Soil Science

Notes from Soil Science course in NCHU

The ability of a greenhouse gas to trap extra heat in the atmosphere over time relative to CO₂

Global warming potential (GWP)

Intentional consumption of earth or soil-like substances such as clay

Geophagia

6 ways soils act as media for plant growth

1. Physical support (anchoring)

2. Air (respiration/ventilation for roots)

3. Water (held in soil pores)

4. Temperature moderation

5. Protection from toxins

6. Nutrients

Draw the root structure

Chemical equation for cellular respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Why plants need a continuous stream of water

• Cooling

• Nutrient transport

• Turgor maintenance

• Photosynthesis

Capillarity

The tendency of a liquid in a tiny tube to rise up or down simply due to surface tension

Water holding capacity

Measures how much water can soil retain against the force of gravity

Reasons for phytotoxic substances in soils

• Human activity

• Plant root waste

• Microorganisms

• Natural chemical reactions

How does soil protect plants from toxins?

By ventilating gases, decomposing/adsorbing organic toxins, and supressing toxin-producing organisms.

Mnemonic for plant essential nutrients

I hope Zoe ordered 4 coffees, 3 milks, 2 pretzel sandwiches + 2 nutella brownies.

Define hydroponics

The process of growing plants in sand, gravel, or liquid, with added nutrients but without soil.

Practices to enhance soil carbon sequestration (6)

1. Planting cover crops during off-seasons.

2. Avoid tillage farming.

3. Integrate trees/shrubs into farmland (agroforestry)

4. Add compost/manure

5. Rotational grazing

6. Reduced use of synthetic fertilizers

What is a diatom?

A single-celled photosynthetic alga characterized by a unique, jewel-like cell wall made of transparent silica, called a frustule.

What is a rotifer?

A tiny, multicellular aquatic animal characterized by a wheel-like ring of cilia (the corona) around its mouth.

4 properties of soil that must be considered for engineering

Bearing strenght, compressibility, shear strength, stability

Differentiate lithosphere, atmosphere, biosphere and hydrosphere

Litho = rock
Atmo = air
Bio = living things
Hydro = water

Pedosphere

Often defined as the soil mantle of the Earth, it represents the intersection of the lithosphere, atmosphere, hydrosphere, and biosphere

Regolith

The layer of unconsolidated solid material covering the bedrock including the O, A, B, and C horizons

C horizon

Part of the regolith that unlies the solum and is slowly changing to soil in the upper parts.

Solum

The altered layer of soil above the parent layer that includes the A and B horizons

Saprolite

Chemically weathered bedrock

What is soil basically a product of?

Destructive processes: weathering, microbial decay of organic residues

Synthesis: formation of new materials from destructive processes, horizon creation

Soil morphology

The science of the technical description of soil characteristics as seen in the field.

Edaphology

The study of how soil influences living things

Draw the soil horizons

Describe A horizons

A horizons are dominated by mineral particles and have darkened from the accumulation of organic matter. Sometimes referred to as topsoil.

Describe E horizons

E horizons are intensely weathered and leached so they do not have accumulated organic matter. Between A and B horizons.

Hapludalf

A well-drained and intesively farmed soil type in tropical regions

What materials are often washed down through horizons?

Silicate clays, iron and aluminium oxides, gypsum, calcium carbonate

Differentiate the size of sand, silt, and clay particles

Sand: 2 - 0.05mm
Silt: 0.05 - 0.002mm
Clay: 0.002mm

Differentiate sand and silt from clay in terms of minerals

• Sand and silt are composed of primary minerals ie. minerals that persisted with minimal change in composition since they were extruded by lava.

• Clay is composed of secondary minerals ie. that were formed by the breakdown of less resistant minerals

What is special about the smallest particles of clay (0.001mm)?

They have colloidal properties