Effects of excessive weather on the micro-climate of apple plantations under the hail protection nets

At present, fruit growing farms using hail nets are still few in Hungary. Costs of investment are expensive. Knowledge and experiences concerning the use of hail nets are still scarce. In the literature there are numerous publications dealing with the object, especially on the question of the preferred colour of the plastic net, which is decisive which spectral regions are transmitted or sorted out: Castellano et al. (2008) Hemming et al.(2008) under the net. It was stated that the black colour secure high constancy to the composition. Al-Helal and Abdel-Ghany (2010) explain that the colour, porosity and mesh density influence the photosynthetic intensity. They stated that less than 150W/m2 PAR is sufficient to normal growth of plants. Numerous papers dealt with the possibility to promote photosynthetic efficiency by mulching, when the mulched or specially covered surface reverberate the light Solomakhin and Blanke (2007), Blanke M.M. (2008). Recently, research was concentrated to the examination of effects exerted on the quality, i.e. development of anthocyanines as covering colours of fruits (Jakopic et al. (2007), Romo-Chacon et al. (2007) The modified microclimate was explored by Hunsche et al. (2010). They stated that black nets diminished light intensity by 6–10% and increased the relative humidity, which does not cause concern until normal phytosanitary measures are observed. The present study aimed to communicate the knowledge accumulated on the topic of using hail nets in the practice under various meteorological conditions comparing the parameters raised under and outside of the areas covered by the net. The locality of the experiments was the experimental orchard of the Debrecen University at Pallag. The hail net applied was black and had the form of a tent, its mesh size was 3x9 mm, the product of the Frustar enterprise. The apple variety was Early Gold volt, planted in 2003. Planting design was 3x1 m. Data characterising the microclimate were raised by an agrometeorological station of HWI type.