Soil quality Soil quality means the ability of the soil to "perform its functions." Healthy soil is a mixture of living organisms,
organic matter, and inorganic material. Soil should have texture so that air and water can diffuse through the void spaces in the soil. Air and water typically make up half of the volume of healthy soil. Air and water flow are important for keeping microorganisms and root systems alive, transporting nutrients, and wearing down inorganic components. Soil is integral to a variety of ecosystem services. These services include food, animal feed, fiber production,
climate moderation, waste disposal, water filtration, elemental cycling, This symbiotic relationship maintains living biomass, primarily fungal, in soils which increases the carbon content of the soil. Healthy soils are sites of decomposition of dead biomass. Macro- and micro-
organisms assist with processes such as
decomposition, nutrient cycling, disease suppression, and moderating
CO2 in the
atmosphere. One third of the globe's land has degraded soil, especially the
tropics and
subtropics with around 500 million
hectares degraded. • Erosion - soil is displaced as the result of water run-off of wind. Typically this occurs when agricultural fields are left bare. • Physical - the structure of the soil is changed in a way that inhibits the flow of water and air into the soil. Compaction by large vehicles is typical form of physical degradation. • Chemical - the soil becomes contaminated with pollutants such as heavy metals or hydrocarbons. • Biological - the loss of biological activity in the soil typically as a result of
eutrophication, where the accumulation of fertilizer inhibits microorganisms that
fix nitrogen. Many agricultural practices can cause soil degradation. Excessive or unnecessary
tillage, particularly
ploughing, is a common cause of degradation. The effects of agricultural soil degradation can create a positive feedback loop. For instance, the decrease of
soil fertility as a result of mechanical degradation can be compensated with the use of chemical fertilizers, which decrease the rhizospehere's capacity to produce ammonia, which requires more fertilizer applications.
Urbanization can also cause soil degradation. The construction of urban environments frequently involves the compaction of soil and the sealing of soils under layers of concrete, asphalt, and other materials. Sealing materials also decrease the natural absorption of rain water by soil causing intensification of water run-off during storms. The increased flow of water causes soil erosion. Cities also concentrate pollutants that can leach into soils. The maintenance of aesthetic
monocultures such as grass lawns can also have deleterious effects on soils. Biodiversity is lost in the rhizosphere as a result of monoculture. Practices such as frequent mowing also inhibit the development of deep root networks and the use of fertilizers and pesticides result in further biological degradation.
Acidification,
salinization, nutrient
leaching, and toxin contamination are a few types of chemical degradation. Toxins can accumulate in the soil from industrial processes like
mining and
waste management. Some biological examples include
biodiversity loss, emitting
greenhouse gasses, reduced carbon content, and a reduced capacity to sequester carbon. One of the most predictable ways to determine whether soil degradation has occurred is to measure its
organic carbon content The soil organic carbon pool is extremely important for soil fertility. == Climate change and the carbon cycle ==