The use of shading nets for the greenhouse cultivation of sweet pepper in the Mediterranean area.

The Mediterranean area is characterized by hot summers that, especially inside greenhouses, can determine non-optimal conditions for the growth of vegetable crops. In Southern Italy, the use of shading nets or the application of calcium hydroxide (whitening) on the cover material of the greenhouse is often used by farmers to improve micro-climatic conditions for crops and to obtain a healthier environment for workers. In recent years, thanks to their cheaper price accompanied by improved photo selective properties, plastic nets are often used for shading purposes, combining the shade effect with their specific features useful for the crop growth. Like other vegetable crops in the Mediterranean area, sweet pepper cultivation in greenhouses can benefit by shading during the late spring and summer months. With the aim of determining the effects of different greenhouse shading methods on the cultivation of sweet pepper, a trial was carried out in Battipaglia (Campania Region - Southern Italy), comparing cover whitening, made by slaked lime, with two plastic nets, a reflective aluminized cloth having 50% of shade level (Aluminet) and a photo-selective red net having 30% of shade level (red Chromatinet), resulting the colored shading nets most used by farmers in the study area. In addition, an unshaded greenhouse was utilized as a control. The plastic nets, as well as allowing a shading effect, contributed to avoid the decrease in the greenhouse temperature overnight (Aluminet), as well as to modify the spectrum of the transmitted light (Chromatinet). In order to investigate the influence of the studied nets on the growth of sweet pepper, yield quantitative and qualitative traits were performed. Furthermore, spectro-radiometrical and mechanical characterizations of nets, through laboratory tests, were carried-out . The results obtained by these tests, confirming the relationship between the porosity of a net and its transmittance in the solar range, allow to evaluate the different shading and transmittance effects.