALFACE

Determinou-se as modificacoes ambientais causadas por tuneis baixos de polietileno transparente perfurado instalados no Departamento de Fitotecnia da Universidade Federal de Santa Maria, RS. As densidades de perfuracao estudadas foram 100, 200, 300 e 400 perfuracoes por m2 correspondendo, respectivamente, a uma area perfurada de 0,78% CT1), 1,57% (T2), 2,35% (T3) e 3,14% (T4). Os resultados evidenciam que a densidade de perfuracao nao modificou significativamente a disponibilidade de energia solar. A medida que aumentou-se a densidade de perfuracao ocorreu um decrescimo no valor medio diurno da temperatura do ar, aspecto que demonstra a viabilidade de ventilar o tunel baixo atraves da perfuracao do plastico. Tambem observou-se que nos tuneis perfurados, os valores medios da temperatura do solo, minima e media diurna do ar e umidade relativa do ar foram maiores que no ambiente externo.

OCORRÊNCIA E DURAÇÃO DAS TEMPERATURAS MÍNIMAS DIÁRIA DO AR PREJUDICIAIS À FECUNDAÇÃO DAS FLORES DO ARROZ EM SANTA MARIA, RS. l - PROBABILIDADES DE OCORRÊNCIA

SUMMARY Daily minimum temperatures obtained at Santa Maria, RS, were used to determine the occurrence probabilities of number of days per month or per 10 days time period as well as sequency duration of consecutive days, for every month, with minimum temperatures injurious to fecundation of rice flowers. Results indicate that during the flowering there are risks that low temperatures could affect fecundation of rice flowers but those risks are lower during February.

Sistema de produção de alface em ambiente parcialmente modificado por túneis baixos

O objetivo no trabalho foi obter um sistema para a producao de alface em tuneis baixos, ao longo de todo o ano, e que minimize o manejo de ventilacao. Para isso, foram realizados 13 cultivos de alface no periodo de outubro de 1994 a julho de 1997. Os tratamentos de inverno constaram dos seguintes tipos de coberturas: a) Cultivo em tunel convencional com cobertura de polietileno de baixa densidade e com manejo conforme as condicoes meteorologicas; b)cultivo em tunel plastico com 3% de area perfurada, sem manejo diario de ventilacao; c) cultivo em tunel plastico tipo guarda-chuva com as laterais abertas na base o ano inteiro, sem manejo diario de ventilacao; d) cultivo testemunha sem cobertura durante todo o ano. Os tratamentos de verao constaram dos anteriormente citados, sendo as coberturas, dos tratamentos com tuneis convencionais e perfurados substituidas por tela plastica preta de 30% de sombreamento. Os resultados obtidos permitem indicar como sistema para producao de alface ao longo de todo o ano a utilizacao de tuneis cobertos com polietileno transparente em forma de guarda-chuva. Recomenda-se esta tecnica, sendo necessario apenas o ajuste da altura das aberturas laterais de acordo com a epoca do ano.

SOIL TEMPERATURE MODIFICATIONS CAUSED BY SOLARIZATION IN NURSERIES

Solarization effects on soil temperature were evaluated during the autumn. The increase in soil temperature caused by the use of transparent polyethylene (PE) low tunnels over solarized nurseries, in subtropical central region of the Rio Grande do Sul state, Brazil, was also quantified. Treatments were: a) solarization with 100µ thickness PE (T1), b) solarization with 100µ thickness PE, covered with low tunnel (T2), c) solarization with 50µ thickness PE (T3), d) solarization with 50µ thickness PE, covered with low tunnel (T4), and e) bare soil (T). The low tunnel consisted of a 100µ thickness PE and measured 0.5m height in the center of the nursery. The results showed that additional use of low tunnels have increased, on the average, 5.0oC over the maximum temperature of the superficial layer of the soil in the solarized nurseries. In addition, it was observed several days in which the maximum temperature exceeded 45oC.