1.  Plants and Soil  Soil Degradation  Addressing Soil Degradation

2. Soil characteristics  Soil classes (or orders): From richest (and darkest) to least fertile – mollisols, oxisols, alfisols, and aridisols  Soil profiles – layers of soil produce horizons Soil profiles  Soil texture – depends on proportions of clay, sand, and silt and classified according to the soil texture triangle  Texture affects workability, infiltration, and aeration

3. Alfisol: Moderately weathered Andisol: Volcanic ash Aridisol: Very dry Entisol: Newly formed Gelisol: Frozen Histosol: Organic, wet Inceptisol: Slightly developed (young) Mollisol: Deep, fertile Oxisol: Very weathered Spodosol: Sandy, acidic Ultisol: Weathered Vertisol: Shrinks and swells Soil Types There are 12 types of soils, which soil scientists call soil orders. The soil orders system is similar to the one biologists use to classify animals or plants into groups:

6.  Nutrient-holding capacity: affected by weathering, leaching, and decomposition  Water-holding capacity: affected by transpiration rates, infiltration, irrigation  Aeration  Amount of compaction  pH  Salinity

8. To support a good crop – soil must have a good supply of nutrients, allow infiltration, have good aeration, neutral pH, and low salt content  Sandy soil is poor  Silt and loam are the best  Detritus and organisms enrich soil  Bacterial composting  Earthworms contribute castings  symbiosis

9.  Mineralization: loss of humus leads to the build-up of particles and minerals  Erosion  Splash erosion – initial, due to rainfall  Sheet erosion – resulting from decreased infiltration  Gully erosion – caused by pressure of greater amounts of running water

11.  Desertification: spread of degraded areas of soil and vegetation  Desert pavement – formed when wind erosion carries the smaller particles and leaves larger pebbles covering soil below (aggravated by human impact)  Drylands  Cover 1/3 of earth’s land area  UN ‘s Convention to Combat desertification

15.  Causes that expose soil to erosion:  Overcultivation  Overgrazing  Deforestation  Irrigation leading to salinization  Corrections  Rotating crops  No-till agriculture  Contour-strip cropping  Shelterbelts

17.  Goals of soil conservation on the individual and public policy levels  Maintain productive topsoils  Keep food safe and wholesome  Reduce chemical fertilizers and pesticides  Keep farms economically viable

18.  USDA Low Input Sustainable Agriculture provides funding for alternative farming methods  Conservation Reserve Program pays farmers not to farm land  Food Security Act of 1985 provide incentives for soil conservation  Federal Agricultural Improvement and Reform Act: “Freedom to Farm”  Fostering sustainable agriculture  U.S.Superfund/CERCLA have cleaned up areas polluted by toxins.Superfund  Soil Conservation Act and SC Service combat erosion.