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Land degradation
Soil degradation has become a major problem worldwide. Five to seven million ha of arable land disappears every year. Tropical soils are now especially threatened as a result of high population growth and pressure on resources. Traditional farming systems can no longer maintain the fertility and production capacity of soils. Two key aims of DMCs are to control soil degradation and regenerate already degraded soils.
SOIL DEGRADATION FACTORS Featured
Land degradation is induced by a combination of factors, e.g. the disappearance of natural vegetation cover, tillage, slopes, climatic hazards and overuse of resources (overgrazing, etc.). The main cause of cropland degradation is water and wind erosion, which leads to considerable land loss, especially on bare soils and recently cleared land. Organic matter and most minerals that can be assimilated by plants are concentrated in the soil surface horizon, which is the most important layer for crops, and these are the first elements to disappear.
DESERTIFICATION—A GLOBAL PROBLEM Featured
Desertification is a complex process involving many natural and human factors. It leads to a decline in land fertility and impoverishment of the communities living on it. This process concerns all agrosystems worldwide where the soil is utilized, including rangelands, cropland and natural areas. A third of humankind is affected by desertification. Some specific features characterize desertification affected areas:The soils are fragile, poor and unproductive. Their structure is unsuitable due to the extremely low organic matter content. The soil also has low porosity or is completely sealed close to the surface.Water is a scarce uncertain resource. Moreover, rather than percolating through the soil, most rainfall is lost via runoff, thus depriving crop plants, rangelands and natural vegetation of water supplies.Severe climatic events are common: short, irregular and violent rain storms, high temperatures.Soils affected by desertification, especially in Africa, have a deep water supply (more than 1 m below ...
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DMCS EFFECTIVE FOR CONTROLLING SOIL DEGRADATION Featured
Impact of DMCs on the soil structure: live or dead plant cover provides efficient protection against different types of physical soil degradation by offsetting the force of droplets hitting the soil. It enhances infiltration of water into the soil, slows runoff and halts soil loss via water erosion. The soils are literally ‘knitted together’ by the cover plant roots. The presence of plant cover limits drying of the surface layer by stabilizing the soil moisture and reducing the temperature at the soil surface. It also keeps fine soil particles from being carried way by wind erosion. The fact that the soil is not tilled and is protected by plant cover reduces compaction, which adversely affects many soils under mechanized cropping conditions in intertropical regions.Impact of DMCs on the physicochemical soil properties: they improve the soil organic matter content and maintain it at a high level (production in the topmost 10 cm surface layer). Organic matter is a key physicochemical factor in the soil ...
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EFFECTS OF DMCS ON VILLAGE LAND, CATCHMENT AND LANDSCAP... Featured
In arid and semiarid areas, erosion, especially wind erosion, is a major cause of desertification and soil degradation. Reducing or even halting erosion should markedly improve desertification control.Indirectly, silting of upstream dams is slower and damage to other public infrastructures (roads, buildings, etc.) is reduced by DMC implementation. Complex and expensive erosion work (soil protection and restoration, and water and soil conservation) is no longer necessary on land cropped using DMCs, e.g. in North Africa and especially Tunisia.With the substantial reduction in runoff, areas upstream of landscapes, depressions, basins and lowlands, and areas under glacis should no longer be hampered by flooding. Village lands and inhabited areas would thus be protected against sudden water inflows.The increased water infiltration in catchments should boost the water table. Village wells could then be less deep and not as susceptible to drying, lowlands would have a better and more regular water supply, thus e ...
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