JPS63251014A - Method for enhancing water holdability of soil - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the properties of soil with poor water retention or dry land soil (soil in general, including sand-only soil).

Yo's mouth In recent years, arid areas and desert areas (deserts) with little precipitation.

A variety of methods are being explored for greening projects and for making crafts (earthenware, imperial land), etc. As a conventional method for improving soil water retention, soil conditioners (hemolecular materials such as sodium polyacrylate and polyvinyl alcohol, and clay mineral materials such as bentonite) are mixed into the soil to improve soil water retention. There are known ways to improve In particular, bentonite has been used as a measure against water leakage in rice fields because it absorbs water several times its own weight in a fine powder state.

However, in severely dry areas such as desert areas, sufficient water retention cannot be obtained even with the use of such soil conditioners. Therefore, in recent years, polymers that form a human O gel (for example, crosslinked water-soluble polymers such as polyacrylic acid polymers, polyvinyl alcohol polymers, starch acrylic acid graft polymers, etc.) have been developed for use in dry areas. Research is being conducted on water retention agents.

Such superabsorbent polymers are provided in the form of fine powder, and absorb moisture and swell extremely quickly. Its water absorption amount reaches about 200 to 1000 times its own weight, and its water retention property is very excellent. However, this polymer has the following drawbacks when used as a soil water retention agent.

■Superabsorbent polymers are the same size as soil particles or even smaller, so they are often mixed into the soil and blown away by the wind or washed away by rainwater. , ■Water-absorbing polymers absorb water rapidly and intensely, so there are issues with how they get mixed into the soil (construction methods), or safety (risk of inhalation through breathing).
The handling management method that takes into consideration is more complicated than that of conventional soil conditioners. ■Since the super absorbent polymer is formed as a single material (pure material), when it absorbs water in the soil, it has a high magnification. Isotropic expansion occurs, which closes the voids between soil particles and reduces the air phase in the soil, inhibiting the circulation of air necessary for plants and hindering plant growth.

. The present invention was created based on this technical background, and instead of using fine powder like super absorbent polymers, water-swellable elastomers with moderate water absorption reactions are used. The purpose is to improve soil properties (water retention) by using water.

This purpose is achieved by: (1) mixing or burying the water-swellable elastomer in the soil in the form of granules or larger objects, or (2) covering the surface of the soil with a network formed of the water-swellable elastomer. This is achieved by fixing it on the soil surface.

Examples of water-swellable elastomers include: ■ Super water-absorbent polymers blended with soft resins such as polyurethane resins, ethylene-vinyl acetate copolymers and vinyl chloride resins, or rubber;
Alternatively, (2) elastomers such as polyurethane resins and epoxy resins, which themselves have hydrophilic groups and have water absorbing properties, can be mentioned.

Examples of water-swellable elastomers include: ■ Super water-absorbent polymers blended with soft resins such as polyurethane resins, ethylene-vinyl acetate copolymers and vinyl chloride resins, or rubber;
Alternatively, (2) elastomers such as polyurethane resins and epoxy resins, which themselves have hydrophilic groups and have water absorbing properties, can be mentioned. This water-swellable elastomer can be used, for example, in the form of particles of about 5 m square, in the form of strips, or in the form of a net (including a sheet with many holes). The granular material is used by being mixed into the soil, the strip material is buried in the soil in rows at intervals, and the mesh material is used by covering the surface of the soil.

To evaluate the water retention capacity of soil, it is necessary to examine whether the water contained in the soil is in a form that can be used by plants. As an evaluation method, it is common in agriculture to use the pF value. The pF value is a value obtained by converting the ability of soil particles to retain water into a water column height (cm) and taking the common logarithm of its absolute value (pF3=1 atm).

It is generally said that soil suitable for plant growth has a pF of 2.
It is estimated that it will be about 4.5 (confirmation by actual measurement has not been carried out). The reason for this is that, according to Test Example 1 described later, the initial growth condition of the medium in which a water-swellable elastomer was mixed or embedded during crushing by the method of the present invention was rather poor compared to the medium containing only sand; The situation is reversed over time, and when Figure 7 is taken into consideration, in the culture medium in which water-swellable elastomer is embedded during crushing by the method of the present invention, water is supplied to the plants through the gas phase (moisture). This is because it can be considered. Therefore, in order to better maintain water retention using water-swellable elastomers, mulching (covering the soil with mulch to prevent water evaporation and maintain a constant soil temperature) is used in combination. is valid.

The water-wetting elastomer used in the present invention has a vulcanized rubber-like appearance and is characterized by being formed into an arbitrary shape. Therefore, the elastomer can be formed into a pea-sized size. The elastomer can be mixed into the soil with a commonly used tillage machine, and the elastomer can be formed into a sheet and applied in the same way as a commonly used agricultural sheet.
Conventional agricultural civil engineering techniques can be applied.

In addition, the water-swellable elastomer used in the present invention has a water absorption reactivity (swelling rate,
The water absorption rate) can be set low, there are few management problems, and it is easy to handle with safety in mind.

Furthermore, in the method of the present invention, ingredients effective for plant growth such as nitrogen, phosphoric acid, and potassium are added to the water-swellable elastomer as soluble salts (Ca(JPOp)2).

By blending in the form of CaCO3, C1, NHHCl2), it is also possible to elute these active ingredients into the moisture in the soil. The amount to be mixed should be determined in consideration of various conditions such as the amount of water-swellable elastomer to be applied, the density of vegetation, and the expected number of years for which the effect will last. However, when carrying out the method of the present invention in places such as dry areas and urban areas where plants have difficulty growing and the soil itself has poor fertilizing capacity, excessive fertilization may lead to problems such as accumulation of salts. It is necessary to keep this in mind.

A water-swellable rubber that absorbs about 10 times its own weight in water was prepared by blending fine powder of sodium acrylate/polyvinyl alcohol copolymer into styrene/butadiene rubber.

■Prepare water-swellable rubber particles 4 (400g) formed as granules of approximately 5 #lff1 square mixed in sand 1 (26Kg), and form many holes 3 for water drainage at the bottom. water (4Kt) into a polystyrene resin container 2.
) was given (Figure 1).

■Similar to the case in the previous section■, put sand 1 (26/
(y), and a strip of water-swellable rubber 5 (dimensions: 30 x 40 x 5 m) was buried in the sand 1 along with a nonwoven fabric 6. The water-swellable rubber strips 5 are arranged in a lattice pattern on the same horizontal plane, and sand is poured onto the strips of water-swellable rubber 5. The strips of water-swellable rubber 5 are made of non-woven fabric so that the spaces between adjacent water-swellable rubbers 5. Stacked 6. The combination of the strip-shaped water-swellable rubber 5 and the nonwoven fabric 6 was arranged on the top and bottom at intervals. For such a soil composition, water (4Ks) as in the previous section ■! (Figure 2.

Figure 3).

■ Prepare a container with sand 1 (26Ng) in it,
Water (4 kg) was given to this (Figure 4).

■Changes in water retention amount were investigated for the above items ■, ■, and ■, and the results are shown in a graph in FIG.

Evaluation of test results> The water retention of a sample made only of sand is good immediately after water absorption, but it decreases significantly over time. On the other hand, samples using water-swellable rubber (especially water-swellable rubber particles 4
It can be seen that there is little change in water retention in the case of the water-retaining method, and that the water supply effect lasts for a long time.

Chikugasa V1 Using three types of samples similar to items ■, ■, and ■ in Test Example 1, with the zero hanging being the same <26 kg, 30 g of bahia grass (plant) seeds were mixed into the surface layer of 6 kg of sand, and then The plants were left with sufficient water supply (plant germination growth test).

Test results〉 From germination to early growth, the best results (good growth) were obtained using the sand-only sample (Figure 4), but after about 30 days, withering began to become noticeable, and after 50 days, the seeds began to die. After a while, it completely died. In contrast, in the samples using water-swellable rubber (Figures 1 and 2), the number of survivors was higher even after 50 days had passed. This result also agrees with the result of Test Example 1.

As shown in FIG. 6, a water-swellable rubber sheet 7 (120X
160 The accompanying changes in humidity during crushing were investigated. The results are shown in FIG.

<Evaluation of test results> In the case of a sample made only of sand, the humidity during crushing decreased significantly over time, whereas in the sample using water-swellable rubber, there was little change in humidity during crushing. Considering this result and the result of Test Example 2, it is estimated that moisture is supplied to plants when water-swellable rubber is used.

Specific usage examples of water-swellable rubber are shown below.

(Fig. 8) The strips of water-swellable elastomer 8 are regularly arranged at intervals in the vertical and horizontal directions (lattice arrangement), and then the non-woven fabrics 9, 9 are arranged.
The material is sandwiched from the top and bottom and buried in the soil in an almost horizontal position.

The nonwoven fabric 9 is provided to prevent soil from entering the space between the water-swellable elastomer strips 8 and 80.

The strip-shaped water-wetting elastomer 8 expands isotropically, and the amount of expansion is larger in the vertical and horizontal directions than in the thickness direction, so water can be retained with less pressure on the soil above and below.

4LHL! 1Ji (FIG. 9) A cylindrical body 10 is formed from a water-swellable elastomer (FIG. 9(a)). When the cylindrical body 10 is swollen in a free state, the ninth
As shown in Figure <b>, even if it swells in the soil, it is crushed by the earth pressure (Figure 9 (C)), so there is little change in external dimensions, and soil displacement can be sufficiently suppressed.

■1 (Fig. 10) A non-f
5 Wrap the moisturizing cloth 11 to suppress external change. 10th
As shown in FIG. 10(a) and FIG. 10(b), the cylindrical body 10 is I! !
It can moisten the soil and prevent soil displacement.

Marukojo A (Fig. 11) A semi-cylindrical body 12 is formed from a water-swellable elastomer, and non-swelling layers 13 are integrated on the outer periphery of the semi-cylindrical body 12, which are arranged at intervals, and a non-woven fabric 14 is also used to form a semi-cylindrical body 12. Bury inside (11th
Figure (a)).

When the semi-cylindrical body 12 swells, the entire body tends to become flat due to the restraint of the non-swelling layer 13 as shown in FIG. 11(b), so there is no pressure on the surrounding soil.

Use ff1 (Fig. 12) If the combination of the strip-shaped wettable elastomer 8 and the nonwoven fabric 9 shown in Fig. 8 is fixed in the soil 1816 with stakes 15, it will be possible to prevent the soil from being easily washed away by rainwater. Even if it is a strip-shaped swellable elastomer8. It is possible to prevent the nonwoven fabric 9 and the soil itself from flowing out.

Stool J, 9th (Fig. 13) The so-called net-covering method involves covering the surface of places (gently sloped areas) where the erosion and drying of surface water are noticeable using straw, straw, etc. is covered with a net-like body 17 made of a water-swellable elastomer sheet, and fixed with stakes 18, 18... According to this method, it is possible to prevent erosion of the soil surface, and also to ensure water retention and the growth of plants.

UUJLL (Figure 14) It is known to install static sand fences (4m square, 2m square, 47FL x 2m square) made of soda, yoshi, wheat straw, etc. for the preservation of coastal sand dunes.

This static sand fence is formed from a sheet made of aqueous AR4 echelastomer (having a large number of windows 20). The lower half of the sheet 19 is embedded and fixed in sand 22 using stakes 21 to form a rectangular static sand fence.

According to this method, it is possible to serve both as a sand fence and a water retention structure, and it is possible to improve the sand sand efficiency through greening.

11 Rikuno 1 As is clear from the above explanation, ■ a method for improving water retention of soil, which is characterized by mixing or burying a water-swellable elastomer in the soil in the form of granules or larger shapes; and (2) Water #3 A soil water retention method has been proposed, which is characterized by covering the surface of soil with a network formed of a full-type elastomer and fixing it to the soil surface.

According to this method, the following effects can be obtained.

(2) The water-swellable elastomer can be formed into any shape. When it is formed into pea-sized granules, it can be mixed into the soil using a general-purpose tillage machine, and when it is formed into a sheet, it can be applied in the same way as a commonly used agricultural sheet. By mixing such a water-swellable elastomer into soil, water retention can be imparted to soil such as dry land or sandy land, thereby contributing to agriculture and greening projects.

■Even when water-swellable elastomers are formed into granules, each particle can have a large weight, so
Unlike conventional fine powder superabsorbent polymers, it is not easily blown away by the wind.

■Water-swellable elastomers are formed into larger granules than conventional fine powder superabsorbent polymers, so there is no risk of workers inhaling them during construction.

■Water absorption reaction of water-swellable elastomer (fast swelling rate).

Since the water absorption rate (water absorption rate) can be reduced compared to that of conventional super absorbent polymers alone, there is no safety problem and handling is easy.

■When conventional fine powder superabsorbent polymers were mixed into soil, when they expanded, they closed the gaps between soil particles, significantly reducing the air phase in the soil and inhibiting plant growth. In the method of the present invention, the expanded shape can be controlled by selecting the shape of the water-swellable elastomer or by combining it with other materials, and the decrease in the gas phase in the soil can be suppressed.

■By selecting the shape of the water-swellable elastomer and devising a construction method, it is possible to prevent soil erosion due to rain and wind and ensure the water retention capacity of the soil.

■A fertilizing effect can be obtained by incorporating a fertilizer into the water-swellable elastomer.

[Brief explanation of the drawing]

Figure 1 shows a sample in which water-swellable rubber particles were mixed during crushing, Figure 2 shows a sample in which water-swellable rubber strips were arranged and buried during crushing, and Figure 3 shows a sample in which water-swellable rubber particles were mixed in during crushing. Figure 4 is a diagram showing the arrangement of strip-shaped water-wetting rubber in the sample, Figure 4 is a diagram showing a sample made only of sand, and Figure 5 is the result of examining the water retention properties of each sample as changes in the amount of water remaining during crushing. Figure 6 is a diagram showing a sample for measuring humidity change during crushing in which a water-swellable rubber sheet was buried during crushing, and Figure 7 is a graph showing a sample for measuring humidity changes during crushing in which a water-swellable rubber sheet was buried during crushing. Graphs examining changes in humidity during zero temperature after water supply in the case of only water supply, and FIGS. 8 to 14 are diagrams showing different construction modes of the method of the present invention, respectively. DESCRIPTION OF SYMBOLS 1...Sand, 2...Container, 3...Net, 4...Water-swellable rubber particles, 5...Strip-shaped water-swellable rubber, 6...Nonwoven fabric, 7... Sheet, 8... Strip-shaped water jITR elastomer, 9... Nonwoven fabric, 10... Cylindrical body, 1
1... Non-WBrB layer, 12... Semi-cylindrical body, 13...
・Non-Il! Junju, 14... Non-woven fabric, 15... Pile, 1
6...Soil, 17...Reticular body, 18...Pile, 19
...sheet, 20...window, 21...pile, 22...
・Sand Figure 1 Figure 2 Figure 3 Figure 5 Number of days elapsed Figure 6 Figure 9 (a) (b) (C) Figure 10 Figure 11 Figure 12 Figure 1'3 Figure 13 Procedure amendment book Showa 1962 May/I Representative Representative: 1962, Agent: 6, Number of inventions increased by amendment: 7, Subject of amendment: Specification 8, Contents of amendment: As attached, page 4 of the specification, Nos. 8 to 14 Line description “Water-swellable EX1~mer~
be able to. ” first.

Claims (2)

[Claims] (1) A method for improving the water retention capacity of soil, which comprises mixing or burying a water-swellable elastomer in soil in the form of particles or larger particles. (2) A method for improving the water retention capacity of soil, which comprises covering the surface of the soil with a network formed of a water-swellable elastomer and fixing it to the soil surface.