What is soil?
A: Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life.
Soil consists of a solid phase of minerals and organic
matter (the soil matrix), as well as a what?
A: A porous phase that holds gases (the soil atmosphere) and water (the soil solution).
Accordingly, soil is a three-state system of what?
A: Solids, liquids, and gases.
Soil is a product of what factors?
A: The influence of climate, relief (elevation, orientation, and slope of terrain), organisms, and the soil's parent materials interacting over time.
It continually undergoes development by way of what?
A: Numerous physical, chemical and biological processes, which include weathering with associated erosion.
Given its complexity and strong internal connectedness,
soil ecologists regard soil as what?
A: An ecosystem.
Little of the soil of planet Earth is older than the
Pleistocene and none is older than what?
A: The Cenozoic, although fossilized soils are preserved from as far back as the Archean.
Soil science has what two basic branches of study?
A: Edaphology and pedology.
Edaphology studies what?
A: The influence of soils on living things.
Pedology focuses on what?
A: The formation, description (morphology), and classification of soils in their natural environment.
In engineering terms, soil is included in the broader
concept of what?
A: Regolith, which also includes other loose material that lies above the bedrock, as can be found on the Moon and other celestial objects.
Soil is a major component of the Earth's what?
With respect to Earth's carbon cycle, soil acts as an
A: Carbon reservoir, and it is potentially one of the most reactive to human disturbance and climate change.
As the planet warms, it has been predicted that soils
will add what to the atmosphere?
A: Carbon dioxide, due to increased biological activity at higher temperatures.
Since soil has a tremendous range of available niches
and habitats, it contains a prominent part of the Earth's what?
A: Genetic diversity.
A gram of soil can contain what?
A: Billions of organisms, belonging to thousands of species, mostly microbial and largely still unexplored.
Organic carbon held in soil is eventually returned to
the atmosphere through what process?
A: The process of respiration carried out by heterotrophic organisms.
A substantial part is retained in the soil in the form
A: Soil organic matter.
Tillage usually increases the rate of soil respiration,
leading to what?
A: The depletion of soil organic matter.
Since plant roots need oxygen, what is an important
characteristic of soil?
This ventilation can be accomplished via networks of
A: Interconnected soil pores, which also absorb and hold rainwater making it readily available for uptake by plants.
Since plants require a nearly continuous supply of
water, but most regions receive sporadic rainfall, the water-holding
capacity of soils is what?
A: Vital for plant survival.
Soils can effectively remove impurities, kill disease
agents, and degrade contaminants, this latter property being called what?
A: Natural attenuation.