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Part Six, Issue 19 Soils and Sustainable Societies.

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Presentation on theme: "Part Six, Issue 19 Soils and Sustainable Societies."— Presentation transcript:

1 Part Six, Issue 19 Soils and Sustainable Societies

2 Objectives After reading the assigned chapter and reviewing the materials presented the students will be able to understand: What can be done to ensure fertile soils in the future? How significant are soils to sustainable societies?

3 The Nature of Soil Soils are composed of decomposed and disintegrating bits of rock and mineral matter. Humans degrade soil by: Paving soils with asphalt and buildings (urbanization), accelerating soil erosion, poor agricultural practices, desertification, irrigation practices leading to salt buildup, adding toxins to kill soil microbes.

4 Urbanization and Soil Loss American Farmland Trust (AFT) estimates that by 2050, one third of America’s most important agricultural region, the Central Valley of California will be paved over with suburbs. Forests permit little topsoil to erode: runoff is minimal, plant cover and roots allow rainwater to seep slowly into soil, water filters slowly through ground to stream, which results in stable stream flow.

5 Accelerating Soil Erosion According to the World Resource Institute, the two greatest sources of topsoil loss are sprawl development and improperly managed agricultural land. Five to 6 million hectares are lost to severe soil degradation annually. Soil erosion often results from water runoff caused by poor farming practices.

6 Salt Buildup & Toxins In arid regions, sodium may accumulate in the soils where there is insufficient rainfall to wash them below the water table. This process is called salinization. Conventional strawberry and wine grape growers like to sterilize their soils to kill pests which can feed on the roots of young plants and thus reduce yields. When there is a flood, a toxic brew of pesticides, fungicides, silt, and fertilizer is washed downriver. The Sierra Club has determined that organic strawberries can be grown for 25 to 30 cents a pound more than conventional strawberries.

7 Agricultural Practices that Reduce Soil Loss One of the greatest threats to agricultural production is the loss of topsoil. About two thirds of topsoil loss is caused by rain erosion, with another one third by wind erosion. The loss of topsoil directly affects agricultural productivity. Planting a crop each year reduces soil erosion.

8 Can Aid Stop Soil Degradation? According to scientists at the International Food Policy Research Institute (IFPRI), soil degradation has already had an impact on the productivity of about 16 % of the globe’s agricultural land. Threats to the world food production capacity are compounded by three disturbing trends: One and a half billion additional people will be on the planet by 2020, almost all in poorer developing countries, the natural fertility of soil is generally declining, and it is increasingly difficult to find productive new land to expand the agricultural base. Addition of inorganic fertilizers (nitrogen, phosphorous, and potassium) can maintain productivity of farms.

9 CO 2 and Causes for Concern According to the American Geological Institute, world soils contain about 1, 100 to 1,600 billion metric tons (bmt) carbon, more than twice the carbon in living vegetation. As soil fertility declines and water becomes scarcer, what will be the impact on food prices. Distribution of agricultural products is dependent on fuel prices and roads. Protecting soils and agricultural systems and ensuring adequate water supplies are among the greatest challenges facing humanity in the twenty first century.

10 Summary Soils are composed of decomposed and disintegrating bits of rock and mineral matter. Humans degrade soil by: Paving soils with asphalt and buildings (urbanization), accelerating soil erosion, poor agricultural practices, desertification, irrigation practices leading to salt buildup, adding toxins to kill soil microbes. Forests permit little topsoil to erode: runoff is minimal, plant cover and roots allow rainwater to seep slowly into soil, water filters slowly through ground to stream, which results in stable stream flow. In arid regions, sodium may accumulate in the soils where there is insufficient rainfall to wash them below the water table. This process is called salinization. One of the greatest threats to agricultural production is the loss of topsoil. About two thirds of topsoil loss is caused by rain erosion, with another one third by wind erosion. Threats to the world food production capacity are compounded by three disturbing trends: One and a half billion additional people will be on the planet by 2020, almost all in poorer developing countries, the natural fertility of soil is generally declining, and it is increasingly difficult to find productive new land to expand the agricultural base. Addition of inorganic fertilizers (nitrogen, phosphorous, and potassium) can maintain productivity of farms. According to the American Geological Institute, world soils contain about 1, 100 to 1,600 billion metric tons (bmt) carbon, more than twice the carbon in living vegetation. Protecting soils and agricultural systems and ensuring adequate water supplies are among the greatest challenges facing humanity in the twenty first century.

11 Home Work 1. How do humans degrade soil? 2. What is salinization? 3. What are the 3 threats to world food production capacity?


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