RESUMOEste trabalho propôs avaliar a influência das malhas de sombreamento (termorrefletora) instaladas externa e internamente em ambiente protegido coberto com polietileno de baixa densidade (PEBD), cultivado com gérbera, na radiação solar global (Qg) e nos parâmetros da planta: crescimento, desenvolvimento e qualidade da gérbera. O experimento foi conduzido em dois ciclos no ano de 2004, na ESALQ/USP, em Piracicaba, SP, em ambiente protegido, dividido em dois módulos de produção. Os ambientes foram diferenciados um do outro pela instalação da malha termorrefletora (50%): malha externa (ambiente 1 -A1) e malha interna (ambiente 2 -A2). Nesses ambientes, os resultados dos dois ciclos mostraram alteração na Qg; nos ambientes A1 e A2 as Qg foram respectivamente 33,6 e 21,7 (1º ciclo) e 27,2 e 17,9% (2º ciclo) em relação à observada externamente. Considerando-se os dois ciclos conclui-se que os resultados indicaram que não houve diferenças na qualidade das plantas nos dois ambientes, mas, analisando-se separadamente os dois ciclos da cultura, o A1 (malha externa) foi o que mais favoreceu a qualidade das plantas de gérbera e somente as gérberas presentes no A1 (malha externa) atenderam às exigências mercadológicas, quanto aos números de botões florais.Palavras-chave: malha de sombreamento termorrefletora, plasticultura, Gerbera jamesonii Greenhouse cover management: Solar radiation effects on production and quality of a gerbera crop ABSTRACTThe objective of this study was to evaluate the influence of low density polyethylene (PEBD) as a greenhouse cover in association with thermal shading screen installed in two different positions (outside and inside), cultivated with gerbera, on solar radiation (Qg), as well as on the growth and quality of gerbera plants. The experiment was carried out during two crop cycles in 2004, at ESALQ/USP, in Piracicaba, State of São Paulo, Brasil. A greenhouse was sub-divided into two parts and covered with PEBD differing from each other by the position of the thermal shading screen (50%), witch was installed inside (at 3 m height) and outside (covering the plastic cover). The environment with the thermal screen outside was named A1 and the other one with the thermal screen inside was named A2. The results from the two crop cycles showed that the microclimate was changed by the covers of the greenhouses. Qg inside for A1 and A2 were respectively 33.6 and 21.7 (first cycle), and 27.2 and 17.9% (second cycle) of the values measured outside. Considering the two crop cycles, the results showed that there were no differences in plant quality in both environments. However, A1 was the most favorable environment for plant quality when considering the two crop cycles, separately the results separately. Also, only gerberas from A1 showed themselves to have marketable characteristics.
A B ST R A C TThis study had as its objective the evaluation of the influence of shading screens of different colors on the different microclimate variables in a greenhouse covered with transparent low-density polyethylene (LDPE). The experiment was conducted with five treatments: thermo-reflective screen (T1); a controlwithout screen (T2); red screen (T3); blue screen (T4); and black screen (T5), all of them with 70% of shading. An automatic micrometeorological station was installed in each treatment, measuring air temperature (T), relative humidity (RH), incoming solar radiation (Rg), photosynthetically active radiation (PAR) and net radiation (Rn) continuously. The control (T2) and red screen (T3) treatments promoted the highest solar radiation transmissivity, respectively 56.3 and 27%. The black screen (T5) had the lowest solar radiation transmissivity (10.4%). For PAR and Rn the same tendency was observed. The highest temperature was observed under blue screen (T4) treatment, which was 1.3 °C higher than external condition. Blue screen (T4) treatment also presented the highest relative humidity difference between inside and outside conditions.
The use of plastic cover in vineyards minimizes effects of adverse weather conditions. The northwest of São Paulo State is one of the largest grape producing regions in Brazil; however, few studies investigate the effects of different plastic covers on vineyards in this region. This study compared the effect of black shading screen (BSS) and braided polypropylene film (BPF) on BRS Morena vineyard microclimate, grown on an overhead trellis system in the northwestern São Paulo. The experiments were carried out during three growing seasons (2012-2014). BSS allowed superior incoming solar radiation (SR) transmissivity, resulting in higher net radiation (Rn), and higher ratio between photosynthetically active (PAR) and SR. No differences were observed between the average air temperatures (T) and relative humidity (RH) of covered environments (BPF and BSS) and outside condition (automatic weather station-AWS), due to high air circulation, despite wind speed (WS) reduction caused by plastic covers. BPF provided better conditions for vineyard growth with higher fruit yield than vineyard under BSS regarding the number of shoots with bunches per plant, bunch and stem weights, longitudinal diameter of berries, quantity of fertile buds per shoot, and yield per shoot and per plant. BPF covers also influenced leaf size and growth speed of plants in vineyards.
In regions with intense solar radiation it is common the use of aluminated covers in greenhouses, with the aim of reducing the inside temperature. However, the use of these covers reduces photosynthetic active radiation (PAR) transmitted into the greenhouse. The objective of the present study was to evaluate the influence of different covers on microclimate in greenhouses cultivated with cherry tomato during three growing seasons. The environment I was covered with plastic film anti-UV and with thermo-reflective screen (40%) disposed internally. The environment II was covered with diffusive plastic film (55%). The transmitted solar radiation to the interior of covered environments was, on average, 5.5 MJ m -2 day -1 in the environment I and 8.2 MJ m -2 day -1 in environment II. The air temperature in environment II was, on average, 1°C higher than external conditions. The highest difference for the relative humidity (RH) was also observed between environment II and the outside conditions, with 10.7% for the minimum RH during the first growing period. Considering all growing periods, the diffusive plastic film provided higher solar energy availability inside the greenhouse than the plastic film with thermo-reflective screen, without causing major changes in air temperature and relative humidity, and promoting greater productivity of tomato grown under this environment for the three periods evaluated. Keywords: greenhouses; plastic covers; microclimate. RESUMO:ALTERAÇÕES MICROCLIMÁTICAS PROVOCADAS POR DIFERENTES COBERTURAS PLÁSTICAS EM AMBIENTE PROTEGIDO CULTIVADO COM TOMATE TIPOCEREJA NO SUDESTE DO BRASIL Em regiões de intensa radiação solar é comum o uso de malhas aluminizadas em cultivos protegidos, com o intuito de reduzir a temperatura no interior de estufas plásticas. Porém, o uso dessas malhas provoca diminuição da radiação fotossinteticamente ativa (RFA) transmitida ao interior do ambiente protegido. O presente estudo teve por objetivo avaliar a influência de diferentes coberturas plásticas no microclima de ambientes protegidos, ao longo de três períodos de cultivo com tomate cereja. O ambiente I foi coberto com filme plástico anti-UV e com uma malha termorefletora (40%) disposta internamente. O ambiente II foi coberto com filme plástico difusor (55%). A radiação solar transmitida ao interior dos ambientes protegidos foi, em média, de 5,5 MJ m -2 dia -1 no ambiente I e 8,2 MJ m -2 dia -1 no ambiente II. A temperatura do ar no ambiente II foi, em média, 1°C superior ao ambiente externo. As maiores diferenças para a umidade relativa do ar também foram encontradas entre o ambiente II e o externo, chegando a 10,7% para a UR mínima, no primeiro período de cultivo. Considerando-se todos os ciclos de cultivo, o plástico difusor foi o que proporcionou a maior disponibilidade de energia no interior do ambiente protegido, sem causar, no entanto, grandes alterações na temperatura e na umidade relativa do ar, e promovendo uma maior produtividade do tomate cultivado sob este ambiente, nos três períodos avaliado...
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