Bài giảng Environmental Sciences - Chapter 8: Soil

Chapter 8:SoilGoalsUnderstand how the soil quality determines what can grow Understand how soil quality can determine the survival of societiesNote: Fig. 8-4 in our book also includes the “E horizon”O HorizonHumus- dark, soft, spongy residue of organic matter as a result of decomposition of organic matter such as leaves and dead wood1۫ source of nutrients in soil systemsA HorizonTop soil-mixture of humus and leachial mineral soilThin roots extend into this layerE HorizonEluviation process of leaching (note: You may see this word spelled with and I, A, or E)Minerals are “leached” into this layer from H2O moving downwardAccumulation of elluvial organic matterOften high in iron, aluminum, and calciumOften high in clay contentUnweathered parent materialShows little or no sign of soil formation (primary succession)Glacial deposits, volcanic ashReveals history of the landTextureSand 2.0-.02 mmSilt .02-.002 mmClay.002mm ≥ some microscopicPorosity and PermeabilityLOAM: 40%sand 40% silt 20% clayLoam is theoretically the ideal soilltpwww.gsfc.nasa.gov/ globe/pvg/texture3.htm Classes of SoilMollisols- very fertile, dark, found in temperate grasslands, best agricultural soil, Deep A horizonOxisols- soil of tropical and subtropical rainforest layer of iron and Al oxides in B horizon, little O horizonAlfisols- weathered forest soil, not deep, but developed OAE+B typical of most temperate forest biome. Need fertilizer for agricultureAridsols- dry lands + desert, lack of vegetation, lack of rain  unstructured vertically, irrigation leads to salinization because of high evaporation.The Public Policy and SoilLow Input sustainable Agriculture (LISA) -started by US Defense of Agriculture in 1988 Conservation Reserve Program- 1985Food Security Act of 1985Federal Agriculture Improvement and Reform (FAIR) 1996Environmental Quality Incentive Program (EQUIP)Know these Acts and Laws:LOAM: 40%sand 40% silt 20% clayLoam is theoretically the ideal soilltpwww.gsfc.nasa.gov/ globe/pvg/texture3.htm