If you are a cucumber grower and you are looking for ways to increase your yield of the vegetable, or just looking to extend its growing season well into the autumn, then you may be interested in a recent scientific study from Poland looking at the different types of supplemental grow lighting on the yield and quality of cucumbers.
Natural light during the autumn months is usually not sufficient to grow cucumbers very efficiently and commercial cucumber growers often use supplemental lighting in the form of high pressure sodium (HPS) lamps to extend the period in which they can successfully grow the vegetable. However, as it is becoming increasingly accepted in more recent times, HPS lamps are seen as energy guzzlers and being able to switch to more efficient LED lighting presents significant benefits.
In this study, the researchers compared HPS lamps with LED lamps in three different supplemental top-lighting and inter-lighting combinations (HPS top-lighting alone (HPS), HPS top-lighting plus LED inter-lighting (Mix), and LED top-lighting and LED inter-lighting (100%LED)):
Testing cucumber growth under 3 different supplemental lighting combinations
In all of the test conditions, the total amount of supplemental light was kept constant at 320µM / m2 / sec PAR. However, since this was an experiment focused on the use of supplemental lighting for sub-optimal natural light levels, the top lights were switched off when natural sunlight in the greenhouse exceeded this limit as might be done in a commercial setting to conserve energy.
Technology-wise, the LED lighting was derived from Phillips GreenPower fixtures range, with the LED top-lighting consisting of red and white lights that contained relatively little blue wavelengths. These were chosen in order to make a fairer comparison with HPS top lights, which emit significantly more red than blue wavelengths. As for the LED inter-lighting modules, these were chosen for their peak emission in the red and blue part of the spectrum, which is generally considered to be more efficient at stimulating plant growth than white light.
At harvest time, the scientists examined several aspects of the cucumber crop including its yield, some of its chemical characteristics, as well as some other sensory aspects of the crop such as smell and general appearance. From this, the most significant result obtained was that the yield of cucumbers per unit area was greatest in the third test condition where 100% LED lighting (i.e. LED top-lighting together with LED inter-lighting) was used as the supplemental grow lighting.
Another notable result from this study was that using inter-lighting also showed its potential for increasing yield as it has done in other studies, in that even in the HPS lamp test conditions (HPS alone vs HPS plus LED inter-lights), the yield was greater from plants exposed to intercrop lighting than from those plants with only top-lighting alone.
What information can the home indoor gardener glean from this study?
For the indoor gardener, three key takeaways can be derived from this study. Firstly, supplemental lighting can have a significant positive effect on the production and yield of cucumbers in home greenhouses and conservatories. This is because light levels in indoor spaces might be subtly lower than the outside environment or light levels during certain times of the growing season might be sub-optimal such as during the autumn or spring. Secondly, the supplemental lighting indoor gardeners should use should be of the LED kind as it is more effective (not to mention more economical) than more traditional types of lighting like HPS. Finally and if possible, supplemental lighting should include light fixtures in and around the plants themselves in the form of inter-lighting which will fully maximise the yield from cucumber plants.