Overview and 3.71 Soil Contains a Living Complex Ecosystem

1. Overview and 3.71 Soil Contains a Living Complex Ecosystem By Colton Ruggery

2. Major Topics • A.) Soil Textures • B.) Inorganic and Organic Components • C.) Sustainable Agriculture • D.) Phytoremediation

3. 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

4. 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)

5. 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

6. 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 groundwater Click here for an 8 minute video on cation exchange

7. 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

8. 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

9. Sustainable Agriculture • Sustainable agriculture is committing to farming methods that are… • Conservation minded • Environmentally safe • Profitable

10. 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

11. 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