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Using LED grow lights and less irrigation makes stronger plants

Hort Americas is currently working on a germination and propagation project of leafy greens and culinary herbs. The project is in collaboration with their demonstration greenhouse partners, The State Fair of Texas and the Big Tex Urban Farms. Big Tex Urban farms provide the labor needed to grow and manage plants on-site while Hort Americas provides advice and oversight.

“For many leafy greens growers in the USA, the average growing cycle is 10 to 15 days in propagation from seeding to transplanting.  Hort Americas is challenging this concept by using LED grow lights and an ebb and flood irrigation standard to challenge this norm,” Chris Higgins, Co-founder of Hort Americas explains.

Using less water makes a stronger plant
Higgins adds: “While most of the industry is focused on LED lighting alone, we want to make sure we focus on all the variables needed to produce a stronger young plant. This has meant paying special attention to our irrigation strategy and airflow.” He continues, “drying down the substrate allows us to force the roots down as they chase the water and nutrients. Improving airflow allows us to strengthen the plant while avoiding common pathogen issues. A stronger young plant allows us to finish faster while having many fewer problems along the way. It doesn’t learn from it.”

He says that professional growers should develop a protocol to determine the water content of their substrate. Growers should not rely on an irrigation calendar, but on the moisture content (which can also be measured by weighing the substrate. Understanding that as the weight decreases, the product is getting dryer.) They will then establish certain parameters that require them to irrigate. “All variables have to be in balance, if you add more light, you’ll dry out your plants quicker and the irrigation cycle will need to happen faster. If the power goes out, and you lose all your light and it’s a dark period of time, with high humidity the plants are going to transpire way slower, so you don’t need to irrigate at all for however many days.” 

Affecting plant roots
“The most remarkable outcomes can be divided into three characteristics,” Higgins says. “Namely, consistency, uniformity and profitability.” Growing this way under LEDs, (while continuing to focus on climate and irrigation,) this allows growers to create a more consistent, uniform ultimately more profitable crop. “What we’re really affecting is not the top of the plant as much as the root development. The correct LED spectrum allows us to focus on root development because we’re changing the structure of the top of the plans. This allows the plants to stay in the propagation area longer. We have then seen that the plants will finish much quicker after transplanting to the finished growing density or spacing.” Higgins affirms. 

There are then other secondary benefits that Hort Americas has yet to quantify. These include less loss in transplanting while at the same time improving space and labor efficiency. Theoretically, this could lead to even bigger benefits for farms large enough to automate these processes as more compact and uniformed plants lend themselves well to automation. LED grow lights have allowed us to explore the physical structure of the crop which has then enabled us to enhance other aspects of cultivation and business strategies.

High plant density
Higgins notes: “We are trying to hold the plants longer, from 17 to 21 days. Because this is any areas where growers can afford to make the most investments. This is the area where we have the highest plant densities which gives us the best use of real estate and the best chance to spread our investments out over the most amount of plants.”

“We found that by using the combination of the right light spectrum and the right irrigation strategy, we can grow a stronger young plant that when it transplants in the finished growth space, it reaches the harvestable weight or yield in a quicker period of time,” Higgins notes. The goal is to increase efficiency, fine-tune the technology in the part of the farm where it has the highest value and then increase uniformity.

Improving growing parameters
Their team didn’t only focus on light quality, but also on climate management and the irrigation strategy. “We’re growing much drier today than when we first started. We want to be sure that we do not lose focus on airflow and a consistent environment”, Higgins states. He admits that the climate is the most difficult thing for them to manage because of the limited technology options that have at their facility in Dallas, Texas. Their climate changes significantly at different times of the year, they do what they can to limit the plant's exposures to molds, mildews and other pathogens. If the air movement is inadequate, it creates opportunities for spores to take place and become prolific.

Lighting
“Depending on the growing system, we choose the right light fixture that best suits the growing system. It doesn’t matter what kind of light it is. Most important is that we choose the right fixture that is engineered to deliver the light in the right amounts at the given distances from the plant, based on the structure of the cultivation system.

In a multi-layer growing facility (vertical farm), we’d use a light that has a lower wattage, because the lights are put up closer to the plant. If a grower has a grower propagation system that are tables in a greenhouse, we’d use a top light style product. We need a light with more wattage and power so that we can throw the photons a further distance. Any type of light can be used, it’s just making sure the light is designed and engineered for the environment it’s put in”, Higgins explains. 

Consistency
Higgins says that they want a more compact plant. “That allows us to keep it in a higher plant density for a longer period of time.” That plants will then have less damage whether they are transplanted to another location or if they are transported and shipped to another farm or greenhouse. Next to that the compactness makes it easier to handle, also when having an automatic transplanter, it makes it easier for the robots to grab the plants and transplant it. If growing in a higher plant density and plants get too big, they overlap each other, causing inconsistency.

For more information:
Hort Americas
Chris Higgins, Co-founder and President of Hort Americas
chiggins@hortamericas.com 
www.hortamericas.com 


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