Types of growing systems in Vertical Farming

According to the Food and Agriculture Organization of the United Nations (FAO), agriculture is responsible for almost 90 percent of global deforestation. Moreover, the current population of 7.2 billion people is expected to hit 9 billion by 2050, increasing the food demand by several folds. Additionally, traditional agriculture faces a major challenge of keeping a steady supply of fresh produce due to several problems such as scarcity of land and water, and unexpected weather changes leading to post-harvest loss.

However, in recent times, the dynamics of agriculture are slowly transforming. We are developing diverse ways to produce food with lower land and water requirements while maintaining high quality. One solution to ensure a steady food supply is vertical farming.

What is vertical farming?

It is a crop production method which utilizes the space in the air to grow crops in stacks, unlike traditional agriculture, which needs abundant land and water. Vertical farms can also produce crops around the year, so you don't have to wait for a specific season to enjoy your favorite herbs or berries.

Let us further dive into the prospects of modern agriculture, which is bringing a revolution to the food-growing practices.

The technique of vertical farming involves growing food vertically by using stacked trays on top of each in a closed space with optimum growth conditions required for the crop. The major distinction between traditional agricultural methods and the modern vertical farm is the land, water, and fertilizer use. While the former needs everything in abundance, the latter uses these entities sparingly while more food per square foot. Moreover, the crops produced in vertical farms will also be of superior quality. They receive optimum controlled nutrition, water and are also pest-free because of the enclosed growing facility. Vertical farms usually have one of the three major growing systems, namely Hydroponics, Aeroponics, and Aquaponics, discussed further.

Nutrient requirements and plants in vertical farming  

Like humans, plants also need nutrients to flourish and can not function without them. All the growing systems use a different mixture of essential nutrients classified as macronutrients and micronutrients. Some vital nutrients are nitrogen, oxygen, sulfur, potassium, and phosphorus.

One vital decision that makes a vertical farm successful is the type of crop you grow! The most preferred crops for vertical farms include lettuce of all kinds, swiss chard, tomatoes, small herbs, tomatoes, and last but certainly not the least, strawberries. Do you know you can also grow tuber vegetables using one of the vertical farming techniques?

Hydroponics

Also known as soil-less farming, is a Greek word made of two separate words: hydro, water, and ponics,' to labor, toil.' This technique dates back between 605-562 BC, when the first documented vertical garden was made and came to know as the 'Hanging garden of Babylon.' However, the first commercial vertical farm was opened in Singapore, constructed by Sky Greens Farms, a robust model of hydroponics and aquaponics farm with its own ecosystem of fish, shrimp, and plants.  

So, let us further dive into the hydroponics method. How do the plants even survive without soil or culture media? The answer lies in the flowing water under the plants, carrying all the vital nutrients required for the proper growth and development of the crop.

Let us dig further into the mechanism of hydroponics. The primary mechanism of hydroponics is simple: crops are suspended in a mixture of nutrients and water. This water mixture, which you could compare to the culture media, is recycled and circulated through the system multiple times. Although it is a relatively simple technique, it has many variations. Let us briefly talk about them:

1. Nutrient Film Technique or NFT
2. Deep Water Culture or DWC
3. Ebb and Flow
4. Root Dipping Technique
5. Capillary action technique
6. Floating technique

From the above mentioned, we will discuss four widely used techniques in commercial as well as the home garden setting:

Nutrient Film Technique or NFT

This technique includes a tilted hollow pipe with holes holding the plants and passing the nutrient solution to the roots. This hollow pipe system is connected to a water reservoir tank and a pump. A thin layer of nutrient water slowly passes from the tilted pipe, and the roots can absorb the required nutrients while the rest of the water will fall back into the reservoir tank because of the tilt. 

Deep Water Culture or DWC

In this method, the plant roots are entirely immersed in the nutrient solution, which would be aerated continuously using an air stone and a pump for roots to get sufficient oxygen.

Ebb and Flow

This technique is also known as Flood and Drain method! Yes, that is right. This involves plants growing in an inert substrate such as perlite; the pots then sit on a grow tray. The nutrient reservoir beneath would intermittently flood the grow tray. One of the two holes in the grow tray acts as an inlet that brings the nutrient water into the grow tray using a pump, and another as an outlet that drains the water back to the reservoir tank using gravity.

Root Dipping Technique

The crops are cultivated in small pots filled with growing materials such as gravel. The pots are half-submerged in nutrient water such that a portion of roots are in the water to absorb nutrients, and the rest are exposed to the air for oxygen absorption.

Aeroponics 

Aeroponics is a technology also known as air water cultivation system that allows the crop to grow in the air instead of soil or a growing medium inside a closed environment. The significant difference between aeroponics and hydroponics is how nutrients are delivered to the plants. The aeroponics system is a closed container. The plant roots are then misted with a mixture of water and nutrients adjusted to the plant's requirements.

However, the drawbacks are managing crops with big roots and a continuous power supply to keep the misting sprays working, making it a fairly complex procedure.  

Aquaponics

This integrated system gives us the best of aquaculture and hydroponics combined. Aquaponics works as a closed-loop system with a fish tank and plant growing bed. The waste produced by fish, which is high in ammonia, is fed to the plants as biofertilizers via a pump, and in turn, the roots filter the waste and send the clean water back to the fish tank. 

The major fish species compatible with aquaponics are tilapia, trout, perch, Arctic char, and bass. The selection of fish is based on the tolerance to the fluctuation of temperature, oxygen, nutrients, and pH. Generally, aquaponics farms require round-the-clock monitoring for the first few weeks of establishment as any stress to fish can kill them, leading to an unsuccessful set-up and lots of dead fish!

With the advances in crop production methods like vertical farming, the future of food availability and security looks promising despite limited natural resources. In the future, these technology-driven cropping techniques will make sure that fresh food reaches every doorstep.   

By Swati Jagani | 11 October 2022

Born in India, Swati Jagani now lives in the charming city of Stuttgart in Germany. She holds a master's degree in Horticultural Sciences and Biotechnology. She is working as a research scientist at the University of Hohenheim. Sharing her knowledge of the plant world through writing gives her immense pleasure. By day she is a researcher who loves to be in a lab working on experiments, and when she's not working, she wishes to travel the world with her dogs and read a book with a freshly baked brownie on the side.

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