IL134129A - Method for afforestation of sands and the like and structure used for the method - Google Patents

Description

METHOD FOR AFFORESTATION OF SANDS GROUND AND THE LIKE AND STRUCTURE USED FOR THE METHOD vpnp *Tiy»l7 nwv BACKGROUND OF THE INVENTION 1. Field of the invention: The present invention relates to a ntethxd for afforestation and to a structure used for the method. This method is designed for afforestation of deserts, dunes, and sands suffering extreme croughtiness due to a larger amount of evaporation compared with rainfall.

With this method, one will be able to grow plants and vegetables in deserts, dunes, and sands, thereby making them iartile. 2. Description of the Related Art: There have been proposed various methods for afforestation of extremely droughty lands, such as deserts, dunes, and sands, where evaporation exceeds rainfall.

For example, Japanese Patent Laid-open »>. 60613/1989 discloses a method for afforestation of deserts. This method consists of driving sheathing boards into the land for planting at s boarder,digging out soil in the surrounded area, forming an impervious la:¾r on the bottom and wall of the hole, placing watering pipes and compostii g soil in the hole for forming a vegetation layer, seeding inthe vegetation layer, covering the surface of the vegetation layer with a breathable protective film and a shading film, and allowing germination.

Also, Japanese Patent Laid-open No. 104741/1992 discloses a method for afforestation of arid land. This method con!fists of burying boards in soil of arid land, thereby forming a partitioned part surrounded by the buried boards, mixing the soil in the partitioned part with a water holding material in a certain ratio, planting trees in the partitioned part, tightly closing the top of thepartitioned part efter planting, and watering the partitioned part until the planted trees are rooted deep to ground water.

Japanese Patent Laid-open NO. 197626/1954 discloses a method for afforestation of deserts. This method consists c forming partly in sand a substance or structure having both water retent- ity and airpermeability, and then seeding or planting in the upper part cf the substance or structure.

In addition, Japanese Patent Laid-open N3. 49722/1985 discloses a method for vegetation. This method consists of miking holes at certain intervals in scree, desert, coastal sand dune, or slope, and setting in each hole a bottomless cylindrical body containing a nirsery plant therein, said cylindrical body being reticulate, perforated, a;: of fibrous structure to impart water permeability and water absorptivity through capillary action and to permit lateral roots to grow through it.

OBJECT AND SUMMARY OP THE INVENTION Of the above-mentioned four Japanese patents, the first and second are intended to create in land a water holding pert suitable for plant growth, thereby growing plants in such a part. Therefore, afforestation in this manner takes a great deal of labor and expenses to form the vegetation layer, in addition, planted trees need innegligi le labor and expenses for watering. Thus, the methods disclosed therein «tre not practicable in a vast deser .

By contrast, the third (which employs a water-retentive and air-permeable cylindrical structure) is advantageoui over the first and second because it permits the vegetation layer to be fcxmed easily and economically. However, the substance or structuie does not retain water necessary for plant growth in desert where the (faytime temperature is 70-80 ° C or the average temperature is 40-50 ° C ever in the ground 30-50 cm deep. In such an environment, water evaporates easily due to ground heat, and hence there is an acute need for watering. Ihe method of the third reference is effective in areas of comparatively moderate climate but is not effective in arid land (such as desert) where ths daytime temperature is high and the water evaporation is rapid.

The method of vegetation disclosed in ths fourth reference seems effective in that the planted trees can have root downward; however, like the method of the third reference, it will not w¾rk effectively in arid land such as desert.

The present invention was completed in v.'.ew of the foregoing. It is an object of the present invention to provide a nethod for afforestation of sands and the like, said method permitting one to grow easily trees and vegetables in tropical arid land where the daytiiie temperature is high and the water evaporation is rapid. It is another ob ect of the present invention to provide a structure to be used for ί aid method.

The first aspect of the present inventior resides in a method for afforestation of sands and the like, the method comprising digging the ground to form a vertical hole with a prescribed sectional area and depth, fitting an outex cylindrical body into the hole filling the outer cylindrical body with soil controlling a water-holding material, making a hole with a prescribed sectional area and depth at the center of the soil in the outer cylindrical body, placing in the hole an inner cylindrical body with a prescribed sectional area and length which is filled with soil containing a water-holding material and has a lixge number of vent holes in its lower section, watering the soil in the out«r cylindrical body and the inner cylindrical body so that the water-holdin material absorbs sufficient water, sowing a seed or transplanting a nursery tree in the soil in the inner cylindrical body, and growing the plant, v th the outer cylindrical body preventing water from escaping from the so l therein, and the soil in the outer cylindrical body isolating the soil in the inner cylindrical body from the ground heat, thereby keeping the soil for vegetation in a cool and wet condition.

The second aspect of the present invention resides in a structure used for afforestation of sands and the like, t i structure comprising a heat-insulating outer cylindrical body with a priscribed sectional area and length, and a heat- insulating inner cylindrical body with a prescribed sectional area and length, the inner cylindrical body being filled with soil for vegetation containing a water-holding material and being inserted into a hole formed at the center of the outer cylindrical body.

The third aspect of the present invention resides in a structure used for afforestation of sands and the like, the structure comprising a heat-insulating outer cylindrical body with a prescribed sectional area and length, which is filled with soil containing a water-holding material such that a hole with a prescribed sectional area and length is left at the center of the soil, and a heat-insulating inner cylindrical body with a prescribed sectional area and length, the inner cylindrical body being filled with soil for vegetation containing a water-holding material and being inserted into the hole formed at the centi r of the outer cylindrical body.

BRIEF DESCRIPTION QP THE DRAWINGS Fig. 1 is a partly cut-away perspective view illustrating the method for afforestation of sands and the like according to the present invention. Fig. 2 is a sectional view showing the structure in which a plant grows.

Fig. 3 is a sectional view illustrating another embodiment of the method for afforestation of sands and the like iccording to the present invention.

Fig. 4 is a graph showing how the soil temperature changes with time. The soil temperature is that in the inner cylinder placed in the outer cylinder, that in the inner cylinder buried alaris in soil at the site, or that in soil at the site.

Fig. 5 is a graph showing how the ratio of water content varies with the depth of soil. The ratio of water content is that in the inner cylinder placed in the outer cylinder, that in the inner cjylinder buried alone in soil at the site, or that in soil at the site.

DESCRIPTION OF THE PREFERRED EMBODIMENT According to the present invention, the method for afforestation of sands and the like is characterized by employing a cylindrical body consisting of an outer wall and an inner wall, loth filled with soil containing a water-holding material. This cylindrical body is buried in the land to be afforested. Soil in the inner cylinrier is for vegetation, and soil in the outer cylinder is for insulation of ground heat. Therefore, the soil for vegetation is kept moist, so that it hi lps germination of sown seeds or growth of planted nursery trees.

A detail description is given below of the method of the present invention for afforestation of sands.

Pigs. 1 and 2 illustrate the basic idea of the method for afforestation of sands and the like according tc the present invention.

Afforestation starts with digging the soil of the land like desert to make a cylindrical vertical hole (X) below the ground level (G). The hole has a prescribed sectional area (or diameter) and depth. Digging may be accomplished by using a powered earth auger. Into the hole (X) is fitted an outer cylinder (1) whose diameter is approximateLy equal to that of the hole (X) and whose length is approximately equal to tie depth of the hole (X).

Then the cylinder is filled with soil (Si) containing a water-holding material. At the center of the soil is ::ormed a space having a prescribed sectional area and depth. One way to form this space is to fill the hole with soil (SI), with a cylindrical body1 placed vertically at the center thereof, which is removed afterward. Thin cylindrical body has a prescribed diameter and length. Another way is by digging with a powered earth auger the soil (SI) which has been placed in the hole (X) . The resulting hole should have a prescribed diameter and depth.

On the other hand, an inner cylinder (2) is filled with soil (S2) for vegetation containing a water-holding material. This inner cylinder has a diameter which is slightly smaller than that of the hole made in the soil in the outer cylinder (1) and also has a length which is almost the same as the depth of the hole made in the soil in the outer cylinder (1) . It is closed at the bottom and open at the top. Filled with soil (S2), the inner cylinder (2) is loosely tied at certain intervals so that soil (S2) does not move downward. The tied parts are indicated by 2a.

The inner cylinder (2) has vent holes (ί , 3, ...) at least in its lower surface, preferably in its entire surface, so that the soil therein is supplied with sufficient water. The filled and tied inner cylinder (2) is immersed in water so that the soil (S2) becomes sufficiently moist and the water-holding material absorbs sufficient water.

The inner cylinder (2) filled with soil (S2) containing a water-holding material is inserted into the hole made at the center of the outer cylinder (1). The gap between the inner cylinder (2) and the soil (SI) in the outer cylinder (1) is filled with soil. Then, the soil in the outer cylinder (1) is watered so that the soil (Si) bisomes sufficiently moist and the water-holding material absorbs sufficient water.

In deserts, the soil temperature outside the outer cylinder (1) at a depth of about 30-50 cm is about 40-50° C, whereas the temperature of soil (SI) inside the outer cylinder (1) is kept at abMit 30° C and temperature of soil (S2) inside the inner cylinder (2) is kept it about 25 β C. Thus, the soil (S2) inside the inner cylinder (2) permits rcLinary seeding or transplanting at a depth of about 50 mm below th» surface.

The assembling of the outer cylinder (1), the inner cylinder (2), the soil (SI), and the soil (S2) may be carried out at the site of afforestation. However, it may also be possible to bring previously assembled sets into the site of afforestation.

One embodiment of the structure may be ramposed only of the outer cylinder (1) and the inner cylinder (2). This structure and the water-holding material are brought into the site of aiforestation, and the soil (SI) and the soil (S2) are made by mixing local soil with the water-holding material .

An alternative embodiment of the structure is an assembly of the outer cylinder (1) filled with the soil (Si) containing a water-holding material, and the inner cylinder (2) filled with the soil (S2) containing a water holding material. This structure can be easily set once holes are dug in the ground at the site for afforestation. This contributes to afforestation in a simple way.

The outer and inner cylinders constitut ng the structure of the present invention may be formed from any material which is not specifically restricted so long as it retains their shape whan they are filled with the soil containing a water-holding material. It is desirable that at least the outer cylinder should be made of a material whic ι effectively prevents water from escaping out of the soil (SI) therein.

The outer cylinder may be formed from a isheet of plastics such as polyvinyl chloride, polyethylene, and polypropylime. It may also be molded from such plastics. The same holds true with t i: inner cylinder as a matter of course.

Moreover, the outer and inner cylinders nay be formed from a material selected from biodegradable plastics, kiaft paper, sisal hemp, cedar bark, carbon paper, and regenerated corruga ed board, which decompose and vanish spontaneously in soil. This is desirable from the view point of environmental protection.

The outer and inner cylinders are not l:jnited to those which have a circular cross section. They may have a polygonal or elliptic cross section, although a circular cross section is desirable.

The dimensions of the outer and inner cylinders may be determined according to the region, climate, weather, soil property, soil temperature, and soil moisture content. The ratio of the se ional area of the inner cylinder to the sectional area of the outer cylinder may preferably be from 1:15 to 1:20.

The length of the outer and inner cylinders may preferably be from 500 to 1500 cm, which is equivalent to the depth of the stratum water necessary for plant growth without artificial watering in deserts.

The outer cylinder has an open top but rcay or may not have a closed bottom. The open top may be covered with, a sheet (4) after seeding or transplanting in order to prevent water evaporation. In the case of transplanting, a hole is made in the sheet for tie nursery tree to pass through. The sheet permits water vapor to condeise on the back side thereof due to temperature difference in the daytime and night. Condensed water drops are recycled for watering. The sheet may ]« replaced by small pebbles for the same effect.

By contrast, the inner cylinder should bijsically have a closed bottom. However, this is not mandatory, if the Inner cylinder is constructed such that it does not permit the soil therein to slip down by gravity. The inner cylinder may have a large nurtber of small vent holes at least in the lower part thereof. These vent holes permit the soil and water-holding material to be supplied with water for germination and also permits the roots to grow outward through the inner cylinder. These vent holes may also be formed entirely in the wall oJ the inner cylinder.

According to the present invention, the method for afforestation of sands and the like employs the structure as shovn in Figs. 1 and 2 as mentioned above. This structure may be modified as shown in Fig. 3 in order to improve the water retentivity of the soil in the outer and inner cylinders.

An example of such modification is to meke the ground surface (GL) partly concave as indicated by GL1. The concave part forms a slope which gently declines toward the center, so that it collects rainwater and lets it flow into the soil (SI) and (S2) in the outer ard inner cylinders.

Another example of the modification is t> provide the outer cylinder with an upper rim (la). This rim extends inward from the upper end of the outer cylinder such that it covers the soil (SI) in the outer cylinder. The second modification is similar to the first one in that the opening of the outer cylinder is covered; however, it has the advantage of not requiring the sheet (4) to cover the opening.

The object of the above-mentioned modifi-iation may be achieved by placing rocks (R) on the top of the outer and inner cylinders. These rocks produce the shade which prevents evaporation, keeping the soil moist for a long period time.

Another means for water retention is to j:orm a water container at the lower end of the outer cylinder (1). When the outer cylinder (1) is buried, the water container (lb) filled with water functions as a weight which facilitates burying. In addition, a certain period of time after burying, the water container breaks in the soil to supply the soil with water.

According to the present invention, the soil in the outer and inner cylinders is incorporated with a water-holding material. This water-holding material may preferably be a substance which ho.ds water and serves as a fertilizer. It is exemplified by charcoal, peat moss, compost, husk (of sorghum and peanut), seaweeds, dung {cow dung), weeds, and bentonite.

The soil into which the water-holding msterial is incorporated may be one which is available at the site for afforestation. The mixing ratio of the soil to the water-holding jnaterial varies depending on the degree of dryness at the site for afforestation. It is usually 1:1 for the soil in the inner cylinder and 1:0.3 to 1:0.5 for the scil in the outer cylinder.

The method for afforestation of sands and like according to the present invention may be applied to any of the following trees and i vegetables. (1) Trees • Forest trees: white popinac, parkinsonia, acacia albida, and acacia trotilis.

• Tall trees: Indian ceder, big-leaved popinac, r^unarind tree, Chinese date, Chinese tamarisk, coast oak, eucalyptus, "kotateishi" , and Avicennia maria. • shrubs: jojoba, "tougoma", and "shionoki".

■ Flowering trees: royal poinciana, "kidac&ibeninouzen", sambucus, caesar pinia, hibiscus, sweet-scentet. oleander, bougainvillea, jusmine, red sage, green pisojria, red pisonia, acalypha, Sansevieria trifasciata, and creen acalypha.

• Fruit trees: mango, guava, orange, mandarin, PCnkan mandarin, lemon, pomegranate, blue-crown passion r!lower, and "uchivra" cactus. ( 2) Vegerables ■ Leaf vegerables: "komatuna" (Brassica campestjis), "pakuchoi", spinach, Jew's marrow, and cabbage.

• Root vegetables: turnip, carrot, Japanese radish, and edible burdock.

• Fruit vegetables: okra, tomato, sweet pepper, green pepper, cucumber, pumpkin, and melon.

• Pulse crops: kidney bean, "edamame" , soybean, and pea.

In tropical arid land, such as desert, the temperature on the ground surface usually reaches 70-80 ° C and the temperature in the ground (30-50 cm deep) is also as high as 40-50 ° C. One reason why it is difficult to grow plants (such as trees and vegetables) in such arid land is that the environmental temperature (including the ground temperature) is close to the upper growth limiting temperature. At such a high ground temperature, transplanted plants do not take root easily, and they often die off or have their growth greatly inhibited.

Thus, the present invention provides a mithod for afforestation of sands and the like and a structure used for said method, which are designed to create an environment for seeds to germinate easily or for nursery trees to grow easily. This environment is not one which is created easily by irrigation. The environment created by irrigation supplies plants with water but plants spread their roots only in the jurface layer of soil. By contrast, the environment produced by the method and structure according to the present invention permit plants to take root deep downward so that plants by themselves seek water in soil and get water permanently.

In order to collect data for afforestation of tropical arid land, the present inventors carried out the following fundamental experiments.

Large containers each containing soil (600 mm tlick) were placed in a facility for artificial weather conditions.

(A) In the first container was placed a douMe-walled cylindrical structure composed of an outer cylinder (150 mm in diameter and 400 mm long) and an inner cylinder (50 mm in diameter and 400 mm long), with both cylinders filled with soil.

(B) In the second container was placed a sirgle-walled cylindrical structure, 50 mm in diameter and 400 mm long, filled with soil.

(C) In the third container was placed no cylindrical structure.

The above-mentioned three containers were allowed to stand in the facility, and the ground temperature (at a depth of 50 mm) was recorded a < certain intervals for 24 hours {from 0:00 to 24:30, July 15). The results are shown in Fig. 4.

Moisture content was measured at different depths, and the ratio (%) of the measured value to the original moisture content was plotted against depth. The results are shown in Fig. 5. it is noted from Fig. 4 that the ground temperature varies less throughout 24 hours in the case where the doubl -walled cylinder was used than in the case where the single-walled cylinder was used or no cylinder was used. It is also noted from Fig. 5 that the ratio of moisture content at different depths is better in the case where 1he double-walled cylinder was used than in the case where the single-wallet, cylinder was used or no cylinder was used.

The foregoing suggests that the outer cylinder and the soil (containing a water-holding material) therein provide good heat insulation, and water retentivity for the soil (containing < water-holding material) in the inner cylinder.

Incidentally/ in Figs. 4 and 5, A repres'ents data in the case where the double-walled cylinder was used, B represents data in the case where the single-walled cylinder was used, and C represents data in the case where no cylinder was used.

The results of the experiments show that the method and structure for afforestation of sands and the like accordirg to the present invention produce the following effect. The soil containing a water-holding material is kept moist because the outer cylinder isolates the soil therein from the external soil which has a ground temperature clcse to the growth limiting temperature. The outer cylinder also prevents evaporation of water from the soil therein. The soil in the outer cylinder functions as a heat insulator and effectively prevents the soil in the inner cylinder from getting hot and from losing moisture. Therefore, the soil in the inner cylinder is kept at about 25° C adequate for plant growth in good moist conditions.

Under the above-mentioned conditions, plants take root easily and absorb nutrients from the soil in the cylinder. The inner cylinder causes roots to grow only downward, so that the roots absorb water and nutrients from the soil through the vent holes made in the lower part of the cylinder wall. Eventually, the roots seek water by themselves in the wet layer or water vein where rainwater is held deep in soil. Thus the transplanted nursery trees grow, and the object of afforestat:,on is achieved in a short period of time.

The invention will be described in more detail with reference to the following examples and comparative examples.

Example 1 Afforestation of desert was carried out in Djibouti (in northeastern Africa) as follows. The desert in this country is composed of clay, silt, and sand, and it has a wet layer at a depth of about 1-2 meters.

The ground for afforestation was dug by using an earth auger to make a vertical hole, about 150 mm in diameter and atout 1000 mm deep. An outer cylinder made of polyethylene sheet, 150 mm in diameter and 1000 mm long, with an open top and bottom, was inserted into the hole. This outer cylinder was filled with soil (at the site) mixed with peat moss as a water-holding material. The mixing ratio of soil to teat moss was 1:0.5 by volume. t At the center of the soil in the outer cylinder was made a vertical hole, about 50 mm in diameter and about 900 mm long, by using an earth auger.

A bag with an open top, about 50 mm in diameter and about 900 mm long, was made of polyethylene sheet. A large number of vent holes were made in the lower part (about 300 mm long) of th» bag. This bag was filled with soil (at the site) mixed with peat moss as i water-holding material. The mixing ratio of soil to peat moss was 1:1 by volume. The filled bag was loosely tied at three positions. Thus, there wau obtained the inner cylinder.

The inner cylinder was immersed in water for 24 hours so that the peat moss absorbed water. It was then inserted into the hole at the center of the outer cylinder. The gap between the inn r cylinder and the soil in the outer cylinder was filled. The soil in the outer cylinder was watered so that the peat moss absorbed water sufficientl . The soil in the inner cylinder was sown with a seed of white popinac is a leguminous evergreen tree.

Comparative Example 1 The inner cylinder filled with soil and peat moss was prepared in the same way as in Example 1. It was immersed in water so that the peat moss absorbed water. The inner cylinder alone vas buried in soil and sown with a seed of white popinac.

Comparative Example 2 Soil at the site was sown directly with a seed of white popinac, with the cylinders not used.

The height of the white popinac was measured 75 days after sowing to examine its growth in Example 1 and Comparative Examples 1 and 2.

The results are shown in Table 1.

Table 1 Examples Height (cm) Example 1 22 (double-walled cylinder) Comparative Example 1 9 (single-walled cylinder) Comparative Example 2 5 (without cylinder) Example 2 and Comparative Examples 3 and 4 The same procedure as in Example 1 and i fcjmparative Examples 1 and 2 was repeated respectively except that the White popinac was replaced by acacia albida as a leguminous evergreen tree.

The height of the acacia albida was measured 75 days after sowing to examine its growth. The results are shown in Table 2.

Table 2 It is noted from Tables 1 and 2 that thfi method for afforestation in Examples 1 and 2 is by far superior to that in Comparative Examples 1 to 4. It has been proved that the present invention piovides an effective method for rapid afforestation of sands and the like.

According to the present invention, affPrestation of sands and the like is accomplished in the following way. Firit, the soil is dug out to make a vertical hole. In the hole is placed an outer cylindrical body filled with soil containing a water-holding material. At the center of the outer cylinder is placed an inner cylindrical body filled with soil for vegetation containing a water-holding material. This inner cylinder has vent holes at least in its lower part. The outur cylinder isolates the soil therein from its surrounding soil, thereby preventing the evaporation of water from the soil therein. The soil in the outer cylinder functions as a heat insulator which isolates the soil therein :ram the surrounding soil whose temperature exceeds that for plant growth Moreover, the soil in the outer cylinder keeps wet the soil in the inner <ylinder, so that the seed or seedling is supplied with sufficient water for growth at an adequate temperature. After gemination or rooting, the young plant takes root deep in search of wet layers or water veins where rainwater is retained. With sufficient water supply in this manner, the young plant grows rapidly. Thus it is passible to achieve afforestation of sandM and the like easily and rapidly.

According to the present invention, the method of afforestation of sands and the like employs a double-walled cylindrical structure. The inner cylinder filled with soil for vegetation mixed vith a water-holding material is surrounded by the outer cylinder filled with soil containing a water-holding material and having a certain thickness. The inner cylinder is placed in the soil in the outer cylinder. The cuter cylinder prevents the evaporation of water from the soil and water-hoJding material. The soil in the outer cylinder functions as a heat-insulatir g layer which protects the soil in the inner cylinder from an excessively high ground temperature inadequate for plant growth. In addition, the soil in the outer cylinder keeps cool the soil in the inner cylinder through water evaporation from it. Thus, the temperature and water content of the soil in the inner cylinder are kept adequate for plant growth at all times.

The method for afforestation according to the present invention is superior in that it permits afforestation with a small amount of material and labor without requiring special skills. X*: permits economical and efficient afforestation without large-scale confJtruction work. Therefore, the present invention greatly contributes to afiPrestation of deserts and tropical arid land.

According to the present invention, the structure used for afforestation of sands and the like is conrposed of an outer cylinder having a heat-insulating effect and for holding therein soil containing a water-holding material and an inner cylinder placed at a central portion of the outer cylinder, having a heat-insulating effect and for holding therein a soil for vegetation containing a water-holdinq matirial. Alternatively, the structure for afforestation is composed of iin outer cylinder filled with soil containing a water-holding material and an inner cylinder filled with soil for vegetation containing a water-holding Material, with the inner cylinder being placed within the outer cylinder, Either of lthese structure permits effective afforestation of deserts whert! water evaporates vigorously and the soil temperature is inadequate for plant, growth.

Claims (14)

20 134,129/3 WHAT IS CLAIMED IS:

1. A method for afforestation of sands and the like, said method comprising digging in the sand to form a first bore with a prescribed sectional area and depth, fitting an outer heat-insulating cylindrical body into the first bore, filling the outer cylindrical body with soil containing a water-holding material, making a second bore with a prescribed sectional area and depth at the center of the soil in the outer cylindrical body, placing in the second bore an inner heat-insulating cylindrical body with a prescribed sectional area and length which is filled with soil containing a water-holding material and has a large number of vent holes in its lower section, watering the soil in the outer cylindrical body and the inner cylindrical body so that the water-holding material absorbs sufficient water, sowing a seed or transplanting a nursery tree in the soil in the inner cylindrical body, and growing the plant, with the outer cylindrical body preventing water front escaping from the soil therein, and the soil in the outer cylindrical body isolating the soil in the inner cylindrical body from the sand heat, thereby keeping the soil for vegetation in a wet condition.

2. The method for afforestation of sands and the like as defined in claim 1, wherein the first bore in the soil in the outer cylindrical body is formed by positioning an inner cylindrical body with a prescribed sectional area and length vertically at the center of the outer cylindrical body, and the space between the outer cylindrical body and the inner cylindrical body is filled with soil containing a water-holding material, and finally removing the inner cylindrical body.

3. A method for afforestation of sands and the like as defined in claim 1, wherein the second bore in the soil in the outer cylindrical body is formed by filling the outer cylindrical body with soil containing a water holding material and then digging the soil at its center to make a vertical second bore with a prescribed sectional area and depth. 21 134,129¾^

4. The method for afforestation of sands and the like as defined in claim 1, wherein the surface of the soil within a certain area gently declines toward the inner cylindrical body.

5. A method for afforestation of sands and the like as defined in claim 1, wherein the water-holding material is any one or more selected from char coal, peat moss, compost, husk of sorghum and peanut, seaweeds, dung such as cow dung, weeds, and bentonite.

6. The method for afforestation of sands and the like as defined in claim 1, wherein the inner cylindrical body is one which is prepared by filling a cylindrical body with a prescribed sectional area and length with soil containing a water-holding material, loosely tying at certain intervals along the length, and immersing in water so that the water-holding material absorbs sufficient water through vent holes made at least in the lower section of the inner cylindrical body.

7. A structure used for afforestation of sands and the like, said structure comprising a heat- insulating outer cylindrical hollow body with a prescribed sectional area and length, and a heat-insulating inner cylindrical body with a prescribed sectional area and length, said inner cylindrical body being filled with soil for vegetation containing a water-holding material and being inserted into a bore formed at the center of the outer cylindrical hollow body.

8. A structure used for afforestation of sands and the like, said structure comprising a heat- insulating outer cylindrical hollow body with a prescribed sectional area and length, which is filled with soil containing a water holding material such that a second bore with a prescribed sectional area and length is formed at the center of the soil, and a heat-insulating inner cylindrical body with a prescribed sectional area and length, having a number of vent holes in the lower section, said inner cylindrical body being filled with soil for vegetation 22 134, 129/2 containing a water-holding material and being inserted into the second bore formed at the center of the outer cylindrical hollow.

9. The structure used for afforestation of sands and the like as defined in claim 8, wherein the inner cylindrical body is one which is formed from a plastic sheet or one which is molded from plastics.

10. The structure used for afforestation of sands and the like as defined in claim 7 or claim 8, wherein the inner cylindrical body is one which is formed from a plastic sheet or one which is molded from plastics or a pipe of polyvinyl chloride.

1 1. The structure used for afforestation of sands and the like as defined in claim 7 or claim 8, wherein the outer cylindical hollow is provided with a water container at its lower ends, said water container functioning as a weight and supplying water to the soil upon breakage.

12. The structure used for afforestation of sand and the like as defined in claim 7 or claim 8, wherein the outer cylindrical hollow body is one which is formed from a material selected from biodegradable plastics, kraft paper, sisal hemp, cedar bark, carbon paper, and regenerated corrugated board, which decompose and vanish spontaneously in soil.

13. A method for afforestation of sands and the like according to claim 1 , substantially as hereinbefore described and with reference to the accompanying drawings.

14. A structure used for afforestation of sands and the like according to claim 7 or claim 8, substantially as hereinbefore described and with reference to the accompanying drawings. for the Applicant: WOLFF, BREGMAN AND GOLLER