Science Focus Topic 5 Notes: Sustaining the Soil | Print |
Healthy soil is critical in natural ecosystems and sustains our need to grow plants for food and fibre. Soil gives plants a place to sink their roots and anchor themselves. Soil is also a community with billions of organisms.

How Do Soils Develop?

Five factors determine how soils develop:
Parent material (mineral matter - rock, soil clay)
Climate (determines the kinds of plants, how fast they grow and decompose)
Vegetation (determines the amount and type of organic matter in the soil)
Landscape (helps to prevent erosion)
Time (all these process happen over long periods of time)

Soil: A Lively Community

Healthy soil contains soil-dwellers and decomposers. The decomposers break down plant and animal tissue, forming humus, which helps roots grow by trapping water and air.
The four main types of decomposers are:
Fungi (including moulds and mushrooms) - make nutrients available to plants
Microscopic actinomycetes (a special type of bacteria)
Earthworms (eat soil, grind, digest and mix it - their tunnels provide air and the mucus helps stick soil particles together)

All You Can Eat

Plants require 6 basic nutrients from the soil in order to grow healthy.
These nutrients are: nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca), and magnesium (Mg).
Typical nutrients in fertilizers:
The first number in a fertilizer formula is the amount of nitrogen in the fertilizer ... Nitrogen ? which is used by plants for producing leaf growth and greener leaves.
The second number is the phosphorus amount of ... Phosphorus ? which is used by plants to increase fruit development and to produce a strong root system.
The third number is the amount of ... Potassium (potash) ? which is used by plants for flower color and size. It is also helps to strengthen the plant.

Challenges and Solutions

Production practices have over time, sometimes damaged large areas of soil throughout the Prairie Provinces.

Salinization: Salty Soil

The white crusty ring around a body of water is salt, which has run off the land into the water. This condition is called salinization and can have the same effect as a drought.
Two factors lead to increased salinization:
not enough vegetation
too much water (irrigation)
This problem can be corrected by replanting the areas where there is very little vegetation, so the plants can use up the water that falls before it runs off as excess or seeps into the soil dissolving the mineral salt in the soil and getting into the groundwater.

Organic Matter and Erosion

Loss of organic matter is a very serious problem and can lead to soil erosion. If the soil has lost this organic matter (which has been built up over many years) the plants may not grow very well, because of the lack of sufficient nutrients in the soil. Ploughing and cultivating the soil too much and the practice of regular summer fallow (cultivating the land to control weeds - by not planting a crop) exposes the soil surface to sunlight and higher temperatures, encouraging bacteria to decompose organic matter at a rapid rate and exposes it to sun and wind - thus increasing topsoil erosion.

Saving the Soil

Soil erosion can be solved by planting a cover of vegetation on the surface to slow the flow of water runoff (giving it more time to absorb more water). This vegetation also helps to anchor the soil particles from the wind. Zero Tillage is one way to accomplish this and it also helps control the growth of weeds. Special farming equipment is also used (seed drills), Shelterbelts (rows of trees), Modification of waterways, and Crop rotation (forage crops to add more organic matter - manure from livestock)

Hydroponic Technology

Hydroponics is a technique for growing plants, without soil in a water solution. (This occurs in greenhouses in Canada)

Saving Soil in Forests

Forestry can also have an impact on soils. Removal of trees from a particular areas can lead to erosion by wind and water. Cut areas often are littered with debris, which has been left to lower erosion (and add organic matter to the soil) and replanting programs are started after the trees have been harvested. Vegetation near waterways is usually left undisturbed.

Topic 5 Review p. 162