Cucumbers are subtropical plants, which means that they require conditions of high light intensity, temperature, and humidity in order to thrive. The quantity as well as the quality of the crop is directly affected by the surrounding lighting conditions. This means that a carefully composed spectra adapted to the special needs of cucumber plants can increase productivity and promote desirable properties, while inadequate lighting conditions will affect yield and fruit quality negatively.
Broad spectrum white light has been shown to increase yield, both in terms of fresh weight of fruit and total fruit number compared to narrowband spectra, while also creating a more comfortable working environment. A full spectrum with a proportion of green light in addition to red and blue light more effectively enhances photosynthesis in a strong white light background than red and blue light alone, since green light can penetrate deeper into the leaf tissue and excite photosystems in lower cell layers.
A study published in 2020 compared the yield, efficiency of production processes and impact on cultivation costs of three light treatments, one HPS toplight fixture, one combination of HPS toplight fixture and LED interlight fixture and one LED toplight and interlight fixture. The report concluded that LED-LED was the most effective treatment in terms of light use, resulted in higher yields and significantly increased production value and gross profit margin. The report pointed out that due to the loss of radiant heat from the HPS lamps, the LED-LED treatment had an increased need for thermal energy during the winter months. However, they concluded that the increased value of production from the LED treatment covered for the costs of thermal energy and still made LED the most advantageous light source.
