Title Soil Science Part-1.pdf ✅

www.iaritoppers.in Whatsapp : +91-9694095242 Page | 1 Soil Science 4 th Edition 2023-24
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 2 Soil Science Introduction: Soil Science is the study of soil as a natural resource on the surface of the earth including soil formation, classification and mapping, physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils. (A) Edaphology: “Edaphology” word is derived from two Greek words- Edaphos: Soil Logos: Discourse  Eduphology is the study of soils in relation to crop growth, nutrition and yield. (B) Pedology: Pedology word is derived from two Greek words- Pedon: Soil Logos: study  Pedology is the study of origin, formation and geographic distribution of soil in nature. Soil can be compared to various systems of Animals:  Digestive System: Organic matter decomposition  Respiratory System- Air Circulation & exchange of gases  Circulatory System- Water movement within the Soil  Excretory System (blood) – Leaching out of excess Salts  Brain – Soil Clay  Colour - Soil colour  Height – Soil depth Planetisimals: Planetesimals are bodies of solid materials formed in the earliest planetary nebulae that have grown large enough to begin to draw other materials to them by gravitational attraction. Soil origin & weathering:  Soil in formed from weathering of rocks.  Soil found at the site of formation is called sedentary Soil.  Soils found far away from the site of formation are called cumulous or transported soils.
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 3 Weathering: weathering is the breakdown of rocks and minerals into soils Interior of Earth:  The earth Ball consists of 3 concentric rings namely: Crust, mantle and Core. 1)Crust:  5 to 56 km on the Surface of the earth.  Density of rocks is 2.6 to 3.0 gcc-l  Distance 5 to 11 km. in oceans and 35 to 56 km. in the continents.  The crust has been divided into two sub- zones called Sial and Sima.  The Sial is a heterogeneous mixture of rocks.  The Sima homogenous plastic or semi- plastic concentric layer that behaves like a solid.  Sial contains about 65-75% silica.  The sial floats on the Sima, which in turn floats on the lower concentric layer called the mantle.
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 4 2)Mantle:  A massive solid to semi solid layer below the crust : 2900 km in thickness.  Comprises mixed metals and silicate and basic rocks with density of 3.0 to 4.5 g cc-l 3)Core:  Inner most portion of Earth.  3500 km in thickness.  Contains molten metals like Nickel, iron.  Average density : 9.0 to 12.0 gcc-l Exterior of Earth :  Solid lithosphere, liquid hydrosphere and gaseous atmosphere.  The atmosphere is of 320 km above the lithosphere.  70% of Earths surface is covered by water (Hydrosphere).