LED lighting and the light recipes that go with it are developing rapidly. This, in turn, makes it easier for growers to adapt to crops' differing qualities and yields, while reducing energy costs. More and more crops are able to benefit from developments in the LED-lighting field, and more and more growers are making the step from HPS to LED or hybrid (a combination of HPS and LED). This is because a higher light intensity is desired, but with lower energy costs and without additional radiant heat.
Cultivation under LED lighting is very different to cultivation using HPS fixtures. This is because the energy balance when cultivating using LED is different to the balance when cultivating under HPS light. HPS gives off 45% radiant heat, while LED fixtures chiefly produce grow light, emitting virtually no radiant heat. The lack of radiant heat can have positive or negative effects on production, depending on the crop. LED lighting also presents more options for making adjustments within the light spectrum.
Many growers who use LED lighting implement a light recipe consisting of red-blue/low blue. This light recipe is largely chosen because it is highly energy efficient. The grower gets the maximum quantity of grow light from the energy used. This is particularly evident in crops such as tomatoes and cucumbers, where the aim is to produce as many kilos as possible.
For the human eye – for example, to aid in crop recognition – white light is often added as well. The LED fixture's spectrum then becomes red-white/low blue. Changes are made to these recipes if the grower wants to influence an aspect of quality or change the plant structure. This is often the case in ornamental plant cultivation, and may involve (for example) the plant's compactness, development of the stems, buds, and shoots, and the bud structure.
Testing different light recipes
There are various ways to achieve the desired light recipe. The test method chosen depends on the desired timeframe. When sufficient time is available, a grower will choose fundamental research without daylight, for example in a climate chamber. When less time is available, testing will start on location.
Both tests on location and tests in a climate chamber begin with a rough test. The next step is an examination of which changes to the plants' physiology have been realised. Based on these changes, increasingly more specific tests are carried out, with adjustments to the different colours of the light spectrum.
If testing produces the desired result, the financial feasibility of the light recipe is then considered. In other words: the crop yield is compared with the energy consumption and the cost of the light source.
Efficient use of LED lighting
Achieving the highest possible crop yield with the lowest energy consumption is strongly related to how efficiently the crop converts the grow light. In other words: the extent to which the plant efficiently converts the received light into assimilates (sugars), and thus into crop or fruit growth.
The point at which a plant optimally converts light into sugars (i.e. 100%) is different for each crop and is constantly influenced by the greenhouse's relative humidity, CO2, and temperature. The optimum can therefore differ from minute to minute.
The Hortisense grow light software enables the grower to monitor important performance indicators from the cultivation strategy, using this information to adjust the quantity of grow light. The grower can also call on Hortilux's Growlight Performance Consultants, who assist in interpreting grow light data. The grower can then be sure of making the right decisions for optimal crop results.