The Science of Indoor Farming
The Science of Indoor Farming
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Every plant requires the same core essentials: light, CO₂, water and nutrients.
That’s the simple part.
However, these core essentials combine with a multitude of additional factors depending not only on what crop you are looking to grow, but also what you want in terms of nutritional value, visual appearance and taste. When out of balance, these factors can also have a catastrophic effect on the plant, potentially causing death at the extreme or a lower yield in a best-case scenario. Such factors include temperature and humidity, airflow, length of growing day and more.
The ability of growers to control just about every element of the recipe for growth means that we can truly ensure that every plant reaches its maximum potential. However, each element must be carefully monitored in order to optimize its impact on plant morphology.
Can LEDs Replace the Sun?
Light is one of the most crucial elements for plant growth. Outside, the sun’s light spans a broad spectrum from UV through to infrared wavelengths. The green wavelengths are reflected and transmitted more strongly by the plant’s leaves than the red and blue wavelengths, which are absorbed more effectively within leaves for photosynthesis. The available light spectrum and intensity will be affected by geography, weather and seasons. In addition to the core function of photosynthesis and growth, light can also act as a signal to the plant, encouraging it to develop in a certain way, such as to promote greater leaf mass, produce taller stems or encourage flowering.
However, different plants have different light needs, and they respond differently to the light wavelengths used, the length of the growing day and the night period. Take flowering for example: you have short day and long day plants, with both requiring different photoperiods to induce optimal growth.
In the natural world, plants may also have to compete with their neighbors for light, nutrients and water. All this uncertainty and guesswork can be removed through vertical farming.
Understanding the Light Spectrum
In recent years, lighting experts have discovered how to effectively isolate and combine different light wavelengths. By varying the light spectrum “recipe”, you have far greater control over how plants will grow.
The three major categories of Growth Spectrum look like this:
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| Reproductive To promote leaf coverage and fruit generation. |
Balanced To promote overall growth performance. |
Vegetative To promote plant structure and leaf mass. |
Fluorescent lights were previously used for indoor farming, but advances in LED technology, including their processing ability when it comes to light generation, light extraction and re-absorbance, have made LED grow lights the most efficient product available on the market. As well as having the potential to run 24/7, LEDs offer a greater level of control as specific light recipes can be designed within the three main growth spectrum categories to maximize the results for individual crops. LEDs also offer a much longer lifespan than previous lighting technologies and can be manufactured in a way that makes them easy to clean and cheap to maintain.
Different light recipes can also be employed at the end stage of growth to increase anthocyanin synthesis and pigmentation in produce like red lettuce, where a green plant would be less appealing to the end customer.
However, light isn’t just critical to maximizing growth, manipulating color and shortening the cycle from sowing to harvest. Light also governs the circadian rhythms of pests, bacteria and fungal pathogens, which may be found in growing rooms. Light can therefore be used to design traps to limit the movement of stray insects or to prevent fungal spores from spreading through the crop.
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Type R 6:1 (R:B) To promote leaf coverage and fruit generation. |
Type B 3:1 (R:B) To promote overall growth performance. |
Type V 1:1 (R:B) To promote plant structure and leaf mass. |
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Heat and Humidity Control
Temperature and humidity both have the potential to accelerate growth or ruin a crop and are possibly the two most challenging elements of managing your vertical farm.
Temperature has a significant impact on the speed of growth, alongside the physiology of plants. The ideal temperature for a plant depends on a number of factors, and the correct balance between air temperature, relative humidity and light must be achieved. The growth habit of the plant also impacts this process.
Additionally, as you increase temperature within a defined range, you get an increase in gas and water exchange between the plant and the environment. When the temperature rises, you increase the loss of water, which is why you need to worry about the humidity of the environment even though warmer air can hold more water.
Humidity impacts photosynthesis. This is due to the need for water from plants, which is used to keep them cool and retain their cell flexibility6. The ability to retain water is determined, in part, by the humidity of the air which can increase levels of evapotranspiration.
Humidity also impacts the ability of the stomata to draw in carbon dioxide and release oxygen and water. Too much humidity can effectively stop the plant from functioning on a basic level7. As the racks of lights filling the growing floor are the major source of heat in the facility, airflow and HVAC systems are crucial to reducing cases of tipburn and wilt.
Plant Nutrition
Plants require a range of nutrients to grow properly, but you will need to tailor your nutrient mix specifically to the crop, as well as your planned growth cycle, root mass and other variables. The three main types of nutrients are nitrogen, phosphorous and potassium, but calcium, sulphur and magnesium are also important8. A deficiency in key nutrients can result in everything from death of the tissue and discoloration to abnormal growth9 so it’s crucial that you deliver the right nutrients at the right level of concentration to the roots at the right moment of the growth cycle. When it comes to supplying plants with nutrients, there are several methods and substrates that you can use. These can be living substrates (soil, peat) or inert (non-biological). For the foreseeable future, irrigation and delivery of nutrients via hydroponics is considered the most viable and widespread method for indoor vertical farming. Aeroponics and aquaponics are expected to remain fairly niche, holding only 27.1% and 16.7% of the market in 2017 and 28.7% and 17.6% of the market in 2024, respectively10.
The advantage of a recirculating hydroponic system is that we can potentially cut the use of water by 90% versus traditional farming methods if you re-condense and re-use the humidity from the growing environment. This makes vertical farming an ideal option for regions where water is scarce or expensive and helps vertical farms to do their bit for environmental sustainability by reducing waste of inputs without compromising on output.
READ: Indoor Farming: How Can You Ensure Success?
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