Terms for ESS Test 29/9

Soil

Forms the outermost layer of the Earth’s surface and consists of weathered rock, organic matter, air and water

Soil Inputs

• Solar energy

• Heat

• Nutrients from weathered bedrock

• Moisture

• Organic matter

Stores in Soil

• Weathered materials

• Organic matter

• Air

• Moisture

Soil Outputs

• Sediment (solid particulate matter that settles at the bottom of a liquid or is deposited by water, wind, or ice on the Earth’s surface)

• Organic matter

• Nutrients

• Air

• Moisture

Litter

Decomposing plant and animal matter

Humus

Decaying organic matter

Mineralization

Refers to the nutrients (especially nitrogen, phosphorous, and sulfur) that are released when organic matter is broken down.

Soil Pores

Spaces in the soil that may be filled with air and/or water. Macropores are large pore spaces (that may contain both air and water) whereas micropores are small spaces (that are often filled with water).

Ion

An electrically charged particle that is produced when an atom gains or loses an electron.

Three Main States of Water in Soils

• Gravitational water: Unavailable for plant roots; lost by gravity; refers to water moving down through the soil due to gravity

• Capillary water: Available for plant roots; lost by evapotranspiration; refers to water held by surface tension on small particles in the pore space

• Hygroscopic water: Unavailable for plant roots; always present; refers to water that is held in a very thin layer around each individual soil particle

Field Capacity (Related to Gravitational Water)

Occurs when all the smaller pores are filled with water and the larger pores are filled with air.

Permanent Wilting Point (Related to Hygroscopic Water)

Occurs when plants are unable to withdraw any water tightly held by the soil.

Weathering

Refers to the breakdown of rocks in situ (without movement). The weathering of bedrock provides mineral particles in the lower horizon.

Two Types of Weathering

• Mechanical (physical) weathering: Leads to the development of smaller particles of the same rock (scree or pebbles/stones)

• Chemical weathering: A rock substance is transformed into a different, new material

Soil Horizons

Refers to the development of soil over time into into distinct layers.

Soil Profile

Refers to the combination of soil horizons. Shows the vertical changes of layers in a soil from the surface to the bedrock

Pedon

A three-dimensional sample of a soil that is large enough to show its characteristics.

Soil Fertility

The ability of soil to sustain plant growth by providing essential nutrients, water, and a healthy physical and biological environment.

Soil Aggregation

The natural process where individual mineral particles (sand, silt, and clay) bind together into stable clusters called aggregates or peds.

Oxidation

A chemical reaction where an atom, molecule, or ion loses electrons, gains oxygen, or loses hydrogen.

Parent Material

The underlying geological deposit or weathered rock from which a soil develops.

Waterlogging

The saturation of soil by water when the rate of water input (rainfall, irrigation) exceeds the rate of drainage, filling all pore spaces and cutting off oxygen to plant roots.

Soil Salinization

The process where water-soluble salts accumulate in the soil to levels that harm plant growth and reduce agricultural productivity.

Biomass

Renewable organic material that comes from plants and animals.

Manure

Organic matter that primarily consists of animal feces mixed with bedding materials like straw.

Podzol

Soil leached under acidic conditions.

Fermentation

A natural metabolic process where microorganisms convert sugars into acids, gases, or alcohol without using oxygen.

Podzolization

A form of leaching under acidic conditions in which iron and aluminium are leached from the upper horizons and deposited in the lower horizons.

Examples of Solutes

• Calcium

• Nitrates

• Chlorine

• Potassium

• Sulfates

• Bicarbonates of sodium, magnesium, and dissolved gases

• Sulfur dioxide

• Carbon dioxide (CO2)

• Nitrous oxide (N2O)

• Oxygen (O2)

• Methane (CH4)

Germination

The process where a plant or fungus grows out from a seed or spore after a period of dormancy.

Albedo

A measure of how much sunlight a surface reflects.

Radiation

Energy that travels through space or matter in the form of waves or particles.

Convection

The transfer of heat through the physical movement of fluids like liquids or gases.

Conduction

The process where heat moves through a substance by direct physical contact.

Latent Heat

The energy absorbed or released by a substance during a change in its physical state without changing its temperature.

Soil Bulk Density (SBD)

The mass of dry soil divided by its total volume (including pore space). Express as g/cm³ or MG/m³.

Synthetic Fertilizers

Human-made products that are used to increase the level of nutrients in the soil and enhance plant growth.

Agro-Chemicals (Pesticides, Herbicides, and Insecticides)

Organic compounds used in modern agriculture for crop protection and disease control.

Irrigation

Refers to the additional input of water into agricultural systems to encourage plant growth

Sodicity

The presence of large amounts of sodium ions in relation to other cations.

Decomposition

The process whereby complex organic materials in dead plant and animal tissue are broken down into their original inorganic materials such as CO2, water, minerals, and elements.

Nitrification

Release of inorganic nitrogen (N2).

Soil Erosion

The wearing away and removal of the fertile top layer of soil by natural elements or human activity.

Evapotranspiration

The combined process of water moving from the Earth's surface to the atmosphere via evaporation from soil and water bodies and transpiration from plants.

Permeability

The capacity of a porous material to allow fluids and gases to pass through it

Leaching

The process where water or another liquid dissolves and extracts soluble substances or chemicals from a solid material, such as soil, ore, or waste.

Soluble

A substance can dissolve in a liquid.

Diffusion

Occurs when there is a greater concentration of molecules or ions at one point compared to another.

Infltration

The process by which water soaks into or is absorbed by the soil.

Infiltration Capacity

The maximum rate at which rain can be absorbed by soil in any given condition.

Runoff

Excess water from rain, snowmelt, or irrigation that flows over the land surface because the soil cannot absorb it fast enough.

Percolation

Refers to water moving slowly downwards from the soil into the bedrock.

Water Table

The upper layer of the permanently saturated zone (where nearly all the pore spaces are filled with water).

Aeration Zone

The zone that is seasonally wetted and seasonally dries out.

Aquifers

Rocks which contain significant quantities of water.

Aquiclude (Aquifuge)

A rock that will not hold water; are impermeable rocks that prevent the large-scale storage and transmission of water.

Aeration

The process of introducing air, oxygen, or gases into soil or liquids to improve health, reduce compaction, or remove unwanted gases.

Seapage

The slow flow of a fluid through a porous material.

(Soil) Seed Bank

A natural reserve of viable, dormant or semi-dormant seeds present on the soil surface or buried within the leaf litter and soil.

Heterotrophs

Organisms that feed on other organisms.

Autotrophs

Organisms that convert sunlight energy into food energy.

Wilting

Loss of rigidity in the non-woody parts of plants when water loss exceeds water absorption.

Volatilization

Conversion of chemical substances from a liquid/solid state to a gaseous state.

Soil Texture

Refers to the proportion of differently sized materials, usually sand, silt and clay, present in a soil.

Primary Productivity

Primary productivity of soil depends on its:

• Mineral content

• Drainage

• Water-holding capacity

• Air spaces

• Biota

• Potential to hold organic matter

Soil Structure

Refers to the way in which soil particles are combined to form larger soil aggregates.

Workability

How ‘light’, ‘medium’, or ‘heavy’ specific soil is.

Loam

A well-balanced soil with significant proportions of sand, silt, and clay.

Influence of Soil Texture on Properties and Behaviour of Soils

Drainage

The natural or artificial removal of surface water and groundwater from a specific area.

Terracing

The method of turning a sloped or hilly piece of land into a series of flat, step-like platforms to make it usable for framing.

Land Reclamation

The process of creating new land from oceans, seas, or lakes, or restoring damaged or abandoned land for agricultural, industrial, or urban use.

Nutrition Transition

Change in diet with increasing income (up to a point).

World Agriculture

Produces enough food to feed everyone on Earth, but the food produced is not equitably distributed, and at least one third of the food produced is wasted.

Outputs of Farming

• Arable (crops)

• Pastoral (livestock)

• Mixed (arable and pastoral)

• Non-food (e.g. tobacco and cotton)

• Monoculture (farming of a single product)

• Diverse (farming of many products)

Reasons for Farming

• Commercial (aiming to sell products to make a profit)

• Subsistence (aiming to provide food products for the household)

Sedentary

The farmer farms the same area each year.

Shifting Cultivation

An agricultural system where farmers clear a plot of land, which is cultivated for a few years, and then left dormant for a long period to naturally recover its fertility.

Nomadic Pastoralism

A mobile way of life where herders move livestock continuously to find fresh water and grazing land.

Intensive vs Extensive Farming

• Intensive (maximises productivity from a given unit of land with a relatively high number of inputs per hectare)

• Extensive (low levels of inputs of fertilizers, pesticides, machinery, and and outputs per unit of land, although the total cost of the inputs can be very high)

Hydroponics

Growing crops in water.

Aquaculture

The controlled farming of aquatic organisms.

Organic vs Inorganic Farming

• Organic: Attempts to be a natural form of farming

• Inorganic: May use synthetic fertilizers and pesticides

Corporate Farms

Large-scale farms that are owned by companies and their shareholders, and the work is mainly done through a farm manager and hired labour.

Family Farms

Farms that are owned and run by families.

Irrigated Farming

A type of farming in which extra water, taken from rivers, groundwater and/or reservoirs, is provided for crop growth.

Market Gardening/Horticulture

A type of farming involving the production of only one type of crop.

Nomadic Farmers

Farmers that move seasonally with their herds.

Rain-Fed Farming

A type of farming that relies on natural rainfall for crop germination and growth.

Soil-Based Farming

A type of farming in which crops are grown in soil in fields.

Intercropping

Growing two or more crop species simultaneously in the same field or plot of land.

Crop Rotation

Growing different crops families in the same plot of land in a planned sequence year after year.

Fallow

Farmland that is plowed and left unseeded for a season or more to recover its fertility and retain moisture.

Agribusiness

Highly commercialized and large-scale farming.

Farm Fragmentation

A farmer owns many different plots of land rather than just a single of piece.

Transhumance

Seasonal movements up to higher slopes in summer and down to lower slops during winter.

Bush Encroachment

The aggressive, unchecked increase in density of native woody plants and shrubs that outcompete grass and herbaceous layers in grasslands and savannas.

Green Revolution

Involved the application of science and technology to increase crop productivity.

Eutrophication

Over-enrichment of a water body with nutrients like nitrogen and phosphorous, leading to excessive plant and algal growth that depletes dissolved oxygen.

Organic Fertilizers

Fertilizers that are derived from animal matter, human excreta and/or vegetation matter (compost)