Components & Properties of Soil

Parent Material Unconsolidated mass of rock and mineral from which soil is formed Soil formation occurs where it is exposed at the earth ’ s surface Weathered by both physical and chemical processes

Parent Material

Types of Parent Material Residual Develop from underlying bedrock

Types of Parent Material Transported Moved to final location by water, wind, ice, or gravity

Types of Parent Material Cumulose Develop through decay of plant residues in shallow lakes

Components of Soil Mineral matter Organic matter Water Air

Soil Composition Mineral matter consists of some 64 elements, 16 of which are essential for plant growth Organic matter consists of decomposed plants and animals Both water and air are necessary - Ratio of water to air varies with rainfall - Some water adsorbs to soil particles

Soil Properties Soils differ in properties or characteristics Properties affect soil management Soil management can also affect certain soil properties over time

Soil Properties Color Texture Structure Consistence Fertility Productivity

Soil Color Topsoil color is often a good indicator of organic matter content and texture Classified as dark, moderately dark, light, or very light Dark usually indicates higher organic matter content Light often indicates low organic matter content and high sand particle content

Soil Color Subsoil color is usually a good indicator of soil drainage Classified as red, yellow, brown, gray, or mottled Red or brown indicates good drainage Yellow indicates fair drainage Gray indicates poor drainage Mottled soil indicates soil is saturated part of the year and dry part of the year

Soil Texture Refers to the sizes of individual particles in the soil Most physical and chemical processes involve reactions at soil particle surface Particles with more surface area are more reactive Reactivity determines capacity to retain moisture, nutrients, and soil structure

Soil Particle Sizes Sand Largest particle Can be seen with the naked eye Silt Smaller than sand and larger than clay Clay Smallest particle Microscopic

Textural Classes 12 classes Based on percentage of particles of each size Soil triangle indicates classification

Using the Soil Triangle Textural class determined by the intersection point of the lines corresponding to the percentage of each of the three particle sizes The percentage lines for each particle size are those lines properly oriented to the number For example, 40 % Silt would be marked on the line shown in brown

Using the Soil Triangle CLAY LOAM A soil consists of the following: 30 % clay 30 % silt 40 % sand Following the lines for: 30 % Clay 30 % Silt 40 % Sand Textural Class: Clay Loam

General Characteristics of Soil Textural Classes Sandy soils are relatively infertile, dry out quickly, and erode easily Silty soils tend to form a crust when it rains and erode easily Clay soils dry out slowly and become cloddy unless properly managed

Soil Structure Refers to the arrangement of individual soil particles into aggregates Fine particles are drawn into loose clusters Clusters are cemented together with organic polymers

Soil Structure Well-defined structure aids in water and air infiltration and root penetration Reduced plant cover leads to reduced polymers and reduced structure Physical manipulation, or cultivation, also degrades structure

Types of Soil Structure Granular Blocky Platy Prismatic Structureless Single grained Massive Type refers to the shape of the aggregates

Classes of Soil Structure Classes vary by type Generally, there are three classes: Fine Medium Coarse Class refers to the size of the aggregates

Grades of Soil Structure Structureless soils are single-grained or massive Weak contains indistinct aggregates Moderate contains distinct aggregates that tend to break down when soil is disturbed Strong contains distinct aggregates that separate when soil is disturbed Grade refers to the strength of the aggregates

Soil Consistence Wet soil plastic, non-plastic, sticky, or non-sticky Moist soil loose, friable, or firm Dry Soil loose, soft, hard Consistence refers to the soil’s cohesiveness, or resistance to rupture. Different terms are used for consistence at different soil moisture content.

Soil Fertility & Productivity Soil fertility is the ability of the soil to provide nutrients for plant growth nutrients must be returned to the soil in order to maintain fertility as fertility decreases, plant growth decreases Soil productivity is the ability of the soil to produce a specified plant or sequence of plants under certain management practices dependent upon soil fertility, climatic conditions, organic matter content, texture, and structure