Artificial lights have long been used in agriculture to supplement the natural light and increase crop yield. The scenarios where external lighting may be of use may include growing in areas with shorter day-light duration, cold climatic zones, growing indoors, or growing in Vertical farm, etc.

There are different kind of artificial lights that can be used for supplementing growth like incandescent bulbs, fluorescent lights, metal halides, high-pressure sodium halides, LED lights, etc.

The scope of this primer is limited to LED based grow lights used in Vertical Farms.   

How is it measured?

The standard unit of measuring light is lumens (or foot-candles or lux). This unit measures the brightness of light as measured by human eyes. This measure will have the highest reading in the yellow-green spectrum, and lowest on either end (the red and the blue spectrum.)

Do plants see the light in the same way as humans do?

Plants do not see (read use) the light the same way as humans do. Different frequencies of lights show different impact on different biochemical processes within the plants. As such it is not ideal to use the measures (like lumens) developed for human eyes to measure and understand the impact of light on plants.

How do plants use light? 

Different wavelengths of light pack varying amount of energies in them. This energy is carried by photons. When the photons fall on plant's surface, they get absorbed by specific pigments (ex chlorophyll a, chlorophyll b, carotenoids, etc.) within the plants and the energy thus released helps in carrying out the process of photosynthesis. As such, for plants, instead of measuring how bright a light is (lumens), it is more relevant to measure how many photons are being emitted by the light.

Going by above understanding, one may ask, is PPFD the holy grail of plant lighting? Is it the only parameter one should consider while evaluating lights?

The answer would be a resounding NO!

Using the PPFD measure, we can find out how many photons are reaching the plant surface. Yet, by using PPFD alone, we cannot figure out the distribution of these photons. As stated earlier, different photons carry a different amount of energy in them. Photons of a few specific wavelengths have a greater impact on the process of photosynthesis than the photons of other wavelengths. 

During our journey in CityGreens, we have met many Consultants, Competitors, Collaborators, Govt. Dignitaries, Investors, Entrepreneurs, Aspirants, and so forth. These encounters have helped us develop deep insights into the industry. It will not be an understatement to say that the Vertical Farming industry in India is still in its infancy. The way this industry shapes up will depend upon a lot of factors, primarily being the establishment of a few successful commercial models at a scale that can help the fence-sitters to make an informed leap of faith.

In this series starting today, we will share with you a few insights (specific to Indian context) that we have gained over time. These insights are based on our understanding and the inferences we have drawn. These may not be directly applicable in your specific set of circumstances. However, we do hope that these will help you think more in-depth about the issues that you may face in your journey of Urban Farming.

The first insight that we will cover today is the one that we have observed most commonly and has the potential to inflict the maximum damage on the success potential of a farm.

1. Use of LEDs: Take a step back and look at the problem that LEDs solve; they help you grow indoors. And why do you want to grow indoors?

a. the land cost is too high. 

b. The temperature outdoors is not conducive to growth (its either sub-freezing or too hot). 

c. one wants to grow in multiple vertical layers (say 10 - 15 levels at least).

In the Indian context, the first two will not hold. What LEDs will result in, in such a scenario, will be a manifold increase in the Cap-Ex and the Op-Ex, thus pushing away the break-even period further, or increasing the input cost so much that the output product becomes uncompetitive in the market. The third reason may still be the right reason for someone to set-up an LED-based farm in India. But it is cap-ex heavy and should be pursued if one is willing to wait for a long gestation period to break-even.

2. Growing Lettuce: Surprisingly, we rarely come across any Urban Farming aspirant who does not want to grow Lettuce. The question we like to ask is, after all, how much lettuce can Indian's consume? People in the west grow lettuce because they eat lettuce day in and day out (as a part of salads or sandwiches which form their staple diet). Indian's don't.

If one observes, one will see that the palate preferences that get developed over time, do so based on the demographic dividends. In semi-arid and desert regions of western India, when our ancestors had to travel long distances, they needed the food that can stay edible for long periods in the hot environment. And you see a lot of gram flour-based snacks in those cuisines (think Gujarati / Rajasthani cuisines). Similarly, in the economically lesser developed eastern parts of the country, potato served as one of the cheapest sources of quick energy, and you can see that influence even today (think Bengali Chicken biryani) in most of the eastern cuisines. Similarly, when it comes to greens, the Indian palate prefers the one that can be grown in tropical regions. Lettuce is definitely not the one.

Unless India transforms into a salad eating nation or lettuce becomes a part of mainstream Indian cuisines (think lettuce paneer instead of Palak Paneer), the market for lettuce will remain limited. In such a scenario, if all the vertical farms start producing lettuce, it will flood the market and lead to price erosion.