Hydrogel to promote plant growth

By Our Agriculture Correspondent

Sky Gel has found increasing use in the roof-gardens of Tokyo,

Sky Gel has found increasing use in the roof-gardens of Tokyo,  

A SUPER-ABSORBING polymer (SAP), which can retain at least 200 times its weight of water, has been found to promote the growth of plants.

Developed by a distinguished polymer engineer Prof. Yuichi Mori, a visiting professor at the Advanced Research Centre for Science and Engineering, Waseda University, Tokyo, Japan, the new SAP is named `Sky Gel', and it is being extensively used in roof-gardens, afforestation, tissue culture and in hydroponics and aeroponics.

"Sky Gel has excellent water retaining properties, and in laboratory experiments with radish and cucumber have shown that it promotes root and shoot establishment. When Sky Gel is applied to the root zone, it retains the moisture and slowly releases it to the growing plants. It has been used successfully in stabilizing the hill slopes of Mount Fuji, and it can be used for arresting the march of the desert. It can help in preventing the wind erosion of the sand and stabilizing the sand dunes," explains Prof. Mori.

The conventional SAP (cross-linked sodium polyacrylate) has excellent water absorbing capability (over 200 ml of water per g of SAP), and it was widely believed that that it prevented plants from absorbing water. "The real reason for the growth inhibition by SAP is not its excellent water absorbing capability, but the ion exchange property — that is the absorption of calcium ion, which is essential for plant growth and the release of sodium ion, which is harmful to the plants," points out Prof. Mori. If the SAP is added above a critical concentration (above 0.1 volume per cent) to soil, the plants suffer poor germinability and heavy growth inhibition.

"We synthesised Sky Gel by partially substituting sodium acrylate groups of SAP with calcium acrylate and acrylic acid groups.

The water-absorption capability of calcium of Sky Gel is significantly suppressed keeping a high water-absorbing power similar to SAP," explains Prof. Mori. Sky Gel production is carried out by using a conventional SAP production plant in Japan. "Its production cost shall be very close to SAP if the demand of Sky Gel increases to the level of SAP, which is about 100 million tonnes a year," says Prof. Mori.

At present, the price of Sky Gel is about ten times that of the conventional SAP, according to him.

The plant compatible hydrogel can be used as a moisturizing agent for plantlet culture by a small cellular tray in a greenhouse. The conventional seeds business is being replaced by plantlet business because of low production cost and high quality of plantlets achieved by using the cellular tray.

The new hydrogel in combination with some porous material would form an ideal matrix for plantlet culture, according to Prof. Mori.

"The newly developed functional hydrogel technology has resulted in high-valued products in bio-medical fields as well," says Dr. Samuel JK Abraham,Faculty of Cardiac Surgery, Yamanashi University, Tamaho, Japan.

At present several experiments are underway to prove its application in bio-medical fields, according to him. Now, Sky Gel is widely used in the roof-gardens of Tokyo, and it has several promising applications in the field of horticulture, tissue culture and afforestation, and the developing countries in the tropical belt should take advantage of its potential, according to him.

Sky Gel is a photodegradable product with a field life of over five years. It is manufactured through environmentally sound methods, and it is safe for use in agriculture and afforestation programmes, according to Dr. Abraham.