Unit 2: Soil

((Unit-2)) ((Soil)):- -((part-1)) Introduction The coord soil is derived from pacthy material in which plants grout. a Latin word "Soum" meaning The stody of Soil is known as "sol science" ore "Pedology" (pedos earth) on Edaphology Cedaphos = soil). The study of soil is important respects. animais. Solig natural habitat Sofon prants cand St porviides water and nutrients to soil:- Sofi may Defination of humus & pre sent. living organism. ybe defined as the part of earth Crust in which "Soft & the upper part of earth croest in which plants are anchored, and upes firias layer of earth creust with which are mingled living as weathermed Supes firias organisms and products of theil decay. (RIF Daxbenmire) Soil is the upper weithersing layer (te layer subjectatto physical and chemical charges) of the sorid enath Crust (Raman, 1928) "Soil is a nadras body developed Usvary differentiated constituent by naturas forces acting on naturas materials. honizans of minerds and organic of variabre depths which differ from parcent materiass in morphology, , Physicas consti toente allons, chemical and biologicar characteristics". (Soffe and marbul)" properties, compositi OL Soil is a mixture of organic matter, minerals, gases, iquids, and that togethere support ife. συγρπίδης soil con be defined of the region on the paruth Euroface where geology and listogy reced each other Formation of soil: The Foremation and evolution of soil involve a series of Physical chemirou and blangical process which red penge progressieveryo oven time, are controlled by cilmatic variables and an anc by topography. The whore process of soil Formation is ge greatly intend into two Stages (1) weathening mineral particies, -break doun of generally divided bigger rocks in fine, Smatier and (1) soil development on pedogene Sfe - modification of the mineral retters through interaction between biologicas "petential Sol's Himalary lead to the development topographic and climatic effects, which of1fmotor any of a great variety of types. Oracathering process Bare rock surfaces are exposed to various types of physical, chemical and biologicau chemical and biological Pancesses processes which lead to physicals which lead to disruption of the in Components. prooeess of wealth ing Physical proo Incivde action of water temperatione glaciers, gravity exe?, which I cause weath weathering The chemitas prices of wrathersing Prinde hystration, hydraylis, oxided ion -reduction, cacbonation, chelation composition of rocks, chemicals boctena result of etc. which ane due to chemicas In the atmosphere, as well of these algaedong h blive-green algaell, such as lichens, fungi, brayophytes ex. - In biological processes bane rocks Lichons, Fing lichens ane able to extract nutrients fimm and bacteria ста nock Surufere retain the water For a long period during which the chemicae proces can popred -Aigue patitine's of lichen through photosynthesis, and inverseases the amount of avaliable organie maarters at nock Surifare various exudater Freem these organisms and the respiratory carbon dioxides arcelaerate the process of weathering as some of the lichen aulds forgrote acid) generally dissare mineral components. The a cweathering Parcesses are physical as well as chemiaul. a) physicas process: This may be of flowing types. ( (1) wetting - Draying it is the disruption of minerals when swen on wetting. layes lattice (reguar patiem) (ii) Heating-coolings- is disruption of heterogeneous crystaline socks - in wnich Pactucions have differntial coefficients of thermos expresion. 4 occurs pareticolourly in dery Climates. (1) Free zing- nocks by This is the Odisruption of persus lamelio's os vesicetour fost shatters due to expansion of contes (iv) Glaciation: Langer masses of Snow and ice dusing Fiscezing. grariess, white filling my cause (v) Solution: Some more mobie through grinding process composants of of coactum chirrides, Sulphates ete, like cuater ane rocks Such simply removed by agents physion ens? Docks (v) sand blast in anid, desent conditions the rocks are dimopted by by physical action of wind sand et (b) Chemical processs- This include the (1) Hytsadin As a result of taking water, due to revesible change of resos 3Hg), the rock swells. This Swaing rasmatite to limonite (regos Resos 3 Couses the disruption of Sandstimes edi. را Hydrolysis & In this process, components Bee aluming- breakdown, during which elements Silicates of sock Such as potassium and surplus Sulphurs, Stilton are washed out which give rise to simpler mineral like clay aluminosiliates, for example, hydrolysis of orthocinse (ky2516016) to balinire (A163, 2510g, 24७). lin) Exidation-Roduction : Some oxidation -reduction reaction ( reversible cange of fest to ret cause disnυρίση more Soluble than feat, of nucks, Such as be cause ret (iv) Carbonation- and those dosing Cartbonation Some chemicals, Produce Produced in cond those the metabority of miere bogaistmasphere and t As Fore example reversible change of eaco e to calicos) lead to solution cacos cemented monks rocke soluble than carbonation logob limestone or disruption as the hydrogen cacbonate is more (4) chelation :- Some chemical exudates, produced through biochemical activity of mina onganitims live ons, bacteria, ete achons, ane abreto dissolve out minerse components of the rocks. These, medals dessoove with ongshere products of microbial activity are known as Example, arias chelates. howe ngon cheating propertied by lickeds and bacteria For 2 Pedogenesis During weatherring, the rocks ane broken into smalier particies. But this is not the tove soil and pa plants can't grow in this matter. The weathered material under goes further number of charges, which is a complex process, known as pedogenesis on soil development. - whereas in weather pedogenesis Physices and chemical factors are invaved cweatherring, mostly Physic is largely Da biological phenomenon. ipving organism such as lichens, molluscs, bacteria, fungi, argare During this phenomenon bacteria, fungi, algae, micro-anthropods, micro anthropods, molluscs, etc asa result of secretion of organic acids, enzymes, Can Anduction & addition of organic matter after theire death, bring about geochemicas biochemical and biophysicae procese. Due to are this the crusts of weatherd rook deris cane converted to trave Soils consisting of a complex mineral matrix in casuciation alitha mpy variety of organic compounds, and a rich mien-oganism population. added various organic ampards - Thus atuncing pedogenests, there are addes dead organic meter matter and siving organism etc. to the minersae mortiter. As a result o알 dead organic mattes, the minerals are then gronduvly added to different layers of deveraging soil. this so when funy developed can be seen howing number of layers- of so known og soll profin horizons of U a soil, The aor-all peress of formation of soll is to shown belas (Ronent pack) hysiose weathering (Canttingsdaging, heating, con mezing, Raziasten, soutien (diercuption into fragments) Sond Map)" chemical weathering (habendion, habulytis, σχίλωνίση reduction, catchmallen, chelation) (ithe, smanners, minersas panticies podagine sts Congenre made, pads organismos (Sopi prorfive development) Soil Profile: Gopis ane described and identified by reference to there proflies. soli proflie is " the Sequence and nature of the horizong (layers, superimposed one above the nather?. Sofi profie is a vertical cross sections of. the soil, made of layers sinnin sinning parales to the surface. These layers are so known as son horizong A soli horizon is defined as "layer which is approximately panasies to the soil surface and that has properties produced the soif forming processes iningtured of myers!! but that are unlike to those of adjoining The soil protites pofiles consists of the following Five main horizons: "Horizons "A" Autizons Rthari zone "Anni zang The 'o' Horizons - These arce the organic horizons Farcoming above the rcomposed of the mine Raceratrix this acimy horizon is divided into follocauing enganic matters. Scomposed of the Sub layers: (Aoo) region: This is the uppers most dead organic matten layer consisting of frorshry Faiten as dead leaves, branches, flowers and Fruits dead parts of animais etc. ()O(A) Region:- has begun. Thus areganic Stf is just berry the of region, in cubich do compositen matten found on different stages micro-organisme lik bacteria, fungi, actinomy'etes in Inhal Stage decomposition Curde Dontly of decomposition and Found upper layers contain detritus In cohlen material can be faintly recognised, where as the lower lages contain fatrey decomposed matter? The A Horizons: These are the minesas horizones formed either at are adjacent tanke Surfare These are rich in eigonic matter. In this layer, the seed germination takes place and te which grow in to a new plant this layers consists of roots are produse organisms Such as earthworms, Fungi, bacteria, etc. This horizon is divided into following two sub layers: (1) A, negion:- St is dark and rich in organic mates. The anonghus, finely divided onpanic matter, herre becanes mixed with mine sal mater whichts now known as "humus", which is dark brown or black coloured. Hence this layer is also known as Humis layer and this Region is the humit wyjen. (ii) A region: This region is of light colour in which the mineral particles of a large size as sand ave more, with little amount of organic matter. in areas with heavy reais fall, the minerne elemen 150 and crapanted chemicals d arte rapidly lost down wands in this region, muring it night-coloured This is Hind also known as prysolle on eluviσα Zone or Zone of leaching. The "B" hasi zen: This is just berow 'A' hori zen, and can also be diunked into Dos (As) By and by regions, depending upon the stages of son devropan of horizons in the area. The "B" horizon is deurk-coloured and roarse-texured due to the Clay, orlyan't compounds silica-rich Clay, presence of silic of aluminium Pron etc. Sinre, the the chem chemicus hydrated oxides leached from A2 Region becomes collected in this region / horizon, hence it is also known ag in dry dre Tilsvine aneas Izone. This zene is porrly developed A, A and B are collectively are known as mineral Sol of Solum. The "c" Hori zong This layer is devoid of any organic matter condis mode of up of breaken bed rock. These are the mikence horizons berow the B but without any characteristics of 'na'e hartzens of netist of incompletery weathered, lange masses of rocks. - These layer is also known as saprolite. The geological moterias present in this zone is commented (1) sa? Minerie matern 8- of consists of Smau Primegulare particies te Particles of differ different sized formed by 2 of parent material (Rock). by varying deeprees ofs weathe They enciose STROLLE Spares Fore holding cand circulation of cwater and air. Depending upon thuaire size (diameter) basis), the international t Science has given different names to these mineral o which are as follows: Society Name of the partfae Diameter range (mm) Gravel and Stone (firepebbles) Coarse sand (Qμαντχισε τίας) 15 mm above 2.0mm 02-2.0mm) Fire Sand (Sing) 0.09 0.8 mm Siit (Very Fire quartz gons) - 0.002002 mm Clay (Hytrated silicates of Aluminim) less tou than 0.002 Sand paretimes are chemicaly Stenine. They enclose langer non whien can hold air evader. cray pantieres capilary pone are chemically aume are which can hold and they enicose fiver capillary spare aire. Silt has intermediate e Ocharacter die matersately. enciosing Spares fore both contes and aps. asanter bur not active chami chemiony (ⅱ) Son Ain There ane spares in between mineral ponteres (pore sparis) as cuen af between aggregates of the solal. These spaces ane occupied, in addition to vulous Soil. liquids, size and numbere by the gases, Such wnich make the atmosphere off • Spaces differ in different terutaine groups of soil. Thus coarse textured soil like Sard howe larges porre Spring (but loss in number) than the fine textured soil like Sopi aeration is thus influenced by parre spaces. clay of sillt. Gases present Prothe soil atmosphere and more os les fimilar to there found in the external atmosphere. less and that of a highers. Hows over oxygen concentrsation is in the soll than those in atmosphere. In a good soil 25% of totne voume of the soil is fined with arr. (in) Soil moisture - it is one of the most impactant ecological fouter in the distribution of biota. soll moisture is derived from raiη. θη σπερ Fields înnigation is another sourcedf sol water. ncin on incalgation water flows as over the soil as A pand of which goes nun-away water bua back for the Souttre te sea, oren, and somle is evaporation & BED A the during exap water forbre (groung). Like Soli aercation, Port of pencatates downwardly into the coaters content of soll is algo much related te its texterse and structure, and allo with the moignitude off Plast Forces as capillang Madhesion Such phyrlove attraction, cohesion and adhesion Thos Size of the mine brae pentries and their shape and number of pored Spares are important in the amount of water retained by the soil. Sand which ane coarse- textuned with tangor particies winder only trasach cat genitaly, loa sony dues bigger peres spaces The water in such suil reint down rap layers Thus Gandy soil arce Cane hold wicke well drained rapidly maching to cay son, with much proportion of colloidal fractions af humus ete.can melain much wahes. Spits also like clays are able to meitenin much water sits attolike Cloys are Loams, ahich are a mixture of sund and silt and/or clay, clay, ane supposed as Such soils are very best cils for pant's growth, as rich in nutrients, have proper fertile, being rich a ematen, and hold fodning amount of water. - excitern in soil is generang prosent in the farowing the forms (Standes): (1) Hygroei scoppe coaten:- This is the water which is held by the surfenere force of the son particles. The waters is held tightly careand the particies ang adhesive forces and it con not be eavily remond as a result of cohesive and by the plants. capitany cooter This conten in sollis mouniy hod between Spaces (pure spores) of the Soi 10 pasticces, this to the most important form of water to plants. (Gravitational This is the woocker that meres docenciocund though a moist Sofi in the response to gravity. (iv) combined coates this is the form of water ocuns boing upin chemicalt Suenas hydinted orlites of cutiminium inos, Silicon etr. in the Sofy. (4) a cooker vapour 8- Some water in soil is also present in its vaporr state inave pare Spaces lactuced son pantieres. (1) Sen, saution - theme existe a tweak saution of various saits, along with other liquids and gases in the soil man. The sti sitt solution contains armast all the essentiate minerale coveprex mixture of minemigall as carbonates, Ripote nitrates, Chionites, and organic salts of ca, my, Na, kete are found arseve in water. The chemicas native of soil Belution depends upon the nature of the parent medies and the cimate and albers, fasters (inruding chemicas nature of cogente matter) involved in pedogenesis. (v) soll engaiata matre (timus): 94ts derived frons littore Crioganic remaing Stredin oves the soil Surface, ilke fallen leaves, tuigs, excmetim of Jos organify and their dead bodies undichibuted littes forums a Sord of mat own the surfove of soll. It undergoes slow decomposition to produce humus. Hurus is dark brown comorphous gummy Sobstances formed by the pantial decomposition of plant and animece matter that constitute origanic ce component Humus is amy slightly Soluble in water and there fere angely Stays in top sell only Brave quantity seeps down wanas The same contes soli panties, bind them together and forms stii aggongaks - Himus is Formed from ongante memouine thoough the activity of doamposer πίπτει σπαμπίδης procex Jof Formation of humus form sawl organic remains & called humification, stis slow because many enstituents organite matter ane slow to degrade 2 e lignin, cellulase. Hemus com con khỉn Pandiony decomposed products of cellulose, hemicemulase and ligain. with time they ane brookion doun compretery. There-fose, in order to maintain oregonte component of soils, ain noul inermis has to be formed meguiarty, (vi) i Orupam- In addition to its Sald, liquid and gustas components each call has lits own distinctive flored bind Fauna (bacteria Firgi, actinomycetes, cougar, be bive green argue, protozoans, retifers nemabal's, eanth wesme, melloses, arthopeds etc.) chich make the trogical System" Among there organisin Some herwin mahtenonieof. So Fertility through nitrogen firation and others Returning nutrients back to the environment. deamposer exce TRole of climate on Sofi devaopment:- -Rainfal, temperature, hemidity / evaporation and wind are the climatic factors thal Strongly infivence soit formation. Rainfo Rain fall, determines the direction of solute translocation according to Precipitation cuith other factors also determines depth of water table that would affect the level of caprinarcy water Tempersatire governs P/E ration. Physicochemical turenovere in soil. and aeration. "Pobless rationis Through quereren Ocontrols the rate of organic - Humidity levaporsation interaction in fivences rainfall and amount of coater movement. Thus climate of an area is a major factor in soil Farmation. It tends to redure differences caused by the parent material. That is why to different parent materiaus may be developed the same soil in one type of climate regime. Like wise the same parent materiae may produse different types of soil in different types of climates. Crystalline granites produce laterite soil in melatively moist pards of the monso0 FOR non-lactersitic tourmals its chries margins. ion and districts of Tamil Nadu Following develops brick Soil as found in some Kamil Nadu, irrespective of the parent sooth focock. ane same climatiz condition fen which different types of soil crreformal;" Hot Summers and tow sain fall (1) undere high temperature regimes and high moun-foul in the Stiicate minerous are very unstable Veryenstable and a as colloidal stilca acid Vacurs tropics, the lange loss of silica, probab (ii) on humid, temperate Citrates, penticulously with moderate rain coupled with a nutrient-deficient, wen drained paresld metetion, decomposition Process is very low" () extremely cold chimed climates, high grounds water rretention of Sumface cuader level on the the soil, water-logging and consequently reequelry conditions are fairly commen, unded such rreduced carolitions firstly due to Ferrous compounds becomes bive- gray decomposition of organic matter are the ind Very the the soil coloυς Brates of Ustow. These together "Jaccumreation of a sicky compact layer of of bive-grey or grey colours of the bottom of "B" horizons. This procey is known as greization and the soil Das gelays (iv) In the carid and Sompanid climates, partiaiting exponitrans piration exceeds precipitation, so the rein unter is drawn back towarels the westiere Surinferte subsequent to movement into Sofi by "Cagliary action and root transport. The rainfall is in Bulbicient to reach the much of the calcium foom the soil Proflle and, there-fore, thes soils have fairey high perccentage of bare Saturation. The soil is fertile because it is not leached out, but the cunter balanse is ach that soil is moist enough for cos of himve giving a have abundance of rretain both nutrients and crop coltivation. The son dark colour to the soil & It cao Son moisture. - en acid and Semiarid areas, there are areas of inadequate drainoge The evaporictive water leaves behind various fait in ore on the Sunfare intense in decont The process of I sallt concentration in Soil surface is fo basins Caroljarent to maimy occupied bya Calt take on.. mountain) that landsrape can be dry pain or salt-fiat." The concentration of Salt at crust on the soil. Surufare may 1. plantsource absent on Produce a whitish or grey they Parce salt sith very high minerad mtio. including succulents with very adapted enrules,