Functions of Soil in Our Ecosystems of Soil Sciences | ENST 200, Study notes of Environmental Science

Download Functions of Soil in Our Ecosystems of Soil Sciences | ENST 200 and more Study notes Environmental Science in PDF only on Docsity! ° =| Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store using simple and easy self-serve stations. — = | Purchase with the help of clerk that can answer your questions about a book or class. lm 4509 Coli = 301-209-9313 Pw us to 3: more then Cash Now. www.BookHolders.com Me eet) HTTP://NOTES.BOOKHOLDERS.COM Soil Science Notes Functions of soils in our ecosystem, - Medium for plant growth © Plants get from soil * Physical support, an anchoring root system so the plant does not fall over or blow away * Air—plants get oxygen from soil for the process of respiration to obtain energy, soil acts as a ventilation system for air allowing oxygen in and CO2 out * Water — soil pores absorb and hold rain water where it can be used by plant roots, allow plants to survive for a while without rain * Temperature moderation — soil a few centimeters deep can be 10 degrees cooler or warmer than the surface temperature * Protection from toxins — soils can ventilate gases, decompose or absorb org nic toxins, or suppress toxin-producing organisms * Nutrient elements ~ a fertile sail provides a continuing supply of dissolved mineral nutrients © 17ess complete their life cye * Micronutrients — elements used in smaller amounts by plants ential nutrients — macronutrients — plants cannot grow or s without these elements ~ Regulator of water supplies o All water in rivers, lakes, estuaries and aquifers have traveled through soil Soil purifies water as it travels through the upper layers by processes that remove many impurities and kill potential disease organisms © However shallow or impermeable s runoff © Nature and management of soil in a watershed caninfluence the purityand il can cause a flash flood of muddy water by amount of water in aquatic systems yeler of raw materials » Decomposes organic matter for reuse of materials and nourishment Recycles material into beneficial humus, that can be used by plants'and animals 9 Releases CO2 to be used by plants} greenhouse effect - Modifier of the atmosphere o Can distribute great quantities of dust. to the atmosphere in places where soil is dry and unvegetated © Inplaces where soil is moist and vegetated, soil can prevent dust-laden air HTTP://NOTES.BOOKHOLDERS.COM How to Buy Textbooks Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Evaporation of soil moisture is a major source of water vapor in the atmosphere that can aller (emperature, composition and weather patterns - Habitat for soil organisms A handful of soil can hold billions of organisms © Complex ecosystems with areas of aerobic and anoxic conditions Engineering Medium © One of the worlds widely used building materials Different types of soils are more stable than others for roadbeds or building foundations Pedosphere as an environmental interfé Soil is an interface between the lithosphere (rock), the atmosphere, the hydrosphere and the biosphere - Where all four worlds interact is the most productive and complex places on earth - Soils channel water from rain to rivers and transfer mineral elements from bedrocks to oceans - Remove vast amounts of atmospheric gases Soil as a natural body - A soi] ~a three dimensional natural body such as a mountain or lake is - The soil —a collection of individually different soil bodies that cover the land aa péel covers an orange Soils — natural bodies composed of soil plus roots, animals, rocks, artifacts and so forth surface that has crumbled and decayed,to produce Regolith — rock exposed at the earth’s a layer of unconsolidated debris overlying the hard, un-weathered tock - Soil horizons — process of the formation of contrasting soil layers The soil profile and its layers Weathering if the regolith occurs first at the surface and works its. way down The upper layers of the profile have been changed the most'while the deepest layers are most similar to the original regolith which is.referred tovas the soil’s parent material In places where the regolith was originally uniform the:material below the soil may have similar composition to the parentmaterial from which it was formed - In other cases the regolith material has been transported long distances by wind, water or glaciers and deposited on top of dissimilapmaterial. In thi ¢ the regolith material found below a soil may be quite different from the upper layers of regolith from which the soil was formed HTTP://NOTES.BOOKHOLDERS.COM @ How to Buy Textbooks Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Purchase at local store using simple and easy self-serve stat Purchase with the help of clerk that can answer your questions about a apne book or class. I) « ti 2 3x more then Cash Now. www.BookHolders.com MeL coe) HTTP://NOTES.BOOKHOLDERS.COM Managed carefully soil can be a renewable resource, however in the scale of human lifetimes they cannot be considered renewable - All soils best suited for growing crops are already being farmed, and the around of cropland per person is rapidly declining - Soil quality ~ a measure of the ability of a soil to carry out particular ecological functions - Resilience — the ability to recover from minor degradation if left to revegetate on its own Chapter 2 : Formation of soils from parent materials Weathering of rocks and minerals ~ Characteristics of rocks and minerals © Igneous rocks — formed from molten magma and include common rocks such as granite and diorite * composed of primary minerals as light colored quartz, muscovite. feldspars, dark colored biotite, augite, and hornblende * Mineral grains give a salt and pepper look if they are coarse enough = Dark colored igneous rock such as gabbro and basalt are more easily weathered than are granite and other light colored igneous rocks o Sedimentary rocks rocks collect under water as sediment and eventually reconsolidate into new rock form when weathering products released from other, older * Quartz sand weathered from granite and deposited near a prehistoric sea may become cemented by calcium or iron in water to become sandstone = Clays can be compacted into shale * Resistance of sedimentary rocks to weathering are determined by its particular dominant mineral and its cementing agent = Most common type of rock encountered, 75% of earth's land surface 1 Metamorphic rocks — formed from other rocks by a process of thange termed “metamorphism” * Plates shift and sometimes collide which subjectigneous andisedimentary rocks to tremendous heat and pressure to slowly compress or distort rocks and break bonds holding original minerals together * Recrystallization during metamorphism may produce new crystals of the same minerals, or elements of the original minerals may recombine to form new minerals = Granite can be formed into gneiss where light and dark minerals have been reoriented into bands instead of the salt and pepper look These rocks are usually harder and more strongly crystalline than the sedimentary rocks fom which they formed - Weathering A biochemical process that involyes both destruction and synthesis Can be destroyed by both physical disintegration and chemical decomposition HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store using simple and easy self-serve stations. — = | Purchase with the help of clerk that can answer your questions about a a sos-zopests book or class. lm 4509 Coli , eee www.BookHolders.com " maT ued HTTP://NOTES.BOOKHOLDERS.COM ) Minerals that remain in highly weathered soils are * Silicate clays * Resistant end products including iron and aluminum oxide clays = Very resistant primary minerals such as quartz » Physical Weathering * ‘Temperature * Rock exposed to sunlight heat up during the day and cool down at night causing expansion and contraction of the minerals that cause stress that eventually cause the rock to crack apart * Since the surface of the rock is either cooler or warmer than the inner portions, some rock weather by exfoliation where the outer layers peel away; accelerated by ice and wind * Abrasion by water, i « Water has tremendous cutting power when loaded with sediment; valleys and rounding of riverbeds © Windblown dust and sand also wear down rocks by abrasion ¢ Inglacial areas huge masses of ice grind down rocks in their path and carry away large volumes of material «Plants and animals * Plant roots enter cracks in rocks and break them apart * Burrowing animals disintegrate rocks » Biogeochemical weathering * Chemical weathering is enhanced by geological and biological processes = Hydration — water molecules bind to minerals = Hydrolysis * Dissolution — water di - water molecules split and displace a cation/from a mineral issolves minerals till cations and anions are dissociated from each other * Acid reactions — weathering is accelerated by thepresence of acids * Oxidation — reduction — when exposed to aif Jromis easily oxidized, which changes the valance electrons and causes destabilizing’adjtistments in the crystal structure of the mineral * Complexation — biological proces8és, remove cations from minerals and then is subject to further disintegration Factors influencing soil formation - Parent Materials © Influence characteristics of the soil © Residual parent material = Develops in place by weathering of the underlying rock © Colluvial parent material HTTP://NOTES.BOOKHOLDERS.COM Ls How to Buy Textbooks l= 4509A College Ave = 301-209-9313 Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Poorly sorted rock fragments detached from the heights above and carried downslope by gravity * Rock fragment slopes, cliff rock debris and avalanches are made up largely of such accumulations * Colluvial parent materials are coarse, stony, angular and unstable because physical rather than chemical weathering has been dominant © Alluvial stream deposits * Soils derived from alluvial sediments are seen as desirable for human settlement and agriculture since nutrient-rich minerals lost by upland soils are deposited on the river floodplain and deltas * Uniquely suited to forestry and crop production * Use for home sites and urban development should b * Floodplains © Part of the river val oided ley that is inundated during floods * Sediments carried by the swollen stream is deposited during floods with the coarser materials laid down first at the river channel where water is deeper and flowing with more turbulence and energy * Finer materials settle out in the calmer flood waters further from the channel * Each flood lays down a distinct layer of sediment, creating the stratification that characterizes alluvial soils * The cutting down of alluvial deposits if there is a change in grade creates different levels of terraces * Alluvial fans. * Streams that leave a narrow valley in an upland ¢ descend to a much broader valley below to deposit sediment imthe shape of a fan as the water spreads out and slows. down nd suddenly * The rushing water sorts particles by:size first dropping gravel and coarse sand, then depositing finer materials toward the bottom * Soils prove very productive and important agricultural areas, although they might be quite coarse textured * Delta deposits « Much finer sediment that is earried!by streams is not discharged till itreaches the lake,feservoir or Ocean into which the stream flows « Suspended sediment settles near the mouth of the river or as a continuation of a flood plain forms a delta Coastal Sediments. = When sediments from sfteams build up and become hundreds of meters thick and rise above sea level creating a coastal plain HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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Wile tr te 3x more ten cash Now. www.BookHolders.com " wWWiBookHolders com HTTP://NOTES.BOOKHOLDERS.COM lm 4509 Coli = {f warm temperatures and abundant water are present in the soil profile the process of weathering, leaching and plant growth will be maximized - Biota : Living Organisms o Role of natural vegetation = Organic matter accumulation * Different vegetation can have an effect on soil profiles in grasslands and forests are very different * Ingr land, most of the organic matter is added to the soil from the deep fibrous grass root systems and a large A horizon with much deeper organic matter is formed with no E horizon; productivity below ground * In contrast organic matter is added to soil mostly by fallen leaves where there is lite A horizon, an E horizon and a large B horizon: productivity above ground * Cation cycling by trees * Natural vegetation can accelerate the release of nutrient elements from minerals by biogeochemical weathering To take up these elements from the soil can greatly influence the characteristic of the soil that develops * Soil acidity develops under coniferous vegetation because of theif low Ca, Mg and K minerals * Rangelands © Inarid and the properti weathering and declining fertility miarid rangelands, widely tered vegetation effects of the soils lowering the soil pH and inereasing © Role of animals = Tunnels open to the surface encourage moVement of water and air into the subsurface layers = Earthworms, ants and termites mix soil as they burrowcalled pedoturbation, increases the stabilityof soil aggregates and assuring infiltration of water * This also counteracts the tendeney.of other soi! forming processes that accentuates the differences among soil'horizons » Human influence * Human destruction of natural vegetation, tillage of soil for crop production, irrigation and fertilizer has modified soil formation - Topography HTTP://NOTES.BOOKHOLDERS.COM Ls How to Buy Textbooks l= 4509A College Ave = 301-209-9313 Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Steep slop the soil before running off, ultimately preventing soil formation from getting very encourage rapid soil loss by erosion and allow less rainfall to enter far before being destroyed In lower areas a deeper soil profile has been developed by intense weathering and have a richer and darker A horizon Where soils commonly occur together in the landscape in sequence is called a catena where each portion have different soil characteristics influenced by the fopography of water movement and drainage Topsosquence — a type of catena where differences in soil result entirely from the ape because the soils share the same parent material and have similar transition zones usually create depressions where soil is wetter and creates a different type of soil than in upland positions - Time o Rates of weathering = A “young” or “matun but the degree of weathering and profile development = Time interacts with other facto * A warm climate with a lot of rain and permeable parent material will oil is not referring to the age of the soil in years s of soil formation weather and form soil profiles more rapidly than in a cool and dry climate in the same amount of time © Chronosequence * Aset of soils that share a common community of organisms, climate. parent material and slope but differ with regard to the length of time that the materials have been subject to weathering and soil formation * Can be found among soils forming on alluvial terraces of differing seg * Carbon dating methods and presence of fossils and/human artifacts are used to measure time related changes ina soil profile Residual parent material have generally been subject tothe soil forming pro for longer periods of time than transported parent materials Four basic processes of soil formation - Transformations Occur when soil constituents are chemically or physitally modified or destroyed zed from the precursor materials ing of primary materials and disintegrating and altering some to and others are synthesi Involve weathi form silicate cl » Can involve decomposition of organic matter to the synthesis of organic acids, humus and other products - Translocations HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store using simple and easy self-serve stations. — = | Purchase with the help of clerk that can answer your questions about a a sos-zopests book or class. lm 4509 Coli , eee www.BookHolders.com " maT PL ued HTTP://NOTES.BOOKHOLDERS.COM Involve movement of organic and inorganic materials laterally within a horizon or vertically from one horizon up or down to another horizon Percolating water or water rising up by capillary action is the most common translocation agent Materials that move within the profile include fine clay particles, dissolved salts and dissolved organic substances. © Soil organisms also move particles from one horizon to another - Additions ) An input of materials to the developing soil profile from outside sources * Input of organic matter from fallen plant leaves and sloughed-off roots * Dust particles falling on the surface of the soil blown by wind from somewhere else * Addition of salts * Humans and animals add manure and fertilizers issolved in groundwater - Losses © Materials lost form the soil profile by leaching to ground water or erosion of surface materials * Evaporation and plant use can cause loss of water se loss * Leaching and drainage « £ of water, salts and organic acids ‘osion removes finer particles leaving surface horizons sandier and ,léss h in organic matter ~ A horizon development © Organic mineral mixture near the soil surface develops rather quickly and is the first horizon to develop © Darker in color from organic matter, which causes clumps and differentiates w from lower layers - Formation of B and C horizons © Carbonic and other organic acids are percolated-through the.soil where they stimulate weathering reactions such as dissolving minerals (transformation) and leach soluble products (translocation) » ‘The combination of transformation and translocation ¢reates zones of depletion in upper layers and zones of accumulation of lower layer Soil Profile - Six master soil horizons » Ohorizon = The organic horizon abaye the mineral soil * Derive from dead plant and animal residues HTTP://NOTES.BOOKHOLDERS.COM  o Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store Search by class, author, title, BN at bookholders.com. pee off lm 4509A Colley = 301-209-9313 using simple and easy self-serve stations. 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Found in cold regions, mountains and steep slopes Andisols Formed on volcanic ash and found near the volcano source Low bulk density © High in allophone Light fluffy soil easily tilled Gelisols © Permafrost layer o Very cold climates, typically in tundras Stores CO2, melting of these soils contribute to global warming Histosols © Accumulation of organic matter; dark color © Usually formed in water logged area; bogs and marshes Highly productive when drained; forms peat Vertisols © Shrinking and swelling of clays o Wide deep cracks during dry s eason: ells during wet season — very st ks and inverts its self © Need wet and dry seasons - Aridisols © Dry soils in dry climates o Spat Productive if irrigated vegetation singly weathered soils ~ Mollisols © Accumulation of calcium rich organic matter usually found'on prairies and grasslands o Thick, dark mollic epipedon or A and B horizon o NoEhorizon Basic, calcium Alfisols Argillic or nitric horizon Moderately sloped © Develop under native deciduous forests in moderate climates Distinet accumulation of clayin Bthorizon with high percent of Ca and Mg Ultisols. = Accumulation of clays in B horizon B horizon is leached, low in Casand lower pH than Alfisols © Found in warm, wet climates or deciduous forests; MD HTTP://NOTES.BOOKHOLDERS.COM  o Purchase for pickup at local store during convenient hours| Search by class, author, title, BN at bookholders.com. jm S0r209 8313 book or class. 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Sold fm 45094 Colle your questions about a www.BookHolders.com - Spodosols Sandy and acidic, forest soils, highly leached Ash like E horizon ) OM and iron leached into dark B horizon © Found in coniferous forests, cold-wet climates and sandy materials - Oxisols © Highly weathered, oxic horizon (Fe and Al oxides) > Low activity clays © Uniform with depth Found in humid climates, millions of years old Chapter 4 ; Soil architecture and physical properties - Soil color Mainly due to = Humus = black color = Water content — dry soil = lighter color and vise versa = Mineral colors © Iron=red or yellow * Manganese ~ black * Glauconitic = green Interpretations of soil color can include * Soil productivity * Horizon boundaries * Soil drainage class * Mineralogy = Wetland soils * Extent of weathering * Climate HTTP://NOTES.BOOKHOLDERS.COM  Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Soil Science Notes Chapter 4 Soil texture - Distribution of soil particle Nature of soil separates Coarse fragments such as gravel that are greater than 2mm in diameter are not considered part of the fine earth fraction to which soil texture applies ) Sand ity and visible to the naked eye * Consists mainly of quartz or other primary silicate minerals * Not many nutrients for plants nor are they likely to be released = Sand particles have large pores so water drains down * Promotes the entry of air into the soil have low specific surface area — surface area for a given mass of particles © Little capacity to hold water or nutrients and do not stick together into a coherent mass = Sandy soils are well aerated and loose but als drought = Sand partici infertile and prone to o Silt * .0Smm-.002mm * Similar to sand in shape and mineral composition * Invisible to the naked eye * Feels smooth or silky like flour * Holds weatherable minerals * Mostly quartz with primary silicate minerals and some other secondary minerals = Small size of silt particles allows weathering rapid €nough to release significant amounts of plant nutrients * Pores are much smaller and much more numerous * Retains water and lets less draiaithrougl, however is not sticky enough to hold water as a barrier = Silt and sandy soils are prone to erosion * Less than .002mm * Very specific surface reas * Tremendous ability to absorb water and other substances HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Prismlike = Columnar and prismatic * Vertically oriented prisms or pillar like peds * Vary in height and may have diameter of 150mm or more * Columnar © Distinct rounded tops found in subsoils high in sodium * Prismatic o Angular and flat top * Associated with swelling types of clays and found in n arid and semi arid regions and fragipans subsurface horizon: © In humid regions found in poorly drained soi 2 Deseription of soil structure = ‘Type (shape) * Size (fine, medium, coarse) = Distinctness (strong, moderate, weak) sier to observe when dry - Formation and stabilization of soil aggregates © Granular aggregation in surface soils amic soil property > Some are disintegrating as others are forming anew o Smaller aggregates are more stable than larger ones © Hierarchical organization of soil aggregates = Large macroaggregates are comprised of smaller microaggregites * Micro aggregates are comprised of tiny packets of clay and Grganic matter a few micrometers in size = This organization is characteristic of most soils except oxisols and. entisols * Ateach level in the hierarchy different factors Are responsible for binding together each subunit Factors of aggregate formation = Biological and physical-chemical proces * Physical-chemical processes are most important at the smaller end of the le — Clays * Biological processes are more important at the larger end — sandy soils ical — chemical processes = Flocculation = Mutual attraction among cle * Aggregation begins with the flocculation of clay particles into microscopic ehimps or floccules and organic molecules HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Cations between two clay particles attract the negative charges on both clay particles to stick them together * ‘These eventually form clay stacks ora more random formation of a house of cards called clay domains ® These clay and humus domains then form bridges that bind to each other and to fine silt particles that creates the smallest size grouping in the hierarchy of soil aggregates « Provides the much needed long term stability for the smaller microaggregates * Inhighly weathered soils such as ultisols and oxisols the cementing action of iron oxides produce very stable small s called pseudosand © Soils with only Nat and no Ca2+ or Al3+, the clay particles cannot cohere as well and the soil remains a structureles aggreg like condition impervious to water or air, no plant growth * Swelling and shrinking of clay mas: © As soils dry the water is withdrawn together causing the domains and hence the soil mas es nd clay platelets move shrinks * As the mass shrinks, cracks will open up along zones of weakness and over times these cracks become very defined * Plant roots grow in these areas and contribute by taking up water in the cracks vicinity * Water intake by roots accentuates the physical aggregation process associated with wetting and drying * Freezing and thawing cycles have similar effect 2 Biological Processes * Soil organisms * Burrowing and molding acti encdiirage apgteagtion © Earthworms ingest partidles and form thém into pellets © Plant roots move partieles asithey’push through the soil » Serve as large pores helping to define larger structural units + Enmeshment of particles by sticky networks of roots and fungal hyphae Bind tdgethér individual soil particles and tiny microaggregates into larger macroaggrega Mycorthizae produce glomalin, as effective cementing agent * Production of Organic glues by microorganisms such as bacteria and fungi HTTP://NOTES.BOOKHOLDERS.COM  . =|| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Jues are resistant to dissolution be water, which enhance formation and stability up to a few years © Notable in surface soils where roots and animal activities are greatest * Organic Matter ¢ Temperate zone soils are influenced by soil organic matter for the formation of granular aggregates * Provides energy substrate that makes the biological processes possible * Mineral particles become encrusted with bits of decomposed plant residue and other organic materials during aggregation process which help them bind together * Influence of tillage * Can promote and destroy aggregation * Ifsoil is not too wet or dry tillage can co break clods into natural aggregates to create a loose, porous condition good for young plant growth © incorporate organic material into soil and kill weeds over longer periods tillage encourages loss of organic matter, weakening aggregates * iftilled when wet, tillage crushes or smed s small aggregates condition resulting in loss of macroporosity = puddle * tron and Aluminum Oxides + Inhighly weathered soils these oxides coat soil partitles and cement them together * Prevents breakdown if soil is tilled = Tropical soils have greater aggregate stability and less dependent on organic matter Tillage and Structural Management of Soils Tillage and soil Tilth * Tilth refers to the physical condition 6f the soil in relation to plant growth * Depends on aggregate formation and stability, bulk density, moisture content, aeration, rate of water filtration, drainage and capillary water capacity * Soil is friable if ¢lods are not sticky or hard but crumble easily revealing their constituentaggregates * Enhanced when the tensile strength of individual aggregates is high compared to the tensile strength of larger clods HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com lm 4509A Colley = 301-209-9313 * Effect of soil Texture * Fine textured soils s ich as silt loams, clays and clay loams have low bulk densities than do sandy soils © Fine textured soils have pore spaces between and within granules * Sandy soils only have pores between granules which gives less total porosity and a higher bulk density © Packing arrangement of sand grains affects bulk = Loosely packed grains have lower bulk density = Tightly packed grains have higher bulk density © Sand particles of one size (well sorted) have lower bulk densities © Sand particles of different sizes (well graded) have higher bulk densities * Depth in soil profile ¢ Deeper in the soil profile bulk densities are generally higher ¢ Results from lower organic matter and compaction y soil has a bulk density of 1.3 Mg/em*3 = This soil cut one hectare long and 15 cm deep weighs 2 million Kg » Management practices affecting bulk density * Forest lands. ical arable surf « Surface horizons have lower bulk densities and the forest ecosystem is sensitive to increases in bulk densities * Timber harvest disturbs and compacts 20 to 40% of floor * Use of cables minimizes compactive degradation * Recreational bulk densiti Seen in campsites where bulk density is,greatest in the es and transport in forestscan lead to increased high use zone and gets lower as the-radius goes out * Damage from hikers can be minimized by trails that include a layer of wood chips or @ raised. boardwalk * Urban soils * Trees planted contend with severely compacted soils * Desirable to create artificial soilof coarse gravel and organic matter * Green roofs * Mass of soil must be minimized so roof can carry soil load * Grow shallow rooted plants HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Select a natural low bulk density soil, well aggregated loam or peat soil * Agricultural land © In long run tillage increases soil bulk density because it depletes organic matter which weakens soil structure * Heavy machines creates soil compaction 30 Forms plow pans or traffic pans which are dense areas immediately below the plowed layer © Particularly dama o Carefully restricting traffic to specific lanes can leave ing. on wet soil most areas free of compaction — controlled traffic » Orusing machines with wider wheels to spread out the compaction and it wolnt go as deep, however this increases the amount of soil surface that is compacted © Influence of bulk density on soil strength and root growth * Increased bulk density inhibits root growth, has poor aeration and has slow movement of air and water * Compaction increases both soil strength and bulk density = Higher bulk density creates greater soil strength and inhibited root growth * Soil strength — resistance to deformation — measurement of the force needed to push a standard cone tipped rod into the soil = Effect of * Moist conditions favor root growth because of a lower bulk density than dry soils * Effect of soil texture il water content * The more clay present the smaller average pore:size and the greater the resistance to penetration ata given bulk density * The growth of roots into a moist'soil is limited by bulk densities ranging from 1.45 in clay soils and {.85%in loamy sands ct of land use and management t soil bulk density and.strength in v restrict or enhance root growth’and Water movement © Land us - Pore space of mineral soils » Bulk density can be used fo calculate pore density The lower the bulk density the higher the percent pore space or total porosity © Factors influencing total pore space HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store using simple and easy self-serve stations. — = | Purchase with the help of clerk that can answer your questions about a a sos-zopests book or class. lm 4509 Coli Pw us to 3: more then Cash Now. www.BookHolders.com Me eet) HTTP://NOTES.BOOKHOLDERS.COM * And ideal medium textured, well granulated surface soil in good condition tor plant growth has approximately 50% pore space with half the pore space air and half water * Cultivation tends to lower the total pore space compared to that of uncultivated soils because of decrease in organic matter content and a subsequent lowering of granulation 1 Size of pores * Ma pores Larger than 08mm * Allow the ready movement of air and drainage of water «Can accommodate plant roots and tiny animals © Occur in spaces between individual sand grains in coarse textured soils © Sandy soils have relatively low porosity « In well structured soils macropores are found between peds » Interped pores occur between loosely packed granules or as the planar cracks between tight fitting blocky and prismatic peds *¢ Biopores — macropores created by roots, earthworms and other organisms * Biopores are principal form of macropores in clayey soils * A decrease in organic matter and an increase in clay that occur with depth in many soils profiles are associated with ashift from macropores to micropores * Micropores « Usually filled with water in field soils * [fnot filled with water, too small to permit much air movement « Water movement is very slow, and ustially not available to plants * Fine textured soils have a numerous amountof micropores allowing slow gas and water moyement despite the large volume of total pore space * Aeration in subsoilsimay, be inadequate for root development or microbial activity + Larger micropores may accommodate plant root hairs and microorganisms * Smaller micropores or nanpores are too small to permit the entrance of anything thereby protecting it from breakdown over Jong periods 6f time HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com lm 4509A Colley = 301-209-9313 « Derived their open particle arrangement from sedimentation beneath past or present bodies of water = When wetted the excess water will dissolve the cementing agents such as gypsum and are prone to a sudden loss of strength © Similar behavior is exhibited by oxisols in humid tropical Settlement — Gradual Compression * Most foundation problems result from slow uneven vertical subsidence or settlement of the soil * Compaction control * Soil used for planting should avoid compaction * Soil used for foundation or roadbeds should be compacted on purpose to avoid uneven settlement later ® Soils containing silicate clays and micas tend to reverse compaction by themselves after they have been compacted by heavy machinery and are not stable bases for roads and foundations * The proctor test is used to guide efforts at compacting soil materials before construction © a specimen of soil is mixed to a given water content and compacted by a drop hammer, the bulk density is measured, this is repeated with increasing water content until a proctor curve can be drawn co the curve indicates the maximum bulk density achievable and the soil water content that maximizes compactability = Compressibility * How much its volume will be reduced by a givetapplied force * Very sandy soils resist compression once the particles have settled into a tight packing arrangement which makes excellent foundations ® Clayey soils and soils‘high if organie’matter are unsuitable for foundations * Wet clayey soils compress Very Slowly even after a building is built (ledning,tower of pisa) o Expansive soils = Many clays swell When wet.and shrink when dry * Soils high in smectites clay = Crack building foundations, burst pipelines and buckle pavements HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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Cale your questions about a Pane book or class. www.BookHolders.com /NOTES.BOOKHOLDERS.COM HTTP W © Atterberg Limits * The limits of a clayey soils state based on water content * Lf soil is dry it isa hard and rigid solid = Ifalittle * Adding more water brings it to its plastic state_ ¥ ater is added is becomes a crumbly friable semisolid * The soil remains in the plastic state until the liquid limit is exceeded # * Plasticity index * Difference between the plastic limit and the liquid limit * Indicates the water content range over which a soil has plastic properties: Pl = LL —PL ® Soils with plasticity index greater than 25 are usually expansive clays that make poor bed roads and foundations © Smectite clays generally have high liquid limits and plasticity indices sk = COLE = coefficient of linear extensibility © Change in volume of a plastic limit and molded into the shape of a bar with length Lm The bar is allowed air dry and will shrink to length Ld, The COLE is the percent reduction in length of the soil bar upon drying; ((Lm-Ld)/Lm)x100 4k © Unified classification system for soil materials * Used to predict the engineering behavior of different soils imple of soil that is moistened to its * First groups soils into coarse and fine grained = Coarse materials * Divided on bases of grain size (gravels and sands) «* Amount of fines present * Uniformity of grain size (well or poorly graded) * Fine grained * Silts, clays or organic materials ¢ Bases of liquid limit and plasticity index fication based on its particle size, atterberg = Given a two letter cla: limits and organic matter content HTTP://NOTES.BOOKHOLDERS.COM Ls How to Buy Textbooks l= 4509A College Ave = 301-209-9313 Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com soil Water: Characteristics and Behavior Chapter 5: Structure and related properties of water Cohesion and adhesion of water make it po: and control its movement and use » Also makes possible the property of plasticity possessed by clays Surface tension ~ the greater force of the attraction of water molecules to its sible for soil solids to retain water self than to the air around it; seen at liquid air interfaces Cc apillary fundamentals and soil water Capillary forces are at work in all moi Not entirely based on pore size but pore siz Coarse sand will have lower capillary rise than fine sand © Medium to large sized capillary pores permits a rapid initial rise but limits oils e distribution height of rise 6 Clays have a high proportion of fine capillary pores but frictional forces slow down the rate at which water moves through them il water energy concepts > Potential energy is most important in determining the status and movement of soil water © Forces affecting potential energy = Adhesion property of water or the attraction of water to the soil solids provides a matric force that reduces the energy state of water near particle surfaces * Attraction of water to ions and other solutes in the soil results in osmotic forces that tends to reduce the energy state of waler in the soil solution * Gravity acts on soil water which always pulls the water downward thus the energy level of soil water given ata eértain elevation in the profile is higher than that of water of some lower level: this difference in energy level causes water toflow downward © Soil water potential = The difference in soil energy from one site or condition to another like between wet soil and dry soil @eterntines the direction and rate of water movement in soils and in plants = Ina wet soil most water is retained in large pores or thick water films around particles so most of the water is not held very tightly by soil particles and have considerable freedom of movement so energy level is higher as if in a pool of water outside the soil HTTP://NOTES.BOOKHOLDERS.COM  Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com The Flow of Liquid Water in Soil Saturated flow through soils * Takes place when soil pores are completely filled with water * K saturated is the saturated hydraulic conductivity which is how fast water runs through a soil when it is saturated * Saturated flow can happen down a soil profile, horizontal and even up * Hydraulic conductivity factors of saturated soils * Macropores — account for nearly all water flow in saturated © Interconnectedne: going Presence of bio pores in a soil or sandy soils have higher saturated conductivities * Soils with stable granular structure also have more rapid water flow s of pores is important to keep water flow * Saturated conductivity is higher in soils under perennials rather than annual plants © Preferential flow — in non uniform porosity soil non uniform walter movement increases the chances of groundwater pollution (solutes runs right through the big pores and bio pores and cracks before the rest of the soil is even saturated) * Soils that have macropores throughout the entire profile instead of only near the surface encourage preferential flow * Can be increased in shrinking clays, when shrink the clays crack allowing water to move very rapidly down the:profile « Unsaturated flow * Macropores are filled with air leaving the mierepores for water movement * Driving force of water movement is thé diffetentes i matric water potential from one area té another = mairie potential gradient * Influence of texture ~ in high potential levels hydraulic conductivity is higher in san@than in clay but when potential is lower this switches béGause’all poresiin sandy soils are empty and in clay water is still flowing in the micropores as unsaturated flow Infiltration and percolation o Infiltration = The process by whichwater enters the soil pore spaces and becomes soil water HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Is initially very fast in clays then dramatically drops rate = Can be measured using a double ring infiltrometer * Pressed into the soil and the depth of the water is measured periodically to get the rate of infiltration > Percolation * The downward movement of water into the soil profile * Both saturated and unsaturated flow is involved * The rate of percolation is related to the soils hydrauli¢ conductivity = Wetting front — a dark differently colored boundary between a dry and wet soil * Moves as saturated flow near the soil surface during a heavy rain or irrigation = Atthe wetting front water moves in response to matric potential gradients as well as gravity © Water movement in stratified soils = An abrupt change in the texture of the soil in different layers can act as a barrier to water flow * A layer of coarser soi) below a layer of finer soils acts asa barrier to water flow because the water is more attracted to the finer pores than the larger pores of the coarser soil so the flow stops as it encounters the sandy soil and spreads outward instead by capillary action = The same things happens in the opposite way if sand is above a'layer of finer soil, the coarser soil will stop the flow upward - Water Vapor movement in soil 0 Internal ~ occurs in the soil pores » External — occurs at the land surface and water vapor is lost by surface evaporation © Water vapor moves from one point to another in response-to differences ini vapor pressure ~ will move from moist soil where soil airis 100 percent saturated to drier soil where air is less'saturated Salt lowers water vapor pressure so water vapor will also move to an area of higher salt content Water vapor pressure is decreaséd in Cooler fémperature so waier vapor will move toward cooler temperatures and away from warmer temps © The amount of water Vapor ita soil that is optimal for plant growth is very small compared to the amount of water needed HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Qualitative description of soil wetness Maximum Retentive Capacity * When all soil pores are filled with water and is water-saturated a soil is said to be al its maximum retentive capacity * Matric potential is close to 0 as free water * Volumetric water content is same as total porosity * Termed gravitational water ) Field Capacity = Matric forces play a larger role in movement of the remaining water * Water has moved out of the macropores and air has moved to take its place = water movement is taking place in micropores by capillary action termed capillary water = Matric potential is generally -10 to -30 kPa * At this capacity soil is holding the maximum amount of water useful to plants; anymore water the soil doesn’t have enough air for plant growth = At this capacity soil is also near its lower plastic limit - optimal wetness for ease of tillage or excavation s filled with air to allow optimal aeration for most aerobic microbial activity and for the growth of most plants ing Percentage or Wilting Coefficient * As soil continues to dry past field capacity it becomes harder and harder for plants to obtain water from the soil = Atabout -1500 kPa plants cannot get any more water from soil and * Sufficient pore spa o Permanent Wil start to wilt = The water content at this stage is called the wilting coefficient and. appears to be dusty dry * Plant available water is considered to be that water retained in soils between field capacity (-10) to the wilting coefficient (-1500) * Even at this stage a substantial amount of water cam still be held in fine textured soils or soils high in orgaftic matter it "Water films are only 3 or 4imolecules thik and water potential is at about -3100 kPa ) Hygroscopic Coeff - Factors affecting amount of plant available soil water o Available water holding eapacity “relationship between the water potential of a given soil and the amount of water held at field capacity and at permanent wilting percentage HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com « Heavy clay soils with instable structure resist infiltration and encourage runoff ~ The Soil-Plant-Atmosphere Continuum © Interception, surface runoff, percolation. drainage, evaporation, plant water uptake, ascent of water to plant leaves, and transpiration of water from the leaves back to the atmosphere > Water potentials = The same basic principles govern the retention and movement of water whether it is in soil, plants or the atmosphere * Water potential is highest in soil and gets lower in the plant root, and lower in the leaf surfaces and even lower in the atmosphere to explain why waler goes through the cycle as it does Two points of resistance in the SPAC = Root —soil interface ~ the rate at which water is supplied by the soil to the absorbing roots = Leaf cell — atmosphere interface — the rate at which water is transpired from the leaves Evapotranspiration = The loss of water content form the soil is measured by evapotranspirtaion combined = Evaporation is considered a loss of water that plants could have used * Water lost by transpiration however at least provided the plant’with useful water * Potential Evapotranspiration Rate (PET) — how fast water yapor would be lost from a densely vegetated plant-soil system if soil water ¢ontent were continuously maintained at an optimal level © Determined by water pressure gradient betweena wet soil, leaf or body of water and the atmosphere * PET =.65 x class A pan evaporation * Hot, arid areas can lose 1500mm per year and cold regions only 40mm per year . ffect of Soil moisture om of soil * Mast evaporation comes from the top 15 to 25 * Determined by the ability of a soil to replenish its surface soil water supply * Since plant roots penetrate deep into the profile water lost by evapotranspiratioticar’ come from subsoil layers HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com = Plant water stri = If water roots the plants will loose turgor pressure and wil! apor evaporates from leaves faster than it enters the = Under these conditions actual evapotranspiration is less than potential and the plant experiences water stress * Under stress conditions plants close their stomata on their leaf and reduce water vapor loss to prevent wilting Plants growth is arrested because cannot photosynthesis without CO2 © Cannot cool its self by evaporating * Plant characteristics * The larger the leaf area index the more transpiration by plants and the less evaporation in the soil = Water use efficiency * The amount ofa plant produced while a given amount of water is used * Huge amounts of water are needed to produce the human food supply, and the efficiency is driven by climatic factors (arid regions use more water than humid regions) * 7000L for single day of food supply for adult * ET Efficiency * Most efficient is when plant density and other growth factors minimize evaporation from the soil = Higher yielding plants have a higher water us ficiency (closer plant spacing) * Water looses from sui soil and transpiration areGetermined by climate, plant cover in relation to soil surface, efficiency of water use by different plants and length and season of thé plant growing period Control of Evapotranspiration ) Control of Transpiration * To limit transpiration to not deplete available water prematurely it may be necessary to limit LAT or spacing plants further apart * Unwanted v ° We establishment and growth of desirable forest, range, and crop ation heavily use Water in the Soil which interferers with the plants © Cultivation to remoye weeds can disturb nearby desired plants and expose bare soil to increase water loss = Herbicides HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com s labor and * Advantages over cultivation because it requires le energy and allows soil to be left undisturbed ¢ However is costly and eventual evolution of weed resistance and can be toxic to animals = Alternative weed control * Biological control — introduce diseases and insects * Fires, well timed mowing and grazing * Fallow in dryland cropping e Alternating bare soil and cropland every other year can conserve soil moisture in low rain fall environments > Control of surface evaporation = Vegetative Mulches ® Reduce soil borne di * Provide a clean path for foot traffic ses spread by splashing water ¢ Reduce weed growth * Moderate soil temperatures; overhearing in summer months * Increase water infiltration * Provide organic matter and nutrients to the soil * Encourage earthworm populations * Reduce soil erosion * Plastic mulches * Plastic films control evaporative water losses * Crop residue and conservation tillage aves a higher percentage off crop residue onthe sail * Stubble mulch tillage © Residues such as wheat stubble and corstalks from previous crop are uniformly spread on the Soil surface Losses of water from the soil Percolation or drainage water or leaching = Amount of rain entering the soil exceeds the water holding capacity by percolation will o¢cur * Percolation water recharges thé groutid Water and moves chemicals out of the soil * Losses are influenced by the amount of rainfall and its distribution, runoff from the soilevapofation, character of the soil and nature of the vegetation o Runoff water carries soil as well as dissolved chemicals HTTP://NOTES.BOOKHOLDERS.COM How to Buy Textbooks Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Reasons for enhancing soil drainage * Engineering problems ~ difficult to operate machinery. cannot withstand recreation traffic, uneven settlement and flooded basements. capillary rise of water to foundations * Plant Production — almost impossible for plant production, farm equipment gets bogged down, not enough oxygen in the soils for plants Benefits of Artificial Drainage * Increases bearing strength and soil workability eT « Enhanced rooting depth. growth and activity due to more oxygen ss frost heaving foundations = Reduced levels of fungal disease in young plants * More rapid soil warming, earlier mature crops = Less production of green house gases methane and nitrogen gases = Removes excess salt from irrigated soil Detrimental Effects of Artificial Soil Drainage * Loss of wildlife habitat; waterfowl breeding and overwintering sites * Reduces nutrients and biochemical functioning’: * Increased leaching of nitrates to groundwater * Loss of soil organic material and subsidence of soils of wetlands * Increased frequency of flooding due to loss of runoff water retention capaci = Cost of damages when flooding occurs Surface Drainage Systems * Used when landscape is level and soils are fine textured with slow internal drainage » Removes water from the land before it infiltrates the soil * Surface drainage ditches with gentle side slopes aré used to drain surface runoff from landscaped lawns = Often combined with land smoothing to eliminate ponding of water and facilitate its removal from the land Subsurface Drainage * To remove the groundwater from within thé soil and lower the water table = Require deep ditches onunderground|pipes or mole tunnels = Deep open ditch drainage = excavated 'to a depth below the water table and levels outthe water table which lowers it, goes from high to lower energy in the diteh * Buried pipes — layed into the ground so water moves into the pipes through perforations HTTP://NOTES.BOOKHOLDERS.COM  ° =\| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Foundation drains — surplus water around building foundations can cause serious problems; perforated pipes are placed alongside and slightly below the foundation or undemeath the floor Septic Tank Drain Fields > Operation of a septic system * Operates like the artificial drainage ystem is the opposite way * Puts waste water into the soil instead of pulling water up from the soil * The waste water then percolates downward and goes through many purifying processes before entering the groundwater + 70% of waste is dropped in the septic tank before going into soil * Water is drained out of the tank in the drain field this water is the effluent © Soil properties for suitable septic tank drain field * Soil should have a saturated hydraulic conductivity so that the effluent passes fast enough not to back up the field and saturate the soil surface with it but slow enough so that the effluent is purified before it reaches the groundwater * Soil should be well aerated to encourage microbial breakdown of wastes and destruction of pathogens * Should have some fine pores and clay or organic matter to absorb and filter contaminants from the wastewater «Cannot have impermeable layers like fragipan and heavy claypan, too steep a slope or exces = Suitability rating ively drained sand and gravel * Depends on soil properties that affect water movement/and ease of installation * Should have low water table because septic drain fields will raise the water table under the field «Pere fest * Determines percolation rate of water entering the soil per hour * Indicates whether or notisoilhean accept wastewater rapidly enough to proyide a practieal disposal medium: should be carried out during wettest season.ofthe ar * Low percolation rate can be made up for by increasing the length of the drain field ) Alternative * Low lying regions are not'suitable for septic tanks because water table is too high HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com lm 4509A Colley = 301-209-9313 = Mound drain field system — pipes for drain field are laid above ground on a bed of sand and covered by a mound of sand * Wetlands can purify wastewater if effluent is made to slowly flow through a serics of shallow vegetated ponds - Irrigation Principles and Practices Importance of irrigation today * Food production — 15 higher production in imigated lands opposed to non irrigated: » of worlds agricultural land is under irrigation: * Landscaping — needed in arid regions all year round to keep lawn green with trees and flowers ts — irrigation water is slowly dwindling due to sed competition for water from people in urban water use, the overpumping of water that has lead to falling of water tables, reduction of storage capacity of existing reservoirs by siltation with eroded sediments and increased recognition of the need to allow a portion of river flows to go unused by irrigation to maintain fish habitats downstream ) Water-use efficiency = Used to compare benefits of different irrigation practices and s = Compares output of a system (crop biomass) to the amount of water allocated as an input to the system * Application efficiency « Amount of water available to irrigate the field to the amount of water actually used in transpiration by the irrigatéd plants ems are inefficient with only 10 to 30% of water is transpired by the desired plants * Much water loss occurs by evaporationor leakage into stems, reservoirs and can be lined with plastic to help id Water Efficiency = Wat fficiency in the field is (Watérifanspired by the crop/water applied to the field) x 100 e Values are usually lower than 50% use Surface irrigation = Applied to upper end of the field and allowed to distribute its self by gravity flow; must be level land * Can be distributed in furrows or as a border irrigation system = Water control * Water is broughtto the fields by in supply ditches or gated pipes HTTP://NOTES.BOOKHOLDERS.COM Ls How to Buy Textbooks Search by class, author, title, or ISBN at bookholders.com. 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Chapter 7: Soil Aeration and Temperature Soil Aeration- The Process - For plant roots and soil organisms to carry on respiration the soil must be well ventilated - Ventilation allows the exchange of gases between the soil and the atmosphere to supply enough oxygen while preventing the accumulation of toxic gases - Oxygen availability is regulated by three principles © Soil macroporosity © Soil water content o Oxygen consumption - Poor soil aeration refers to the condition where the availability of 02 in the root zone is insufficient to support growth of upland plants and aerobic microorganisms - Occurs when more than 80 to 90% of the soil pores are filled with water or the concentration is below .1L/L Excess Moisture © Nearly all the soil pores are filled with water, said to be waterlogged © Typical of wetland soils, or may occur temporarily after a heavy rainstorm o. Plants adapted to waterlogged soils are called hydrophytes = Oxygen is transported down to their roots via hollow structures in their ‘stems and roots known as aerenchyma © However, most plants rely on a supply of 02 in the soil ~ Gaseous Interchange The more rapidly roots use up oxygen and release CO? the greater the need for xchange of gases between the soils and the atmosphere ‘acilitated by mass flow and diffusion © Mostly by diffusion where each gas moves in a direction determined by iis own partial pressure © Diffusion allows extensive gas movement from one area. to,another even though there is no overall pressure gradient © Since there is a greater concentration of O2 in the atmosphere:this will result in a net movement of O2 into the soi! and CO2 out of the soil Means of Characterizing Soil Aeration Soil aeration is characterized by © Content of OZ and other gases in the soil atmosphere © Airfilled soil porosit © Chemical oxidation — reduction potential HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com lm 4509A Colley = 301-209-9313 Gaseous components of the soil air Oxygen * Soil air has about 78% nitrogen, 19% oxygen and 3% CO2 * Oxygen levels may drop to less than 5% in the lower horizons of a poorly drained soil with few macropores = Once the supply of 02 is virtually exhausted the soil is said to be anaerobic Carbon Dioxide * An inverse relationship with oxygen = (2 decreases as CO2 increases = There may be very little CO2, but it has a significant effect on the soil * When there is only 35% CO2 in the soil, the gas is [0 times as concentrated as it would be in the atmosphere = If CO2 become: Other Gases high as 10%, it can be toxic to plant growh = Soil air is much higher (essentially saturated) in water vapor than is the atmosphere * Under water logged conditions methane and hydrogen sulfide are produced by the decomposition of organic matter and have higher concentrations than water vapor = Ethylene is also produced by anaerobic metabolism and can be highly | and the toxic to plant roots if gas exchange rates between the s atmosphere are too slow - Air filled porosity 5 Microbial activity and plant growth become severely inhibited when air filled porosity falls below 20% of the pore space or 10% of the total soil volume: © Water filled pores block the diffusion of oxygen into the soil to replace that used by respiration > Oxygen diffuses 10,000 times same pore filled with water ster through pore space filled with aif'than the Oxidation-Reduction Potential Redox Reactions As an element is oxidized H+ ions are formed andthe pH is lowered Vise versa for reduction o The potential for electrons to be transferred from one substance to another in such termed redox potential Can be measured using a platinum electrode in volts or millivolts Pa » If supplies neutrons = reducing agent reactions is epts electrons = oxidizing agent HTTP://NOTES.BOOKHOLDERS.COM Ls How to Buy Textbooks l= 4509A College Ave = 301-209-9313 Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com - Role of oxygen gas © Strong oxidizing agent © Rapidly accepts electrons from many other elements © Allaerobie r oxidize carbon to release energy for life spiration requires O2 to serve as the electron acceptor as organisms Can oxidize or o As it oxidizes, it is in turn reduced 2FeO + O +H20 = 2FeOOH Ina well aerated soil, the redox potential (Eh) is about .4 to.7 volts ic and inorganic substances As the oxygen level is depleted this declines to .3 - Other electron acceptors © As O2 becomes depleted, only anaerobic microorganisms can survive o The © Aselements are reduced the pH becomes ¢ organisms can use iron as electron acceptors When iron is reduced it turns from its red oxidized color the greys of reduced iron © ‘The Eh value at which a redox reaction can occur depends on the element to be oxidized or reduced and the pH at which the reaction takes place © Oxygen has the highest value, than nitrogen, magnesium, iron, sulfur, carbon and hydrogen © When O2 of the soil is devoid, the redox potential falls to about .35 sformation of different elements requires different degrees of reducing o Tra condtions © Hence soil aeration helps determine the specific chemicat species present in soils ible toxicity of many chemical elements and in turn the pos Factors affecting soil aeration and Eh Drainage of excess water » Drainage of excess water out of the soil profile occurs inmacropores © Volume of the soil macropores influences the aeration of well drained’soils stability, OMC and biopores are properties that determine ao Texture, density macropore content and in turn soil aeration ~ Rates of respiration in the soil © Oxygen and CO2 in the soil are dependent on microbial activity which are dependent on carbon compounds as food o Incorporation of organic matter may alter the soil air composition Plant residues and such proyide substrate for microbial activity and respiration The soil profile Subsoil’s are deficient in oxygen, May still be enough to replace that being used by repiration ater content is higher and pore aerobic if organic substrates are low in supply if 02 diff HTTP://NOTES.BOOKHOLDERS.COM How to Buy Textbooks l= 4509A College Ave = 301-209-9313 Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Nutrient and water uptake * Low oxygen levels constrain root respiration and impair root function = ell membrane may become less permeable to water and have difficulty taking up water and will wilt in a water logged soil * May exhibit nutrient deficiency symptoms even though nutrients may be in good supply in poorly drained soils * Toxic substances produced by anaerobic microbes may harm plant roots and plant growth Soil compaction * Decreases the exchange of gases but not completely responsible for poor aeration * Soil density and strength can impede root growth even if adequate oxygen is available Aeration in relation to soil and plant management Container grown plants o Potted plants suffer from waterlogged and poor aeration conditions © Potting mixes should contain no mineral soil at all to achieve maximum aeration and minimal weight o Should contain some peat, bark, woodchips, or other organic material that adds macroporosity and holds water © Even with holes the bottom of the container creates a perched water table that muerobic conditions ufier a while create Use of a tall pot allows better aeration, and water should be deferred until the soil near the bottom of the container has begun to dry - Tree and lawn management © In transplanting a woody species caution should be taken to prevent waterlogged or poorly aerated area around the young roots o Aeration of mature trees should also be safeguarded * Surplus excavated soil should not be putat the base of'a tree * Trees feeder roots near the soil surface beeome deficient oxygen * Protective wall around the tree should bevinstalled before grading operations begin Heavily trafficked lawns should implore management systems such as perforated drainage pipes that enhance soil aeration © Core cultivation — increases aeratiomin compacted lawn areas * Removes thousands of small coréSiaround the lawn from the surface horizon permitting gas exchange to take place HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store using simple and easy self-serve stations. — = | Purchase with the help of clerk that can answer your questions about a book or class. lm 4509 Coli = 301-209-9313 Pw us to 3: more then Cash Now. www.BookHolders.com Me eet) HTTP://NOTES.BOOKHOLDERS.COM Wetlands and their poorly aerated soils - Defining a wetland Ecosystems that are transitional between land and water Soils are water saturated near the surface for prolonged periods when soil temperatures and other conditions are such that plants and microbes can grow and remove soil oxygen thereby assuring anaerobic conditions » Wetter end of wetland occurs where the water is too deep for rooted, emergent vegetation to take hold Drier end is the boundary where non wetland characteristics are seen and not influenced by presence of anaerobic soils o Controversial in determining what is and is not protected as a wetland © Environmentalists are employed to determine the drier end bound of a wetland for many development projects Characteristics of any wetland = Wetland hydrology ar water regime * Hydri * Hydrophytic plants - Wetland hydrology » Water balance soils = The balance of incoming and outgoing water to and from wetlands as well as the water storage capacity of wetlands determines how wet it will be. and for how long Hydroperiod * Temporal pattern of water table changes * May be daily for coastal marshes as tides rise and fall = May be * May be only flooded for a month or so each year ‘onal for inland swamps, bogs and marshes * May never be flooded but saturated in the upper/horizons = Tf saturated occurs in cold weather that inhibits microbial or plant root activity oxygen may be dissolved in water * Anaerobic conditions may notdevelop * Itis the anaerobic condition, not just the saturation that makes a wetland a wetland Residence time = The slower water moyes through a wetland the longer the residence time and the more likely wetland functions will be carried out * Actions that speed Water flow are generally considered degrading to wetlands and are to be avoided © Indicators = Many wetlands are not saturated all of the time HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com * Inthe field even during dry periods there are many signs that indicate where saturated conditions frequently occur * Past periods of flooding will leave water stains on trees and rocks and a coating of sediment on plant leaves and litter © Drift lines on once floating branches, twigs and other debris © Trees with extensive root masses above ground indicate adaptation to saturation © Presence of hydric soils is the best indicator - Hydric Soils Histosols in the aquic suborder Defining hydric soils = Subject to periods of saturation that inhibit diffusion of oxygen into the soil = Undergo reduced conditions for substantial periods of time * fixhibit certain features termed hydric soil indicators. * Carbon accumulations © Grey reduced iron * Reduced Mn - Hydrophytic Vegetation co Evolved special mechanisms to adapt to life in saturated anaerobic soils co Hollow aerenchyma tissues that allow plants to transport oxygen down towards. their roots 9 Certain trees produce adventitious roots, buttress roots or knees Spread roots in a shallow mass on or just under the surface of the soil where oxygen can diffuse Wetland chemistry o Low and varied redox potentials © Low oxygen * Oxy oxidized zone en can diffuse to support the top | or'2 em of soil creating an * A few em deeper the oxygen is eliminated and redox potential becomes low enough for nitrogen reduction te takerplace * Close proximity of aerobic and anaerobic zones allows water passing through to be stripped of nitrogen. by being oxidized and then reduced into gases that escape into the atmosphere Redox = To be considered a wetland redox potentials should be low enough for iron reduction to produce redoximorphic features * Even lower redox potentials will allow reduction on sulfate to produce sulfide gas HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Little of solar energy that reaches earth results in soil warming (10%), most goes to evaporation of water in the soil Albedo is reflected by the land surface arily the hottest soils Radiation tha o Dark soils are not neces © Dark soils found in low spots with ex Aspect jive water that is not warmed as easily the soil Plants should be planted on the south facing slopes of ridges to have warmer soils Rain Spring rain warms surface soil as water moves into it © Summer rains cool soil b/c the rain is cooler than the soil to begin with Soil cover Bare soils warm up and cool more quickly than soils covered with vegetation, snow or mulch s even have a considerable effect on soil temp © Low growing vegetation like grass > Cooling effect due to heat dissipated by transpiration of water © Timber harvest should leave at least 50% shade or hot soil temperatures could heat soil enough to lose organic matter and creat Thermal properties of soils - Specific heat of soils © Dry soil more easily heated than wet soil HS ‘ \ o More energy is required to heat water by | degree than | degree of soilsolids © Specific heat is when heat capacity is expressed per unit of mass)(cal/g) - Heat of vaporization © 540 kilocalories per kilogram of water vaporized © Must be provided from solar radiation or from surrounding soil o Potential of cooling the soil © Soil would be cooled 12 degrees if 1 gram of soil was vaporized in.100 g of soil oil is 3 to 6 degrees lower a Upper few cm of wet - Thermal conductivity of soils Rate of flow of heat in soils is determined:by adriving forée and by the ease with which heat flows through the soil expressed as Fourier’s law = Q = K*(delta T/x) Q is the thermal {lux or the quantity Of heat transferred across a unit area in a unit time K is the thermal conductivity Delta T/x is the temp gradient over distance x that serves as the driving force for the conduction of heat HTTP://NOTES.BOOKHOLDERS.COM How to Buy Textbooks l= 4509A College Ave = 301-209-9313 Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Thermal conductivity K * Determined by moisture content of the soil * Heat passes through water faster than through the air * As water content of a soil increases the easier it is to transfer heat of compaction of the soil © Heat travels through soil particles even faster than through water * When soil particles are closer to each other (compacted) heat transfer rates are increased * Wet, compacted soil would be the poorest insulator and the best conductor of heat = Dry soil makes good insu tor of heat; buildings underground can take advantage of low thermal conductivity and high heat capacity of soil Variation with Time and Depth ) Surface layer temperatures vary more or less with the air temp © Subsoils lag in temperature with the air temperature © Subsoils are cooler in the summer than the surface soil and air temps and are warmer in the winter than the surface soil and the air temp Soils reach maximum temp later in the day than the air temp due to lag time Lag time is greater and more pronounced the deeper you go Soil temperature control - Organic mulches and plant residue management o Buffer extremes in soil temperature © In hot weather keep soil cooler and cold weather keep soil warmer o Mulches from conservation tillage = Leaves most or all of crop residue at or near the soil surface = Grows mulch in place rather than transporting it to the:field * Soil temps at depths as great at 70 cm are lowered during spring in no tillage systems which leaves all crop residae’as mulch Concerns in cool climates * Mulches in cool climates do not help in raising the temperature at night when it gets too cold * Push aside the residues in a narrow band overthe’seed row in a no tillage system can alleviate problem. * Orplant on the drier, warmer side of a ridge © Advantages in warm climates * Can reduce heat stress on planis. during summer * Conserve soil moisture bydecreasing evaporation and results in cooler and moister surface soils important to no tillage systems HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Plastic Mulches Plastic mulches increa ¢ soil temperature, clear better than bh ) Biodegradable piastic films help with problems disposing the plastic wmmer months » Should not be used in warmer climates during s - Moisture control Controlling soil moisture can control soil temperature Poorly drained soils are lower in temperatures than well drained soils © Water regulation is key to temperature control in field Chapter 8: The Colloidal Fraction: Seat of soil chemical and physical activity General propertics and types of soil colloids - Size o Clay and humus are the soils colloidal fractions - Surface area © The smaller the size of the particle the greater the surface area exposed for different reactions © Silicate clays poss platelike crystal units s extensive internal surface area between the layers of their harges ©. Soil colloids electronegative charges predominate © Charges attract or repulse substances in the solution as well as neighboring particles - Adsorption of cations and anions © Cations are attracted to negatively charged soil colloids co Exchangeable and absorbed ions are same: at or near surface Adsorption of water © Soil colloids also attract water molecules © Water adsorbed between clay laye! volume s can cause layer tojtiove apart and swell in Types of soil colloids © Silicate clays - Non = Do not exhibit ordered crystalline’sheets © Iron and aluminum oxides ystalline structure like a book stalline silicate cl = Highly weathered soils )bsite and goesite—erystalline = Among smallest soil colloids HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store pee off using simple and easy self-serve stations. 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BOOKHOLDERS. com outer sphere complex is when water molecules form a bridge between the adsorbed ion and the charged soil colloid surface © thus the ion never becomes close enough to forma bond with a specific charged site, and instead is only weakly held by electrostatic attraction and therefore easily replaced inner sphere complex does not involve any water molecules one or more direct bonds are formed between the ion and the colloid surface Cation Exchange Capacity ~ negative colloids attract positive cations Important in Soil fertility- holds nutrients informs plants can use © Groundwater protection — filters water percolating through the soil © Pesticide-soil interaction — binds, inactivates and immobili es pesticides Toxic waste disposal — binds many organic chemicals - CEC= number of charges/unit mass of soil (emol/Kg) ~ CEC of various soil: o Sand-1or2 o Oxisols- 2 © MDsoils— 3-20 » Mollisols = 10-30 © Vertisols — 30-50 3 Histosols — 50-100 Is Principles o Reversibility = AILCEC are reversible o Charge Equivalence * ‘The same amount of charges are exchanged imany reaction * Ca2+ for 2 H+ ions 1 mol Ca2+= 1 gram of atomic weight/2charges per atom * | mol Ca2+~=40g/2+ charges = 20g/mol of charge * 1 emol=20g/mol / 100 =.2 g per emol or. 200mg per emol * | mol H+=1g/mol charge /100 1 mol of charge exchanges with | mol of c Olg/emol or 10mg per cmol Chapter 9: Soil Acidity Soil pH controls the chemistry of soil and water » Solubility of metals like cadmium and lead HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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Purchase with the help of clerk that can answer your questions about a book or class. , eee www.BookHolders.com " maT Pe ued HTTP://NOTES.BOOKHOLDERS.COM ) Availability of iron, zinc and copper to plants ) Toxicity of aluminum to plants and fish and humans » Loss of cations needed by forests Process of soil acidification Dissociation of hydrogen atoms from carbonic acid Accumulation of organic matter acidifies soils © Contains numerous acid functional groups Oxidation reactions usually produce H+ ions Acids in precipitation Plants can exude H+ ions in the soil solution to balance positive and negative charges that the plant takes up Typical pH of different soils Active acid sulfate soils 1-4 > Forest soils 3-6 ) Humid regions arable soils 5-7 © Sodic soils 8-11 Aluminum in soil acidity Major constituent of soil minerals and clay When H+ ions are absorbed on clay surfaces they release AI3+ ions in the soil solution Pools of soil acidity Active acidity © Defined by the H+ ion activity » Small compared to exchangeable and residual » Determines solubility of many substances and provides the soil solution environment to which plant roots and microbes are exposed © Very acidic soils contain AI3+ ions in solution which addito active acidity Exchangeable acidity Salt replaceable acidity Exchangeable aluminum and hydrogen ions that ate present in large quantities in very acidic soils Can be released into the soil solution by cation exchange Aluminum hydrolyzes to form additional H+ fons © Highest for smectites, intermediate for vermiculite: Residual acidity » Associated with hydrogen and altiminum ions that are bound in nonexchangeable forms by organic matter and clay and lowest for kaolinite HTTP://NOTES.BOOKHOLDERS.COM  o Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store Search by class, author, title, BN at bookholders.com. pee off lm 4509A Colley = 301-209-9313 using simple and easy self-serve stations. 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Buffering of pH in soils Ensures stability in the soil pH Resist the acidifying affect of rain Influences the amount of lime or sulfur required to bring about a desired change in the pH Clay soils have highest buffering capacity and sandy soils have the lowest Determination of soil pH = May vary dramatically over very small distances - Plant roots may raise or lower pH in their immediate vicinity - Fertilizers can cause sizeable pH variations - Different horizons can have different pH values - Upper horizons are more acidic than deeper horizons High amounts of Ca and Mg create higher pH levels Process of liming to increase soil pli Factors to consider Plants soil pH preference © Soil properties © Initial pH (active acidity) Soil buffer capacity * Organic matter percent «= CEC Amount of soil to be treated, depth of mixing Nature of liming material (% CaO) Reactions of liming materials © Limestone * CaCO3 +H20 > Ca2+ - Gypsum can also be applied to increase the soil pH 2 Moves down the soil profile more readily than lime Organic matter can also lower pH Acidifying the soil For acid loving plants when alkalinity is to high(blueberties, strawberries) - Sulfur, iron, aluminum Sulfur oxidizes with water to form H2S04 - Iron and aluminum hydrolyzes water to form H+ fons Effects of soil pH Strongly acidic or alkalinic soils reduce the amount of nutrients available to plants HTTP://NOTES.BOOKHOLDERS.COM ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com uses clays to clump or flocculate Exchangeable calcium Exchangeable sodium causes clays to disperse Types of salt affected soils Saline soils = Soils that contain sufficient salinity to give EC values greater than 4 but have ESP less than 15 * Exchange complex dominated by calcium and magnesium — not sodium * pH below 8.5 * not constrained by poor infiltration, aggregate stability or aeration = evaporation of water creates a salt crust on soil surface Saline-sodie soils * Detrimental levels of neutral soluble salts and high proportion of sodium ions Sodic soils = Most troublesome * High levels of sodium on the exchangeable complex * pH values greater than 8.5 * carbonates react with water to release hydroxyls * dissolved humus mo - Adding water to Na soils makes a sodic soil and makes worse salis upward can give soil surface black color Management to control excess o Add extra water for leaching © Will not work for sodic 1» Adding synthetic polymers with gypsum ils. © Prevent rise from water table * Drainage = Avoid over irrigation * Grow deep rooted perennial plants s out of the root zone © Move sal - Plants become stunted when grown in high salinity soi with dark blueish green | Chapter | 1: Ecology of the soil - Most complex ecosystem Fauna =anima - Flora = planis - Transformation of organic wastes thfough'the soil. community or food web Soil organisms recycle nutrients that plants can use Trillions of microflora in the surface soil layers o Bacteria Fungi HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, Self-Serve or Purchase for pickup at local store during convenient hours| l= 4509A College Ave = 301-209-9313 www.BookH: BN at bookholders.com. 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BOOKHOLDERS. com Algae Actinom: Thousands of fauna Protozoa Nematodes o Mites thworms Size of organisms © Macro organisms (> = Earthworms * Mammals * Insects * Plant roots Meso or; ns (.1 32mm) * Collembolans * Mites = Some nematodes nisi = Plant roots © Micro organisms (<.1 mm in diam) = Protozoa = Rotifers = Some nematodes * Bacteria = Fungi al engineers Ecologia Make major alterations to their physical environment that influence the habitats of other organisms © Dung beetle * Conserve nutrients in the soil by cutting round balls from largé mammal feces and transporting them to new locations * Protects nutrients from runoff Roles of soil fauna in soil fertility Enhance microbial activity * Fragment liter «Mix organic matter with mierobes in theif guts * Aid in dispersion of micrabes = Stimulate growth by. burrowing Transport of OM * Burrowing, nest building (ant, earthworms, beetles) HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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Sold your questions about a book or class. lm 4509A Colley = 301-209-9313 Improve soil structure * Burrows. channels * Aggregation » Damage to plants * Herbivores = Parasites Earthworms — natures tillers © Dominate in temperate areas Likes = Well drained soils * Lots of high NOM * Lots of Calcium Dislikes = Sandy soils * Acid soils = Very wet or very dry = Tillage * Shallow soils = Bare soils Activities = Incorporate OM = Make burrows, channels = Improve aggregation * Excretion of casts * Improve drainage, aeration, infiltration * Enhance nutrient availability and cycling - Termites © Dominate in tropical areas © Do not have a beneficial effect on soil productivity Nematodes Feed on bacteria, fungi or algae Or are predators of other nematodes, protozoa or insectlarvae = hard teeth and large mouth for catching prey Or parasite = spear like mouth part - Plant roots Primary producers Feeder root (100-400um)> root hair (10-50um)> mucigel > root cap with sloughed off cells © 25 to 50% of total plant dry matter 100 kilometers of grass roots in a liter of prairie soil HTTP://NOTES.BOOKHOLDERS.COM  ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com l= 4509A College Ave = 301-209-9313 Chapter 13: Nitrogen and sulfur of soils Nitrogen Cycle Key component of SOM - Key ingredient in proteins, DNA, enzymes, chlorophyll - Key pollutant in water Nitrate toxicity » Ammonia toxicity Eutrophication Key green house gas - Ke Deficiency in plants show a yellowish or pale green leaf color ake up nitrogen as nitrate (NO3-) and ammonium (NH4+) component of acid rain Plant roots Nitrogen cycle © Inputs of N to soil org: o D aatter as plant and animal residues composition of residues and release of N by mineralization * Decomposed by good aeration = Warm temperatures = Easy to digest carbon o Conversion of N from soil organic matter to soluble forms © Balance between mineralization and immobilization determine the soluble mineral N * Mineralization conyerts nitrogen form R-NH2 (amine groups) to séluble NO3- ions * Immobilization is the opposite Oxidation of N to nitrate = Needs oxygen, warm temps, nitrifies Ratio of carbon to nitrogen influences the amount of nitrogen ayailableduring decay Dentrification * Conversion of N form soluble forms to gaseous forms * NH4+ to NH3 gas = Wet soils * Anaerobic conditions * Microbial food * Nitrate present * Faster with warm temperatures, Ammonia volatilization * Dissolved ions to gas = High pH HTTP://NOTES.BOOKHOLDERS.COM  o Purchase for pickup at local store during convenient hours| Self-Serve | Purchase at local store Search by class, author, title, BN at bookholders.com. l= 45098 Colle: apne book or class. Test eint aleraedd be using simple and easy self-serve stations. Advantage U | Purchase with the help : of clerk that can answer =. sold your questions about a www.BookHolders.com * Drying soil * Sandy soil * Hot temp N fixation N triple bond N, NOx to N2 * Symbiotic relationship with rhizobia (legums) and non legumes » Requires energy = Certain microbes = Most efficient with plants Huge nitrate reservoir discovered in deep desert subsoils Phosphorous - Converted into calcium phosphates - Iron, aluminum phosphates - Organic phosphorus Phosphorous strongly absorbs to iron and aluminum mineral surfaces (P-fixation) © Occurs at very low and very high soil pH - Phosphorous deficiency plants are stunted, thin stemed, and has dark bluish-green foliage Micronutrient availability - Causes of deficiency Bigger harvests > Purer fertilizers © High PH Sandy © Organic soils soils - Causes of toxicity Impurities Air pollution Sewage and sludge application Low pH Anaerobic conditions Organic fertilizer Coffee grounds Wood ashes Bone meal Soil degredation has occurred on some 2 billion hectares of land HTTP://NOTES.BOOKHOLDERS.COM  ° o B extboo ° =| Search by class, author, title, or ISBN at bookholders.com. 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BOOKHOLDERS. com Erosion by water and wind accounts for about 85% of the worlds degraded land The more ernsion the less productivity for yield of crops Wind erosion Conductive to wind erosion » Dry soil Loose pulverized soil Open treeless land Smooth soil surface o Fine sand and silt textures Inhibits wind erosion Moist soil © Unplowed soil » Tree and windbreaks Rough, cloudy soil surfi o Clay or coarse sand Wind erosion of the southern high planes of the U Soil Erosion Soil is destroyed on the eroding sire and sediment buries fields and pollutes water downfield Environmental damages from sedimentation (soil out of place) Causes water turbidity * Low light for SAV = Clogs fish gills © Covers gravel fish spawning grounds Fills reservoirs and channels © Carries nutrients and chemicals o Difficult to filter for drinking, 2.2 billion MT/y of sediment carried by major streams Erosion is most prominent in deserts and semi regions rangeland because of little precipitation People now move more soil than nature Erosion vs. Sediment load Erosion is the detachment and displacement of soil Not all eroded soil is delivered to a Streamas sediment load » Eroded soil x delivery ratio = sediment Joad Delivery ratios range from .1 in largé gentle watersheds to .5 or more in small steep watersheds Three step erosion process HTTP://NOTES.BOOKHOLDERS.COM