SDK and Yamaguchi Univ. Develop New Cultivation Method


Showa Denko K.K. (SDK) and National University Corporation Yamaguchi University have jointly developed a new cultivation method for plant growth facilities using light emitting diodes (LEDs).

The new method will enable these facilities to shorten shipment cycles and increase the amount of harvest through the irradiation of light optimized for plant growth, using LED chips produced by SDK. SDK will start licensing the technology to encourage the spread of LED-based plant growth facilities, which will contribute toward ensuring stable supply of safe food.

1. Characteristics of LED-based plant growth facilities; tasks to be achieved

In the process of growth, plant responds to light. The response includes photosynthesis and photomorphogenesis. The former is catalyzed by chlorophyll, which is activated by red light with wavelengths of 660-700 nm. Meanwhile, the latter is achieved by different kinds of chromoprotein, which is activated by blue light with wavelengths of 450-470 nm and red light with wavelengths of 660-730 nm. The desirable ratio between red and blue lights varies, depending on the kind of plant.

The LED lighting has a narrower range of wavelengths compared with other light sources, enabling selective irradiation of light with suitable wavelengths and, as a result, ensuring efficient cultivation of plants. SDK has developed LED chips which emit red light with a wavelength of 660 nm, and is marketing the product. To the best of our knowledge, the product showed the world’s highest luminous efficiency as of May 2012. (Luminous efficiency: the ratio of emitted light to the power input, as expressed in lumens per watt.)

LED-based light sources help to reduce power consumption to about one-third of the power consumption of fluorescent lamps, and provide high levels of light quantity without the influence of heat. Furthermore, a wide variety of plants, such as fruit, vegetables and grains, can now be cultivated, in addition to conventional leaf vegetables. As a result, LED-based light sources have been adopted by universities, research institutes, and commercial plant growth facilities. However, LED-based light sources require larger amounts of initial investment compared with fluorescent lamps. To enable full-scale introduction of LED-based light sources into commercial facilities, it is necessary to shorten the payback period for the investment.

2. Characteristics and advantages of the new cultivation method

Professor Masayoshi Shigyo, Faculty of Agriculture, Yamaguchi University, and SDK have developed a new method of LED irradiation optimized for plant growth, based on their joint researches concerning the relationship between a plant’s response to light and its growth.

It has been found that the newly developed cultivation method (the Shigyo Method) increases the amount of leaf vegetable harvests up to three times* the conventional level for the same length of cultivation period, compared with cultivation under fluorescent lamps or LED lighting with fixed ratio of red light to blue light.

*Plant growth depends on the complex combination of various factors, including temperature, humidity, wind, nutrient liquid, and CO2, in addition to response to light. Conditions of growth and cultivation results will also differ materially depending on the kind of plant and individual plants. Although the latest research results suggest the effectiveness of the newly developed cultivation method, we do not guarantee the results.

The new method provides advantages of lower electricity costs and the increase in the amount of harvests, enabling a shorter payback period for investment in LED-based plant growth facilities. The Shigyo Method has also been found effective for cultivation of Algae, opening the way for the production of useful substances and biofuels from Algae.

3. Efforts to spread the Shigyo Method

In cooperation with Yamaguchi University, SDK will start licensing the Shigyo Method for use at commercial facilities and lighting equipment manufacturers. SDK will also sell the Group’s cultivation equipment, centering on LED lighting, and related materials. In the initial year, SDK will focus on licensing and marketing aimed at commercial facilities in Japan. In the future, SDK will aim to license the technology to overseas large-scale facilities, and widen the scope of activities to cover the fuels and biomass complex businesses.

We will promote plant growth facilities based on our new cultivation method, aiming to contribute toward realizing the sufficient supply of safe food, a major goal for mankind in the 21st century.


Effect of the Shigyo Method (as compared with cultivation under fluorescent lamps)

Results of leaf lettuce cultivation:

14th day under fluorescent lamps

14th day under LEDs (Shigyo Method)

21th day under fluorescent lamps

21th day under LEDs (Shigyo Method)