HOW TO TAILOR-MAKE A GREENHOUSE COVER

Recently, the ability to manipulate the physical and spectral characteristics of plastic film has dramatically improved. This ability enables us to tailor-make a greenhouse cover adapted for climate conditions, crop requirements, insects and diseases behavior and different other specific requirements. The additives in the greenhouse cover are usually added to change a specific property of the plastic film, but they affect other properties as well. For example, blocking the UVA spectrum by introducing UVA absorbers to the greenhouse cover reduces Botrytis infection and the insect's navigation in the greenhouse. However, the same UVA absorber might also interfere with pollination of the flowers by bumblebees. Using the common IR additives will result in the production of a thermal greenhouse cover linked with the possible reduction of the total light transmission as a side effect. Supplementary to that, IR additives increase the diffused light which positively affect some crops (e.g. peppers) but can reduce total light transmission and reduce yield in others (e.g. tomatoes). One of our goals was to optimize the use of thermal additives for specific conditions under various climate zones and crop requirements. We will present new additives that enable to produce thermal films with no negative effect on light transmittance. These additives also have a minimal effect on diffused light. We will also introduce a new additive that reduces the diffused light originating from the polyethylene and show that it is possible to get an overall higher light transparency. Achieving an in-depth understanding of how to manipulate the optical properties of the plastic enables us to adjust greenhouse covers according to climate conditions and crop requirements.