THE GREENHOUSE EFFECT
The greenhouse is an area isolated from the rest of the environment by a transparent cover that allows maximum transmission of sunlight, through which the plants’ photosynthetic process takes place.
The radiation reaches the greenhouse directly from the sun and is diffused back from several reflecting celestial bodies throughout the heavens (clouds, dust etc.).
Not all the radiation that reaches the covering sheets reaches the plants. Depending on the properties of the cover material and the angle of ray’s impact on the cover, some of the radiation is bounced back into the sky, and some is absorbed in the material itself.
The light that passes into the greenhouse is absorbed in the plants, the soil, and parts of the structure itself and warms them (since the energy contained in the absorbed radiation turns to heat.) The air in the greenhouse also comes in contact with the heated areas, is heated by these, and the result is an increase in the general temperature in the greenhouse.
Covering materials in greenhouses usually block long-wave radiation (light emitted from bodies having low temperatures.) Therefore, the heat that is emitted from the heated areas is absorbed in the cover, causing it, in turn, to warm as well.
This conversion of energy from radiation to heat in a covered area is commonly called “the It should be remembered that the amount of energy available to the plants inside the greenhouse depends upon many variables:
First and foremost, the amount of solar energy outside: Outside energy is affected by geographical location (latitude), time of year, time of day, celestial brightness, etc.
Outside energy, upon entering the structures, is somewhat reduced due to the physical properties of the cover, the geometrical shape of the structure and its position in relation to the north (which determines the angle between sunlight and the cover surface, in turn affecting the transmitting radiation.) Add to that the mutual shading of the structure’s skeletal parts, shading from support systems that are installed above the plants and so forth (and therefore the amount of sunlight inside the structure will be lower than outside of it).
This process (the greenhouse effect) enables reaching a much higher temperature inside the greenhouse than outside of it. In a low-temperature environment, this will naturally be considered a positive thing. In areas where temperatures are sometimes lower than freezing point, plants in the open either die or yield nothing.
Cultivating under cover is therefore crucial to achieving any produce at all. However, when and where the outside temperature is naturally high (such as summer in Israel), the temperature inside the greenhouse will be extremely high. In order to avoid these extreme temperatures, special measures should be taken, such as ventilation, cooling, shading, etc.
In point of fact, cultivating crops in a greenhouse is far more complex. Aside from influences on the temperature, due to water vaporization from the plants, there is an increase in humidity compared to outside conditions. In this context, the increased humidity can be regarded as positive and beneficial within certain boundaries. However, if humidity rises too high and for long periods of time (when the greenhouse is closed and unventilated), there is a high probability of damages.
THE BENEFIT OF THE GREENHOUSE
Greenhouses are structures that enable the cultivation of fresh agricultural produce (such as fruits, vegetables, flowers, etc.) in qualities, quantities and time periods otherwise impossible to achieve when cultivating on the same region in the open.
The area of the greenhouse is separated from the outside environment by a transparent cover that lets sunlight through and provides a wide variety of services to the plants and to the farmer:
- Physical protection from natural phenomena, such as winds, rain, hail, snow etc.
- Protection from damage by animals, whether large or tiny, by not allowing them to come into contact with the plants.
- Efficient application of pesticides in a closed environment.
- The possibility of maintaining a climate different from the climate outside, in order to improve the growth conditions.
- Protection from rain, and maintaining control of irrigation and fertilization conditions.
- Allowing work and harvest in any kind of weather.
Depending on the natural environmental conditions, the type of crop, and the farmer’s requirements, different technical solutions can be found to achieve the same goal.
Therefore, tropical regions usually have many greenhouses whose main function is to provide physical protection for the crops – to protect the plants from winds and natural harms, to protect against rain in order to control the irrigation and fertilization routine, and sometimes in order to overcome diseases and pests.
These designated greenhouses are usually simple and cheap structures, covered in thin plastic sheets, with set ventilation openings and without unnecessary means of monitoring and control.
In areas where winters are cold and snowy, such as Europe, Canada or the US, or in areas that have a very cold winter and a very hot summer, like China or certain areas of Russia. Providing proper conditions for the plans throughout the year requires the use of more complex and sophisticated technological systems which are usually more expensive both in installation and in use. Such systems may be heating systems that consume large amounts of fuel during the winter, cooling systems that consume water and electricity, monitoring systems and more.
Providing one’s crops with optimal growth conditions is not always economically viable. Usually, realities on the ground require compromise solutions. Sometimes they compromise on the quality of their equipment, sometimes they avoid growing some crops part of the year. At times they install only some of the auxiliary systems, with an option to add more when money becomes available. Any combination is possible and probably already in effect somewhere.
What is Hydroponics?
Put simply, hydroponics is the science of growing plants without soil, also known as “soil-less culture”. The same natural elements necessary for plant growth in soils are used, with the advantage that plants are not restricted by weeds or soil-borne pests and diseases. Hydroponics employs technology that converts a greenhouse into a type of agricultural factory, with calculated processes and proprietary knowledge, resulting in predictable production schedules and quality output ? much like any other industry.
Hydroponic techniques, although use of the method is the latest trend, have been in use for centuries. The earliest known use of hydroponics are in the Hanging Gardens of Babylon, in the Floating Gardens of Kashmir and by the Aztec people of Mexico, who used rafts on shallow lakes to grow plants. Also, hieroglyphic records in Egypt dating back to several hundred years B.C. describe the growing of plants in water. More recently, mobile hydroponic farms had been used to feed soldiers during the Second World War in the South Pacific.
Today, hydroponics is beginning to play a more important role in the world’s agricultural production. Increasing populations, climatic changes, lack of water and poor water quality are all factors influencing the trend towards alternative methods of horticulture. Hydroponics enables many to have fresh food, rather than having to have it shipped in or stored for long periods. A prime example of this is on naval submarines, where hydroponics is used to supply the crew with fresh fruit and vegetables. Of wider benefit is the use of hydroponics in developing countries, where it provides intensive food production in areas of limited growth potential. The only restraints to a viable hydroponic system are the availability of water and nutrients. In areas where fresh water is not available, desalinated seawater can be used.
Hydroponic gardening has been used commercially since the 1970s, although it was not until recently that it has become more popular for the home grower. The demand in the community for environmentally-friendly products has been a major factor in the growth of this trend. By growing plants in a hydroponic system, growers know exactly what has gone into the plants and can ensure that no harmful pesticides have been used that could damage people?s health and the health of the environment.
How it Works
Hydroponics is a highly efficient method of growing plants. In soils, nutrients and water are randomly placed, and often plants need to expend a lot of energy to find the water and nutrients by growing roots to find them. By expending this energy, plant growth is not as fast as it could be. In a hydroponic garden, the nutrients and water are delivered straight to the plants roots, allowing the plants to grow faster, and allowing harvesting to be done sooner, simply because the plants direct more of their energy into growing above the ground, instead of under it.
Once a plant is established, it gives higher than average yields, whether being grown in a greenhouse, a backyard or a balcony. Also, hydroponics allows growers to increase plant growth per square meter, because the plants do not need to compete with weeds and each other for the food and water that is in soil, as food and water is delivered straight to them.
It is also very important to note that plants grown using hydroponics have the same physiology as plants grown in soil. Plants grown in a hydroponic system require the same nutrients as those grown in soil, though the content can be more accurately controlled. The basic difference between the two methods is the way in which nutrients and water are delivered to the plants.
In hydroponic systems, the nutrient salts are already refined and the plants do not need to wait for the nutrients to break down into their basic form. However, with soil-based agriculture, plants are fed nutrients via manures and composts which must break down into their basic form (nutrient salts) before the plants can use them.
Commercially, hydroponic systems often use artificial lighting. This can make the initial cost of a lighting system much more expensive, but is generally not the major hassle and ongoing expense growers may expect. If sunlight is readily available, then this is unnecessary
Among its advantages, hydroponic systems enable more efficient plant growth, using in some cases up to 95% less water than soil based horticulture. With many plants, hydroponics will result in a higher quality plant, and a higher yield.
Other advantages are as follows:
- Slightly denser planting, allowing greater use of available space
- Produce looks better and lasts longer
- Water stress in hot conditions is reduced
- Suited to areas with non-arable land
- Plants reach maturity in much shorter time
- Soil pests and diseases are significantly reduced
- Hydroponic gardens require less maintenance
Although hydroponics is still less common than other methods of growing plants, it is an efficient and economical option and is certainly no more difficult than growing plants in soil. Top Greenhouses has vast experience with hydroponics and proposes its use to customers in a variety of circumstances, when it presents an advantage over other cultivation methods.
Greenhouse Control Systems are dedicated, computer-operated systems which are indispensible for the control and monitoring of climate, irrigation and fertilization. By controlling these factors, growers are able to maximize production and quality, while planning and managing costs, cultivation, harvests and pricing with a high level of accuracy.
Climate Control – Greenhouse accessories such as windows, curtains, fans, heating / cooling systems, and sprinkler systems are operated according to user-defined specifications to control the climate of a greenhouse, based on the optimal conditions for the produce being cultivated. System parameters include temperature, humidity, light and wind.
Irrigation Control – Considerations for controlling irrigation are managed for each product being grown and each plot cultivated. The system manages irrigation schedules and quantities, as well as water density in soil and other parameters. The irrigation control also implements the fertilization program, while checking EC, pH and other elements involved.
Fertigation Control – To implement fertilization, in conjunction with the irrigation program, there are diferent types of fertigation machines, Mixer, Bypass and Online Fertigation Machines – All three machines ensure the right proportions between irrigation water and the amount of fertilizer required by each crop. A Spirit Controllersupervises accuracy.
Heating Control – In cold contries it is needed to heat the greenhouse in order to be able to grow all year arround, there are many types of heating systems, based on hot water or hot air.
Light Control – Supplying light to the plants is a demanding task, using ligt supplement is an option that may need to be evaluated.
Irrigation and Fertilization Turnkey Projects – Top Greenhouses plans and implements turnkey irrigation and fertilization projects, starting from pumping the water from reservoirs and up to the last dripper. This includes engineering drawings, supply of all materials and systems, installation and post-project consultations.