Manejo da cobertura de ambientes protegidos: radiação solar e seus efeitos na produção da gérbera

Abstract

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.

Climate variations in greenhouse cultivated with gerbera and relationship with external conditions

“…Solar radiation is important because it acts decisively in all life processes of the plants, such as: photosynthesis, transpiration, photoperiod, tissue growth, flowering, etc (GUISELINI et al, 2010).…”

Effects of light intensity modification by reflective aluminized screenhouse on sweet pepper growth and yield

“…Attenuations in SR and PAR were due to reflection of solar radiation by reflective net, which decreased solar radiation incidence inside the shading net house (GUISELINI et al, 2010). SR attenuation by RS was higher than the commercial specification (40% commercial shading rate).…”

“…Attenuation caused by RS was 46.3% and 48.3%, respectively to SR and PAR. This behaviour maintains unchanged PAR and infrared (IR) radiation ratios and only changes the amount of available energy that reach surfaces inside the protected environment (GUISELINI, et al, 2010). Table 2 presents average values of phenological variables for both environments.…”

“…Considering SR and PAR have been the unique weather element unchanged from those reported in field conditions, a higher number of leaves under RS environment was influenced by PAR attenuation. GUISELINI et al (2010), evaluating thermal reflective net effect on Gerbera jamesonii production, reported that differences on leaf area and flower bud number were due to solar radiation reduction by shading.…”

“…Since the solar radiation has decisive importance in all plant vital processes such as photosynthesis, respiration, photoperiod, tissue growth and flowering, among others, a correct choice for protected environment cover material is a crucial issue for plant development (SAPOUNAS et al, 2010). Therefore, spawning suitable weather conditions inside protected environments may be obtained by several techniques, in which the most economical are those that employ use and combination of different types of roofing materials (GUISELINI et al 2010;LOBOS, et al 2013). …”