Unlocking the Potential of Greenhouses with Light

Since the 1800s, light has been a fundamental part of the greenhouse value chain, with sunlight being the main constant in growing everything from food to flowers. As the industry has evolved and controlled environment horticulture has grown, researchers and growers have joined forces to identify the best seed stock, the right nutrients and the most effective pesticides to increase both the volume and quality of greenhouse harvests. Yet our approach to light hasn’t evolved in line with these other inputs and greenhouse growers now have an opportunity to unlock new value in their commercial operations by looking at light through a different lens.

According to analysts “The global Commercial Greenhouse market was valued at 29,600 million US$ in 2018 and will reach 57,300 million US$ by the end of 2025, growing at a CAGR of 8.6% during 2019-2025.”* This predicted 94% increase in market value in just seven years reflects both the opportunity and the imperative that growers now face; with the global population set to top 9.7 billion people by 2050, producers must find new methods to increase food supplies using the finite resources that are available.

However, these targets and challenges aren’t necessarily as insurmountable as the headlines may lead us to believe. The balance of power in horticulture between art and science is shifting as global researchers unlock more secrets of plant biology, increasing their understanding of how plants develop from seed through to maturity. Growers can now take these insights, combined with accelerating technological advances and evolve their operations to become leaner, more productive and sustainable.

Light: the new precision tool of greenhouse growers

It could be argued that until recently, light was seen as a fairly blunt instrument in the grower’s toolkit. The two primary aspects that could be manipulated were the amount and intensity of light reaching the plant. Aside from relying on the sun, growers could use traditional high-pressure sodium (HPS), compact fluorescents (CFLs) or metal halide lamps to extend the length of the growing day (photoperiod) as well as the intensity of light delivered. HPS lamps deliver a warmer coloured white light, as well as infrared radiation, whereas CFLs and metal halide lamps tend to deliver a cooler, white spectrum light. However, these lighting solutions are typically energy-hungry and, particularly in the case of HPS, can also generate a lot of wasted heat. Although this can be useful in greenhouses located at high latitudes and in colder climates, it also adds a new variable that greenhouse operators have to manage in order to create the perfect growing conditions for their chosen crop.

Today, far more is known about the light spectrum and the precise impact of different light wavelengths on plant morphology. Light has a crucial impact not only on plant shape and size, but also on elements like taste, nutrition and colour. The development of LED technology by companies like GE Current, a Daintree company, has enabled the use of bespoke LED solutions that harness this scientific insight and deliver a tailored lighting recipe depending on the needs of the plant.

Light quality is a factor in the biosynthesis, metabolism and accumulation of phytochemicals. By providing a specific light spectrum in addition to controlling the photoperiod, growers can optimise the production of phytochemicals (via plant photomorphogenesis), which govern elements such as taste, nutritional content, aroma and others important characteristics such as the shelf life of fresh produce.

Hans Spalholz is a plant scientist who has spent his career understanding the impact of different light wavelengths on plant morphology. He is now helping Current to develop and refine its specialist range of horticulture LED solutions to help indoor farmers achieve high-quality, commercially viable yields. He notes, “Even though modern greenhouses have been around for decades, we are now just scratching the surface of their potential.”

Harnessing complexity for success

As plant science reveals more and more insights into how plants react to the basic inputs of CO2, water, nutrients and light at different stages of growth, the ways in which greenhouses produce food, flowers or even plants for medicinal use such as cannabis, can be refined to drive higher yields than ever before.

“By understanding the exact role of different light wavelengths on different biological processes in a particular plant cultivar, we have far greater control over what the end product looks like, simply by giving the plant the exact blend of raw materials and light needed at that precise stage of growth,” explains Spalholz. However, with this knowledge comes the realisation that greenhouse cultivation has the potential to be infinitely more complex as the ability to fine-tune each variable becomes possible at every step and individual factors such as geography, climate and custo