Soil and Rock Properties Quiz

Soil and Soil Components

• Soil is a three-dimensional natural body.
• The father of soil science is Dokuchaev.
• The most abundant element in the earth's crust is oxygen.
• Organic matter in soil is typically 5% or less.
• Soil is a complex mixture of solids, liquids, and gases.
• Pedology is the study of soil genesis, classification and mapping.
• Edaphology studies soil in relation to plant growth.

Origin of Earth

• The approximate age of the Earth is 4.54 to 4.57 billion years.
• The most accepted theory about Earth's origin is the Big Bang theory.

Rocks

• Rocks are the fundamental components of the Earth's crust.
• Important rock types include igneous, sedimentary, and metamorphic.
• Igneous rocks form from the cooling and solidification of magma or lava.
• Sedimentary rocks are formed from the accumulation of sediments.
• Metamorphic rocks are formed from existing rocks (igneous or sedimentary) under high temperature and high pressure.

Minerals

• Minerals are naturally occurring, inorganic solids with a definite chemical composition and a crystalline structure.
• Important minerals for soil include silicate clays, iron and aluminum oxides, and humus.

Secondary Minerals

• Secondary minerals are products of weathering.
• Kaolinite is the most common 1:1 type clay mineral.
• Montmorillonite is the most common 2:1 type clay mineral.

Weathering of Rocks and Minerals

• Weathering is the breakdown of rocks and minerals at or near the earth's surface.
• Physical weathering is the disintegration of rocks into smaller pieces.
• Chemical weathering is the decomposition of rocks.
• Biological weathering is the breakdown by organisms.

Soil Forming Factors

• Soil forming factors include climate, organisms, relief, parent material, and time.
• Climate influences soil formation through temperature, precipitation, and wind.
• Organisms (plants & animals) decompose organic matter, create pore spaces, and alter soil composition.
• Relief (topography) affects soil formation through erosion and deposition.
• Parent material (underlying bedrocks) is an initial source for the soil to develop.

Soil Profile

• A soil profile is a vertical section showing the soil horizons.
• Soil horizons develop due to the interaction of different soil forming processes.
• Common soil horizons include O, A, B, and C horizons.

Soil Texture

• Soil texture refers to the proportions of sand, silt, and clay particles in a soil.
• Soil texture influences water retention, aeration, and drainage.
• Coarse textured soils or sandy soils have low water holding capacity.
• Fine textured soils or clayey soils have high water holding capacity.

Soil Structure

• Soil structure refers to the arrangement of soil particles into aggregates (peds).
• Soil structure influences water movement, aeration, and root penetration.
• Well-aggregated soils have good structure.

Soil Density

• Particle density measures the mass of the soil solid material per unit volume.
• Bulk density is the mass of oven-dried soil per unit volume.
• Soil structure and organic matter content significantly influence bulk density.
• Higher organic matter and well-aggregated soils have lower bulk densities.

Soil Color

• Soil color reflects soil properties such as organic matter content, iron oxide content and drainage.
• Darker colors indicate higher organic matter content.
• Reddish colors usually indicate well-drained soils.

Soil Water

• Water is essential for plant growth and microbial activity.
• Water exists in different forms: gravitational, capillary, and hygroscopic.
• Soil moisture constants include wilting point and field capacity.
• Available water is the amount of water in soil that is readily available to plants.

Soil Air

• Soil air is a mixture of gases similar to the atmosphere.
• It differs from atmospheric air in higher CO2 concentration and lower O2 concentration (depending on soil conditions).
• Oxygen is essential for many soil organisms.

Soil Organic Matter

• Soil organic matter is produced by the accumulation of partially decomposed plant and animal residues.
• SOM is essential for nutrient cycling and soil structure and health.
• Factors influencing organic matter include decomposition rate, climate & soil moisture.

Soil Organisms

• Soil organisms are important for nutrient cycling, soil structure, and aggregate formation.
• Major groups of soil organisms include bacteria, fungi, algae, earthworms, and insects, etc.

Soil Reaction (pH)

• Soil reaction (pH) refers to the acidity or alkalinity of the soil solution.
• Factors affecting soil pH values include climate, soil parent material and soil organisms.
• Soil buffering capacity influences the fluctuations of soil pH.

Soil Electrical Conductivity (EC)

• Soil EC is the measure of soluble salts in the soil.
• It is influenced by the soil's texture, structure and water content, as well as by salinity.
• High soil salinity can negatively impact plant growth.

Soil Colloids

• Colloids are the smallest particles in soil, having a large surface area and significant charge properties.
• Factors impacting soil colloid properties include size, surface charge and the presence of hydrated ions.
• Soil colloids possess very large cation and anion exchange capacities.

Soil Color Chart

• The Munsell soil color chart is used for accurately determining soil color.
• It is based on hue, value and chroma.