In this age and time when the cost of living is on the upswing, characterized by rising inflation, sundry taxes, unemployment, and government’s increasing failure to protect the citizens’ lives and property, growing at least part of one’s food needs has become a way forward.
Not only does agriculture come in as a means of self-reliance, making good use of modern methods goes a long way to ensuring food security. One of these methods is growing plants in the absence of soil, available in vast farmlands.
This becomes more helpful for the urban dwellers. So, what is hydroponics all about?
HYDROPONICS
According to Wikipedia, the Free Encyclopedia, Hydroponics is a subset of hydro-culture. It is a method of growing plants without soil, but instead using mineral nutrient solutions in a water solvent. Terrestrial plants may be grown with only their roots exposed to the nutritious liquid.
Alternatively, the roots may be physically supported by an inert medium such as perlite, gravel. Despite inert media, roots can cause changes of the rhizosphere pH and root exudates (chemicals released by roots) can impact the rhizosphere biology.
The rhizosphere simply means “the region of soil in the vicinity of plant roots in which the chemistry and microbiology is influenced by their growth, respiration, and nutrient exchange”.
The nutrients used in hydroponic systems can come from an array of different sources, including (but not limited to) fish excrement, duck manure, purchased chemical fertilisers, or artificial nutrient solutions.
Plants commonly grown hydroponically on inert media include tomatoes, peppers, cucumbers, lettuces, marijuana, and model plants like Arabidopsis thaliana.
Hydroponics offer many advantages. One of such is a decrease in water usage for agriculture. To grow 1 kilogram of tomatoes in Intensive farming normally requires 400 liters of water. But in hydroponics 70 liters of water and only 20 liters of water for aeroponics.
HISTORY
The earliest published work on growing terrestrial plants without soil was the 1627 book Sylva Sylvarum or ‘A Natural History’ by Francis Bacon, printed a year after his death. Water culture became a popular research technique after that. In 1699 John Woodward found that plants in less-pure water sources grew better than plants in distilled water.
By 1842, a list of nine elements believed to be essential for plant growth had been compiled, and the discoveries of German botanists Julius von Sachs and Wilhelm Knop, in the years 1859–1875, led to a development of the technique of soilless cultivation.
Growth of terrestrial plants without soil in mineral nutrient solutions was called ‘solution culture’. It quickly became a standard research and teaching technique and is still widely used.
In 1929, William Frederick Gericke (August 30, 1882 – September 29, 1970) of the University of California at Berkeley began publicly promoting that solution culture be used for agricultural crop production. He introduced the term hydroponics, water culture, in 1937, proposed to him by W. A. Setchell, a psychologist with an extensive education in the classics.
Between then and now, some progress has been made towards popularizing hydroponics. In fact, as at 2017, Canada had hundreds of acres of large-scale commercial hydroponic greenhouses, producing tomatoes, peppers and cucumbers.Due to technological advancements the global hydroponics market is forecast to grow from US$226.45 million in 2016 to US$724.87 million by 2023.
TECHNIQUES
There are two main variations for each medium: sub-irrigation and top irrigation. For all techniques, most hydroponic reservoirs are now built of plastic, but other materials have been used including concrete, glass, metal, vegetable solids, and wood. The containers should exclude light to prevent algae and fungal growth in the nutrient solution.
In static solution culture, plants are grown in containers of nutrient solution, such as glass Mason jars (typically, in-home applications), pots, buckets, tubs, or tanks. The solution is usually gently aerated (by allowing in air) but may be un-aerated. If un-aerated, the solution level is kept low enough that enough roots are above the solution so they get adequate oxygen.
A hole is cut (or drilled) in the top of the reservoir for each plant; if it a jar or tub, it may be its lid, but otherwise, cardboard, foil, paper, wood or metal may be put on top. A single reservoir can be dedicated to a single plant, or to various plants. Reservoir size can be increased as plant size increases.
A home-made system can be constructed from food containers or glass canning jars with aeration provided by an aquarium pump, aquarium airline tubing and aquarium valves. Clear containers are covered with aluminium foil, butcher paper, black plastic, or other material to exclude light, thus helping to eliminate the formation of algae.
The nutrient solution is changed either on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an electrical conductivity meter.
In raft solution culture, plants are placed in a sheet of buoyant plastic that is floated on the surface of the nutrient solution. That way, the solution level never drops below the roots.
In continuous-flow solution culture, the nutrient solution constantly flows past the roots. It is much easier to automate than the static solution culture because sampling and adjustments to the temperature and nutrient concentrations can be made in a large storage tank that has potential to serve thousands of plants.
A popular variation is the nutrient film technique or NFT, whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is re-circulated past the bare roots of plants. This is done in a watertight thick root mat.
Subsequent to this, an abundant supply of oxygen is provided to the roots of the plants. A properly designed NFT system is based on using the right channel slope, the right flow rate, and the right channel length.
The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen, and nutrients.
In all other forms of production, there is a conflict between the supply of these requirements, since excessive or deficient amounts of one results in an imbalance of one or both of the others. The result of these advantages is that higher yields of high-quality produce are obtained over an extended period of cropping. A downside of NFT is that it has very little buffering against interruptions in the flow (e.g., power outages).
The same design characteristics apply to all conventional NFT systems. While slopes along channels of 1:100 have been recommended, in practice it is difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without ponding in locally depressed areas.
As a general guide, flow rates for each gully should be one liter per minute. At planting, rates may be half this and the upper limit of 2 L/min appears about the maximum. Flow rates beyond these extremes are often associated with nutritional problems.
On rapidly growing crops, tests have indicated that, while oxygen levels remain adequate, nitrogen may be depleted over the length of the gully. As a consequence, channel length should not exceed 10–15 meters.
More urban dwellers should attend courses on hydroponics for their own good.
Ayo OyozeBaje
