JPS6052766B2 - How to supply nutrients for seaweed cultivation - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for supplying nutrients for seaweed cultivation.

Recently, in order to improve the efficiency of seaweed cultivation, nitrogen components,
Liquid or powder nutrients containing phosphorus as a main component are applied to seaweed farms, but the effects of the supplementation are temporary and are not sustainable, so they are applied repeatedly. Therefore, the amount of effort required for spraying is large and the amount of nutrients consumed is large.

In addition, there is a risk of seawater pollution problems such as red tide and methane gas being generated due to the effects of distributing large amounts of nutrients into the sea and undissolved substances settling on the sea floor. It is known that nutrients such as nitrogen and phosphorus are solidified by adding carboxymethyl cellulose, gum arabic, gum tragacanth, etc., and the solids are gradually dissolved in the sea to fertilize seaweed ( Special Public Service 1977
(See Publication No. 39546, Special Publication No. 39-13015)
In these known products, the daily elution amount of nutritional components hardly changes. However, seaweed cultivation requires a large amount of nutrients during the larval stage, and as it grows, it tends to require more nutrients, so as mentioned above, the amount of nutrients eluted per day changes. A problem with solid nutrients without this was that they did not match the trends over time in the amount of nutritional components required by seaweed. As a result of intensive research to solve the above-mentioned conventional problems, the present inventors have come up with a supply method that allows nutrients for seaweed cultivation to be eluted into the sea in a sustained manner.

That is, in this invention, 0.5 to 3.
A viscous seaweed culture nutrient solution containing 0% by weight or 1 to 5% by weight of carboxymethylcellulose is added to an air permeability of 2.
The sealed container is sealed in a sheet for 5 to 120 seconds, and the sealed container is immersed in seawater. Initially, the amount of the nutrient eluted is large, but as days pass, the eluted amount decreases, and the nutrient component is concentrated. This is a method for supplying a nutrient for seaweed cultivation, characterized in that most of the nutrient is eluted during the period of time when the seaweed leaves are picked.

The nutrient for seaweed cultivation used in this invention is an aqueous solution containing mainly nitrogen and phosphorus components, specifically urea 10
~25% by weight, 4 to 6% by weight of dibasic sodium phosphate, and some organic components and inorganic components, which are commonly used.

The thickeners that are mixed to impart viscosity to the aqueous nutrient solution are xanthan gum (also known as xanthan gum, a polymeric polysaccharide produced by microbial fermentation), carboxymethyl cellulose (CMC), starch, agar,
Other thickeners such as locust bean gum and polyvinyl alcohol are not preferred because they separate into two layers or gel in an aqueous solution over time and cannot be stored for long periods of time.

The mixing amount of the thickener is preferably 0.5 to 3% by weight in the case of xanthan gum, and 1 to 5% by weight in the case of CMC, based on the total viscous nutrient solution. Although the viscosity of the nutrient solution increases exponentially as the amount of thickener mixed increases, it is noteworthy that there is not a large difference in the amount of nutrient components eluted into seawater. If the amount of the thickener mixed is less than the lower limit above, the viscosity will be too low and the nutrient solution sealed in the bag may leak from the bag before it is immersed in seawater. This poses a problem in storage and transportation. Moreover, if the above upper limit is exceeded, the viscosity of the nutrient solution becomes too high, making it difficult to handle such as filling it into a container. The bag for enclosing the nutrient liquid containing the above-mentioned thickener has an air permeability of 25 to 1.
20 seconds.

The air permeability here is a value measured according to JIS-P8ll7 (air permeability test method for paper and paperboard), and is 645W.
A sheet of paper with an area of 11 is heated by 1007 LL of air. It is expressed in the average number of seconds it takes to pass, so the higher the air permeability value, the lower the air permeability. The above sheets are wood valve, cotton,
A polyethylene film made of a polyethylene homopolymer and a polyethylene copolymer containing a small amount of propylene or vinyl acetate is laminated on a breathable base material such as Japanese paper or nonwoven fabric made of rayon or the like. A laminated sheet having a coating provided with a large number of grooves or dotted grooves is preferable, and its air permeability can be arbitrarily set by adjusting the density of the grooves or dotted grooves of the polyethylene coating.

Note that the sheet forming the bag is not limited to a laminated sheet, and may be a single plastic film provided with desired air permeable holes. When the above-mentioned nutrient solution for seaweed cultivation is sealed in the above-mentioned bag, it will not leak from the bag, so it can be stored and transported in a sealed state in the bag.

When a bag filled with the above-mentioned viscous nutrient solution is suspended from a seaweed net or support at a seaweed farm and immersed in seawater,
The nutrients in the bag are gradually eluted into seawater and replaced with seawater.

In general, seaweed cultivation is divided into a budding stage, in which seeded spores germinate or secondary buds multiply, and a growth stage and senescence stage, in which the leaf body greatly elongates and grows. Although the body requires large amounts of nutrients, it is said that only a small amount of nutrients is required during the aging period.

When the sealed bag containing the nutrient liquid according to the present invention is immersed in seawater, a large amount of the nutrient is eluted initially when the nutrient component in the bag is concentrated, but as days pass, the nutrient component in the bag becomes diluted. This trend is consistent with the trend over time in the amount of nutrients required during seaweed cultivation. The cycle for picking the leaves that have grown to a predetermined length varies depending on natural conditions such as the temperature at the time of cultivation, the seawater temperature, and the speed of the current, but is usually 20 to 30 days. On the other hand, the elution rate of the nutrient liquid is correlated with the air permeability of the sheet that is the material of the bag, so the nutrient liquid in the bag that is newly replenished after picking the leaves is It is preferable to set the air permeability of the sheet so that all or most of the material is eluted from the container by the appropriate time. Therefore, if the air permeability of the above-mentioned bag is less than 2, and the air permeability is high, the nutrients in the bag will be eluted into the seawater too quickly, and the sustainability will be low, and the nutrients will not be absorbed at all during the leaf growth period. Not only will the nutrient solution not be supplied, but the nutrient will leak when the nutrient liquid with a low viscosity is sealed, causing trouble in storing and transporting the bag containing the nutrient.

On the other hand, if the air permeability exceeds 12C@7 and the air permeability is low, the elution of the nutrients in the bag into the seawater will be too slow, and it will be difficult to discard the old bag after picking the leaves. A large amount of nutrients remains and is lost. According to the supply method of the present invention, the nutrient component and the nutrients required during the cultivation period of seaweed are eluted, so that the effect of cultivation of seaweed is greatly improved. Furthermore, it is possible to prevent the occurrence of red rot in seaweed and prevent diatom stains, and is expected to improve the quality and increase production of seaweed. Examples of the present invention will be described below.

Example 1 The composition of the nutrient solution is as follows.

10y of nutrient solution with the above composition (nitrogen amount 988m9) was filtered through 2
Seawater (solid content 2. 8% by weight, pH 7. & nitrogen component 0.08
4m9/y, specific gravity 1.025), hang it by a string so that it is completely immersed in the seawater, and add seawater every 175ff using a magnetic stirrer (size of stirrer: diameter 87m, height 40w).
Stir for 2 minutes at a rotational speed of 40 [Pm] and measure the amount of nitrogen eluted into the seawater every two days using a conventional method. The relationship between and the number of days elapsed is shown in Table 1 below and the graph in the drawing.

Example 2 In place of the xanthan gum in the composition of the nutrient liquid of Example 1, 3% by weight of CMC was mixed, and a nutrient liquid (nitrogen 970 m9/10 y) with a viscosity of 830 ps and a specific gravity of 1.13 was used. The elution test was carried out in the same manner as in Example 1, and the results are also shown in Table 1 below.The amount of elution was the same as in Example 1.

As shown in Table 1 and the graph in the drawing above, the number of days it takes for the cumulative amount of nitrogen elution to reach 97% of the original nitrogen amount of the nutrient varies depending on the air permeability of the storage bag, and (1
) Comparative example using a second bag takes 62 days, and approximately 20% by weight of the nutrients are wasted during the 30-day picking cycle of the seaweed leaves.

Also, elution amount per day (difference between measurement days of cumulative elution amount)
is high at the beginning and gradually decreases as days pass, indicating persistence. In Example 1, a similar test was conducted using bags with air permeability of 10 seconds and 30@, but the former had no sustainability as the total elution amount reached 97% in 1.5 days, while the latter had 97% of the elution amount in 1.5 days. %, and the cumulative elution amount on the 30th day was 68.4%.

Example 3 In (a) of Example 1 above (air permeability 5 [phase]), the amount of xanthan gum in the nutritional supplement was 0.5, 1.0, 2.0.
Table 2 shows the results of an elution test conducted in the same manner as in Example 1, except that the viscosity was changed to 3.0%.

As shown in Table 2, even if the viscosity of the nutrient filter increases, there is no significant difference in the amount of nutrient elution depending on the number of days that have passed.

Example 4 In Example 1 (a) above, 10% of urea in the nutritional composition
When an experiment was conducted in the same manner as in Example 1 (a) by reducing the contents of , dibasic sodium phosphate, and other components by 4%, there was no difference in the change in elution amount from Example 1 (a).

[Brief explanation of the drawing]

The drawing is a graph showing the relationship between elution amount and elapsed days in Example 1.

Claims (1)

[Scope of Claims] 1. A viscous seaweed cultivation solution containing 0.5 to 3.0% by weight of xanthan gum or 1 to 5% by weight of carboxymethyl cellulose as a thickener in an aqueous nutrient solution mainly containing nitrogen and phosphorus components. The nutrient solution is sealed in a bag made of a sheet with an air permeability of 25 to 120 seconds, and the sealed bag is immersed in the sea.At first, when the nutrient components are concentrated, a large amount of the nutrient is eluted, but as days pass, A method for supplying a nutrient liquid for seaweed solubilization, characterized in that the amount of the nutrient eluted is small and most of the nutrient is eluted during the period of time when the seaweed leaves are being picked. 2. The method for supplying a nutrient liquid for seaweed cultivation according to claim 1, wherein the sheet forming the bag is a laminated sheet of a fiber sheet and a plastic coating.