Overview and 3.71 Soil Contains a Living Complex Ecosystem

By Colton Ruggery

Major Topics A.) Soil Textures B.) Inorganic and Organic Components

C.) Sustainable Agriculture D.) Phytoremediation

Soil contains a living, complex ecosystem

This “A Horizon” is the topsoil Topsoil contains a wide range of

living organisms The organisms interact with each

other and the physical environment

Plants absorb nearly all the water and minerals they require from the upper layers of the soil

Soil Texture Texture depends on sizes of soil particles Sand, silt and clay make up soil texture Soil particles range from coarse sand (0.02-2 mm in

diameter) to silt (0.002-0.02 mm) to microscopic clay particles (less than 0.002 mm)

Soil Texture Mechanical fracturing by water freezing in rock

crevices and chemical breakdown through weak acids in the soil

Organisms that penetrate rock cause mechanical and chemical breakdown

Example: Plant roots secrete acid that dissolves rock-chemical. Their growth in fissures leads to mechanical fracturing

Inorganic and Organic Components Inorganic materials in soil provide positively charged

ions called cations These cations are attracted to negatively charged soil

particles Cation exchange is the process that allows minerals to

enter the soil solution Negatively charged ions called anions do not bind to

soil particles and leach into the groundwaterClick here for an 8 minute video on cation exchange

Inorganic and Organic Components Humus- produced by decomposition of dead

organisms, feces, fallen leaves, and other organic matter by bacteria and fungi.

Humus allows for proportional water to air ratio and increases capacity to exchange cations in soil.

Many living organisms live within the soil The activities of these organisms affect the soils

physical and chemical properties They excrete material such as acids and move the soil

around mixing clumps of clay allowing for better gaseous diffusion and water retention

Sustainable Agriculture Soil mismanagement has always been a big problem for farmers –

both in ancient times and today The American Dust Bowl in the 1930s was caused by soil

mismanagement More than 30% of the world’s farmland is impacted by poor soil

conditions today Sustainable agriculture is committing to farming methods that

are… Conservation minded Environmentally safe Profitable

Sustainable Agriculture Sustainable agriculture is committing to farming

methods that are… Conservation minded Environmentally safe Profitable

Sustainable Agriculture Techniques Irrigation – most effective way to use water resources to grow

plants Drip irrigation is a popular method to effectively water crops

Fertilization – replacing depleted soil nutrients without negative environmental impacts

Adjusting soil pH – to maximize cation exchange and mineral availability

Erosion control – to help prevent soil degradation No-till agriculture is one plowing technique used to limit

erosion

Phytormediation Certain plants have a natural ability to collect soil pollutants Plants are grown in the poor soil and the harmful nutrients are absorbed and

concentrated When harvested, plants can be removed for easy disposal