Nature of the parent material Weathered Rocks from the will greatly influence time it lithosphere are the parent takes to make soil and the materials for soils nature of the soil that is formed Colluvial debris: Types of Parent Material Rocks that have fallen down hills • Residual • Colluvial • Water • Ice • Wind • Organic material Residual:Parent material in Arawak series, US Virgin Islands place The Arawak series consists The Castelleia series (CO) of shallow, well drained, consists of well drained soils slowly permeable soils on formed in thick summits and side slopes of noncalcareous, stony limestone hills and medium to moderately fine mountains. They formed in materials weathered locally material weathered from soft from quartz, latite, or limestone bedrock. similar rocks. 1 Water:Alluvial• deposits Sediment that is deposited by rivers • Forkwood soil, Wyoming Water:Alluvial deposits The Forkwood series consists of very deep, well drained soils Sediment that is deposited by rivers formed in slopewash alluvium derived from interbedded shale and argillaceous sandstone. Water:Marine (sediments deposited Pamunkey soil, Virginia by oceans) Soils of the Pamunkey series are very deep and well drained. They formed in Piedmont and Coastal Plain sediments. 2 Glacial till: Water:Lacustrine (materials deposited by lakes) Material transported by glacial ice Pleistocene Epoch 2 million years Glacial till: Material Eolian: Materials transported by wind transported by glacial ice Loess Glaciers - Loess Loess - Illinois • Summer Peoria - – Melt water from glaciers would carry 25,000 - 12,000 fine particles or sediment • Winter – Water would dry out leaving dry Roxanna - sediment 60,000 - 26,000 – Winter winds would transport the sediment 3 Loess - China Loess - Washington Lanzhou - 440,000 sq km 50 - 300 meters deep Paloose hills in From Gobi desert eastern Washington Soil series Wallawalla Paloose Athena Eolian: Materials transported by wind Volcanic ash Organic:Wet areas where accumulation> decomposition Peat bogs (1)Parent materials + 4 other factors of soil formation • Climate • Topography • Time • Biota 4 We talked about rocks, rock For soil formation: weathering and parent materials Soil Science Taxonomy • Soil as a natural body • Each soil as a unique individual How soil is formed – Developed as a result of the 5 factors of Factors of soil soil formation formation Different scenarios Regolith Solum O Soil formation is, A Regolith- simultaneously weathered rock E and soil that • Breakdown of old overlays bedrock • Synthesis of new Solum - portion of X Y B • Losses the regolith that shows the • Additions development of • Translocations C layers called soil horizons Bedrock (1)Parent materials + 4 other Climate factors of soil formation • Moisture • Climate – Quantity • Topography – Intensity – distribution • Time • Temperature • Biota Can be interrelated and interact 5 Rainfall: Intensity and Role of water duration • Essential for chemical weathering • Transport materials through horizons • Determine type of plant cover Effective precipitation Temperature • Water has to go into the soil • Rate of – Infiltration - not biological overland flow activity – Rainfall exceeds Rate of evaporation chemical reactions Soil Development Time Line Effect of Time Topography Same parent material, same climate Organic Matter Accumulation CaCO Structural 3 Development Accumulation Unweathered Loess CaSO4 Accumulation Location, location, location Time 6 Toposequence Biota - plants Well Excessively Poorly Very poorly drained drained drained drained Type of plant : Soil Profile Grass • Dense root system A - mollic horizon • Above ground foliage will die annually • Grows where moisture < trees • Thick A horizon Tree - deciduous Deciduous - • Leaves high in cations (Ca, Mg, Fe..) • Annual leaf fall • Larger A horizon • Well developed A horizon • More cations –Decomposed OM • Less acidic –High nutrients • More clay translocation 7 Coniferous Tree - coniferous Acidic • Leaves low in cations Thin A • Little leaf fall • Thin A horizon E (eluviation) –Oi - slightly decomposed • E horizon –eluviation Animals Animals • Pedoturbation • Earthworms – Animal burrows effectively mix soil from – Soil mixing different horizons – Soil structure – Soil aeration Animals Start with a pile of rocks • Humans • Physical and chemical weathering –Agricultural – Breakdown particles practices – Change mineral structure –Accelerate soil loss –Accelerate soil formation 8 Plant starts growing First stage of soil formation • Organic matter is added to soil • Increased organic surface matter in A horizon • Root exudates further break down minerals Next stage will involve When a plant starts growing development of a B horizon • Organic matter from plants is a • Cations that have been solubilized nutrient source for other organisms by plant exudates, microbial activity,and acidification will start moving lower into the soil • Secondary clays have been formed in A and are also moving down the profile Beginning of a B horizon • Dark A horizon – Organic matter – Clays • Something below the A that looks different from the parent material • Parent material 9.