Lettuce production in the town centre of Bangkok

In many ways the Thai lettuce nursery ACK Hydro Farm is a special company. Its location for example in the centre of Bangkok is certainly no place one would expect a high-tech nursery to be in Lettuce ACK is also an exceptional case and the Thai people are eating more and more of this vegetable.

When the taxi comes closer to ACK Hydro Farm in On Nuch road in Bangkok, it is hard to believe that the address is correct. With the area being dominated by shops, bank, bats and hight-rise flats, it is certainly not the surrounding where you would expect a lettuce nursery to be. But once the gate of the ACK has been passed, aagain it is hard to imagine that this nursery is located in a town; the noise from the streets has gone, the main sound come from the fans which have to keep the greenhouses cool.

The garden centre is still there, but smaller, since 80% of the 1 ha plot is used for the lettuce production together with the packing house where part of the lettuce is pre packed for ready made supermarket products.

The hot climate is probably also an important reasen why lettuce is traditionally not common in the Thai kitchen. But with the increasing number of foreigners in the thai capital there is also a growing nee for dishes other main consumers of the lettuce from ACK, but those days are over, as Thai people are becoming more interested in different food and have discovered the sensation that the crispy lettuce leaves can give.

Safety and hygiene are important aspects at Hydroponics Growing for wich reason the Agriculture company works according to the ISO 9001:2000, GMP and HACCP guidelines.(Farm Visit to Thailand:Fruit-Veg Tech)

Types of hydroponics are solution culture and medium culture

The two main types of hydroponics are solution culture and medium culture. Solution culture does not use a solid medium for the roots, just the nutrient solution. The three main types of solution culture are static solution culture, continuous flow solution culture and aeroponics. The medium culture method has a solid medium for the roots and is named for the type of medium, e.g. sand culture, gravel culture or rockwool culture. There are two main variations for each medium, subirrigation 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 growth in the nutrient solution.

Static solution culture
In static solution culture, plants are grown in containers of nutrient solution, such as glass Mason jars (typically in-home applications), plastic buckets, tubs or tanks. The solution is usually gently aerated but may be unaerated. If unaerated, the solution level is kept low enough that enough roots are above the solution so they get adequate oxygen. A hole is cut in the lid of the reservoir for each plant. There can be one to many plants per reservoir. Reservoir size can be increased as plant size increases. A homemade system can be constructed from plastic 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 either changed on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an electrical conductivity meter. Whenever the solution is depleted below a certain level, either water or fresh nutrient solution is added. A Mariotte's bottle can be used to automatically maintain the solution level. 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.

Continuous flow solution culture
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 serves potentially 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 recirculated past the bare roots of plants in a watertight gully, also known as channels. Ideally, the depth of the recirculating stream should be very shallow, little more than a film of water, hence the name 'nutrient film'. This ensures that the thick root mat, which develops in the bottom of the channel, has an upper surface which, although moist, is in the air. Subsequently, there is an abundant supply of oxygen 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. NFT, because of its design, provides a system where all three requirements for healthy plant growth can be met at the same time, providing the simple concept of NFT is always remembered and practised. 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, but overall, it is probably one of the more productive techniques.
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. Consequently, it is recommended that slopes of 1:30 to 1:40 are used. This allows for minor irregularities in the surface but, even with these slopes, ponding and waterlogging may occur. The slope may be provided by the floor, or benches or racks may hold the channels and provide the required slope. Both methods are used and depend on local requirements, often determined by the site and crop requirements.
As a general guide, flow rates for each gully should be 1 liter per minute. At planting, rates may be half this and the upper limit of 2L/min appears about the maximum. Flow rates beyond these extremes are often associated with nutritional problems. Depressed growth rates of many crops have been observed when channels exceed 12 metres in length. On rapidly growing crops, tests have indicated that, while oxygen levels remain adequate, nitrogen may be depleted over the length of the gully. Consequently, channel length should not exceed 10-15 metres. In situations where this is not possible, the reductions in growth can be eliminated by placing another nutrient feed half way along the gully and reducing flow rates to 1L/min through each outlet.

What Is Aeroponics?
Aeroponics is an application of hydroponics without a growing medium, although a small amount may be used to germinate the seed or root a cutting. Plant roots are suspended mid-air inside a chamber kept at a 100% humidity level and fed with a fine spray of nutrient solution. This mid-air feeding allows the roots to absorb much needed oxygen, thereby increasing metabolism and rate of growth reportedly up to 10 times of that in soil. And there is nearly no water loss due to evaporation.

Passive subirrigation

Passive subirrigation, also known as passive hydroponics or semi-hydroponics, is a method where plants are grown in an inert porous medium that transports water and fertilizer to the roots by capillary action from a separate reservoir as necessary, reducing labor and providing a constant supply of water to the roots. In the simplest method, the pot sits in a shallow solution of fertilizer and water or on a capillary mat saturated with nutrient solution. The various hydroponic media available, such as expanded clay and coconut husk, contain more air space than more traditional potting mixes, delivering increased oxygen to the roots, which is important in epiphytic plants such as orchids and bromeliads, whose roots are exposed to the air in nature. Additional advantages of passive hydroponics are the reduction of root rot and the additional ambient humidity provided through evaporation.

Ebb and flow / Flood and drain subirrigation

In its simplest form, there is a tray above a reservoir of nutrient solution. The tray is either filled with growing medium (clay granules being the most common) and planted directly, or pots of medium stand in the tray. At regular intervals, a simple timer causes a pump to fill the upper tray with nutrient solution, after which the solution drains back down into the reservoir. This keeps the medium regularly flushed with nutrients and air. Once the upper tray fills past the drain stop it begins recirculating the water until the pump is turned off and the water in the upper tray drains back into the reservoir.

Raft System

The hydroponic lettuce raft system is easy to assemble from inexpensive, household parts. The Hydroponic raft system operates by floating plants above an Oxygen infused bath of nutrients into which the roots grow. The hydroponic raft system is suitable for short-stature plants such as lettuces, kitchen herbs and other small varieties. ((Wikipedia).

How-To Hydroponics system plans and hydroponic gardening guide

How-To Hydroponics system plans and hydroponic gardening guide details the assembly and operation of do-it-yourself hydro and aeroponic systems and teaches.

What Is Hydroponics?
In Latin, the word hydroponics means literally "water working." Hydroponics is the practice of growing plants in either a bath or flow of highly oxygenated, nutrient enriched water. In soil, biological decomposition breaks down organic matter into the basic nutrient salts that plants feed on. Water dissolves these salts and allows uptake by the roots. For a plant to receive a well balanced diet, everything in the soil must be in perfect balance. Rarely, if ever, can you find such ideal conditions in soil due to the lack of organic matter left behind on the surface, contamination and biological imbalances. With hydroponics, water is enriched with these very same nutrient salts, creating a hydroponic nutrient solution that is perfectly balanced. And since this hydroponic nutrient solution is contained, it does not harm our environment as does runoff from fertilized soil. Additionally, very little water is lost to evaporation in a hydroponic system, owing to its application in drought stricken areas. To support the plants in a hydroponic system, an inert soil-free medium like fiber, sand or stone, may be used to anchor the roots. These hydroponic mediums are designed to be very porous for excellent retention of air and water that's necessary for a healthy plant - roots need to breathe too! In addition to a perfectly balanced diet, hydroponic plants have their food and water delivered directly to their roots. This way, the energy normally used to develop long roots can be redirected to growing more plant, which is a great benefit indeed! With the proper exposure to natural sunlight or supplemental grow lights, your hydroponic plants .

Hydroponics (from the Greek words hydro water and ponos labor) is a method of growing plants using mineral nutrient solutions, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, or Rockwool . Plant physiology researchers discovered in the 19th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics. Hydroponics is also a standard technique in biology research and teaching (Wikipedia).

History

The study of crop nutrition began thousands of years ago. Ancient history tells us that various experiments were undertaken by Theophrastus (372-287 B.C.), while several writings of Dioscorides on botany dating from the first century A.D., are still in existence.[1]
The earliest published work on growing terrestrial plants without soil was the 1627 book, Sylva Sylvarum by Sir Francis Bacon, printed a year after his death. Water culture became a popular research technique after that. In 1699, John Woodward published his water culture experiments with spearmint. He 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 to plant growth had been made out, and the discoveries of the German botanists, Julius von Sachs and Wilhelm Knop, in the years 1859-65, resulted in a development of the technique of soilless cultivation.[1] 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 today. Solution culture is now considered a type of hydroponics where there is no inert medium.
In 1929, Professor William Frederick Gericke of the University of California at Berkeley began publicly promoting that solution culture be used for agricultural crop production. He first termed it aquaculture but later found that aquaculture was already applied to culture of aquatic organisms. Gericke created a sensation by growing tomato vines twenty-five feet high in his back yard in mineral nutrient solutions rather than soil. By analogy with the ancient Greek term for agriculture, geoponics, the science of cultivating the earth, Gericke introduced the term hydroponics in 1937 (although he asserts that the term was suggested by Dr. W. A. Setchell, of the University of California) for the culture of plants in water (from the Greek hydros, "water", and ponos, "labor").[1]
Reports of Gericke's work and his claims that hydroponics would revolutionize plant agriculture prompted a huge number of requests for further information. Gericke refused to reveal his secrets claiming he had done the work at home on his own time. This refusal eventually resulted in his leaving the University of California. In 1940, he wrote the book, Complete Guide to Soilless Gardening.
Two other plant nutritionists at the University of California were asked to research Gericke's claims. Dennis R. Hoagland and Daniel I. Arnon wrote a classic 1938 agricultural bulletin, The Water Culture Method for Growing Plants Without Soil,[2] debunking the exaggerated claims made about hydroponics. Hoagland and Arnon found that hydroponic crop yields were no better than crop yields with good quality soils. Crop yields were ultimately limited by factors other than mineral nutrients, especially light. This research, however, overlooked the fact that hydroponics has other advantages including the fact that the roots of the plant have constant access to oxygen and that the plants have access to as much or as little water as they need. This is important as one of the most common errors when growing is over- and under- watering; and hydroponics prevents this from occurring as large amounts of water can be made available to the plant and any water not used, drained away, recirculated, or actively aerated, eliminating anoxic conditions which drown root systems in soil. In soil, a grower needs to be very experienced to know exactly how much water to feed the plant. Too much and the plant will not be able to access oxygen; too little and the plant will lose the ability to transport nutrients, which are typically moved into the roots while in solution.
These two researchers developed several formulas for mineral nutrient solutions, known as Hoagland solutions. Modified Hoagland solutions are still used today.
One of the early successes of hydroponics occurred on Wake Island, a rocky atoll in the Pacific Ocean used as a refueling stop for Pan American Airlines. Hydroponics was used there in the 1930s to grow vegetables for the passengers. Hydroponics was a necessity on Wake Island because there was no soil, and it was prohibitively expensive to airlift in fresh vegetables.
In the 1960s, Allen Cooper of England developed the Nutrient film technique. The Land Pavilion at Walt Disney World's EPCOT Center opened in 1982 and prominently features a variety of hydroponic techniques. In recent decades, NASA has done extensive hydroponic research for their Controlled Ecological Life Support System or CELSS. Hydroponics intended to take place on Mars are using LED lighting to grow in different color spectrum with much less heat.
In 1978, hydroponics pioneer Dr. Howard Resh published the first edition of his book "Hydroponics Food Production." This book (now updated) spurred what has become known as the 3-part base nutrients formula that is still a major component of today's hydroponics gardening. Resh later went on to publish other books, and is currently in charge of a highly advanced hydroponics research and production facility in the Caribbean.(Wikipedia)