Soil as a Resource Key idea: Soil is an important resource that can be conserved and protected.

The Importance of Soil  The soil is a living entity not just a substrate in which to grow plants. A living soil is teeming with life, from earthworms, centipedes and beetles to fungi and bacteria. Healthy soil has food, air and water to help plants grow. The more nutrients available in the soil, the more the plant can take up. The more nutrients in the plant - the more available for animals and humans. We should believe that for this reason human health is affected by the health of the soil.

Soil Fertility Soil fertility is the ability of soil to grow plants. Most of the plant's nourishment comes from the soil. The nutrients are made up of minerals from the earth. Other nutrients come from dead plants and animals, also broken down over time by insects and organisms which live in the soil.

How Much Fertile Soil Is Available Out There?

 Analyzing the map above, we can see that the land good for agriculture covers a rather small surface on the world’s map.  About 25% of the dry land is suited for some agricultural use, but most of this surface lacks water resources.  Only about 10% of the world’s dry land is used for intensive agriculture. This means that there is enough water for irrigation, and the soil is fertile enough.

Is This Amount of Soil Enough for the Needs of the Mankind?  The answer to this question is NO!  The population of the world grows rapidly, while the cultivated surface at its best might stay the same.  In reality, the surface covered with fertile soils shrinks every year, due to intensive agricultural practices.

What Threatens Soil Fertility?  Soil fertility, or the ability to grow plants, is given by its content in organic matter, mineral matter, and water.  Each type of soil, based on its content, is suited for certain crops. Some soils are best for planting potatoes, but not good at all for corn, for example; this is because different plants have different needs in nutrients and water.

What Threatens Soil Fertility? Soils can loose their fertility in several ways:  Soil depletion  Salinization  Erosion are the most common ways for soil loss. We will analyze each one of them briefly.

Soil Depletion  Soil depletion occurs when the soil gradually looses certain nutrients because of harvesting the same type of crop year after year.  Farmers often use chemical fertilizers to put nutrients back in the ground, but in a long run this practice is not good for the environment.  To prevent soil depletion, good farming practices include: -rotation of crops each year -rotation of crops each year -letting the fields lay fallow (uncultivated, unused), in order to let some nutrients accumulate. -letting the fields lay fallow (uncultivated, unused), in order to let some nutrients accumulate.

Salinization  Because agricultural land is in great demand, many counties expanded their crops in arid (dry) areas, by using irrigation.  As the desert’s dry air rapidly evaporates the irrigation water, the minerals that have been dissolved in water are left behind, and accumulate on the soil surface, a process called salinization.. At some point, the soils lose their ability to sustain crop growth. It is very difficult to restore soils lost through salinization.

Soil Salinization

Soil Erosion Soil erosion occurs naturally, when the top soil is removed by wind, or water. Human activity can accelerate the soil erosion many times. For example, on 2001 one estimate indicated that soil in the United States was being eroded at a rate 17 times faster than the rate at which it was formed.

Soil Erosion

Soil Erosion- The Dust Bowl  In the 1930s several years without rain led favored dust storms. Tons of topsoil were blown off barren fields and carried in storm clouds for hundreds of miles. Technically, the driest region of the Plains – southeastern Colorado, southwest Kansas and the panhandles of Oklahoma and Texas – became known as the Dust Bowl, and many dust storms started there. But the entire region, and eventually the entire country, was affected.

Soil Erosion- The Dust Bowl  The Dust Bowl got its name after Black Sunday, April 14, More and more dust storms had been blowing up in the years leading up to that day. In 1932, 14 dust storms were recorded on the Plains. In 1933, there were 38 storms. By 1934, it was estimated that 100 million acres of farmland had lost all or most of the topsoil to the winds. By April 1935, there had been weeks of dust storms, but the cloud that appeared on the horizon that Sunday was the worst. Winds were clocked at 60 mph. Then it hit.

Soil Erosion- The Dust Bowl

Abandoned Farm During The Dust Bowl

Erosion and Soil Conservation To minimize or prevent erosion, farmers use can use methods such as:  Windbreaks (are barriers against the wind)  Contour farming (reduces water runoff)  Terraces (also slow the speed of runoff)  Strip cropping: farmers plant crops that leave bare ground, like wheat, with crops that remain green, like Alfalfa.  No till- Once the seeds of a crop in the soil, the farmers leave the field untouched until harvest.

Windbreaks

Contour Farming

Terraces

Strip Cropping

Conclusions  The soil is a vital natural resources because it sustains all living things.  Unlike many natural resources which once depleted cannot be replenished, the soil can be preserved using wise farming methods.