**5. Supplemental carbon dioxide in vegetable production in completely controlled environment and in the greenhouses with LED lightning installation**

Carbon dioxide (CO2) gas is the essential component for the process of photosynthesis, and the plants uptake it through their stomata on the leaves.

*Sustainable Crop Production*

mately 18 hours and 6 hours plants are in the dark.

wavelength spectrum (IR—infrared radiation).

ible range will better meet the needs of the plant.

increased sugar content, and higher yield.

flowering, and fruit production, and chlorophyll production.

intense photosynthesis.

In this way, it is possible to grow vegetables in the greenhouses without natural daylight but with the application of the suitable LED lighting (depending on the crops variety, its edible parts, growing requirements and other) and other controlled climatic conditions for optimal plant growth. LED lighting lasts approxi-

The suitable light quality in the greenhouses actually refers to the wavelengths (colors) that are efficient in inducing photosynthesis in plants and other growing processes. The light wavelengths are expressed in nanometers (nm). The visible spectrum wavelengths range from about 390 to 760 nm, which is only a small portion of the sunlight (radiation) electromagnetic spectrum. The visible light consists of: violet (380–430 nm), blue (430–500 nm), green (500–570 nm), yellow (570–590 nm), orange (590–630 nm), and red light (630–760 nm). The visible light range mostly corresponds to the Photosynthetically Active Radiation (PAR) from about 400 to 700 nm. The stated wavelengths have the right amount of energy for the biochemical processes, while their ratio in the available light is of crucial importance for determining the quality of light. About half of the sunlight energy participates in the photosynthetic processes. The rest of the energy comes from the sunlight short wavelength spectrum (UV—ultraviolet radiation) and sunlight long

Blue section of the spectrum, also known as cool light, induces these wavelengths that encourage vegetative and leaf growth through strong root growth and

Red section of the spectrum induces stem growth, tuber and bulb formation,

Far-red light may cause plants to stretch (elongate) and may trigger flowering in some long-day plants. The plants are exposed more to the far-red than to the red light, which may become a problem with the greenhouse vegetable crop production due to possible shading (for whatever reason) or due to the reduced plants vegetative space. Green and yellow sections of the spectrum that reach the plants are reflected, thus giving them their green color. Most of the absorbed sunlight wavelength belongs to the blue and red range of the spectrum. However, the recent studies have shown that plants do also absorb some green and yellow light, using it in the process of photosynthesis [4]. Generally, a light source that provides light in the entire vis-

For the time being, in the greenhouse vegetable crops growing practice, the high-pressure sodium (HPS) lamps are used, but also the LED lamps are gaining (**Figure 1**) an increasing significance in the plastic and glass greenhouses and in special chambers vegetable production. Also, in The Netherlands, the latest studies at the Wageningen and Maastricht universities research centers have their guidelines for greenhouse lighting with little or no natural daylight for special feature vegetable crops growing—increased vitamin C content, reduced nitrates content,

With red, white, and far red light, it is possible to prepare ideal light recipe for particular vegetable species and improve process of photosynthesis and production of assimilates which empower plants. The most important is how plants response on various recipes. So, plants become more resistant toward unfavorable conditions for its growth and toward diseases. In case of adding combination of red, blue, and far red light to combination of red, white, and far red light, it is possible to reach more

**4. Light quality in supplemental lighting in vegetable growing in** 

**completely controlled environment without daylight**

**308**

#### *Sustainable Crop Production*

Photosynthesis is a chemical process occurring in plants in which the light energy is used to convert carbon dioxide into water and sugars (carbohydrates) and oxygen (O2) gas. The sugars in plants, obtained in the process of photosynthesis, are then used for the plant development and growth through the process of respiration.

In the objects with LED lightening and completely controlled environment, without daylight, enrichment of the air with CO2 is necessary because of process of photosynthesis and crop productivity. Due to lack of sun light, in such objects is very important to define right amount of CO2.

In the air (outside the greenhouse), there is about 400 ppm of carbon dioxide. The CO2 concentration is increased when coal, natural gas, oil, and kerosene are burnt. Inside the greenhouse, the amount of CO2 may be significantly depleted as plants use it intensively in the process of photosynthesis (**Figure 2**; [4]), which may lead to a decreased crops productivity or yield. For that reason, "CO2 fertilization" or "CO2 enrichment" is a standard practice in modern greenhouses.

Since there is about 500 times more oxygen in the air than carbon dioxide [4], it makes sense to increase the CO2 concentrations in the greenhouse (particularly in highly equipped glasshouses). It has a positive effect on the oxygen-carbon dioxide ratio. The photosynthesis is higher by 30–50% at CO2 concentrations of about 1000 ppm, regardless of the amount of light.

The increased concentrations of carbon dioxide are good as long as they do not limit the process of photosynthesis. Photosynthesis depends on light, temperature, air humidity, and carbon dioxide contents in the greenhouse. There is often a question of what is the optimal concentration, but it is hard to give a correct answer to it as the process of photosynthesis does not depend solely on CO2. Also, a point should be made that climatic factors affect the stomatal opening mechanism (through which the plants uptake CO2). Generally, a small increase in the plant photosynthesis process may be achieved at 1000–1200 ppm, but then, there is also an increased possibility of damage to the crops. One experiment done on eggplant crops showed that the first damage to the plants occurred at a constant CO2 level of 800 ppm [4]. Quite often, the intensity of the photosynthesis may be higher at lower doses of carbon dioxide and higher intensity of light, and the other way around.

Supplementing the greenhouse air with carbon dioxide may not be necessary at all as long as the processes of the crops development and growth are quite satisfactory for the vegetable grower. Also, in a case of intensive greenhouse ventilation, the carbon dioxide concentration may drop below a level that is necessary for the normal photosynthesis process, so increasing the CO2 concentration may not be an economical measure (unless the greenhouse ventilation rate is lowered).

If the crops quality and production are below the satisfactory level, however, carbon dioxide supplementing should be the next measure. Generally, the production period from late autumn to early spring increases the potential need for CO2 supplementing the greenhouse air, which actually corresponds to a lower ventilation rate due to low outdoor temperatures.

**311**

*Urban Horticulture and Its Modernization by Using LED Lightning in Indoors Vegetable…*

Normal ventilation provides an amount of carbon dioxide that is similar to its levels in the outdoor air (350–400 ppm). But then, frequent ventilation in the greenhouse is not desirable, so that CO2 supplementing has long been a common practice in vegetable crops growing. The necessary greenhouse carbon dioxide concentration is determined upon the type of the crops grown in the greenhouse, the greenhouse total volume and ventilation, lighting, temperature, air humidity,

Since carbon dioxide is one of the products of burning (e.g., fuel for greenhouse heating system), this segment of the heating process can be used for supplementing the greenhouse air. There are various ways of extracting carbon dioxide from other products of burning (fuel), so that the CO2 from the boiler room can be dosed and

Also, pure carbon dioxide can be used, which is delivered to growers in special tanks, in liquid form and then can be converted into gas and distributed in the greenhouse. This way of supplementing the CO2 has become increasingly popular as it eliminates any potential damage to the crops, allows control of other greenhouse climatic conditions that regulate the process of photosynthesis and crops productivity, provides easy control of the carbon dioxide levels, and is more flexible for

One disadvantage of the liquid CO2 is that it is usually more expensive than that

Also, it would be advisable to install a proper system that registers the CO2 concentration and then distributes it in the greenhouse. Such a system, like in other greenhouse installation operations, has corresponding sensors that are linked to a special computer software that registers, monitors, and controls all the greenhouse environment parameters. In this way, it is possible to detect a cause of each change

The distribution of CO2 depends mainly on the air movement within the greenhouse, as CO2 does not travel very far through diffusion. One of the pure CO2 distribution ways is by a central pump that pushes it into a system of flexible perforated plastic pipes (made of polyethylene or other plastic material). The pipes for CO2 distribution are placed below the substrate special gutters with plants (if crops are grown in such gutters) or in the lower sections of the crops (if the plants are not grown in gutters). Then, through the pipe perforation, the carbon dioxide is distributed in the air around the plants. Very important is to obtain conditions that

In greenhouses, LED lightning could be placed on the top of the crops or in between rows of the particular crop. LED light does not have high emission of heat and cannot damage plants if they are placed in between rows in the crop. Even, that type of LED lightning is possible to be moved up and down, what depends on the crop development. Combination of LED lightning and sun light in greenhouses is an excellent combination for saving electrical energy and to empower crops growth. With the progress of the scientific research about LED lightning (**Figure 3**) for horticulture and its interaction with plants in order to achieve better quality of edible parts and improve energy efficiency [7] in crop production, it could be high yield, uniform color, firmness, nitrate control in edible parts of plants. Intensity of

LEDS which is enough for various recipes is approximately 600 μmol m<sup>−</sup><sup>2</sup>

LED lightning [10] is an efficient source of light in horticulture needed for photosynthesis and plant productivity. Advantages of LED lightning in horticulture than the other types of lightning are relatively low energy consumption, lower radiation heat, long lifetime, flexibility in positioning above or inside a crop, the ability to control the light spectrum and produce high light levels. Important characteristic of LEDs is possibility to control and make various light recipes which participate

s<sup>−</sup><sup>1</sup>

[8, 9].

keep the leaf stomata open in order to uptake carbon dioxide [4].

at certain times directed and distributed into the greenhouse.

*DOI: http://dx.doi.org/10.5772/intechopen.90723*

supplementing the CO2 when necessary.

and correct it in a short period of time.

obtained from burning fuel, e.g., natural gas.

and stomatal opening [6].

**Figure 2.** *Photosynthetic process equation.*

#### *Urban Horticulture and Its Modernization by Using LED Lightning in Indoors Vegetable… DOI: http://dx.doi.org/10.5772/intechopen.90723*

Normal ventilation provides an amount of carbon dioxide that is similar to its levels in the outdoor air (350–400 ppm). But then, frequent ventilation in the greenhouse is not desirable, so that CO2 supplementing has long been a common practice in vegetable crops growing. The necessary greenhouse carbon dioxide concentration is determined upon the type of the crops grown in the greenhouse, the greenhouse total volume and ventilation, lighting, temperature, air humidity, and stomatal opening [6].

Since carbon dioxide is one of the products of burning (e.g., fuel for greenhouse heating system), this segment of the heating process can be used for supplementing the greenhouse air. There are various ways of extracting carbon dioxide from other products of burning (fuel), so that the CO2 from the boiler room can be dosed and at certain times directed and distributed into the greenhouse.

Also, pure carbon dioxide can be used, which is delivered to growers in special tanks, in liquid form and then can be converted into gas and distributed in the greenhouse. This way of supplementing the CO2 has become increasingly popular as it eliminates any potential damage to the crops, allows control of other greenhouse climatic conditions that regulate the process of photosynthesis and crops productivity, provides easy control of the carbon dioxide levels, and is more flexible for supplementing the CO2 when necessary.

One disadvantage of the liquid CO2 is that it is usually more expensive than that obtained from burning fuel, e.g., natural gas.

Also, it would be advisable to install a proper system that registers the CO2 concentration and then distributes it in the greenhouse. Such a system, like in other greenhouse installation operations, has corresponding sensors that are linked to a special computer software that registers, monitors, and controls all the greenhouse environment parameters. In this way, it is possible to detect a cause of each change and correct it in a short period of time.

The distribution of CO2 depends mainly on the air movement within the greenhouse, as CO2 does not travel very far through diffusion. One of the pure CO2 distribution ways is by a central pump that pushes it into a system of flexible perforated plastic pipes (made of polyethylene or other plastic material). The pipes for CO2 distribution are placed below the substrate special gutters with plants (if crops are grown in such gutters) or in the lower sections of the crops (if the plants are not grown in gutters). Then, through the pipe perforation, the carbon dioxide is distributed in the air around the plants. Very important is to obtain conditions that keep the leaf stomata open in order to uptake carbon dioxide [4].

In greenhouses, LED lightning could be placed on the top of the crops or in between rows of the particular crop. LED light does not have high emission of heat and cannot damage plants if they are placed in between rows in the crop. Even, that type of LED lightning is possible to be moved up and down, what depends on the crop development. Combination of LED lightning and sun light in greenhouses is an excellent combination for saving electrical energy and to empower crops growth.

With the progress of the scientific research about LED lightning (**Figure 3**) for horticulture and its interaction with plants in order to achieve better quality of edible parts and improve energy efficiency [7] in crop production, it could be high yield, uniform color, firmness, nitrate control in edible parts of plants. Intensity of LEDS which is enough for various recipes is approximately 600 μmol m<sup>−</sup><sup>2</sup> s<sup>−</sup><sup>1</sup> [8, 9].

LED lightning [10] is an efficient source of light in horticulture needed for photosynthesis and plant productivity. Advantages of LED lightning in horticulture than the other types of lightning are relatively low energy consumption, lower radiation heat, long lifetime, flexibility in positioning above or inside a crop, the ability to control the light spectrum and produce high light levels. Important characteristic of LEDs is possibility to control and make various light recipes which participate

*Sustainable Crop Production*

very important to define right amount of CO2.

1000 ppm, regardless of the amount of light.

tion rate due to low outdoor temperatures.

Photosynthesis is a chemical process occurring in plants in which the light energy is used to convert carbon dioxide into water and sugars (carbohydrates) and oxygen (O2) gas. The sugars in plants, obtained in the process of photosynthesis, are then used for the plant development and growth through the process of respiration. In the objects with LED lightening and completely controlled environment, without daylight, enrichment of the air with CO2 is necessary because of process of photosynthesis and crop productivity. Due to lack of sun light, in such objects is

In the air (outside the greenhouse), there is about 400 ppm of carbon dioxide. The CO2 concentration is increased when coal, natural gas, oil, and kerosene are burnt. Inside the greenhouse, the amount of CO2 may be significantly depleted as plants use it intensively in the process of photosynthesis (**Figure 2**; [4]), which may lead to a decreased crops productivity or yield. For that reason, "CO2 fertilization"

Since there is about 500 times more oxygen in the air than carbon dioxide [4], it makes sense to increase the CO2 concentrations in the greenhouse (particularly in highly equipped glasshouses). It has a positive effect on the oxygen-carbon dioxide ratio. The photosynthesis is higher by 30–50% at CO2 concentrations of about

The increased concentrations of carbon dioxide are good as long as they do not limit the process of photosynthesis. Photosynthesis depends on light, temperature, air humidity, and carbon dioxide contents in the greenhouse. There is often a question of what is the optimal concentration, but it is hard to give a correct answer to it as the process of photosynthesis does not depend solely on CO2. Also, a point should be made that climatic factors affect the stomatal opening mechanism (through which the plants uptake CO2). Generally, a small increase in the plant photosynthesis process may be achieved at 1000–1200 ppm, but then, there is also an increased possibility of damage to the crops. One experiment done on eggplant crops showed that the first damage to the plants occurred at a constant CO2 level of 800 ppm [4]. Quite often, the intensity of the photosynthesis may be higher at lower doses of

Supplementing the greenhouse air with carbon dioxide may not be necessary at all as long as the processes of the crops development and growth are quite satisfactory for the vegetable grower. Also, in a case of intensive greenhouse ventilation, the carbon dioxide concentration may drop below a level that is necessary for the normal photosynthesis process, so increasing the CO2 concentration may not be an

If the crops quality and production are below the satisfactory level, however, carbon dioxide supplementing should be the next measure. Generally, the production period from late autumn to early spring increases the potential need for CO2 supplementing the greenhouse air, which actually corresponds to a lower ventila-

or "CO2 enrichment" is a standard practice in modern greenhouses.

carbon dioxide and higher intensity of light, and the other way around.

economical measure (unless the greenhouse ventilation rate is lowered).

**310**

**Figure 2.**

*Photosynthetic process equation.*

**Figure 3.** *LED lightning in protected area without day light.*

in optimizing photosynthesis, photomorphogenesis, and nutrient contents. LEDs make easier monitoring of nitrogen absorption by leafy plants and avoid harmful nitrate concentration in leafy plants and its influence on human health.

Urban farming is carried out mainly hydroponically (NFT system or rockwool) with or without daylight with complete controlled environment [10], which bring some benefits like controlled usage of water, nutrients, pesticides multiple crops per year, high quality of edible parts, less labor, and easier harvesting.

Urban farming provides remarkable reduction in electricity cost for transplants production by using thermally insulated walls, multi-shelves, advanced lighting and air conditioning systems, etc.

Urban farming enables vertical production of propagation plant material and regular crop production in fully controlled environment. It means that the area for urban farms can be various. It can be placed in supermarkets, or other places where people gather and want to refresh with fresh vegetables or fruits, for example. Urban farms can be smaller or larger areas (e.g., of several square meters), and with vertical cultivation, the crop yield is achieved as in larger areas (e.g., in modern greenhouses or completely controlled objects without sun light).
