The Seven Wonders of the Ancient World have always captured the imagination of people all over the world. It would not be an exaggeration to say that the Hanging Gardens of Babylon have left many wondering about the mystery of how the gardens were hanging? Indeed, science had made great advances even in ancient times and the Hanging Gardens were testimony to it. It is widely believed that hydroponics was the technique used for the construction of these gardens.Hydroponics – the science of growing plants without using soil, is gaining popularity the world over. This lesson serves as a starting point for enthusiasts looking to learn about hydroponics.
The roots of Hydroponics can be traced back to the Roman Empire during 1st century when cucumbers were grown during the off-season using this technique. This technique was mostly forgotten during the subsequent centuries and was again revitalized in the 1920s due to soil related problems in greenhouses. The term “Hydroponics” was coined by Dr. W F Gericke in 1936 for the process of growth of vegetative as well as ornamental plants in a liquid nutrient medium. It is derived from the Greek words “hydro” meaning water and “ponos” meaning work/labour.
Hydroponics is the science of growing plants without the medium commonly used i.e it is a soil-less culture of plants. But soil is the medium that carries all the nutrients of plant growth! So, in hydroponics, soil is replaced by another medium and what better than water as the choice of medium. Though, the plant roots grow like they normally do in soil, balanced amount of nutrients are dissolved in the water.When grown in soil, an enormous amount of energy is spent by the plant to develop a root system that can extract sufficient nutrition and moisture from the soil. In hydroponics, the readily available nutrients in the water, helps the plant in conserving energy and channelizing it towards the growth of the plant thus, resulting in greater and faster yield.
The natural environment consists of elements that are critical to plant growth – Carbon, Hydrogen, Oxygen and Nitrogen which are present in their molecular or compound state.
comprises nearly 50% of a plant’s dry weight. It occurs in the cell walls of
plants as well as in chlorophyll which is necessary for photosynthesis.
Hydrogen – is mainly obtained from water absorbed by plants. It is important for cation exchange and is also important for formation of sugars and starches. Hydrogen in water form helps keep the plant structure rigid by maintaining the turgor pressure.
Oxygen – is
essential for the respiration process and helps in plant metabolism. It is
needed to form sugars, starches and cellulose.
Macro-nutrients and micro-nutrients are absorbed in required quantities by plants and each of these nutrients have a key role to play in plant nutrition.
Some of the macro-nutrients are:
Phosporus – is a key ingredient of sugar, phosphate and ATP. It is essential for flower, fruit production and growth of root system.
Potassium – is required for protein synthesis. Manufacture of sugar and starch also requires potassium.
Light plays an important role in plant growth in nature and depending on the availability of sunlight, some plants tend to grow only in specific geographic areas. Chlorophyll present in leaf cells gets activated when it absorbs sunlight and aids the starting of photosynthesis, the two-step process that results in formation of carbohydrates. Light impacts plants in multiple ways:
Life Cycle: The plant life cycle depends on the amount of sunlight varying with seasonal changes. Decreased sunlight results in lesser amount of chlorophyll produced and thus, lesser food to power plant growth.Foliage: An easy measure of plant growth is the increase in its stems and leaves. Absence of sufficient sunlight is the reason for stunted plant growth and sometimes no flowering as well.
Fruiting: Fruit trees require a high amount of sunlight for fruit formation. Depending on other factors such as space between trees, type of fruit etc. the number of hours of sunlight required daily varies.
Geographic presence: Light determines the flora of a geographic region. A region such as the rain forests which receives abundant sunshine coupled with other growth factors, displays the most diverse variety of plants.
All light is not uniform and the variation comes from the quality of light or its source or even the intensity. Light rays comprise of a spectrum of various wavelengths – VIBGYOR. Generally the green and yellow wavelengths are deflected and the other wavelengths get absorbed. The most important amongst these wavelengths are blue – which encourages leaf growth and red – which helps during flowering stages.
Sources of light can be either natural or artificial ones, such as fluorescent bulbs or incandescent bulbs. Natural light is the best option considering that it provides a whole spectrum of wavelengths and has a balance of red and blue light. Amongst artificial lights incandescent bulbs have a set back – they emit excessive heat and lack the most beneficial wavelengths desirable for plant growth.
Light intensity refers to the amount of light received. Different plants require varied lengths of daylight hours, commonly referred to as photoperiod. Photoperiod induces and affects flowering.
From the study of nutrients required by plants, it is understood that the nutrient solution used for hydroponics should have a balanced quantity of all macro and micro-nutrients.
The quality of water is important as it forms the base of the nutrient solution. The Total Dissolved Solids in water should not be greater than 100 ppm and in case the TDS measure is above 300 ppm, the water needs to undergo reverse osmosis.
The pH levels of the nutrient solution needs to be checked on a daily basis especially for smaller reservoirs. If the pH is not balanced, ie. if it is too high (alkaline) or too low (acidic), it can adversely affect the nutrient absorption through the plant roots.
The nutrient solution also needs to be changed after every two-to-four days as absorption of nutrients by plants may cause imbalances in the nutrient solution.
In order to anchor the plants in a hydroponic system, a medium is required. The root system of the plant grows through this medium keeping it anchored. Some of the commonly used Hydroponic mediums are:
Rockwool: is made from rock which is melted and spun into thin long fibers like cotton-candy. These fibres are pressed into cubes of various sizes to obtain the desired size medium. Though as a growing medium, rockwool is beneficial, it has also some disadvantages – not easy to dispose as it does not get decomposed, have high pH and have potentially harmful characteristics for users.
Perlite & Vermiculite: Perlite is made from volcanic rock which on heating expands into a white coloured, light weight material. It holds lesser amount of water and because it is light weight it needs to be used along with vermiculite. Vermiculite is also a super-heated mineral but one that has properties that compliment perlite as it has water retention ability.
Coconut Fibre: is made from the coconut husks. Coconut husks play an important role biologically because of which they are considered amongst the favourite mediums. Fruit of the coconut tree,which generally grow in the tropical regions, many a times falls in the ocean water and the coconut husk protects the seed and salt from sun and saline water damage. The husk acts as a hormone-rich and fungus free growing medium for the germination of the seed and thus, for new plant formation.Clay Pellets: are made by baking clay in a kiln. Tiny air pockets inside the pellets make them very lightweight. Since their water retention capacity is low, they are preferably used in those hydroponic systems which have frequent watering cycles. Clay pellets are generally used in combination with other mediums to enhance its oxygen retention. Clay pellets are not cost effective but make up for it by being reusable.
There are various types of hydroponic systems with different levels of complexity.
Wick System: This system is the simplest type of hydroponic system. The nutrient solution is derived into the growing medium from the nutrient rich reservoir with a wick made of nylon. A variety of growing medium can be used in this system such as perlite, vermiculite, coconut fiber etc. As there is no pump or timer involved, this system is economically viable for first time users. The drawback of this system is that larger plants draw the nutrient solution at a speed greater than the wick’s ability to supply.
Water Culture: The water culture system is another simple hydroponic system that is great for growing high water consumption plants such as lettuce. A platform made of Styrofoam is used which floats on the nutrient solution. Air is pumped into an air stone placed at the bottom of the system using an air pump. The air stone generates bubbles the nutrient solution in the nutrient solution and supplies oxygen to the plant roots.
Ebb & Flow System: In this method, a growing medium such as rockwool, perlite etc. needs to be used to anchor the plant and provide stability to the plant. A tray is required to hold the growth medium and a compartment is placed below to hold the nutrient solution. The growth tray is flooded with nutrient solution alternating with outflow of the excess nutrient solution back into the compartment. A submerged pump needs to be used along with a timer to ensure that the alternate cycle of inflow and outflow of nutrient solution happens. As the timer turns on, so does the pump, facilitating the flow of nutrient solution into the growth tray and vice versa when the timer shuts off. Depending on factors such as type of plant, temperature and humidity, the timer is set for different times of the day. This type of system is suitable for usage in smaller set-ups such as homes.
Nutrient Film Technique: The nutrient solution pumped into the growing tray, which is generally a tube, flows over the plant roots and then flows back into the nutrient reservoir. No growing medium is required in this system. This eliminates the cost involved for replacement of growing mediums required after every crop for other hydroponic systems. Small plastic baskets support the plant with the roots dangling in the tube in which the nutrient solution flows. Power outages and pump failure are a cause of great concern for such systems as the root tips may dry out if the nutrient solution flow is not maintained.
Top Feed Drip System: This system is similar to the Ebb and Flow system. Instead of the nutrient solution flooding the growth tray, smaller tubes are used to ensure flow of nutrients to each individual plant. This system is especially helpful for those plants which do not have a root network strong enough to absorb nutrients properly.
Like every other technology, Hydroponics has its fair share of pros and cons. Thankfully for enthusiasts, the good outweighs the bad. Let us first list down the pros:
Conservation of water: Normal growth of plants in soil uses 10 times the water as compared to hydroponic systems. Thus, hydroponic systems are ideal for water conservation practices and are specifically very useful for plant growth in arid regions.
Better Plant Growth: When plants are grown in soil, there are various
factors that affect their growth. Poor soil texture and unfavourable pH of soil
can be an important determinant as also competition from other plants for
absorbing the plant nutrition. These problems are eliminated in hydroponic
systems where the nutrients are provided in balanced proportions and thus,
there is no inter-plant competition. The yield in hydroponic systems is almost
5 times as much as that of traditional cultivation.
Better Utilization of Space: Hydroponic systems can be set up even on roof-tops and enable better utilization of space in places where space is a constraint.
Lesser Efforts/Time spent on Plant care: In traditional plant growth, lots of efforts need to be put from the farmer’s/gardener’s end such as watering, tilling, removal of weeds etc. These efforts are unnecessary for plant growth using hydroponic systems.
Reduction in Pest and Disease Problems: Plant growth is severely affected by pests which cause diseases in plants. These are mainly because of micro-organisms present in the soil some of which may be harmful and may cause diseases. Since soil is not used, chances of these harmful microbial interactions are also minimized.Much lower pollution: Agricultural run-offs containing traces of pesticides is amongst the most harmful pollutants that has negative impact on flora and fauna of the universe. When fertilizer rich water run-off reaches any water body, it results in heavy growth of algae. Most hydroponic systems use a system wherein the water is rotated in the entire system and hence, water run-offs containing fertilizers is minimized. The disadvantages are:
Cost: The establishment cost of hydroponic systems is on the higher side. A suitable hydroponic system complete with water transmission channels supported by a motor that can rotate the water needs some good amount of initial investment to get the system up and running.
No Power, no nutrition: Power outage for longer periods can be harmful as the plants would be devoid of nutrients due to absence of water circulation.Knowledege: A hydroponics enthusiast needs a lot of technical knowledge to set up a hydroponics system,with the right nutrients and plants and in order to maintain it well in the long term.