Growing Food Indoors: finding the right recipe

 

Do you remember one of your first biology lessons as a child? At some point in elementary school, you were probably given a small Styrofoam cup, a handful of soil and a single seed that you were instructed to bury down into the dirt. And what were the crucial next steps? Keep it watered and place it in a sunny spot, of course. You checked your cup everyday waiting for that magical moment when you’d see a tiny green sprout reaching up towards the light and your teacher would explain that the sun was integral for a process called photosynthesis – the way the plant would convert sunlight into food.

But what happens if you remove one of those key ingredients from the mix? What if you take away sunlight and move your plants indoors? People have experimented with growing plants under lights for many years, but as we’ve discussed before, city farming is currently altering the agricultural landscape in new, exciting, and sustainable ways. Let’s take a deeper look into the concept and explain more about how LED lighting can take over the sun’s role to grow plants such as spinach, lettuce and tomatoes.
 

Traditionally, a range of bulb types have been used as grow lights, such as, fluorescent lights, high-intensity discharge lamps (HID), and light-emitting diodes (LED). And still today, the most widely used lights for professional use are HIDs and fluorescents. Although LEDs are far more energy efficient, HIDs have been a good, cost-effective solution. They offer a lot of light and a lot of heat – both necessary elements that growers could apply to cultivate their crops.

However, if a grower wanted more light, they’d also get increased amounts of heat. And that could burn their plants. That’s where LEDs can be useful for the growing process. With LEDs, farmers can disconnect the heat from the light. This offers a multitude of advantages including what’s called interlighting – a grower can put the lights right down into the rows of growing plants – and this technique can alter the plants in significant ways. For instance, farmers have found they can raise tastier and sturdier tomatoes by lighting the part of the plant that is shaded by the leaves above.
 

This light placement is part of what’s called a growth recipe. What mix of factors will yield the best crops? What soil – if any – is the best? What temperature is ideal? And, of course, to what range of the light spectrum will the plants best respond?
 

A light spectrum shows how much radiation is emitted at each wavelength. Light also can be described as particles, called photons. Each wavelength of light corresponds to a different energy per photon. Shorter wavelengths correspond to a higher energy per photon. For instance, blue photons have almost twice as much energy as deep red photons. 

The highest energy containing light is at the blue end of the color light spectrum. Blue lights have short wavelengths and therefore contain a lot of energy. At the other end of the spectrum, you’ll find deep red light, which has long wavelengths and contains lower energy. Per joule, different colors of light help plants achieve different goals. Blue light, for example, can keep plants more compact when combined with deep red light. Far-red light, which is light at the extreme red end of the visible spectrum (between red and infra-red), can help plants to flower.
 

Farmers can tune the crops to the wishes of the population they’re growing for or steer the crop for desirable traits – for increasing vitamin C in tomatoes or boosting the crispiness of lettuce, for example. However, growing with LEDs is a relatively new field and that means that no one has it down to an exact science yet. Universities such as Wageningen University in the Netherlands and Colorado State University in the USA are continuing to research which growth recipes yield the best results for various crops. 

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