Microclimate under different shading screens in greenhouses cultivated with bromeliads

Abstract

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.

Light Quality in Vitro Growth and Acclimatization of Two Varieties of Phalaenopsis Amabilis Alba Blume (Orchidaceae)

“…Regarding to the LLL, opposite to the results obtained in this work, usually, the red light is the one which promotes the higher results for the length of the leaves in several species (Holcman & Sentelhas 2012).…”

Uso de tela termorrefletora em ambientes protegidos para cultivo do tomateiro

“…Os dados da Tabela 1 mostram que a tela termorrefletora promoveu redução de aproximadamente 37 % da Qsd e Qs e de 45 % da RFAd e RFA quando comparados ao ambiente sem tela termorrefletora. HOLCMAN & SENTELHAS (2012) observaram redução de 76 % da Qs e 80 % da RFA em ambiente coberto com PEBD e tela termorrefletora (70 % de sombreamento), comparado a ambiente coberto somente por PEBD, enquanto SCARANARI et al (2008) registraram reduções de 50 e 53 % na RFA em ambientes cobertos por PEBD com telas de sombreamento (50%), nas cores preta e vermelha, em relação a ambiente coberto somente por PEBD. A atenuação da Qs e da RFA registrada pelos autores foi superior ao nível de sombreamento das telas empregadas, ao passo que, no presente trabalho, essa atenuação foi inferior ao nível de sombreamento da tela termorrefletora empregada, diferença de efeito que pode ser parcialmente atribuída ao fato de que os autores citados fizeram uso fixo das telas, enquanto neste trabalho foi feito o manejo de abertura e fechamento, reduzindo seu efeito redutor da radiação que atinge o dossel das plantas.…”

“…No entanto, destaca-se que as características estruturais dos ambientes protegidos nas condições experimentais dos ensaios restringiram a taxa de troca gasosa, ocasionando aumento significativo da temperatura em relação ao ambiente externo, maior que os valores encontrados por outros autores (HOLCMAN & SENTELHAS, 2012;COSTA & LEAL, 2008).…”

Effects of Cover Whitening Concentrations on the Microclimate and on the Development and Yield of Tomato (Lycopersicon esculentum Mill.) Inside Mediterranean Greenhouses

“…Whitening is a low-cost method to reduce heat build-up and modify the greenhouse environment in hot summers [32,41]. This shading method is performed by mixing a certain amount of calcium oxide or calcium carbonate with water, to make a solution which is used to paint the outer surface of the glass or polyethylene [19,42,43]. Most farmers in Almería (99%) whiten the roof of their greenhouses to increase the reflection coefficient of solar radiation, which reduces the energy input that warms the greenhouse in the peak hours of the day [19].…”