<P> Topsoil is the upper , outermost layer of soil , usually the top 2 inches ( 5.1 cm ) to 8 inches ( 20 cm ) . It has the highest concentration of organic matter and microorganisms and is where most of the Earth 's biological soil activity occurs . Four elements constitute the composition of soil . Those elements are mineral particles , organic matter , water , and air . The volume of top soil consists of 50 to 80 percent of these particles which form the skeletal structure of most soils . This composition allows the soil to sustain its own weight , and other internal matter such as water and overlying landscape . Organic matter , another important element , varies on quantity on different soils . This provokes positive and negative effects or reactions on the soil . The strength of soil structure decreases with the presence of organic matter , creating weak bearing capacities . Organic matter condenses and settles in different ways under certain conditions , such as roadbeds and foundations . The skeletal structure becomes affected once the soil is dewatered . The soil 's volume substantially decreases . It decomposes and suffers wind erosion . </P>
<P> Topsoil is the upper , outermost layer of soil , usually the top 2 inches ( 5.1 cm ) to 8 inches ( 20 cm ) . It has the highest concentration of organic matter and microorganisms and is where most of the Earth 's biological soil activity occurs . Four elements constitute the composition of soil . Those elements are mineral particles , organic matter , water , and air . The volume of top soil consists of 50 to 80 percent of these particles which form the skeletal structure of most soils . This composition allows the soil to sustain its own weight , and other internal matter such as water and overlying landscape . Organic matter , another important element , varies on quantity on different soils . This provokes positive and negative effects or reactions on the soil . The strength of soil structure decreases with the presence of organic matter , creating weak bearing capacities . Organic matter condenses and settles in different ways under certain conditions , such as roadbeds and foundations . The skeletal structure becomes affected once the soil is dewatered . The soil 's volume substantially decreases . It decomposes and suffers wind erosion . </P>
what is the upper most layer of soil
what is the upper most layer of soil
Topsoil
Topsoil