soil

Loose covering of broken rocky material and decaying organic matter overlying the bedrock of the Earth's surface. It is composed of minerals (formed from physical weathering and chemical weathering of rocks), organic matter (called humus) derived from decomposed plants and organisms, living organisms, air, and water. Soils differ according to climate, parent material, rainfall, relief of the bedrock, and the proportion of organic material. The study of soils is pedology.

Soils influence the type of agriculture employed in a particular region – light well-drained soils favour arable farming, whereas heavy clay soils give rise to lush pasture land. Plant roots take in nutrients (in the form of ions) dissolved in the water in soil. The main elements that plants need to absorb through their roots are nitrogen, phosphorus, and potassium.