How Is Nori (Pyropia yezoensis) Cultivated? Sharing 6 Major Cultivation Techniques

Nori is a marine algae with both nutritional and economic value, known as the “longevity vegetable” and “immortal vegetable,” and it has broad market potential. The cultivated nori species in China are Pyropia yezoensis and Pyropia haitanensis. Today we will discuss the cultivation techniques for Pyropia yezoensis.

I. Basic Conditions

1. Sea area selection: The bottom substrate of the sea area should be sandy or muddy-sandy, with a flat beach surface and a small gradient, and a flow velocity of 10 cm/s-30 cm/s. The water quality should be clear, with a salinity of 22‰-30‰. Pole-insertion cultivation is suitable for the low tide zone, and the subtidal zone is also acceptable.

2. Farming method: Generally, pole-insertion farming is used in the Zhejiang region.

II. Farming Facilities

The pole-insertion farming method mainly consists of the following:

1. Net curtains: Net curtains are divided into mesh nets and strip nets. Mesh nets have a specification of 2.0-18 m long and 1.8-4.0 m wide, with a mesh size of no less than 25 cm, square or diamond-shaped; strip nets have a specification of 5 m long and 4 m wide, with a strip spacing of 7.5-8 cm.

2. Insertion poles: Made from whole moso bamboo with a diameter of 7-12 cm and a length of 7-12 m.

3. Floats: Foamed plastic or moso bamboo.

4. Cables: Made of polyethylene, with a length of more than 2 times the water depth at high tide in the farming sea area.

5. Float ropes: Made of polyethylene filament.

6. Hanging ropes: Made of polyethylene, with a length of 5-10 m.

7. Stakes: Made of iron anchors, wood, or bamboo.

III. Seedling Cultivation

The seedling nets should be hung just before the tide rises, and the seedling nets are hung on the racks in three overlapping layers. The seedling nets hung on the float ropes should be pulled as flat as possible and tightened. If the newly hung seedling nets are left for a long time before the tide rises, seawater can be sprayed to keep the seedling nets moist. After the seedling nets are hung, they need to be inspected and managed every day, and the seedling nets must not be loose or sag excessively.

In sea areas with a lot of floating mud, or when there is a lot of miscellaneous algae attached to the seedling nets, the nets should be washed and dried in a timely manner. After 30-40 days of cultivation, the seedling nets will be covered with seedlings of 1 cm~3 cm on the net lines, and net splitting cultivation can be carried out as needed or cold storage net technology can be used for cold storage as backup.

IV. Daily Management

1. Management during the small seedling stage

After conchospore seeding on the net panels, they are put into the sea, and the 8-15 day period is the emergence stage. The main goal is to increase the emergence rate, promote early emergence, fast growth, completeness, and fewer seedling losses. This is the key moment of the year for farming, and management should be strengthened. Generally, net washing starts on the third day after being put into the sea. During exposure to air, after the nets are dried, wash once every three days until the seedlings emerge completely, keeping the net panels free of miscellaneous algae and mud attachment. This period coincides with the warm spell of October, and at high temperatures special attention should be paid to adjusting the water layer to prevent the death of small seedlings.

2. Management during the thallus stage

The yield and quality of nori farming mainly depend on whether the thallus grows normally and the length of the harvest period, and are related to the level of management. Therefore, the following aspects should be focused on:

(1) Promoting growth. After the small seedlings have grown completely, attention should be paid to adjusting the water layer every day, with an exposure time of no less than two hours, to increase the photosynthesis time of the thallus. In the middle areas of overly dense sea regions where fertilizer deficiency occurs, urea can be appropriately sprayed.

(2) Ensuring quality. Improving the quality of dried nori is the key to increasing nori production and income. During management, timely harvesting should be noted. Generally, when the thallus grows to more than 20 cm, the first nori harvest can be carried out, and thereafter once every 7-10 days, so as not to let the thallus age and to keep the algal body tender.

(3) Cutting and retaining. In order to achieve the goal of increasing production and income, in the first nori harvest, the cutting and retaining ratio should be appropriately controlled, generally cutting out one half of the thallus.

V. Disease Prevention

The following prevention methods are mainly used during nori farming

1. Reasonably control cultivation density;

2. Cold storage net technology: A relatively effective method for disease and rot is cold storage net replacement;

3. Increase scientific and technological investment and cultivate disease-resistant, high-quality varieties;

4. Acid-base method and drying method to remove diatoms: Nori is far more resistant to acid and alkali than diatoms.

VI. Harvest

40-50 days after collecting conchospore seedlings, when the nori blades grow to 20-30 cm, the first harvest can be carried out, and thereafter about once every 15 days. About 12 harvests can be made during the entire farming period.