A cultivation technique was developed for the culture of Laminaria japonica, allowing fisherman to cut production time in half, and still produce the same quality of material as that harvested from natural populations. This technique is known as "force-cultivation".

Force-cultivation is divided into two steps:

1. seedling production, in special facilities on land, and

2. the cultivation management practiced in the sea.

Seedling production consists of the seeding and culture of young gametophytes. These stages are carried out in a facility provided with seeding and culture tanks with equipment to control the seawater temperature, light, nutrients and other conditions.

The most important part is the actual cultivation, which takes place after the provisional outplanting. This involves hanging the seeded strings from the main line of the cultivation structures to become acclimated to the natural conditions for approximately 7-10 days. Then the seeded strings are cut into lengths of about 5cm, and then inserted into the main cultivation ropes at 30cm intervals. Approximately 15 pieces of the seed-string are used for a cultivation rope of 5m.

There are two methods of cultivating kombu:

1. the "vertical hanging method", in which the cultivation ropes are hung vertically from the main line at 2m intervals, and
2. the "long-line method", in which the ropes are stretched in parallel with the main line.

The cultivated ropes are checked every few months to thin the plant densities and to remove trapped debris and fouling organisms. The plants are kept approximately 5m below the surface in the winter to avoid winter-storm waves, and 2m below in the spring and summer to get more light for growth.

USES OF LAMINARIA

Laminaria is an excellent source of iodine, which has also been used in China as a dietary iodine supplement to prevent goitre. In Europe, Laminaria has been the main source of alginate in the industry for quite some time. Alginates have been used in paints (for texture), film (as base) and food products ( as an emulsifier and suspender). Burning of kelp was also used to supply salt mixtures in explosives and raw kelp was used as feed supplements for horses during World War I. Laminaria is also a source of mannitol and laminarian. Most of the Laminaria is dried and eaten directly in soups, salads, and tea, or it is used to make secondary products with various seasoning such as sugar, salt and soy sauce.

Laminaria japonica fronds are cut into small pieces of various shapes such as strips or squares, and dried over a fire until they become quite crisp. This is later sold as "kiri" or dried-on-the-fire kombu. Laminaria japonica is high in alcohol-sugar and is thus used for sweet-meat products. Dried pieces of kombu can also be ground into a fine, greenish/greyish powder and is then compressed into small cakes which are often coated with sugar.