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Watch the slide show over soil.
Read the following about soil.
Section 1
Section 1
Soil is a mixture of organic matter and inorganic sediments. The organic content of soil comes from the decomposition of the predominant plant growth. The higher the organic content of soil, the richer it is. Deserts have little plant growth, and so have very little organic matter in their soils, and will continue to be unable to support much plant growth in the future. Forest soils vary. Coniferous forests drop ¼ of their needles every spring and fall, and their decomposition makes the soil more acidic and better able to absorb and retain moisture than other forest soils. This is necessary, since they grow in areas that get less rainfall. Deciduous forests drop their leaves annually, but they can take two or three years to decompose, while new growth begins a few months later, so soils can be less rich. Rainforests support such a huge biomass that nearly all soil nutrients are tied up in living things, and surprisingly tend to have the poorest soils of all forests. Grasses decompose quickly, returning their nutrients to the soil readily, and are enriched by the manure of the herbivores that graze on them, yielding a high organic content. This makes them ideal for farmland. Climate affects soils too; the higher annual rainfall in forests tends to leach nutrients deeper into the soils, and the lower rainfalls in deserts and grasslands leaves the nutrients near the surface. The inorganic content of the soil is usually dependent on the parent rock it formed from. Oklahoma’s red soils come largely from the high iron content of the clays that form from the bedrock below, and our soils in this state tend to be “limey,” since 90% of the rock near the surface is limestone. Our grasses are adapted to it, and near urban areas, acidic rainfall (caused by air pollution) makes the addition of lime necessary to bring the soils back to the proper pH. Sometimes soils end up far from where they originally formed. Floodwaters erode topsoil from lands near their headwaters, where they are still flowing quickly, and deposit them in lands where they slow down, near their mouths. Loess is a type of soil that is moved by wind or glaciers to areas far from its parent rock, too.
A Horizon – Also called topsoil, this layer is found below the O horizon and above the B horizon. Seeds germinate here and plant roots grow in it. B Horizon – Also called subsoil, or illuviation layer, this layer is below the A Horizon and above the C Horizon. It contains clay and minerals like iron and calcium carbonate that it receives from layers above it through leaching.C Horizon – Also called regolith: the layer below the B Horizon and above the R Horizon. It consists of slightly broken-up bedrock. O Horizon – Also called humus, the top layer of soil, made up mostly of partly decomposed leaf litter. This layer is present in dense forest soils, and may be absent in others.R Horizon – Also called bedrock, the layer that is beneath all the other layers., the parent rock of the soil
http://www.cmdowns.com/soil-nf.htm
A Horizon – Also called topsoil, this layer is found below the O horizon and above the B horizon. Seeds germinate here and plant roots grow in it. B Horizon – Also called subsoil, or illuviation layer, this layer is below the A Horizon and above the C Horizon. It contains clay and minerals like iron and calcium carbonate that it receives from layers above it through leaching.C Horizon – Also called regolith: the layer below the B Horizon and above the R Horizon. It consists of slightly broken-up bedrock. O Horizon – Also called humus, the top layer of soil, made up mostly of partly decomposed leaf litter. This layer is present in dense forest soils, and may be absent in others.R Horizon – Also called bedrock, the layer that is beneath all the other layers., the parent rock of the soil
http://www.cmdowns.com/soil-nf.htm
Read the following about soil.
Section 2
Section 2
Soil is a mixture of weathered rock & organic matter that usually covers bedrock (solid rock that underlies all soil). Both chemical & mechanical processes are involved in the development of soils.
· Chemical weathering turns hard minerals into soft ones
· Mechanical weathering breaks solid rock into smaller pieces
· Plant & animals add organic materials in the form of waste products & dead organisms
· The decay of organic matter produces acids which accelerate chemical weathering
· Burrowing Animals, such as earthworms, insects, & rodents, help circulate air and water through the soil & mix mineral & organic remains
The material from which soil forms is called its parent material. Soil that has weathered directly from the bedrock beneath it and therefore matches its parent material is called residual soil.
Soil that does not match the bedrock it is over is called transported soil. It did not weather from the bedrock beneath it but was brought there by agents of erosion such as winds, rivers, or glaciers. Much of New England & the Midwest are covered by soil that was deposited by the movement of glaciers after the last Ice Age.
A cross section of soil exposed by digging is called the soil profile. The weathering of soil produces layers known as soil horizons. The topsoil or A horizon is usually rich in dark-colored organic remains called humus (labeled O horizon below). The subsoil or B horizon contains minerals that have been transported deeper by groundwater. Most of the clay in soil has also been washed down to this layer. The partially weathered bedrock or C horizon is composed of broken up bedrock on top of the solid bedrock (parent material).
Soil erosion is the removal of topsoil by the action of running water or wind. It takes between 100 & 400 years for one centimeter of topsoil to form.
Loss of topsoil can be caused when plants root are no longer present to hold down soil. Salting roads can raise the salinity of the soil and kill the plants. Over grazing can kill plants. Winds construction, & mining can all effect plant cover.
Means of soil conservation include the following:
· Windbreaks – belts of trees along the edge of fields
· Contour farming – crops are planted in rows parallel to land contours
· Terraces- flattening hill slopes to slow the flow of water & erosion
· Strip Cropping – a crop that leaves bare ground between rows is alternated with a crop that completely covers the ground, ex. Corn & Alfalfa
· No-till method- plowing, planting and fertilizing are all done at the same time so there is less chance of wind removing topsoil
· Chemical weathering turns hard minerals into soft ones
· Mechanical weathering breaks solid rock into smaller pieces
· Plant & animals add organic materials in the form of waste products & dead organisms
· The decay of organic matter produces acids which accelerate chemical weathering
· Burrowing Animals, such as earthworms, insects, & rodents, help circulate air and water through the soil & mix mineral & organic remains
The material from which soil forms is called its parent material. Soil that has weathered directly from the bedrock beneath it and therefore matches its parent material is called residual soil.
Soil that does not match the bedrock it is over is called transported soil. It did not weather from the bedrock beneath it but was brought there by agents of erosion such as winds, rivers, or glaciers. Much of New England & the Midwest are covered by soil that was deposited by the movement of glaciers after the last Ice Age.
A cross section of soil exposed by digging is called the soil profile. The weathering of soil produces layers known as soil horizons. The topsoil or A horizon is usually rich in dark-colored organic remains called humus (labeled O horizon below). The subsoil or B horizon contains minerals that have been transported deeper by groundwater. Most of the clay in soil has also been washed down to this layer. The partially weathered bedrock or C horizon is composed of broken up bedrock on top of the solid bedrock (parent material).
Soil erosion is the removal of topsoil by the action of running water or wind. It takes between 100 & 400 years for one centimeter of topsoil to form.
Loss of topsoil can be caused when plants root are no longer present to hold down soil. Salting roads can raise the salinity of the soil and kill the plants. Over grazing can kill plants. Winds construction, & mining can all effect plant cover.
Means of soil conservation include the following:
· Windbreaks – belts of trees along the edge of fields
· Contour farming – crops are planted in rows parallel to land contours
· Terraces- flattening hill slopes to slow the flow of water & erosion
· Strip Cropping – a crop that leaves bare ground between rows is alternated with a crop that completely covers the ground, ex. Corn & Alfalfa
· No-till method- plowing, planting and fertilizing are all done at the same time so there is less chance of wind removing topsoil
Soil Profile & Layers |
Types of Soil |