Influence of coloured mulches on soil temperature and yield of sweet pepper

Summary One of the main objectives of using plastic mulch is to increase soil temperature. However, under high temperature conditions some plastic mulches warm the soil to temperatures that might be harmful to plant growth. A 2-year study was carried out in northern Hungary (Godollo) to determine the optimal colour of the plastic mulch for sweet pepper under specific, unsettled climatic circumstances, in some years with high temperature conditions. The increase of soil temperature caused by certain mulches was the same in both years. In case of light, coloured mulches (clear, violet, light green) the soil temperature was 2.5–2.9 °C higher than in case of the un-mulched control. The dark coloured mulches (black, dark green, red) caused 1.4–2.1 °C soil temperature increase compared to the un-mulched control. The rate of soil temperature values optimal for sweet pepper (between 20 and 30 °C) was the highest in case of dark coloured mulches. Due to the warmer weather in 2003 the soil warmed up under the clear and violet mulches extremely, which had a harmful effect on vegetative growth and yield. According to the higher soil temperatures mulched treatments produced higher yields than the un-mulched treatment except the clear mulch in 2003. The use of dark coloured mulches is the safest solution in the examined region because even in case of high air temperature and solar radiation the soil does not warm to a harmful degree.