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Transcript
Lecture 6 SOIL FORMATION FACTORS Soil Forming Factors 1. Parent Materials 2. Climate 3. Vegetation 4. Topography 5. Time PARENT MATERIAL From rocks or materials brought from sea clay and river clay. Its influence soil formation through: Weathering capacity ; depend on types of mineral in the parent materials Nutrient content influence a lot of alive plant. PARENT MATERIAL Definition: The primary material from which the soil is formed. - bedrock, - organic material, - alluvial: deposit from water, wind, glaciers, volcanoes, or material moving down a slope Organic soil Mineral soil Colluvial material Aluvium Sedimentary rock. Sandstone, } quartz limestone, } carbonate Shale, } clay -Limestones: fast weathering, but commonly make nutrient-poor soils The type of soil that forms depends on the type of rocks available, the minerals in the rocks, and how minerals react to temperature, pressure, and erosive forces Igneous rocks - Mafic vs. felsic: mafic rocks have minerals that weather more readily than those in felsic rocks - Plutonic vs. Volcanic: most plutonic rocks are crystalline and competent where volcanic rocks are more porous and fractured. Thus volcanic rocks allow water to enter into the pores and fractures and contribute to weathering more rapidly. Mendapan marin Size of particle for parent materials (E.g. :sandstone = sand, conglomerat = rocks and shale = clay ) Influence of parent materials depend on time. Hard effect (dominant) for young soil (E.g. Entisol and Inceptisol order). For older soil, factors of climate and organism is more important. (E.g. Ultisol and Oxisol order). Main parent materials in Malaysia : granite, limestone, basalt, clay (river and sea) and sandstone. Temperature, Precipitation Temperature: a. hot temperatures contribute to rapid chemical weathering, b. cool temperatures slow things down, c. freezing temperatures keep water from making any contribution. The hotter and more humid a climate, the faster and more completely big rocks are broken into smaller rocks, then into pebbles, then into tiny particles that make up the loose stuff we call soil. • temperature and rain determine type of plants, animals and microb activities. Examples : Arid temperature – spot plant (grass type) and shrub. Humid temperature – tropical forest Rain erode soil at the slope area. Precipitation (rain, snow, humidity) Water is key to virtually all the chemical weathering processes. Deserts weather mechanically, with very little chemical weathering • • Rain that absorbed into soil transfer clay, humus and dissolve materials from upper layer to down layer through leaching process to cause horizon formation. Arid temperature formed shallow soil, low organic matter content and accumulation of salt at the above horizon. Humid temperature formed inmost soil, high organic matter content and well-decomposed and acidic soil (pH< 5.5) Stratigrafi/lapisan Organisms: - All plants (vegetation) - animals living in or on the soil (including micro-organisms) - humans • Plants and alive animals play important part in soil formation Plant Type of plants influence formation of soil horizon. Grass – A horizon (thick) , good structure and dark in color. Desert Soil Animals living in the soil affect a. decomposition of waste materials b. how soil materials will be moved around in the soil profile. c. On the soil surface remains of dead plants and animals are worked by microorganisms and eventually become organic matter-enrich the soil. termite The location of a soil on a landscape can affect how the climatic processes impact it. Soils at the bottom of a hill will get more water than soils on the slopes, and soils on the slopes that directly face the sun will be drier than soils on slopes that do not. Also, mineral accumulations, plant nutrients, type of vegetation, vegetation growth, erosion, and water drainage are dependent on topographic relief. All of the above factors assert themselves over time, often hundreds or thousands of years. Soil profiles continually change from weakly developed to well developed over time ERA PERIOD QUARTERNARY EPOCH MULA SELANG (juta tahun sebelum sekarang) Holocene 0.01 Pleistocene 2.00 Pliocene CENOZOIC Miocene TERTIARY Oligocene Eocene Paleocene MESOZOIC CRETACEOUS 135.00 JURASSIC 192.00 TRIASSIC 230.00 PERMIAN 290.00 PENNSYLVANIAN PALEOZOIC 65.00 Carboniferous 320.00 MISSISSIPIAN 350.00 DEVONIAN 410.00 SILURIAN 435.00 ORDOVICIAN 485.00 CAMBRIAN 560.00 Soils change over time as they weather. Weathering in the soil takes place over thousands of years. Just like people, soils can be mature or youthful. Each has its particular characteristics based not so much on their age as on their level of development. Slightly developed Highly developed Differences in soil forming factors from one location to another influence the process of soil formation