The influence of differently coloured anti-hail nets and geomorphologic characteristics on microclimatic and light conditions in apple orchards

Abstract

Geomorphologic characteristics like altitude and terrain slope have an important but often neglected impact on light conditions in orchards. The study concentrated on the impact of altitude and terrain slope in combination with various colours of anti-hail nets (red, grey, blue, green and black) on the light and microclimate conditions in apple orchards. The results exhibit a large reduction of the photosynthetically active radiation (PAR) under the nets, most prominently under blue and red nets (reduction between 38.7 and 45.6%), while the impact of coloured nets on other microclimatic parameters (average air temperature, relative air humidity, temperature of dew point, wet-bulb temperature, heat index, minimum air temperature, maximum air temperature) remain irrelevant. The only consistent difference is an average of 2% increase of maximum air temperature under the blue net in comparison to other treatments. The use of the net also significantly reduce the wind speed (on average by 56.3%) and air flow (on average by 63.4%), and changes the distribution of precipitation in the orchard, most prominently in cases of heavy rain and drizzle. Regarding the orchard’s geomorphologic characteristics, a positive relationship exists between altitude and PAR.