Showing posts with label Value of Soil. Show all posts
Showing posts with label Value of Soil. Show all posts

Sunday 24 July 2016

Soil

What is Soil?
Soils are complex mixtures of minerals, water, air, organic matter, and countless organisms that are the decaying remains of once-living things. It forms at the surface of land – it is the “skin of the earth.” Soil is capable of supporting plant life and is vital to life on earth.

Soil, as formally defined in the Soil Science Society of America Glossary of Soil Science Terms, is:
  1. The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.
  2. The unconsolidated mineral or organic matter on the surface of the earth that has been subjected to and shows effects of genetic and environmental factors of: climate (including water and temperature effects), and macro- and microorganisms, conditioned by relief, acting on parent material over a period of time.

So then, what is dirt? Dirt is what gets on our clothes or under our fingernails. It is soil that is out of place in our world – whether tracked inside by shoes or on our clothes. Dirt is also soil that has lost the characteristics that give it the ability to support life – it is “dead.”

Soil performs many critical functions in almost any ecosystem (whether a farm, forest, prairie, marsh, or suburban watershed). There are seven general roles that soils play:
  1. Soils serve as media for growth of all kinds of plants.
  2. Soils modify the atmosphere by emitting and absorbing gases (carbon dioxide, methane, water vapor, and the like) and dust.
  3. Soils provide habitat for animals that live in the soil (such as groundhogs and mice) to organisms (such as bacteria and fungi), that account for most of the living things on Earth.
  4. Soils absorb, hold, release, alter, and purify most of the water in terrestrial systems.
  5. Soils process recycled nutrients, including carbon, so that living things can use them over and over again.
  6. Soils serve as engineering media for construction of foundations, roadbeds, dams and buildings, and preserve or destroy artifacts of human endeavors.
  7.  Soils act as a living filter to clean water before it moves into an aquifer.
Soil Profile
There are different types of soil, each with its own set of characteristics. Dig down deep into any soil, and you’ll see that it is made of layers, or horizons (O, A, E, B, C, R). Put the horizons together, and they form a soil profile. Like a biography, each profile tells a story about the life of a soil. Most soils have three major horizons (A, B, C) and some have an organic horizon (O).
The horizons are:Soil Profile
O – (humus or organic) Mostly organic matter such as decomposing leaves. The O horizon is thin in some soils, thick in others, and not present at all in others.
A - (topsoil) Mostly minerals from parent material with organic matter incorporated. A good material for plants and other organisms to live.
E – (eluviated) Leached of clay, minerals, and organic matter, leaving a concentration of sand and silt particles of quartz or other resistant materials – missing in some soils but often found in older soils and forest soils.
B – (subsoil) Rich in minerals that leached (moved down) from the A or E horizons and accumulated here.
C – (parent material) The deposit at Earth’s surface from which the soil developed.
R – (bedrock) A mass of rock such as granite, basalt, quartzite, limestone or sandstone that forms the parent material for some soils – if the bedrock is close enough to the surface to weather. This is not soil and is located under the C horizon.

Value of Soil
Social issues and soil quality

Nutrient cycling, water regulation, and other soil functions are normal process occurring in all ecosystems. From these functions come many benefits to humans, such as food production, water quality, and flood control, which have value economically or in improved quality of life. People can increase or decrease the value of soil benefits because land management choices affect soil functions. Thus, it is important to understand what benefits we derive from soil and their value so we can appreciate the importance of managing land in a way that maintains soil functions.


What are the social benefits of soil?

People tend to emphasize benefits with the most direct, private economic value. In rural areas, this is usually plant growth especially as  crops and rangeland, but also a recreation areas. In urban/suburban areas, the most direct economic benefits of soil relate to structural support for buildings, roads, and parking. Landscaping, gardening and parklands may also be valued economically.

Those are all on-site, short-term benefits. That is, the landowner who decides how to manage the soil also reaps the benefits (and costs) of those management decisions. In contrast, many important benefits are long-term or go beyond the land being managed. The landholders who make the management choices and pay the costs of managing land may not be the same people who are affected by the landholders decisions. Society should discuss the value of these off-site benefits and to what extent the land owner or society should pay to maintain these soil functions.

Public, off-site benefits of soil relate to the following resource issues:

Water quality of streams, lakes, oceans, and groundwater
Air quality, especially particulates
Greenhouses gases, including carbon dioxide, methane, and nitrous oxide
Biodiversity
Water flow and flood control
Sustainability and land productivity
Aesthetics

Summary of soil benefits

Soil Function

Benefit of Value to Humans

On-site

Off-site

Nutrient cycling
Delivery of nutrients to plants Carbon storage improves a variety of soil functions
Enhances water and air quality Storage of N and C can reduce greenhouse gas emissions
Maintaining biodiversity and habitat

Supports the growth of crops, range land plants, and tress
May increase resistance and resilience to stress 
Reduces pesticide resistance


Helps maintain genetic diversity Supports wild species and reduces extinction rates Improves aesthetics of landscape

Water relations 
Provides erosion control Allows on-site water recharge of streams and ponds Makes water available for plants and animals

Provides flood and sedimentation control Groundwater recharge
Filtering and buffering
Can maintain salts, metal and micronutrient levels within range tolerable to plants and animals
Improves water and air quality
Physical stability and support
Acts as a medium for plant growth 
Supports buildings and roads 

Nutrient Stores archaeological items
Stores garbage


Multiple functions
Sustains productivity
Maintains or improves air and/or water quality