Agriculture is one of the oldest activities learnt by Human beings since the ancient times for their living. With the passage of time, agriculture became the most prominent activity for business. Previously, agriculture shared major portion of the GDP (Gross Domestic Products) of a country. With the revolution in Industry and Service Sector, the share of agriculture is getting depreciated year-by-year. Such data is available by World Bank for the sector contribution in GDP (%) of different countries.
For India, the contribution (%) of different sector (viz-a-viz Agriculture, Industry and Service) to GDP is provided beside for the reference (Source: Calculated from CSO data). Here, contribution of agriculture is approx. 14% of GDP whereas more than 30% population is dependent on agriculture for their living.
Traditional farming (i.e. cultivation) was developed in open farms, which was greatly influenced by factors such as farmland scarcity, depletion of natural resources at fast rate, adverse impact of climate change and global warming. Further, people have migrated to metro-cities for better job opportunities instead of investing their time and money in agriculture. All these factors adversely impact the agriculture products to a great extent and many times may cause loss to the farmer.
Due to above reasons and to cope with losses, agriculture under controlled environment is the emerging technology. Green Houses and Plant factories are such kind of manifestations which are gaining popularity very fast.
Definition of “Horticulture”–
The origin of the term “Horticulture” lies in two Latin words hortus (meaning “garden”) and cultus (which means “tilling”). Horticulture can be defined as the science or art of cultivating plants viz-a-viz fruits, vegetables, medicinal plants, flowers or ornamental plants. It is of worth mention that horticulture crops are comparatively more intensively cultivated than the field crops i.e. horticulture crops need intensive care regarding different parameters such as supply of minerals, water, sufficient & appropriate light, temperature, humidity.
Horticulture is further divided into sub-branches as discussed below –
- Floriculture – this sub-field deals with the cultivation of floral crops. It is concerned about the growing and selling of flowers.
- Landscape Horticulture – This refers to the design and alteration of land by planting material (such as trees, plants, shrubs, turfs, herbaceous perennials, etc.) and land restorations. These help in the improvement of aesthetic view and make the space more vibrant and lively. Regular maintenance is required to keep the landscaping more lively and beautiful.
- Olericulture – This refers to the cultivation and selling of all types of vegetables. Vegetables are essentials part of our food which help to fulfill the requirement of vitamins and minerals of our body.
- Pomology – This deals with the growing of fruits from rising of saplings to final products.
- Post–Harvesting Physiology – The said field of horticulture is relevant to crops reaping, maintaining their quality, reducing spoilage, preservation, etc.
In India, with the advent of the new technologies and acceptance of the same as essential part of economy, there is rise in the products of horticulture. Further, government has initiated special measures and framed policies for the encouragement in the horticulture which has resulted the rise in horticulture products.
Role of Light in Horticulture –
Plants prepare their own food with the help of photosynthesis process (autotrophic mode of nutrition). Leaves are termed as the food factories of plants i.e. food required for growth & development of plants is synthesized in the leaves. For the preparation of food, plants required the nutrients, water (both absorbed by roots from soil), carbon dioxide (absorbed from air through tiny pores present on the surface of leaves) and sunlight (captured by pigments on leaves).
Since, the synthesis of food occurs during sunlight, hence the process termed as “Photosynthesis” (where Photo means “light” and synthesis means to “combine”). During photosynthesis, glucose is prepared and oxygen is released in environment. The process can be shown in figure as –
The process of photosynthesis can also be represented in form of an equation:
Many researchers and scientists have found that light plays a very important and vital role in the growth of the plants, which is briefly discussed in next paragraphs.
Light is an electro-magnetic radiation, which consists of three parts – UV Radiations, Visible Part & Infra-red radiation. Light consist of light particles called photons.
In comparison with human beings, plants have different sensitivity towards light. Humans are most sensitive to green light, whereas plants have much broader sensitivity. This shown in the figure.
Researchers have proven that photosynthesis process is most efficient with blue and red coloured light. Regarding lighting in horticulture, one of the important factors is Photosynthetically Active Radiation (PAR), which is defined as electromagnetic radiation with range from 400 nm to 700 nm, which is used during the photosynthesis process. Horticulturalists measure PAR for both plant research and greenhouse lighting design using specialized photometers. The unit of measurement for PAR is Photosynthetic Photon Flux Density (PPFD), measured as mmolm-2s-1. The role of light in plant growth can be explained as below –
- UV Light often stimulates the plant defence mechanism with the pigment accumulation.
- Blue light (absorbed by Cryptochromes) leads in stretching, stomata opening, dark colored leaves & flowers. 100% blue light leads to excessive stretching.
- Green light counteracts the blue light effects.
- Far red light enhance flowering and stretching.
- Effects of Red / Far-Red ratio (R/FR) (mediated by phytochrome) is as follows –
- High R/FR cause rapid seeding growth.
- Low R/FR increases stretching.
Greenhouses and Plant factories faces following problems – deficiency in illumination, insufficient light intensity, light quality, change in seasons, etc. All these factors lead to serious reduction in crop output. Low light intensity adversely affects the yield and quality of horticulture. Therefore, dependency on sunlight only will not be sufficient for photosynthesis to meet the requirement of crop growth and quality. Provision of supplement lighting may be accompanied with the application of artificial lighting.
Benefits of using LED for Horticulture technology?
Many types of luminaries are available to supplement lighting in horticulture. Light sources used in horticulture are – Electrical discharge (fluorescent, HID, MH), and Solid-state light sources (i.e. LED, Organic LED).
LEDs offer much better and efficient technology in comparison with the conventional light sources used for lighting purposes in horticulture such as high power Metal Halide Lamps or Mercury Lamps. Usage of Conventional light sources for horticulture application, available in the market have de-merits in comparison to the LED technology.
LED technology is efficient, environment friendly and economically much better than in comparison to the conventional light sources. With the application of LED technology, the production of horticulture products can be increased further with more efficiently and environment friendly.
The merits and role of LED technology in Horticulture are discussed below –
- Highly Efficient & Reduced Operational Costs – In comparison with conventional light sources, LEDs are more efficient. More electrical energy is converted into ight energy. Hence, LED gives more photons output per kWh, thus less operational cost. Thus, LED has higher Photosynthetic Photon Flux Density (PPFD). Blue colored light is highly beneficial for plants and release of blue colored photon required more energy. A brief comparison shown in figure –
- Further, due to the high efficiency (more photon output per wattage), the operational cost of LED (i.e. electricity consumption bill) has been reduced to a great extant. Higher efficiency resulted to obtain high quantum flux with fewer quantities of LEDs. This helps in reduction of installation cost.
- Thus, the usage of LEDs has resulted savings on huge expenditure been incurring on paying of electricity bills for lighting.
- Reduced operational costs (upto 40% energy saving) – LEDs are most efficient light fixtures in terms of illuminance output in comparison to conventional light sources.
- Increased / improved plant quality through choice in spectrum. LED technology comes with the diversified colour control with the advent of RGB type of light sources. Thus, LED technology provides the flexibility in the section of light colour desired for plant.
- Uniform Light Distribution – while using conventional type of light sources, uniformity of light was a big concern, due to which light didn’t reach below the canopy area and due to darkness below canopy may resulted poor growth of plants. This is improved with the application of LED technology. LED lights provide the more uniform light distribution across the plants and improve the growth.
- No / less infra-red heating – Also, HID lamps were installed at higher position because of the generation of large amount of heat. Approximately 55% of electrical energy gets converted into radiation heat, which is very much harmful to plants. For the dissipation of heat, air-conditioning system need to be installed inside the premises. This also causes additional burden on electricity bill. Also, due to excess heat generations, these lights could not be placed closure to the plants to brighten the portion below canopy as this may damage the plants. Whereas, LED lights produce very less heat in comparison to conventional light sources. Hence, LED can be provided below the canopy areas to brighten the areas sufficiently.
- Instant light – Conventional light sources used to get time to start-up whereas LED lights illuminated instantly without losing time.
Light plays an important role in growth and development of plants. Dependency on sunlight only, resulted poor production of horticulture products. Production can be improved with the application addition light sources i.e. Plant Artificial Radiation Sources (PARS). These are essential for artificial light cultivation to replace the sunlight for plant growth in protected horticulture such as in green houses or plant factories. This will promote the development of ecological agriculture.
The lack of synchronization in Lighting designers and Horticulturalists is of big concern. Lighting designers are concerned about the lumens and illuminance whereas Horticulturalists have concerned for Photosynthetically Active Radiation (PAR) and Photosynthetic Photon Flux Density (PPFD).
To make the horticulture industry more efficient and effective, it is the essence of time and technology that lighting designers and horticulturalists need to synchronize in the same frequency.
LED technology play important role in Horticulture Lighting with efficient, uniform, lighting.
In the case of unbalance in any of these parameters may lead to drastic damage to crops and will incur huge loss in terms of financial aspect also.
Er. Chaudhary Rajneesh K. Singh
Deputy General Manager/Electrical,
Rail Vikas Nigam Limited, Lucknow