Plant & Soil Sciences eLibraryPRO
Loading
control panel control panel
 

Soil Genesis and Development, Lesson 6 - Global Soil Resources and Distribution

Rate Me

6.3 - Soil Quality

Soil Quality, as a general concept, can be thought of as the ability of a soil to function, in either natural or managed ecosystems, to sustain plant and animal life, and maintain or enhance air and water quality.  For agricultural ecosystems, we may consider Soil Quality as the ability of a soil to produce safe and nutritious crops in a sustained manner over the long-term, without impairing the resource base or harming the environment.

Soil Quality has the potential for many different interpretations, dependent upon factors such as land use, soil management practices, ecosystem and environmental interactions, and the priorities of human societies. When considering Soil Quality in any specific case, it is necessary to identify the major issues of concern with respect to that soil’s function. Whatever definition of the term Soil Quality is deemed appropriate for a specific instance, it should relate to the capacity of the soil to function effectively with regard to productivity; environmental quality; and plant, animal, and human health now and in the future. Since the majority of food and fiber needs of the human population are met by crops grown in managed agricultural ecosystems, we will focus on those systems here. However, the basic principles presented should be applicable to soils in other ecosystems, both natural and managed.


Some soil properties can be relatively easy to observe, measure, and monitor over time:
Table 1: Soil properties used as indicators of soil quality.
 Physical  Chemical  Biological
 Topsoil depth
 Organic matter content
 Soil Respiration (CO2)
 Texture and aggregation
 Salinity-electrical conductivity
 Microbial activity/biomass
 Aeration and infiltration
 Acidity - alkalinity (pH)
 Earthworm counts
 Surface cover
 Nitrate nitrogen
 Plant vigor
 Compaction    

Major factors which lead to reductions in soil quality, land degradation, and soil erosion:
  • Mismanagement: Lands that are improperly managed (e.g., improper tillage) lose their topsoil.  Either in large chunks during extreme erosive events, or little by little over an extended period of time, the soil disappears from the land resulting in reduced productivity and a degraded condition.  
  • Salinization: Results from the accumulation of salts in improperly irrigated soils, most frequently in arid regions.
  • Overharvesting: Occurs on  cultivated soils when repeated harvests are made from land without returning organic residues and mineral nutrients to the soil.
  • Contamination:  Exposure of soil to toxic substances, as a result of industrial processes or chemical spills, can severely damage the ability of a soil to perform its ecosystem function.
Figure 7. Inadequate soil cover on sloping surfaces can result in topsoil removal by erosive forces of water and wind. Here, rills and gullies are visible on a hillside where little fertile topsoil remains. Image courtesy of Tim Kettler


Table 1 - Cultural and environmental factors which enhance or degrade soil quality
 Soil Quality Enhancing
 Soil Quality Degrading
organic material additions
overharvesting
plant growth
bare fallow
fibrous root systems of plants fire
cool, humid climate hot, arid climate
vegetative cover exposed soil
minimal tillage operations intense tillage
wildlife wildlife
  erosion

For plant growth, the topsoil is the richest and most valuable part of the soil. Topsoil formation is a very slow process, which makes it a non-renewable (but re-usable) resource in terms of human lifespans. Keeping the soil in place while it is used for construction or crops is one of the greatest challenges faced by engineers and land managers.
Question 6: Which of the following categories of land degradation would be most likely to leave the soil in a condition making it vulnerable to erosion?

A.  mismanagement
B.  salinization
C.  overharvesting
D.  contamination
E.  none of the above

Man standing by gully caused by soil erosion
Figure 8. Soil erosion losses are greatest when the soil surface is exposed to intense rainfall, resulting in gulley formation as shown above.  Image courtesy of John Doran

Irrigation water quality is of great concern in arid climates. Water high in dissolved salts can lead to salt accumulation in soils.
Soil Surface Ruts of Water
Figure 9. NEED PERMISSION!  Soil erosion losses are greatest when the soil surface is exposed to intense rainfall, resulting in gulley formation as shown above.  Image courtesy of John Doran
 
Question 7: Irrigation of soils in an arid environment can contribute to which of the following?

A.  mismanagement
B.  salinization
C.  overharvesting
D.  contamination
E.  none of the above


Natural soil fertility is largely contained in the remains of formerly living things, also known as organic matter. Continuous removal of plant material for food or forage leads to gradual depletion of natural soil fertility.
Question 8: Which of the following results in a gradual loss of natural soil fertility?

A.  mismanagement
B.  salinization
C.  overharvesting
D.  contamination
E.  none of the above

Figure 10. Cattle grazing in the Nebraska Sandhills.  Grazing by livestock must be carefully managed to maintain grassland productivity and protect soil from degradation.  Image courtesy of Walter Schacht.



Insert Picture
Figure 11. tba
Question 9: Which of the following would cause an otherwise functional soil to lose its ability to perform its natural function in the ecosystem?

A.  mismanagement
B.  salinization
C.  overharvesting
D.  contamination
E.  none of the above



Comments

Be the first to write a comment...

Control Panel cancel

Create activities for your moodle courses. Moodle Go to moodle
Select and group e-Library Lessons to create your own package... My Communities
Community Blogs Community Media

My Joined Communities

 
My Blogs - a journal of my thoughts... My Blogs
 
My Comments - my thoughts expressed as a feedback... My Comments
 
Classes that I am taking Registered Classes
Class Blogs Class Media
 
Check the scores of assesments that you have taken Taken Assessments
 
clear
Please confirm your selection.