A Detailed Explanation of the Porphyra (Nori) Cultivation Process, Key Technical Points and Precautions
AbstractSite selection: choose a sea area with smooth tidal flow, slight wind and waves, and below the high tide line. Cultivation equipment: professional net curtains need to be made, then planned and placed into the sea. Timely stocking: the stocking time is from the end of September to the beginning of October. Seedling cultivation: hang up the seedling nets and patrol every day to keep the seedling nets moist; after 30 days the seedling cultivation is successful. Daily management: during the small seedling stage, wash the nets once every 3 days; during the thallus stage, pay attention to adjusting the water layer. Disease control: the acid-base method and the drying method can be used for active control.
1. Choosing a Suitable Area
(1) The cultivation area for Porphyra needs to be chosen in a sea area with smooth tidal flow, slight wind and waves, located at neap tide and below the high tide line for suitable cultivation.
(2) The bottom of the cultivation area is best if it is sandy mud; in addition, the water quality for Porphyra cultivation should be chosen in a sea area relatively rich in nitrogen and phosphorus elements, generally requiring the nitrogen content of the seawater to be 50 mg per cubic meter and above.
2. Cultivation Equipment
(1) The net curtains needed in Porphyra cultivation should preferably use six-strand small rope blended from vinylon filament and 30-denier luster acrylic filament, then woven into strip-shaped net curtains of 2X1.5 m.
(2) After weaving is completed, new net curtains should be soaked in fresh water for 15 days, and within the 15 days the water should be changed 3-5 times, to wash away the detergent residue remaining in the original vinylon, otherwise it will affect the seedling attachment effect.
(3) When choosing the sea area, the stocking area should be planned; especially in places with many cultivators, care should be taken not to crowd densely in the same patch.
(4) When planning the sea area, the row spacing should be widened and the traffic channels enlarged; only in this way can high cultivation yields be achieved while maintaining the excellent quality of Porphyra.
3. Timely Stocking
(1) Porphyra stocking is generally at the end of September or the beginning of October; when the northern cold air moves south, prepare for seedling collection, and collecting seedlings and putting them into the sea during the second cold air period is the most suitable time for Porphyra stocking.
(2) If the air temperature and water temperature are on the high side, it is not conducive to spore germination, and may even affect the normal growth of Porphyra.
4. Seedling Cultivation
1. Hang the seedling nets at the place about to rise with the tide; three layers of seedling nets need to be hung overlapping on the seedling nets, and at the same time the seedling nets should be pulled as flat and as taut as possible.
2. For newly hung seedling nets, if they are relatively far from the place where the tide rises, the seedling nets need to be sprayed with seawater so as to ensure their moisture.
3. After the seedling nets are hung, patrol every day; note that the seedling nets must not be too loose or sagging.
4. If relatively much algae attaches to the seedling nets, the seedling nets need to be cleaned in time and dried in the sun.
5. After 30-40 days, if the seedling nets are covered with seedlings of 1-3 cm, it means the seedling cultivation is successful.
5. Daily Management
1. Small seedling stage
(1) This is a relatively critical time in the year's cultivation; during this period attention should be paid to strengthening the management of Porphyra, mainly to promote the rapid growth of small seedlings and reduce seedling loss.
(2) Generally, net washing starts on the third day after being put into the sea; during exposure, after the nets are dried in the sun, do it once every three days until the seedlings emerge completely; keep the net pieces free of miscellaneous algae and free of attached mud and dirt; during this period there may be a brief rise in temperature, and during the high-temperature period special attention should be paid to adjusting the water layer to prevent the death of small seedlings.
2. Thallus stage
(1) Quality preservation: during the management period pay attention to adjusting the water layer, and pay attention to properly harvesting the Porphyra; generally when the thallus grows to more than 20 cm the first harvest of Porphyra can be made, and afterwards harvest Porphyra once every 7-10 days on average; this can prevent the Porphyra thallus from aging and keep the algal body tender and fine.
(2) Growth promotion: pay attention to adjusting the water layer every day; in order to increase the photosynthesis of the thallus, the time exposed above the water surface and dried should preferably not be less than 2 hours; if there is a fertilizer deficiency, urea should also be sprayed on it to increase fertility.
(3) Cutting and leaving: when harvesting Porphyra, pay attention to mastering the cutting-to-leaving ratio; generally cutting out one half of the thallus is appropriate.
6. Disease Control
1. Control cultivation and choose high-quality varieties when cultivating.
2. If disease and rot are found, the nets need to be changed in time.
3. When a large amount of algae is found attached to the nets, use the acid-base method and the drying method to remove it.
7. Harvesting
During the entire cultivation period, Porphyra can be harvested about 12 times in total; about 40-50 days after collecting conchospore seedlings, the Porphyra blades can grow to 20-30 cm, and at this time the first harvest can be carried out, after which one harvest can be carried out about every half month.