Radiometric propeties of agricultural permeable coverings

Nets are commonly used for agricultural applications. However, only little is known about the radiometric properties of net types and how to influence them. In order to investigate the influence of net construction parameters on their radiometric properties, a set of radiometric tests were performed on 45 types of agricultural nets. Laboratory tests on large size net samples was performed using a large and a small integrating sphere. Open field radiometric test were carried out by means of an experimental set up (120x120x50 cm) and a full scale shade house. Small differences (less than 5%) occurred between laboratory and open field tests. Results highlighted that the porosity and the mesh size, combined with the colour and secondarily, with the fabric and the kind of threads of the net influenced the shading performance of the net. The colour influenced the spectral distribution of the radiation passing through the net absorbing its complementary colours. Since nets are three-dimensional structures the transmissivity of direct light under different angles of incident of solar radiation changes when installed in the warp or weft direction. Transmissivity could be considered one of the main parameters involved in the agronomic performances of the netting system.