Soil and Agriculture

38% of Earth’s land used for agriculture 38% of Earth’s land used for agriculture Soil Soil – 45% mineral matter Broken rocks Broken rocks – 5% organic matter Microorganisms and decomposing animals Microorganisms and decomposing animals – 50% water and air

soil takes hundreds or even thousands of years to form

How is most soil formed? from the erosion of rocks by physical and chemical weathering Parent material (base geological material) must be exposed

Physical weathering Naturally breaking rock without changing chemically – Wind and rain – Daily and seasonal temperatures (expand and contract) – Living things may also help break up rock

chemical weathering process that takes place when the minerals in rocks react chemically with substances such as water to form new material process that takes place when the minerals in rocks react chemically with substances such as water to form new material Increasing precipitation speeds up the chemical weathering of minerals in rocks Increasing precipitation speeds up the chemical weathering of minerals in rocks – tombstones and monuments made of limestone and marble. Increasing temperature also accelerates the chemical reaction Increasing temperature also accelerates the chemical reaction – humid, tropical climates have highly weathered landforms, soils, and buildings

erosion Wearing away of rock by wind and water helps form soil by depositing soil elsewhere erosion Wearing away of rock by wind and water helps form soil by depositing soil elsewhere

Decompose dead plants and organic debris Add nutrients to soil Earthworms, insects and other small animals – Break up soil Allowing air and water into soil Humus partially decomposed organic material dark, spongy crumbly mass holds moisture well and lots of nutrients

one way to tell whether soil is fertile is: To see if it contains earthworms

Soil Profile