JPH06209644A - Method of vegetation with semipermeable membrane - Google Patents

Abstract

PURPOSE:To carry out vegetation of agricultural products in soil of salt accumulation at a low cost without requiring execution of large-scale facilities by utilizing underground water having a high salt content in soil of salt accumulation, effectively desalting the underground water and feeding crops. CONSTITUTION:A method of vegetation wherein a semipermeable membrane which permeates water or steam but substantially rejects water-soluble salts is laid between a water layer and water absorbing roots of plants.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for agricultural production and revegetation in soil containing high salt water such as salt accumulating soil.

[0002]

2. Description of the Related Art Recently, mainly in arid and semi-arid areas,
The progress of soil salinization due to careless upland irrigation has been regarded as a problem all over the world, and the area of salt-accumulated soil seems to be increasing with the years. The increase in salt-accumulated soil is due to irrigation of water containing salt, rise in groundwater due to overirrigation and leakage from irrigation channels, and severe soil surface evaporation peculiar to drylands. The problem of soil salinization in crop production is not limited to arid and semi-arid areas, and even in humid areas, water with high salt concentration may enter from surrounding areas at high groundwater levels. This is a problem that always occurs in the areas where the soil is cultivated.In addition, as in Japan, where horticultural cultivation has been developed, leaching of water-soluble salts from the soil is suppressed under rainfall interception and high fertilizer cultivation. Salinization becomes a problem. The following methods have been proposed and implemented for agricultural production in such salt-accumulated soils: 1) installation of a culvert for the purpose of reducing groundwater and desalination, 2) formation of a void directly under the soil. How to bury many materials, 3)
A method is known in which high salinity water is once purified by using solar heat and the water is used for irrigation.

[0003]

In order to carry out agricultural production on salt-accumulated soil, a method of utilizing groundwater having a high salinity in the salt-accumulated soil and desalting it to supply to crops is a dry area. Especially desirable in areas with sufficient irrigation water supply, such as the semi-arid area. However, in the above-mentioned publicly known examples, 1) and 3) require enormous execution costs to construct the facility, and 2) has a problem that the soil layer is likely to be overdried. Therefore, an object of the present invention is to utilize high-salt groundwater in salt-accumulated soil without supplying a large-scale facility, and to effectively remove this salt to supply it to crops. It is to provide a method for vegetation such as crops in soil at low cost.

[0004]

Means for Solving the Problems In view of the above object, as a result of intensive studies, the present inventors have found that a semipermeable membrane that is permeable to water or water vapor and substantially immiscible with water-soluble salts is used to absorb water between a water layer and plants. By arranging between the roots, it becomes possible to supply only the water containing no water-soluble salts to the water-absorbing roots of the plant, for example, from the water of high salinity in the salt-accumulated soil, and under normal conditions, the plant It was found that plants can grow in an environment where high salt water cannot grow.

In the present invention, a semipermeable membrane that is permeable to water or water vapor and impermeable to water-soluble salts means that an aqueous solution in which water-soluble salts are dissolved is arranged on one side of the membrane, and a temperature difference and a pressure difference are present on both sides of the membrane. Is a semipermeable membrane in which only water or water vapor in the aqueous solution in which water-soluble salts are dissolved is permeated from the other side of the membrane and water-soluble salts are not permeated. In the present invention, a semipermeable membrane that is substantially impermeable to water-soluble salts does not mean a membrane that is completely impermeable to water-soluble salts, but has a solute permeability coefficient B (cm / s) described later,
It is a semipermeable membrane that exhibits salt exclusion characteristics in which the concentration of water-soluble salts in the permeate decreases when an aqueous solution containing water-soluble salts of 5 × 10 ⁻⁴ or less is permeated. Examples of such a semipermeable membrane include a reverse osmosis membrane that allows only water to permeate from an aqueous solution of water-soluble salts due to a pressure difference, and a water vapor permeable membrane that allows only water vapor to permeate from an aqueous solution of water-soluble salts.

In the present invention, the reverse osmosis membrane is a semipermeable membrane used for desalination processes such as desalination of seawater or sewage by the reverse osmosis method. The reverse osmosis method is a separation technology in which the solvent is taken out through the semipermeable membrane by applying a pressure higher than the osmotic pressure to the supply liquid side through the semipermeable membrane (reverse osmosis membrane) that has the property of allowing only the solvent in the solution to permeate. is there. In the case of the vegetation method of the present invention, the principle of the reverse osmosis method cannot be said to be working to supply water containing no water-soluble salts from the water of high salinity to the water-absorbing roots of the plant, but reverse osmosis The high salt rejection properties of the membrane work well.

In the present invention, the pure water permeation coefficient A of the membrane and the solute permeation coefficient B of NaCl given by the following formulas are used as the indexes of the water permeability and the salt removal property of the reverse osmosis membrane suitable for this application. To be

Pure water permeation coefficient A (g / cm ² · s · atm) = F / (ΔP-Δ
π) × 119.6 × 10 ⁻⁵ Solute permeability coefficient B (cm / s) = (100−R) / R × F × 115.
7 × 10 ⁻⁵ where F: amount of water produced by the membrane (m ³ / m ² · day), R: NaCl rejection of the membrane (%), ΔP: pressure difference (kg / cm ² ), Δ
π: osmotic pressure difference (kg / cm ² ), which can be experimentally determined by a common reverse osmosis method for permeation of a saline solution.

In the present invention, as a reverse osmosis membrane suitable for this application, a membrane having a pure water permeability coefficient A (g / cm ² · s · atm) of 1 × 10 ⁻⁵ or more has a moisture supply characteristic. Excellent and preferable. The solute permeability coefficient B (cm / s) is 5 × 1
A film having a ^particle size of 0 ^-4 or less is excellent in salt exclusion property and is preferable.

In the present invention, as a specific example of the reverse osmosis membrane, in the case of an asymmetric membrane, a cellulose acetate type or polyamide type membrane is particularly preferable because it is excellent in separation performance, durability and chemical resistance. Further, in the composite membrane, examples of the functional layer formed on the porous support layer include polyether-based, aromatic polyamide-based, aliphatic polyamide-based, polyethyleneimine-based, and polyethylene oxide. Above all, it is preferable to use a crosslinked polyamide in view of excellent blocking performance even when the permeation performance is improved by thinning the film, and also in view of chemical resistance. As the preferred polymer of the porous support layer, polysulfone, polyether sulfone, polyphenylene sulfide sulfone, aromatic polysulfone material such as polyphenylene sulfone, cellulose acetate, ethyl cellulose, cellulose-based material such as cellulose, polyacrylonitrile, polypropylene,
Polyolefin-based materials such as polyethylene, polyvinylidene fluoride, fluorine-containing polymer-based materials such as polytetrafluoroethylene, polyamide-based materials or polyimide-based materials can be used, but among these, sufficient permeability, An aromatic polysulfone-based material is preferably used because it is easy to control the pore size. In order to further increase the strength of the support layer, there are publicly known underlayers of the support layer containing polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyamides such as nylon, and natural fibers as main components. It is preferable to have a reinforcing layer such as a woven fabric or a non-woven fabric.

In the present invention, the water vapor permeable membrane is a membrane that allows only water vapor to permeate from an aqueous solution of a water-soluble salt.
In the case of a water vapor permeable membrane, due to the hydrophobic and non-porous nature of the membrane,
The permeation of the aqueous solution is blocked, and the water becomes water vapor, permeates the membrane, and is supplied to the plant.

As a water vapor permeable membrane suitable for this application, a water vapor transmission coefficient of the membrane is preferably 0.5 (g / m ² · atm · 24 hr) or more.

As a membrane having such a function, a known hydrophobic porous membrane or a gas permeable composite membrane which allows only water vapor to pass through without water permeation is suitable. As a specific example of the hydrophobic porous membrane, a hydrophobic porous membrane obtained by melt-casting or wet-casting polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, poly-4-methylpentene, or the like is preferable. Those having a pore size of 5 μm or less in these hydrophobic porous membranes are particularly preferable because they have excellent aqueous solution blocking properties.

The gas-permeable composite membrane is a membrane in which a polymer homogeneous layer is formed on the same porous support layer as the reverse osmosis membrane composite membrane. Specific examples of the polymer homogeneous layer formed on the porous support layer include polyorganosiloxane,
Examples thereof include crosslinked polyorganosiloxane, polyorganosiloxane / polycarbonate copolymer, polyorganosiloxane / polyphenylene copolymer, polyorganosiloxane / polystyrene copolymer, polytrimethylsilylpropyne, and poly-4-methylpentene. Among these, crosslinked polydimethylsiloxane is most preferable in terms of high mechanical strength and high water vapor permeability. This cross-linked polydimethylsiloxane differs in the performance of the thin film obtained depending on the production method, and is disclosed in JP-A-60-257803 and JP-A-62-62803.
The thin film of the crosslinked polydimethylsiloxane obtained according to the production method described in JP-A-216624 / 62-216623 is preferable because it has excellent gas permeability and few pinholes.

In the present invention, a method of arranging the semipermeable membrane between the water layer and the water-absorbing root of the plant is to embed a sheet-shaped semipermeable membrane in the surface layer of soil and grow the plant on it. Examples include, but are not limited to, a method in which soil and plants are put in a semipermeable membrane molded in a cup shape or a bag shape and embedded in the surface layer of the soil. Also, if the semipermeable membrane alone does not provide sufficient water for plant growth or if the rate of evaporation of the supplied water is extremely high, a water retention agent consisting of a water-absorbent gel in the soil near the semipermeable membrane. It is also possible to mix the above, or to cover the soil surface with a film or the like. When the salt concentration of soil is particularly high, it is effective to use a method of reducing salt content of soil by coexisting with a salt-absorbing plant (creaming crop) together with the present invention.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0017]

【Example】

Examples 1 to 4 Water or saline solution having a predetermined concentration was put in the bottom of a medium-deep dish No. 4 having an upper diameter of 12 cm, a lower diameter of 10 cm, and a depth of 3 cm, and the functional layer was contacted with the saline solution on the Toray. Reverse osmosis membrane UTC-60 (Pure water permeation coefficient A: 1.
6 × 10 ⁻⁴ (g / m ² · atm · 24 hr), NaCl solute permeability coefficient B: 2.9 × 10 ⁻⁴ (cm / s), 15 cm × 15 cm)
Was fixed, and 160 g of paddy soil (on which the particle size was adjusted with a 1 mm mesh sieve, water content 0.8%)
Was placed and left at a temperature of 23 degrees. After 26 hours, the paddy soil was weighed. As a result, as shown in Table 1, in all the experiments, 20 g or more of water was supplied to the paddy soil through the reverse osmosis membrane UTC-60.

[0018]

[Table 1] Examples 5 to 12 To the bottom of the container of medium-deep dish No. 4 having a diameter of the upper part of 12 cm, the lower part of the diameter of 10 cm and the depth of 3 cm, water or a saline solution having a predetermined concentration was placed, and the functional layer was contacted with the saline solution. Reverse osmosis membrane UTC-60 (15cm x 15cm)
Was fixed, and 140 g of paddy soil (water content 2.
3%) and place barley and beet seeds (1
3 seeds per dish) were sown and left at a temperature of 23 to 28 degrees. The results of calculating the germination rate by counting the number of germinated individuals after a predetermined number of days are shown in Table 2.

[0019]

[Table 2] Comparative Example 1 Examples 6 to 12 using filter paper instead of the UTC-60 membrane.
A germination experiment was conducted in the same manner as in, but the salt concentration was 100
No germination was observed at any of mM to 600 mM.

[0020]

EFFECTS OF THE INVENTION The vegetation method of the present invention exhibits the following effects for agricultural production on salt-accumulated soil such as dry land.

(1) Agricultural production on salt-accumulated soil such as dry land is possible without requiring the implementation of a large-scale facility or an excessive energy source.

(2) It is possible to use groundwater having a high salinity in the salt-accumulated soil and to effectively remove the salt to supply it to the crop even in an area having a poor water source such as a dry land. No large-scale irrigation equipment is required.

(3) Since agricultural production can be carried out without using unrecoverable chemicals such as chemicals and water retention agents, there is little influence on the environment such as pollution of groundwater veins.

Claims (5)

[Claims] 1. A vegetation method comprising arranging a semipermeable membrane permeable to water or water vapor and substantially impermeable to water-soluble salts between a water layer and an absorptive root of a plant. 2. The reverse osmosis membrane is a semipermeable membrane which is permeable to water or water vapor and substantially impermeable to water-soluble salts.
Vegetation method. 3. The pure water permeability coefficient A of the reverse osmosis membrane is 1 × 10 ^−5.
3. The vegetation method according to claim 2, wherein the solute permeation coefficient B of NaCl is 5 × 10 ⁻⁴ (cm / s) or more and (g / cm ² · s · atm) or more. 4. The vegetation method according to claim 1, wherein the semipermeable membrane that is permeable to water or water vapor and is substantially impermeable to water-soluble salts is a water vapor permeable membrane. 5. The water vapor permeable membrane has a water vapor transmission coefficient of 0.5.
(g / m ² · atm · 24 hours) or more, The vegetation method according to claim 4, characterized in that