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Вы можете ознакомиться и скачать презентацию на тему Soil Erosion. Доклад-сообщение содержит 14 слайдов. Презентации для любого класса можно скачать бесплатно. Если материал и наш сайт презентаций Mypresentation Вам понравились – поделитесь им с друзьями с помощью социальных кнопок и добавьте в закладки в своем браузере.

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Soil Erosion

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Introduction: Soil Erosion Soil erosion is the washing or blowing away (by wind or water) of the top layer of soil (dirt). Erosion also leaves large holes in the earth, which can weaken buildings and even cause them to collapse. Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions Soil erosion occurs when soil is removed through the action of wind and water at a greater rate than it is formed. If the soil has eroded, the crops will not grow very well.

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What is soil erosion? When a raindrop hits soil that is not protected by a cover of vegetation and where there are no roots to bind the soil, it has the impact of a bullet. Soil particles are loosened, washed down the slope of the land and either end up in the valley or are washed away out to sea by streams and rivers. Erosion removes the topsoil first. Once this nutrient-rich layer is gone, few plants will grow in the soil again. Without soil and plants the land becomes desert like and unable to support life.

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Causes of soil erosion Wind and water are the main agents of soil erosion. The amount of soil they can carry away is influenced by two related factors: speed - the faster either moves, the more soil it can erode; plant cover - plants protect the soil and in their absence wind and water can do much more damage. Erosion occurs when farming practices are not compatible with the fact that soil can be washed away or blown away. These practices are: Overstocking and overgrazing Inappropriate farming techniques Lack of crop rotation Planting crops down the contour instead of along it.

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Prevention Planting wind breaks can be effective Terracing can also be effective. The use of contour ploughing Leave unploughed grass strips between ploughed lands (strip cropping) Make sure that there are always plants growing on the soil, and that the soil is rich in humus Avoid overgrazing Allow indigenous plants to grow along riverbanks Conserve wetlands Cultivate land, using a crop rotation system Minimum or no tillage Encourage water infiltration and reduce water runoff.

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IMPORTANCE OF PLANTS IN CONTROLLING SOIL EROSION Plants provide protective cover on the land and prevent soil erosion for the following reasons: Plants slow down water as it flows over the land (runoff) and this allows much of the rain to soak into the ground Plant roots hold the soil in position and prevent it from being washed away Plants break the impact of a raindrop before it hits the soil, thus reducing its ability to erode Plants in wetlands and on the banks of rivers are of particular importance as they slow down the flow of the water and their roots bind the soil, thus preventing erosion.