Your recipe for growth

Basil has been cultivated for centuries and is one of the most popular culinary herbs all over the world. The fresh flavor it offers cannot be matched by any other herb or spice, making this delicate plant an excellent choice to grow indoors. Unfortunately, basil leaves will turn black when they are damaged, which can easily happen when basil is exposed to low temperatures during transport or storage. Due to the delicate nature of the crop, basil is not only one of the most expensive herbs for the consumer, but also one of the most perishable. If blue LED lighting can help strengthen the crop’s metabolic profile, it would increase its value to the retailer, end-consumer, and grower as well.

Studies have shown that the use of blue light in vertical farming can have a strong influence on a variety of crops, increasing their flavor profile and overall quality. But when it comes to the application of blue light, there is no one size fits all approach. Together with Wageningen University, we wanted to see if basil would have a positive reaction to an increased level of blue light as showcased by previous research conducted on lettuce. But we were surprised to find that basil’s performance under increased blue LED lighting did not resemble the previously researched performance of leafy greens and fruits.

In a few years, indoor (vertical) farms have become popular for producing healthy food year-round in urban environments and harsh climates. Leafy greens and herbs are the most commonly grown crops, but growers are looking to expand to a much wider variety of vegetables and fruits. In our Philips GrowWise research Center, we have been running trials on strawberries for several years. Recently we took these trials to the next level. Our goal? Develop a reference design for growing strawberries indoor, find the optimal light recipe and the best performing varieties.

At the Philips GrowWise Research Center in Eindhoven, we research all growth parameters relevant to a crop: light is obviously essential, but factors such as climate, variety choice and substrate are equally important. The idea of growing strawberries indoors was not new to us. In fact, we have been growing strawberries without daylight for over five years already. Despite some disappointments and setbacks, the results and first business case calculations proved encouraging enough to further pursue the topic and build a reference design for growing strawberries.

• Adding far-red light boosts biomass (stem and leaf mass, both dry and fresh weight).
• This does not translate into higher fruit production in kg/m².
• Adding approximately 5% far-red light can improve stem elongation.

Grow light research confirms effect on energy consumption and crop, as experience has shown with other crops

If white light is not strictly necessary in LED installations for grow lights, it is better to avoid it. Compared to red and blue light, it does not add value to the crop, but energy consumption does go up. That’s the conclusion we have drawn after extensive testing with light recipes using the Philips GreenPower LED production module dynamic. The recent results in basil cultivation confirm previous experience in, among others, lettuce, tomato and spinach crops.

There is a lot of talk about the use of white light in LED installations for grow lights. It is more comfortable to work with white light, and you can assess the color of crops better. When people have to work in the crop on a regular basis, a little white light is therefore quite useful at times when there is no daylight available. In other situations, white light does not add any value for the plant, compared to red and blue light, and it only increases costs.

Philips Horticulture LED Solutions and partners collaborated on a trial to help tomato growers find a solution for cultivating a full-LED winter lit crop with a low heat input without impacting yield or quality. LED lighting is an energy-efficient lighting solution that comes with a low radiant heat output. Therefore, when tomato growers switch to full-LED systems, they often find themselves requiring a different heating approach. The trial used active air dehumidification and demonstrated that controlling and optimizing all aspects in a greenhouse enables a lower heat input while enabling sufficient transpiration to support strong and healthy crop production.

Due to high energy prices and the rising importance of sustainability, growers are under ever-greater pressure to decrease their heat input. However, a switch to a full-LED cultivation system risks conflicting with this, since LEDs produce significantly less radiant heat than other lights. Therefore, growers often need to add extra heat from other sources and to adjust their heating strategies. The trial results showed that a holistic approach that optimizes all aspects of a greenhouse can help growers achieve a lower heat input while still producing strong and healthy crops.

By controlling and optimizing all aspects in a greenhouse, the trial demonstrated that a lower heat input can be achieved while enabling sufficient transpiration to support strong and healthy crop production. The results were astounding, with the heat input reduced by more than 50% compared to a typical commercial grower's baseline gas consumption. Read more in the whitepaper below.

With high energy prices here to stay, we’ve seen big changes in the way growers are thinking about their use of light. High Pressure Sodium (HPS) lamps are being switched off and replaced with LED lights, which are not only more economical but have the option to be dimmed. Growers are learning that they still need to use artificial light, but it must be used smarter to combat costs - preferably without limiting crop growth, yield, or quality.

Two concepts are central to the new approach to artificial lighting: cost-effectiveness and flexibility. Plants need Photosynthetic Active Radiation (PAR) to grow. The trick to cost-effective growth is to give plants enough PAR light in the right composition of spectrum and intensity at the lowest possible cost to perform well. And just as electricity costs are not constant but can vary from hour to hour, a plant’s light requirements are not constant either. Research and practice have already shown that it can be beneficial for both plant development and energy bills to treat light as a dynamic growth factor. The days when light installations always ran at full power at fixed times will soon be a thing of the past.

Mid-September 2018, we began a new round of trials in our tomato demonstration greenhouse at the Delphy Improvement Centre. In this project, Merlice vine tomatoes from De Ruiter Seeds are cultivated under a combination of Philips high pressure sodium (HPS) and Philips GreenPower LED grow lights. We try to prove that a hybrid lighting solution can give growers a flexible way to apply high light levels to the crop right through early spring, while still taking advantage of the radiant heat provided by HPS lights at colder times of the year. The goal is to harvest over 55 kg/m² at the end of week 18.

• Far red light in tomato cultivation gives major differences between varieties.
• It can improve the sink strength and lead to a significant increase in harvest, but it can also negatively affect the quality of the green parts.
• At the moment, far red is not of interest for tomato growers. The production increase is disproportionate to the extra energy required.

Growers want to get as much as possible out of their LED lights. That’s why Signify is conducting ongoing research into the optimal application of Philips GreenPower LED lighting for various crops in close collaboration with its partners. Various light recipes are being tested in relation to energy consumption, light spectrum, additional yield, and uniformity. The use of far red has been one of the hot items in recent years and appears to have a positive effect on many crops when applied properly. Because of this, the question arises for many tomato growers who are already producing under full LED to investigate this?

• Lighting conditions applied just before harvest determine the final yield, percentage of dry matter and quality (shelf life and nutrient content) of the crop.
• Lettuce grown in a vertical farm can be just as nutrient-rich and fresh tasting as those grown in a greenhouse or outdoors
• Controlling the light towards the end of production can be applied in vertical farming as well as in a greenhouse to enhance different quality aspects in the product.

It’s a common problem with processed lettuce. After a few days in the fridge, the leaves wilt or turn brown. At Signify, we performed a study to see if increasing the intensity of LED grow lights a week before harvest would improve the quality and shelf life of lettuce. And the results show that high light intensities applied at the End of Production increase key nutritional elements and quality markers, and ultimately extend the shelf life of lettuce.

Leafy vegetables generally have a short post-harvest life due to physical damage and lack of light during storage and transportation. How long a leafy vegetable or any other vegetable lasts on the shelf and how long it looks and smells fresh are determined by the growing conditions of that vegetable. In academic research, scientists are establishing a link between nutrient content and shelf life. Key nutritional elements and quality markers include the levels of carbohydrates (glucose, fructose, sucrose, and starch) and vitamin C defined as the total ascorbic acid (TAsA). Both carbohydrates and TAsA levels are affected by light conditions.

In this study, our objective was to investigate the effect of light treatments applied before harvest on the post-harvest performance of lettuce, as a representative crop of leafy vegetables. Most of the previous research on the effects of light intensity on product quality has been done by applying different light levels during the entire cultivation period. In our experiments, we applied different light levels only at the End of Production – 6 or 7 days before harvest. The advantage is that the light treatments will only have limited influence on other aspects of the crop, such as growth, yield and morphology. And it also minimizes energy usage.