How to Grow Nutrient-Rich Nori? A Detailed Guide to Daily Management Points
Nori is an important economic seaweed, delicious and nutrient-rich. Besides being eaten, it also has disease-preventing and therapeutic effects, and is an important raw material for the emerging agar industry. Nori cultivation has the characteristics of a short production cycle, simple production operations, no damage to feed, low production cost, and high returns, making it an important way for coastal areas to make full use of coastal tidal flats, develop production, and escape poverty and become prosperous. How is nori grown? What are the daily management points?
I. Basic Conditions
1 Sea area selection: The seabed should be sandy or muddy-sandy, with a flat beach surface and a small gradient, and a flow velocity of 10 cm/sec-30 cm/sec. The water quality should be clear, with a salinity of 22‰-30‰. Pole-insertion cultivation is suitable for low tide levels, and the subtidal zone is also acceptable.
2 Cultivation method: Generally, pole-insertion cultivation is used in the Zhejiang region.
II. Cultivation Facilities
The pole-insertion cultivation method mainly consists of the following:
1 Net curtain: Net curtains are divided into mesh nets and strip nets. Mesh nets have specifications 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 specifications 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, with 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 high-tide water depth of the cultivation sea area.
5 Float ropes: Made of polyethylene filament.
6 Hanging ropes: Made of polyethylene, with a length of 5-10 m.
7 Anchors: Made of iron anchors, wood, or bamboo.
III. Seedling Cultivation
Seedling nets should be hung just before the tide rises, and the seedling nets should be hung on the racks in three overlapping layers. The seedling nets hung on the float ropes should be stretched as flat as possible and pulled tight. If a newly hung seedling net is still a long time from the rising tide, seawater can be sprayed to keep the seedling net 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 more floating mud, or when there is more miscellaneous algae attached to the seedling nets, the nets should be washed and dried in time. After 30-40 days of cultivation, the net lines are covered with seedlings 1 cm-3 cm in size, and net separation cultivation or cold storage net technology can be used as needed for cold storage.
IV. Daily Management
1. Management during the small seedling stage
After conchospore seeding, the nets are placed in the sea, and the 8-15 day stage is the emergence stage, mainly to increase the emergence rate, promote early emergence, rapid growth, completeness, and fewer seedling losses. This is the key moment of the year for cultivation, and management responsibility should be strengthened. Generally, net washing starts on the third day after being placed in the sea. During exposure to air, after the nets are dried, once every three days until emergence is complete, keep the nets free of miscellaneous algae and mud attachment. This period coincides with the mild autumn weather of October, and at high temperatures special attention should be paid to adjusting the water layer to prevent seedling death.
2. Management during the thallus stage
The yield and quality of nori cultivation mainly depend on whether the thallus grows normally and the length of the harvest time, and are related to the level of management. Therefore, the following aspects should be focused on:
(1) Promoting growth. After the small seedlings grow completely, attention should be paid every day to adjusting the water layer, with exposure to air of no less than two hours, to increase the photosynthesis time of the thallus. In the middle areas of overly dense sea areas where nutrient deficiency appears, 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, attention should be paid to timely harvesting. Generally, when the thallus grows to more than 20 cm, the first nori harvest can be made, and thereafter once every 7-10 days, so as not to let the thallus age and to keep the algal body fine and soft.
(3) Cutting and retaining. In order to achieve the goal of increasing production and income, at the first nori harvest, the cutting and retaining ratio should be properly controlled, generally cutting out one half of the thallus.
V. Disease Prevention
The main enemies during the nori growth period are mainly plant-type green moss, filamentous green algae, diatoms, etc., which attach to the net curtains, occupy seedling positions, compete for nutrients, block light, and mix with the algal body so that it is difficult to distinguish, affecting the quality of dried products. Animal-type enemies include fish of the family Atherinidae, golden drum fish, and Niangai fish, etc., which directly eat the algal body and cause great harm. Methods of elimination: if plant-type algae attach during the small seedling stage, the nets can be exposed to strong sunlight for twelve hours and then put back into the sea, and this miscellaneous algae turns white and dies in the water. Animal-type enemies are mainly more common in offshore sea areas, and the main removal methods are driving away, blasting, and hanging medicine bags. There is also bacterial green rot, which, due to high temperature, excessive density, poor water flow, and other factors, causes the thallus to rot and turn green, and in severe cases the entire sea area rots. Rescue measures: immediately adjust the water layer, dry the nets for more than 20 hours, and then put them back into the sea for cultivation.
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 once about every 15 days. About 12 harvests can be made during the entire cultivation period.