Agriscience and Technology I Introduction to Soil Science Ms. Lacross April 2015 Agriscience and Technology I Introduction to Soil Science

After this unit you will be able to: 1 Identify and describe soil 2 Describe the importance of soil 3 Describe and draw a soil profile

Soil Introduction

Soil Origin and Development Pedology: The study of soil formation V. V. Dokuchaev (Russian) is credited with laying the foundation of modern Pedology published a careful study of Russian Soils in 1883 Hans Jenny (US) published the Factors of Soil Formation in 1941 developed 5 factors of soil formation

Soils Perform Several Vital Functions Sustaining plant and animal life below and above the surface Regulating and partitioning water and solute flow Filtering, buffering, degrading, immobilizing, and detoxifying Storing and cycling nutrients Providing support to structures

What is Soil?

Soil Components

The Soil Body Soil is a Soil varies across the landscape collection of natural bodies of the earths surface contains living matter that is able to support growth of plants Soil varies across the landscape Pedon: Is a small section of soil extending from the surface to the depth of root penetration

Soil Vs Dirt Soil Dirt Material which nourishes and supports growing plants Soil out of place Compilation of minerals, air, water, animals and other living matter Unable to serve its original purpose Contains an equal amount of Sand, Silt and Clay Can not support plant life

Parent Material Soil Genesis = the process of creating soil from parent material Soils form directly from bed rock Transported soils: developed from weathered material and are transported from their place of original origin glacial ice: carried parent materials over the northern part of America wind water gravity

Parent Material Soil Genesis = the process of creating soil from parent material Soils form directly from bed rock Transported soils: developed from weathered material and are transported from their place of original origin glacial ice: carried parent materials over the northern part of America wind water gravity

Physical Properties of Soil Color, Texture, Structure and Horizons

Soil Components and Texture Soil Texture describes the portion of three sizes of soil particles Sand – largest Silt- medium Clay- smallest

12 Texture Classes The United States Department of Agriculture (USDA) has identified 12 soil texture classes Sand Loamy sand Sandy Loam Sandy Clay Loam Loam Silt Loam Silt Silty Clay Loam Clay Clay Loam Sandy Clay Silty Clay

Importance of Soil Texture Texture is important because it affects: Water-holding capacity—the ability of a soil to retain water for use by plants Permeability—the ease with which air and water may pass through the soil Soil workability—the ease with which soil may be tilled and the timing of working the soil after a rain Ability of plants to grow—some root crops like carrots and onions will have difficulty growing in a fine-textured soil

Soil Texture Triangle Way of showing proportions of sand, silt and clay in the soil Texture determines practices that should be used.

Soil Texture by Feel Texture class can be determined by feel To determine texture a person MUST be familiar with the composition of soils Gather a bit of soil and add water droplets until the soil is moldable

Soil Particles Soil is made of solid particles particles largely consist of mineral matter and organic matter between these soil particles are open spaces called pore space the arrangement of the solid particles and the pore space is called the soil matrix

Soil Structure Aggregate: clumps of soil particles held together by moist clay, organic matter, by organic compounds

Soil Color Described by comparing the color of a soil horizon with a Munsell color chart Soil horizons have several colors Dark colored horizons have MORE organic matter than lighter ones

Soil Color Dark = organic matter Red = iron Brown = well drained Grey (gley) = poorly drained Mottled: redoximorphic concentrations, depletions = restricted aeration, poor drainage

Soil Horizons System for naming soil horizons A, B and C are the master horizons Each layer is identified by a code: O, A, E, B, C and R

Soil Profile O: Organic Matter A: Top Soil E: Zone of Eluviation Surface mineral layer where organic matter accumulates E: Zone of Eluviation depleted in clay, chemicals and organic matter light colored many soils do not have this horizon

Soil Profile B: Subsoil C: Weathered/aged parent material “zone of accumulation”: where chemicals leached out of the A horizon accumulates. lower organic matter content than top soil C: Weathered/aged parent material little touched by soil-forming processes soft, weathered bedrock R: Hard Bedrock limestone, sandstone or granite

Soil Taxonomy

Soil is as variable as leaves so we use a system to name soils Soils Taxonomy Soil is as variable as leaves so we use a system to name soils Soil Taxonomy: Six categories: order, suborder, great group, subgroup, family and series Twelve orders in the world More than 17000 series in the US

Soil orders are defined on the basis of horizons and materials Soil Taxonomy: 6 Groups Soil orders are defined on the basis of horizons and materials Suborder: based on soil moisture regimes Great Group and Subgroup: based on the presence or absence of certain kinds of soil horizons Family: based on particle-size, temperature of subsoil horizons Soil Series: based on a wide set of properties and are named for the local community in which the soil was first identified

Twelve Soil Orders Gellisols Histosols Spodosols Andisols Oxisols Vertisols Aridisols Ultisols Mollisols Alfisols Inceptisols Entisols

Soil Orders Alfisols Soils with a subsoil accumulation of silicate clay that are moderately weathered Abbreviation: ALF Andisols Soils formed from volcanic materials Abbreviation: AND

Soil Orders Aridisols Soils of Arid Environments Arid = dry, climates lacking vegetation Abbreviation: AID Entisols Very weakly developed soils Including sandy soils Abbreviation: ENT

Soil Orders Histosols Soils formed from organic materials Abbreviation: IST Inceptisols Weakly developed soils Excluding sandy soils Abbreviation: EPT

Soil Orders Mollisols Soils wit thick, dark surface horizons They are high in organic matter Abbreviation: OLL Oxisols Highly weathered soils or tropic areas Are high in Iron and aluminum-oxide Abbreviation: OX

Soil Orders Spodosols Soils with a subsoil accumulation or aluminum, organic matter and Iron Abbreviation: OD Ultisols Soils with a subsoil accumulation of clay that are highly weathered Abbreviation: ULT

Soil Orders Vertisols Soils that undergo shrinking and swelling Abbreviation: ERT Gellisols Soils of a very cold climates that contain permafrost within the soils surface Abbreviation: EL

Soil Quality

Soil Quality Soil Quality = the capacity of a specific soil to provided needed functions for human or natural ecosystems over the long term can sustain plant and animal growth can maintain air and water quality support human health

Soil degradation = The loss of soil quality Soil connects intimately to water this also means water problems How to fix it? BMP’s or Best Management Practices involve keeping the soil covered as much as possible employing management methods like mulching and cover cropping

Soil and Climate Carbon sequestration: the process of storing carbon in soils, plans and elsewhere