For proper growth, crops require a reliable medium that would be responsible for capturing and storing the essential plant nutrients. In traditional agriculture, this role is performed by soil. However, the rapid emergence of hydroponic farming over the last couple of years or so has somewhat diminished the importance of soil in agriculture – with ‘soil-less farming’ becoming a very real possibility. A recent study revealed that the value of the global hydroponics industry will be well over $395 billion by the end of this decade (growing at a CAGR of ~6.8%). Over here, we will present some interesting facts, features and characteristics of hydroponic farming:

1. What is hydroponics all about?

   In essence, hydroponic farming is all about growing plants and crops without soil. In this method, plant roots are brought directly in contact with liquid (generally, plain water) nutrient solutions – ensuring healthy growth. The nutrients are either reused or drained off, as required. Since there is no soil involved, the development of large root systems (to draw in nutrients) is not required – and typically, the intake of nutrients by the fibrous roots of hydroponically-grown crops is very efficient (minimal wastage). In hydroponics, soil is replaced by a reservoir or a medium made of a different material – that absorbs the necessary nutrients from the water-based solution.

Note: Soilless agriculture is not, per se, a particularly innovative concept. Reports suggest that farm research experts from the 18th century were well aware of it. Dr. William Frederick Gericke is credited for coining the word ‘hydroponics’ in 1936.

2. What materials can be used as ‘growing medium’ in hydroponics’?

   Several different materials can be used to create the nutrient-absorbing medium (in essence, the substitute of soil). Depending on the precise requirements of crops and, of course, the farmer – materials like sand, hydrocorn, expanded shale and coco peat are used for the purpose. Clay pellets, vermiculite and rockwool are often opted for by hydroponic farmers as well. To be usable as the medium for hydroponic plant growth, the material has to be inert – and ensure that the crops have ready access to the liquid nutrient solution, light, oxygen and other essential enzymes (mixed with the nutrient solution).

Note: The common characteristic of all the hydroponic growing mediums is their ‘inertness’ – their incapability of being able to support the growth of plants on their own, in the absence of additional nutrients. The medium is only responsible for supporting the weight of crops, and to facilitate the passage of oxygen/nutrients.

3. Do plants grow faster in hydroponic farming?

   There are very little doubts regarding that. On average, the growth rate of a plant is close to 40% higher in an hydroponic setup – compared to the traditional soil-based farming method. The annual crop yields can be as much as 75% more – making hydroponics a great technique for large-scale, commercial crop-growers (in particular). The main reason for the shorter crop cycles and much quicker time-to-harvest in hydroponic farming is the direct contact of advanced, high-quality nutrients with the plant roots. It’s like providing the best food directly to plants – ensuring significantly faster growth of the latter. Unlike soil farming, there is no wastage of nutrients, and plant growth happens in a controlled, efficient environment. Since hydroponic farming is considerably less labour-intensive than soil farming, availability of manual resources is not much of an issue either.

Note: There is no soil in hydroponic gardens, and hence, there is no need for spraying pesticides and strong chemicals – which can potentially have adverse side-effects on the crops.

4. Types of hydroponic systems

   There are several alternative hydroponic system setups that farmers can opt for – depending on the exact requirements of the plants/crops they wish to grow.

• The ‘Water Culture’ (also known as ‘Deep Water Culture’) is probably the simplest system, involving careful suspension of the plant roots in the water-based nutrient solution. Growers have to ensure that light does not get direct entry in the system (failing which, there can be significant algal growth), and air pumps are used to provide oxygen supply to the solution (and hence, to the roots). In this method, the plants are put in pots supported by polystyrene ‘floater’ boards. The tank, which contains the nutrient solution, is drained at regular intervals.
• The ‘Nutrient Film Technique’ (or, NFT) can be applied to ensure optimal utilization of nutrients/resources, and superior-quality plant growth. The nutrient solution regularly passes over the tip of the roots (the solution has to be kept at a slight tilt, to facilitate smooth runoff) – and the plant gets the required oxygen both from the solution as well as from air. The solution moves from the tank to the growing medium (usually, rockwool is used in this method) through a tube – and creates a film/layer of nutrients on the medium (that’s how the method gets its name). The used solution can either be recirculated, or drained out (run-to-waste NFT).
• The principle behind the ‘Flood and Drain’ hydroponic system is also simple enough. The growing medium is ‘flooded’ with the nutrient solution at certain time-intervals. A timer is set up in the system, to repeat the ‘flooding’ process. As the solution keeps flowing across the medium, the latter absorbs important nutrients – and that, in turn, supports the growth of plants. Typically, crops that can withstand small periods of dryness are grown by this method (also known as ‘ebb and flow’ system). A point of concern in this system is the risk of a missed alert from the timer – which can lead to excessive dryness and plant suffocation.
• The ‘Dripper’ system has similarities with the ‘Flood and Drain’ method, particularly since this one also requires a pump (for transferring the nutrient solution) and a timer. However, in the ‘drip’ system, the solution is actually dripped on to the roots of the plants and the growing medium. Hydrocorn, clay pebbles and rockwool – which drain slowly –  are the best mediums to be used in this system. Once again, the nutrient solution can either be reused or drained off. A potential downside of ‘dripper’ systems is the chance of the drip tubes/drippers getting clogged due to the formation of nutrient particles (the problem is more common when organic nutrients are used).
• The ‘Wicking’ method of hydroponic agriculture is also popular. In this system, vermiculite or perlite mediums are generally preferred – and farmers have to either connect the plant roots with the nutrient solution through a wick, or plunging the lower portion of the medium directly in the solution (nutrients get directly wicked to the roots). Mediums that have high absorption capacities (e.g., rockwool) are not used, since they can cause suffocation of the plants (due to excess amounts of nutrients absorbed).

        5. The Aeroponics system

Although ‘aeroponics’ is another system of hydroponic farming, its technical differences from the others merit a separate mention. In this setup, the plant roots are kept suspended in the air, and the nutrient solution is sprayed/misted on them. A pump is used to automate the misting activity after every few seconds (a timer is used in the system as well). Like the ‘Flood and Drain’ method, ‘aeroponics’ also relies heavily on air as an important source of nutrients. A pond fogger or a fine spray nozzle is used for misting the roots with the solution.

Note: AeroGarden is a classic example of commercial application of the aeroponics growing method.

6. How does hydroponic farming do away with uncertainties?

   In a soilless agriculture setup, there are none of the uncertainties that are typically associated with traditional farming methods (soil fertility, presence of soil organisms and pests, etc). Farmers get the opportunity of forming a preset ‘nutrient regimen’ – with complete control over the nutrients (volume and quality), pH levels (the 5.8-6.8 range is considered to be ideal) and oxygen availability. Problems, if any, can be easily detected and got rid off, and the entire hydroponic system can be replicated without any hassles. Enhanced reliability is a big factor working in favour of hydroponic farming.

Note: The ‘nutrient regimen’ should primarily have six ‘macro nutrients’, along with smaller amounts of the ‘micro nutrients’. Farmers also often mix the elements of two or more hydroponic systems to create ‘hybrid systems’.

7. Does hydroponic farming help in water conservation?

   Yes, and in a big way. In traditional soil farming, significant amounts of water gets evaporated – resulting in a wastage (both of the water as well as the nutrients present in it). Since hydroponics does not involve dirt in any way, there are no chances of evaporation or unnecessary drainage – and the water-based nutrients can easily be recycled. Experts have reported that the total volume of water required to irrigate hydroponic gardens is about one-tenth of the amount required in soil-based ecosystems. This makes the method highly suitable for growing plants in relatively arid regions (countries in the Middle East, for instance). As a rule of thumb, fresh water is used for soilless farming, and growers have to allow some time (a day, ideally) for chlorine and other chemicals in the water to be removed. After that, nutrients can be mixed to the ‘clean’ water, to create the ‘nutrient solution’. Rainwater is treated as the best possible source of water for hydroponics, while the filtered water made available through reverse osmosis is also good. Using heavily chlorinated water or hard water is an absolute no-no.

Note: The electrical conductivity (EC) level of water used for hydroponic farming should ideally be around 10.

8. What are the best conditions for hydroponic farming?

   As already mentioned earlier, hydroponics is free from the vagaries of soil qualities, while properly prepped freshwater (chlorine, chemical removed) is best-suited for this plant-growing method. The minimum level of dissolved oxygen (DO) in air, which is an important nutrient source here, is 6 ppm (parts-per-million). For typically ‘cool season crops’, the temperature range of 10°C – 21°C is optimal, while ‘warm season plants’ grow best when the temperature is between 15°C and 27°C. Plants in a hydroponic garden also require at least 8 hours of sunlight on a daily basis (in the absence of proper sunlight, farmers can use high-intensity sodium lamps). The water should be drained once every week (plant growth and yield can be affected by contaminated water), the entire system should be leached/flushed just before harvest. In certain hydroponic systems (Flood and Drain, NFT), adjusting the pH levels regularly is also important.

Note: Apart from the removal of chlorine, calibration for pH also becomes easier when the collected freshwater is allowed to rest for a day or two.

9. How does hydroponics help in better resource utilization and managing pollution?

   In the same space, the number of plants that can be grown by hydroponics is nearly four times more than what is possible with soil-based agriculture. The plants can be put in small pots or containers, put on a countertop – and connected to the nutrient solution tank below (the pots can be suspended in the water-based solution as well). In the traditional method, the minimum area requirement for growing plants would be a five-gallon (probably more) bucket. This opens up the possibility of more harvests and much higher yields from hydroponic farming (with the considerably faster plant growth also contributing to this). Soil farming can also pose serious environmental challenges, with water bodies being polluted by soil nutrients not used up by crops, and probable accumulation of salt in the underground water (salination). The runoff of chemical nutrients to lakes/rivers can lead to deoxygenation – putting the life of water animals in threat. Use of pesticides brings in risks of air pollution. In hydroponics, there is no soil, and no such potential environmental hazards. It’s a ‘green’ method!

Note: There are many areas with harsh climatic conditions, where soil maintenance becomes a huge concern for farmers. Hydroponic farming is a great option in such places. Weeding is yet another task that hydroponic farmers need not worry about.

     10. Are there any associated risks or challenges?

Hydroponics is a simple method of alternative farming (the most technical thing about it is probably its name!) – and there are not much in the way of risks in this system. However, growers have to make sure that the plants can access the nutrient solution at all times – otherwise, the roots can become too dry very quickly. In the ‘dripper’ or the ‘Food and Drain’ systems, special care has to be taken about the reliability of the alarms. Any malfunction in the latter can cause serious damages to the plant. In general, while the automated nature of plant feeding and growth has a host of advantages (higher yields, faster growth, better quality, optimal nutrient use, etc.) – but things can quickly go bad in the event of a lengthy mechanical failure. Hydroponic plants tend to be smaller in size (and with smaller, less complex roots) than plants grown in traditional soil fields.

Note: Hydroponics can be applied for both indoor and outdoor farming, including plant growing in greenhouses. The method is best suited for plants that have shallow root systems. A wide range of fruits, houseplants and veggies, right from spinach and herbs, to lettuce and radish, can be grown with hydroponic farming.

While hydroponics might seem to be a variant of organic farming at first, the two are actually entirely different methods. The former does not have any role for soil, while organic farming requires the conversion of nutrients by the soil (so that they can be absorbed by plant roots). In terms of nutritional values and ecological benefits too, hydroponics offer much greater benefits than conventional soil-based farming. The systems are easy to set up, making DIY hydroponics relatively simple too. For professional crop-growers as well as general gardening enthusiasts, it is now possible to grow healthy plants…without having to get their hands dirty!