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In this module, the following topics are covered: 1) soil's importance to society, 2) the formation of soil profiles, 3) soil constituents for plant growth and nutrient uptake, and 4) soil's relationship with agricultural sustainability and ecological processes

Learning objectives

After reading this module, students should be able to

  • define soil and comment on its importance to society
  • describe how soil profiles form
  • explain the importance of soil constituents for plant growth and nutrient uptake
  • understand the importance of soil to agricultural sustainability and ecological processes

Soil profiles and processes

What is soil?

The word "soil" has been defined differently by different scientific disciplines. In agriculture and horticulture, soil generally refers to the medium for plant growth, typically material within the upper meter or two (see Figure Soil Profile ).

Soil Profile Soil Profile
Soil Profile . Photograph shows a soil profile from South Dakota with A, E, and Bt horizons. The yellow arrows symbolize translocation of fine clays to the Bt horizon. The scale is in feet. Source: University of Idaho and modified by D. Grimley.

We will use this definition in this chapter. In common usage, the term soil is sometimes restricted to only the dark topsoil in which we plant our seeds or vegetables. In a more broad definition, civil engineers use the term soil for any unconsolidated (soft when wet) material that is not considered bedrock. Under this definition, soil can be as much as several hundred feet thick! Ancient soils, sometimes buried and preserved in the subsurface, are referred to as paleosols (see Figure Modern versus Buried Soil Profiles ) and reflect past climatic and environmental conditions.

Modern versus Buried Soil Profiles Modern versus Buried Soil Profiles
Modern versus Buried Soil Profiles . A buried soil profile, or paleosol (above geologist 's head), represents soil development during the last interglacial period. A modern soil profile (Alfisol) occurs near the land surface. Source: D. Grimley.

From a somewhat philosophical standpoint, soil can be viewed as the interface between the atmosphere and the earth's crust, and is sometimes referred to as the skin of the earth. Soil also incorporates aspects of the biosphere and the hydrosphere. From a physical standpoint, soil contains solid, liquid, and gaseous phases. The solid portion of the soil consists predominantly of mineral matter, but also contains organic matter (humus) and living organisms. The pore spaces between mineral grains are filled with varying proportions of water and air.

Importance of soil

Soil is important to our society as it provides the foundation for most of the critical aspects of civilization. Our building structures and homes, food, agricultural products, and wood products all rely on soil. Forests, prairies, and wetlands all have a dependence on soil. Of course, soil is also a critical component for terrestrial life on earth, including most animals, plants, and many microorganisms.

Soil plays a role in nearly all natural cycles on the earth's surface. Global cycling of key nutrients, such as Carbon (C), Nitrogen (N), Sulfur (S), and Phosphorous (P), all pass through soil. In the hydrologic cycle, soil helps to mediate the flow of precipitation from the land surface into the groundwater or can control stormwater runoff into lakes, streams, bays, and oceans. Soil microorganisms or microflora can help to modify or destroy environmental pollutants.

Questions & Answers

it is the relatively stable flow of income
Chidubem Reply
what is circular flow of income
Divine Reply
branches of macroeconomics
SHEDRACK Reply
what is Flexible exchang rate?
poudel Reply
is gdp a reliable measurement of wealth
Atega Reply
introduction to econometrics
Husseini Reply
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Jahara
Good morning
Jorge
hi
abubakar
hi
Nmesoma
hi
Mahesh
Hi
Tom
Why is unemployment rate never zero at full employment?
Priyanka Reply
bcoz of existence of frictional unemployment in our economy.
Umashankar
what is flexible exchang rate?
poudel
due to existence of the pple with disabilities
Abdulraufu
the demand of a good rises, causing the demand for another good to fall
Rushawn Reply
is it possible to leave every good at the same level
Joseph
I don't think so. because check it, if the demand for chicken increases, people will no longer consume fish like they used to causing a fall in the demand for fish
Anuolu
is not really possible to let the value of a goods to be same at the same time.....
Salome
Suppose the inflation rate is 6%, does it mean that all the goods you purchase will cost 6% more than previous year? Provide with reasoning.
Geetha Reply
Not necessarily. To measure the inflation rate economists normally use an averaged price index of a basket of certain goods. So if you purchase goods included in the basket, you will notice that you pay 6% more, otherwise not necessarily.
Waeth
discus major problems of macroeconomics
Alii Reply
what is the problem of macroeconomics
Yoal
Economic growth Stable prices and low unemployment
Ephraim
explain inflationcause and itis degre
Miresa Reply
what is inflation
Getu
increase in general price levels
WEETO
Good day How do I calculate this question: C= 100+5yd G= 2000 T= 2000 I(planned)=200. Suppose the actual output is 3000. What is the level of planned expenditures at this level of output?
Chisomo Reply
how to calculate actual output?
Chisomo
how to calculate the equilibrium income
Beshir
Criteria for determining money supply
Thapase Reply
who we can define macroeconomics in one line
Muhammad
Aggregate demand
Mohammed
C=k100 +9y and i=k50.calculate the equilibrium level of output
Mercy Reply
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Amisha
money as unit of account means what?
Kalombe
A unit of account is something that can be used to value goods and services and make calculations
Jim
all of you please speak in English I can't understand you're language
Muhammad
I want to know how can we define macroeconomics in one line
Muhammad
it must be .9 or 0.9 no Mpc is greater than 1 Y=100+.9Y+50 Y-.9Y=150 0.1Y/0.1=150/0.1 Y=1500
Kalombe
Mercy is it clear?😋
Kalombe
hi can someone help me on this question If a negative shocks shifts the IS curve to the left, what type of policy do you suggest so as to stabilize the level of output? discuss your answer using appropriate graph.
Galge Reply
if interest rate is increased this will will reduce the level of income shifting the curve to the left ◀️
Kalombe
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Source:  OpenStax, Sustainability: a comprehensive foundation. OpenStax CNX. Nov 11, 2013 Download for free at http://legacy.cnx.org/content/col11325/1.43
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