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Sweet pepper is the most important vegetable crop of the Hungarian greenhouse industry. Production of red coloured cultivars, having very high nutritive value, is getting popular recently. Shading of plastic tunnels is a common practice in Hungary, but research about its effects on the nutritional characteristics of sweet pepper has just started. The objective of this study was to investigate the effect of different shading methods (shading paint, white, green, yellow and red coloured shade nets) on some nutritional characteristics of a red coloured kapia type pepper, under Hungarian climatic conditions cultivated in unheated walk-in plastic tunnels. Shade net colour slightly affected radiation and hence temperature conditions of the tunnels; especially ratio of supra-optimal temperature values (32 °C

Sweet pepper (Capsicum annuum L.) is one of the main cultivated vegetable species in Hungary mostly produced under plastic tunnel by unheated technology. Sweet pepper plants could suffer high temperature and radiation during summer season. However, photoselective-shading nets can provide a new tool for light quality manipulation and support the plant development and fruit quality. The effect of shading colour nets depends on natural light conditions and other environment factors; therefore it is necessary to evaluate the shading technology. Hungarian sweet pepper variety was grown in South-East part of Hungary under plastic tunnels using different colour nets, as white, yellow, green and red, for shading in 2013. Results of trial proved that green colour shading net usually decrease the yield, while yellow and red nets can increase the yield and the fruit quality of Hungarian type sweet pepper. Growers have to care the shading intensity of the net, which should not be higher than 35-40%. Colour shading nets can be placed onto the plastic tunnels just after the planting.

Shading effect of external nets of different colours (white, green, yellow and red) on the yield of two “kapija” pepper (Capsicum anuum L.) cultivars was examined in walk-in plastic tunnels in Hungary under real cultivation circumstances. Shading nets decreased incoming radiation by 23-39% and reduced photosynthetically active radiation by 32-46%. The highest retention was obtained by yellow and green nets, in the range of 450-550 nm and 550-670 nm, respectively. Relation was reported between the degree of shading and the average air temperature of the tunnels, however, treatments did not decrease tunnel air temperature significantly, compared to that of unshaded and paint-shaded control tunnels. This can be explained by the applied proper ventilation and mist irrigation. A strong and negative relation was noted between the intensity of shading and the relative chlorophyll content (SPAD value) of leaves. Shading net treatments did not increase yields, yellow and green nets even decreased it. Instead of tunnel air temperature, yield was mainly affected by photosynthetically active radiation in the experiment. Strong positive linear relation was declared between the chlorophyll content of the leaves and the yield. Results of the current research led to the conclusions that under Hungarian climatic conditions the use of shading nets was less justified if proper cooling techniques (ventilation and mist irrigation) were applied; even under the relatively high incident radiation experienced during the trials. In greenhouses of less favourable climatic conditions, red or white shading nets are recommended instead of commonly used green ones in Hungary.