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The global cycles


An old fallen Oak tree, rotting down in the forest, releasing all its nutrients back into the soil - part of the global nutrient cycle. Our earth is a truly amazing place but there are few things more marvellous than the natural global cycles. For example, just think about the fact that the total amount of water on earth has remained the same for millions of years. It has been cycled, re-recycled, and re-cycled, again and again over this period of time. It is an essential part of the plants, animals and human beings that use it, then it is returned to the atmosphere and then returns again to the earth's surface as rain or snow, where it is again used by the living beings.

This old town water pump from Hove was once used to draw water from underground to serve the houses nearby. All our drinking water passes through soil as part of the hydrological cycle. Image credit: S.K Wood Water is not the only essential component that is constantly re-cycled. So is carbon, which plants need to make new growth and to form food crops and other resources for the world. Nitrogen, also cycled, is an essential element which plants and other living things need. As part of the nitrogen cycle the inert nitrogen from the atmosphere is gradually broken down into other forms capable of being used by plants and animals, before eventually returning back to the atmosphere. Oxygen, an important part of the atmosphere, moves between the atmosphere and the earth's organisms. It also forms ozone which shields the earth from potentially damaging radiation. Sulphur is transformed from one form to another as it is passes through the atmosphere-plant-animal-soil system.

In addition to nitrogen, oxygen, carbon and water, nutrients important for plants, animals and humans are also recycled between plants and the soil. These include phosphorus and potassium, and many of the other nutrients that are essential to life on earth. This section of Soil-Net explains all about these wonderful cycles of nature.