What is soil?

Soils and the Farm Soil contains water and nutrients needed to grow plants. Farmers cultivate their soils, plant seeds, fertilise the soil and harvest the crops that grow.

Soils and the Town All buildings, roads etc are built on soil. Once the soils covered with the above it is unable to be used for plant growth.

Soils and the Garden Soils are important to gardeners as it allows them to grow veges and flowers. Gardeners look after their soil adding fertiliser and compost.

Soils in the Forest Soils anchor plants, provide nutrients and water.

Other Soil is a major resource in the world Soils form a thin skin over the surface of the earth. Can be very thick, up to 1m or very shallow when it is very young soil. Soil is home to millions of organisms that live below our feet.

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How do soils form? Soils form an almost complete skin over the world, broken only by oceans and by mountains.

Soil Parent Material Soils form from parent materials. Parent materials include such things as rocks (igneous, metamorphic and sedimentary). Parent material is the main factor responsible for the texture of the soil (i.e whether the soil is sandy, silty or clayey). What are the soils around Methven made from?

Climate As climate changes across the world so does the soil type. Temperature, rainfall, snow and ice all influence the way the parent rocks and sediments are converted into soils. They affect the rate at which chemical, physical and biological processes combine to develop soil in a particular place. Rainfall influences the distribution and amounts of nutrients in the soil and hence their availability to plants.

Landscape The way that the landscape is developed has a strong influence on the thickness of soils and how well they develop. On steep slopes, the soils are usually very thin because the soil tends to be washed down the slope by rain. In flat places, the soils tend to be thicker.

Organisms, including vegetation and fauna Soil organisms are important in several aspects of soil formation including organic matter production, release of nutrients to support plant life and in the development of soil structure. Soils under grassland tend to develop fairly thick top organic layers whereas in forest areas the organic layer is thin. Plant cover helps the stabilise soils during their development and they help to prevent erosion.

Time Soils take a long time to develop. It takes hundreds of years to develop a few centimetres of soil. Some soils in the world are millions of years old. Some soils around Methven are very young. Where would we find these soils?

The Influence of Humans Farming soils to produce crops has a big influence on soils. The upper layers are disturbed by cultivation and organic material is mixed in with the mineral soil. Humans can increase the fertility of the soil by adding fertiliser and if they do not look after soils, then erosion etc will occur.