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Conserving Land and Soil. Types of Land Use. Agriculture New farmland must be created by clearing forests, draining wetlands, and irrigating deserts. Types of Land Use. Development Every year in the US, about a million hectares of farmland are developed.
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Types of Land Use • Agriculture • New farmland must be created by clearing forests, draining wetlands, and irrigating deserts.
Types of Land Use • Development • Every year in the US, about a million hectares of farmland are developed. • Reduces the amount of farmland and destroys wildlife habitats.
Types of Land Use • Mining • Strip mining removes nonrenewable resources from the land. • Expose the soil and causes erosion. • In underground mining, minerals are carried up through shafts of tunnels that have been dug out.
Restoring the Land • It is possible to restore land damaged by erosion or mining. (land reclamation) • In some cases, subsoil and topsoil are replaced and grass is planted so that the area can be used as agricultural land.
Protecting the Soil • Erosion • Plant roots usually hold soil in place. • Many uses of land expose the soil and can cause erosion • logging • mining • farming
Protecting the Soil • Desertification • The advance of desertlike conditions into areas that previously were fertile • Climate (drought) • Overgrazing of grasslands by cattle and sheep • Poor farming practices and excessive cutting of trees for firewood
Protecting the Soil • Nutrient Depletion • If farmers plant the same crops in a field year after year, nutrients are used faster than decomposers can replace them. • Prevention • Periodically leave fields fallow • Leave the unused parts of crops in the fields rather than clearing them away. • Crop rotation
The Nitrogen Cycle • The process by which nitrogen is removed from the atmosphere, fixed in the soil by bacteria, incorporated in other living things, and then released back into the atmosphere.
The Nitrogen Cycle • Nitrogen Fixation • The process of changing free nitrogen gas into a usable form of nitrogen • Done by bacteria, some of which live in bumps called nodules on the roots of certain plants (legumes) • Clover, beans, peas, alfalfa, and peanuts
The Nitrogen Cycle • Return of Nitrogen to the Environment • Once the nitrogen is fixed into complex compounds, it can be used by organisms to build proteins and other substances. • Decomposers break down these complex compounds in wastes and dead organisms and return nitrogen compounds in the soil. • At some time, the bacteria completely break down the compounds and release free nitrogen back into the air.
