DPRKorea-Trade

Technique for Greening of Sandy Soil (including desert)

1. General consideration on the improvement of Sandy Soil
31% of continental area on our earth is sandy soil or desert, with a total area amounting to 48,000,000 km2. The majority of rain and irrigated water evaporates into the air or leaks downward. While the world population continuously increasing, the arable area is ceaselessly decreasing due to expanding of deserts.

The desert itself also significantly influences the ecological environment of human life. Therefore, the improvement of sandy soil and deserts is one of the most important tasks facing mankind at present.

The primary important problem in the improvement of sandy soil is to raise the water reserving ability of sandy soil, to a level that of usual arable land.
In general, the amount of water leaking downwards in sandy soil and deserts is 864 - 8610 mm/d, and the majority of soil granule is smaller than 0.25mm in diameter.
Therefore, its water containing and absorbing abilities become very weak.
If we create the same water reserving ability of sandy soil as that of arable land, the condition favorable for the growth of various plants on sandy soil would be provided, and it will also contribute to the improvement of environment.

2. Detailed Description of the technique
This is the technique for providing dry sandy soil with water necessary for plant growth.

It mainly consists of 3 techniques:
- Leaking water prevention technique.
- Water evaporation prevention technique.
- Water reserving technique of plant roots.

2.1 Leaking Water Prevention Technique for Sandy Soil

This is the technique to prevent the leakage of water from sandy soil downwards by forming a complex gel membrane composed of minerals, small amount of organic matters, higher polymer and inorganic materials, where the minerals play the main role in blocking the leakage. And small amount of organic matters, higher polymer and inorganic materials help the minerals disperse and improve the character of the complex gel formed by the action with the soluble salts in the soil, thereby increasing the leakage water prevention effect.

2.2 Water evaporation preventing technique on the surface of soil

This is the technique to prevent the water evaporation and to provide the growth of plants with favorable condition by covering the surface of soil with the sheets manufactured with biologically decomposable materials.
After raining, the water content of soil is usually 30 - 35% or thereabout, and during dry time the humidity of the soil 30cm below from the surface of soil is 20 - 30%, but the humidity of 30cm depth above is less than 17 - 20%, which influenced greatly on the growth of plants.
Polyethylene plastic sheets, now widely used in some countries, have defects with serious environmental pollution due to the trouble in decomposing after using.
Since, the study on biologically decomposable sheets production, which is admitted as one of the present major techniques, is in full swing worldwide.
One of them is the plastic sheet of starch - synthetic higher polymer system, and recently there is a report that the sheet of corn straw is developed.

Nevertheless, these kinds of sheets are severe in manufacturing process and makes environmental pollution, as well as being high in price.

However, the sheets manufactured on the basis of the present technique as biologically decomposable sheets are very effective for the prevention of water evaporation from soil surface. They are also effective for plant growth because they are made of plastics and fertilizer components, both helpful for soil improvement.

2.3 Water protecting agent of tree seedlings roots

Since the roots of tree seedlings have no tissues to prevent the water evaporation, the rate of death after tree transplanting is considerably high due to easy evaporation from the roots when tree seedlings are carried or transplanted.
Hence, investigation in preventing the water evaporation from tree seedling roots is being deepened. At present, arginine acid soda is widely used for this, but it is not proper because the price is very high.

Scientists and researchers of the DPR. of Korea have perfectly solved this problem in the present technique by using cheap organic materials that are abundant in Korea.

The 3 techniques mentioned above can be applied independently of each other or in combination, depending on the conditions. In all cases, positive effects of these techniques have been proven.
Applying theses 3 techniques in combination to tree cultivation, the rate of survival of trees can be considerably raised. Furthermore, scarce and expensive manpower and irrigation water can be economized to a minimum, bringing about undoubted success in farming and grass cultivation.

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