Unit 1 INTRODUCTION AND SOIL PHYSICS.pptx

INTRODUCTION AND SOIL PHYSICS

1. Soil Science and Engineering S. Satheeshkumar Assistant Professor Department of agriculture engineering Kongunadu college of engineering and technology

2. Syllabus Unit – I Introduction and Soil Physics Unit – II Soil Classification and Survey Unit – III Phase relationship and Soil Compaction Unit – IV Engineering properties of soil Unit – V Bearing Capacity and Slope Stability

3. Unit – I Introduction and Soil Physics Soil- definition- major components- Soil forming minerals and processes – Soil profile – Physical Properties –texture- density – porosity- consistence – color- specific gravity – capillary and non capillary – plasticity. Soil air –soil water –Classification of soil water – Movement soil water .Soil colloids- organic and inorganic matter- ion exchange – pH –Plant nutrient availability.

4. Introduction Soil science Definitions: Soil refers to the loose surface of the earth as identified from the original rocks and minerals from which it is derived through weathering process. According to “ Buckman and brady ” Soil may be defined as a “A dynamic natural body on the surface of the earth in which plants grow components of mineral and organic material and living forms.

5. There are two basic concept of soil 1) Pedology A study of orgin , classification ,description of soil A/ tPedology solid is natural body 2) Edaphology A study of soil from the stand pont of hiher plants A/T edaphology soil isnatural habitat Organic soil 20% organic matter is low clay content 30% in high clay content Mineral soil < 20% organic matter

6. Soil physics Study of soil physical parameters Soil Chemistry Chemical composition Soil morphology Study of characteristics of soil

7. Major components of soil The major components of the Earth are water, air/gases, minerals, organic and biological components, microorganisms and gases .

8. The abiotic component of the soil accounts for about 40-45% of the soil volume followed by air and water that occupy 25% each with 5% covered by living things . Soil consists of four major components

9. Soil forming Minerals Minerals are naturally occurring, homogeneous inorganic soild substance having a definite chemical composition and characteristic crystalline structure, color and hardness. Primary minerals Minerals that are original components of rocks are called primary minerals. eg : Feldspar, Mica Secondary minerals Minerals that are formed from changes in primary minerals and rocks are callled secondary minerals. eg : Clay minerals Essential minerals The minerals that are chief constituents of rocks are called essential minerlas . eg : Feldspars, pyroxenes micas.

10. Minerals arranged in the order of their crystallization Primary minerals Ferromagnesian minerals Ortho or Ino silicates like Olivine Pyroxene Amphiboles Phyllosilicates Biotite Muscovite

11. Non ferrous Magnesium Tectosilicates - Felds pars - Anorthite - Albite Orthoclase Quartz Secondary Clay minerals Minerls others

12. Soil forming Processes The processes contributing to soil formation involve gain and losses of materials to the profile, movement of matter from one part of the profile to another and chemical transformation within individual horizons. The sequences of processes in the formation of soil

13. Two processes involved in the formation of soil are: Formation of regolith by breaking down (weathering) of the bed rock The addition of organic matter through the decomposition of plant and animal tissues, and reorganization of these components by soil forming processes to form soil. Weathering: A process of disintegration and decompostion of rocks and minerals which are brought about byphysical agent and chemical process leading to the formation of regolith. Regolith: It is a layer of loose heterogeneous superficial material covering solid rock. It includes dust, soil, broken rock and other related materials

14. Types of weathering I) Physical weathering or mechanical(Disintegration) II) Chemical weathering(Decomposition) III) Biological weathering( Disintegration+ Decomposition) I. Physical Weathering: The rocks are disintegrated and are broken down to comparatively smaller places without producing any new substances 1. Physical condition of rocks 2. Action of Temperature 3. Action of water - i) Fragmentation and transport ii) Action of freezing iii) Alternate wetting and drying iv) Action of glaclers 4.Action of wind 5. Atmospheric electrical phenomenon

15. II. Chemical Weathering Decomposition of rocks and minerals by various chemical processes is called chemical weathering. It is the most important process for soil formation. Chemical Processes of Weathering Hydration Hydrolysis Solution Carbonation Oxidation Reduction

16. Hydration: Chemical combination of water molecules with a particular substances or minerals leading to a change in structure. b) Hydrolysis: It is due to dissociation of H 2 O into H + and OH - ions which chemically combined with minerals and bring about change in crystalline structure. c)Solution: The soluble substance are removed by the continuous action of water and the rock no longer remains solid and forms holes.

17. d) Carbonation: Carbon dioxide when dissolved in water forms carbonic acid The carbonic acid attacks many rocks and minerals and being them into solution . The carbonated water has an itching up on some rocks. e) Oxidation : The process of addition of oxygen to minerals. f) Reduction: The process of removal of oxygen from minerals

18. III. Biological weathering Unlike physical and chemical weathering the biological or living agents are responsible for both decomposition and disintegration of rocks and minerals. Man and animals Higher plants and roots Micro – organisms Factors affecting weathering minerlas 1. Climate condition 2. Physical Characteristics 3. Chemical and structural characteristics

19. SOIL PROFILE The vertical section of the soil showing the various layers from the surfaces to the unaffected parent material is known as a soil profile. Horizons – Individual layer Solum –Horizons above the parent materials are collectively refereed to as the solum

20. O- Horizons It is called as organic layer It is formed in the upper part of the soil dominated by fresh or decomposed organic materials It contains more than 30% organic materials It is mostly available in forest areas. O i - Orgnaic horizon of the original plant and animal residues, only slightly decomposed. O e – Organic horizon, residues intermediately decomposed O a - organic horizon,residue highly decomposed.

21. A - horizon Top most mineral horizon formed adjacent to the surface and darker in colour. E – Horizon Horizon that has been significantly leached of clay,iron , aluminum oxide which leaves a concenration of resistant minerlas such as quartz. It is light colour B- Horizon This is a subsurface horizon in which the eluviation ( washing out) of materials has taken place from above or below.

22. C – Horizon It is the horizon of unconsolidated materials It is relatively less affected by weathering . R – Horizon It is the layer of unconsolidated bed rock. Transistion Horzon It is a layer between the master horizons (O,A,E,B and C)

23. Physical Properties The physical properties of a soil greatly influence its use and behavior towards plant growth The physical properties also influence the chemical and biological behavior of soil The physical properties of a soil depend on the amount, size shape, arrangement and mineral composition of its particles.

24. Important physical properties of soils 1.Soil texture 2.Soil density 3.Soil porosity 4.Soil consistence 5.Soil colour 6. Soil specific gravity 7.Soil capillary and soil non capillary 8.Soil plasticity

25. Soil texture Definition: Soil texture refers to the relative proportion of particles or it is the relative percentage by weight of the three soil separates viz., sand, silt and clay or simply refers to the size of soil particles. The soil separates are defined in terms of diameter in millimeters of the particles. Soil separaters Soil separaters are specific ranges of particle sizes. The smallest particles sizes are clay particles and are classified as having diameters of less than 0.002mm. The ranges of diameters of the three separates are: sand ( mm), silt ( mm), and clay (<0.002 mm).

26. There are a number of system of naming soil separates. The A merican system developed by USDA The international system – WRB by IUSS The English system or British system (BSI) European system USDA - United state department of Agriculture WRB - World Reference Base for soil Resources IUSS – International Union of Soil Science BSI – British Standards Institution

27. Soil textural classes On the basis soils are classified into various textual classes like sands , clays, slits, loams etc. Sands – Sand group includes all soils in which the sand make up at least 70% and clay separates 15% Silt - Slit group includes all soils in which the Slit make up 70 % 80% and clay separates 12% Clay : It a soil must contain at 35% of the clay separates and in most cases not less than 40%. Loams : The loam group, which contains many subdivisions, is a more complicated soil textural class, However exhibit approximately equal properties of sand ,silt and clay.

28. Soil Texture :Texture refers to the relative proportion of sand,silt and clay in a soil. Soil containing equal amount of sand, silt and clay is called “loam”. sand + clay +silt = Loam For ex. 15 % clay, 20% silt and 65% sand is called “sandy loam ”. Soil Texture : size (mm) Clay 5.0 Silt 0.002- 0.02 Sand fine 0.02-0.2 Sand coarse 0.2-2.0 Gravel fine 2.0-5.0 Gravel coarse > 5.0

29. Textural triangle The soil texture triangle gives  names associated with various combinations of sand, silt and clay . A coarse-textured or sandy soil is one comprised primarily of sand-sized particles . A coarse-textured or sandy soil is one comprised primarily of medium to coarse size sand particles. A fine-textured or clayey soil is one dominated by tiny clay particles. Due to the strong physical properties of clay, a soil with only 20% clay particles behaves as sticky, gummy clayey soil . The term loam refers to a soil with a combination of sand, silt, and clay sized particles. For example, a soil with 30% clay, 50% sand, and 20% silt is called a sandy clay loam. Below Figure Soil Texture Triangle Source: USDA

30. Figure Soil Texture Triangle Source: USDA

31. Importance of soil texture The texture of a soil is important because it determines soil characteristics that affect plant growth.  Texture has good effect on mangement and productivity of soil. Sand facilitates drainage and aeration . It allows rapid evaporation and percolation. Sandy soils are poor store house of plant nutrients. Leaching of applied nutrient is very high They have fine pores and are poor in drainage and aeration Loam and slit loam soils are highly desirable for cultivation They have a high water holding capacity and poor percolation which usually result in water logging.

32. Soil density Ratio between mass of the soil and volume of soil Soil density is expressed in two types 1. particle density 2. bulk density 1 . Particle Density: - The weight per unit volume of the solid portion of soil is called particle density. Generally particle density of normal soils is 2.65 grams per cubic centimeter. The particle density is higher if large amount of heavy minerals such as magnetite; limonite and hematite are present in the soil . With increase in organic matter of the soil the particle density decreases. Particle density is also termed as true density

33. Particle Density: - Table Particle density of different Soilt extural classes Textural classes Particle density ( g/ cm3) Coarse sand 2.655 Fine sand 2.659 Silt 2.798 Clay 2.837

34. 2.Bulk Density : The oven dry weight of a unit volume of soil inclusive of pore spaces is called bulk density. The bulk density of a soil is always smaller than its particle density. The bulk density of sandy soil is about 1.6 g / cm 3 Normal soil is 1 – 1.6g/cm 3 Organic matter – 0.5 g/cm 3

35. Soil Porosity : Depending upon the size pore spaces fall into two categories. These are: ( 1) Micro-pore spaces (capillary pore spaces ) <0.05 mm ( 2) Macro-pore spaces (non-capillary pore spaces ) > 0.05 mm Porosity void ratio (e)= Volume of void (or) pores/Volume of soil

36. Specific surface The area occupied per unit weight of soil. In smaller particle surface area is big. In bigger particle surface area is small . Specific graviy Specific graviy = weight or mass of a given volume of a soil/ weight or mass of a given volume of a wter . At 27 C is a specific gravity Specific gravity of water = 1 Methods to find specific gravity 1.Pycnometer 2.Density bottle Typs o f specific gravity 1.Apparent specific gravity 2.Absolutr specific gravity

37. Consistence Resistance of a soil at various moisture content to mechanical stresses. 1.Cohesion 2.Adhesion Cohesion It is an attraction between like molecule Adhesion It is an attraction between unlike molecule

38. Soil consistence is described at three moisture levels namely Wet soil Moist soil Dry soil Wet soil: Consistency is denoted by terms stickiness and plasticity Plasticity Its capacity to be moulded and retained the shape even when the stress is removed. Moist soil: Moist soil with least coherence adhere very strongly and resists crushing between the thumb and forefinger. Dry soil : In the absence of moisture, The degree ofesistance is elated to the attraction of particles for each other.

39. Absorption of electromagnetic wavelength and reflection Combination or adherence of two or more patches of colors in soil is called motting .This due to the presence of iron, manages and copper in soil in patches. Soil colour indicates soil feature. Kinds of soil colour Lithchromic –Red soil from red sand stone Pedochromic – Red soil from granite rock. Soil colour and Temperature 1.Dark colour soil absorb more heat 2. Light colour soil reflect most of heat Soil colour

40. To measure soil – Munsell colour chart Munsell Charts are a standard tool used by geologists, civil engineers, and soil scientists. The tabbed charts include 10R, 7.5R, 5R, 2.5YR, 5YR, 7.5YR, 10YR, 2.5Y, 5Y, and 10Y-5GY color ranges. Charts for tropical and semitropical soils, and for Australia and SE Asia are included .

41. Soil colour: Soil colour gives an indication of the various processes going-on in the soil as well as the type of minerals in thesoil . For example the red colour in the soil is due to the abundance of iron oxide under oxidised conditions ( well drainage ) in the soil; dark colour is generally due to the accumulation of highly decayed organic matter;yellow colour is due to hydrated iron oxides and hydroxide; black nodules are due to manganese oxides; mottling and gleying are associated with poor drainage and/or high water table. Abundant pale yellow mottles coupled with very low pH areindicative of possible acid sulphate soils. Colours of soil matrix and mottles are indicative of the water and drainage conditions in the soil and hence suitability of the soil for aquaculture.

42. Factor affecting soil clour 1.Parent material (Red, quartz,white ) 2.Soil moisture ( DarK ) 3. Organic matter (Dark black colour) 4. Iron component (Red Colour) 5. Slica , lime and other salts 6.Mixture of organic matter and iron oxides 7. Alternate wetting and drying condition 8. Oxidation –reduction condition

43. Capillary and non capilllary Capillary It is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. Capillarity is the primary force that enables the soil to retain water as well as to regulates its movement Non- capillary It is the downward movement of water due to gravity especially that occurs in soil with macropores .

44. Soil Air It is a continuation of the atmospheric air It is in constant motion from the soil pores into the atmosphere and from the atmosphere into the pore space. Soil aeration The circulation of air in the soil and renewal of component gases likeO 2 & CO 2 Composition of soil air Nitrogen – 79.2 % Oxygen – 20.9 % Carbon dioxide – 0.35%

45. Methods to find the soil aeration Oxygen reduction or diffusion rate The rate at which oxygen in soil air replenished .ODR decreases with soil depth. 2.Oxidation reduction potential Oxidized soil Ferric ions (Fe 3+ ) Manganic (Mn 4+ ) Reduction Soil Ferrous ion (Fe 2+ ) Sulphides (s 2- )

46. Factors affecting the composition of soil air 1.Nature soil 2.Types of crop 3.Microbialactivity 4.Seasonal variations 5. Temperature Aeration problems in fields 1.Moisture content is too high 2.Exchange of gases are slow a)By mass flow B)By D iffusion

47. Mass flow Moisture content in loss due to evaporation, absorption, drainage and internal drainge etc., Atmosphere air re-enters into soil pore space Diffusion Gases(Like N 2 ,O 2 )move from Higher concentration to lower concentration Important of soil aeration Soil reaction and properties Oxidation and reduction of inorganic elements Plant and root growth Microorganism population and activity Formation of toxic material Water and nutrient absorption Development of plant diseases

48. Soil temperature It is an Important factor(like air, water & nutrients) for plant growth. It affects plants growth directly and also indirectly by influencing moisture, aeration ,structure, microbial and enzyme activities. Specific crops are adapted to specific soil temperatures. Source of soil temperature Solar radiation Heat from microbial activity organic matter decomposition Respiration Internal heat from earth

49. The rate of solar radiation reaching the earth’s atmosphere is called as solar constant. It has a average value of 2 cal cm -2 min -1 . Factors affecting soil temperature Environmental factors The heat transmission into soil depends on Angle on incident radiation Latitude Season Time of the day Steepness and direction of slope and altitude Insulation by air ,eater vapour clouds smog etc.,

50. b)Soil factors 1.Thermal capacity of soil The amount of energy required to increase the temperature by one degree is called Heat capacity. It is expreseed per unit mass( calories per gram) It is called as Specific heat of water The Specific heat of water is 1.00 cal g -1 The Specific heat of dry soil is 0.2 cal g -1 2.Heat of vapouriation The evaporation of water from soil requires a large amount of energy, 540 kilocalories Kg -1 Soil water utilizes the energy from solar radiation to evaporate The specific heat of wet soil is higher than dry soil because of surface soil will be sometimes 1 to 6 C lower than the –surface soil temperature.

51. 3.Thermal conductivity and diffusivity The movement of heat in soils, the heat is transmitted through conduction Thermal conductivity of soil forming martials is 0.005 thermal conductivity units. 4.Biological activity: More the biological activity more will be the soil temperature. 5.Radiation from soil : Radiation from low temperatures isin longer wavelenths have little ability to penetrate water vapour,air and hence soil remains warming during night hours. 6.Soil colour : The ratio between the incoming and outgoing radiation is called albedo. Albedo = Reflected energy/Incident energy

52. 7.Soil structure, texture and moisture: Compact soils have higher thermal conductivity than loose soils Natural structures have high conductivity than disturbed soil structures. 8.Soluble salts: Indirectly affects soil temperature by influencing the biological activities, evaporation etc. Effect of soil temperature on plant growth 1.Soil temperature required of plants 2. Availability of soil water and plant nutrient optimum range temperature The temperature at which a plant at which thrives produces best growth is known as optimum range temperature .

53. Growth range temperature The entire range of temperature under which plant can grow including the optimum range is known as growth range temperature . Survival limits temperature The maximum and minimum temperatures beyond which the plant will die are called survival limits temperatures. Soil temperatures management Use of organic and synthetic mulches Soil water management Tillage management

54. Methods of measuring soil temperatures Mercury soil thermometer Thermo couple and thermistor Infrared thermo meters Automatic continuous soil thermographs The international meteorological organisation recommends standard depths to measure soil temperatures at 10,20,50,&1000 cm.

55. Soil water and its classification Soil water Water contained in soil is called soil moisture The water is held within the soil pores Soil water is an important component of the soil which influences soil organisms and plant g rowth. Soil water with dissolved salts is called soil solution. Importance of soil water It is a carrier of food and nutrients It is essential for photosynthesis Helpful for chemical and biological activities Play a major role in microorganism metabolic activity It regulates soil temperature It is a principal constituent of the growing plant

56. Retention of water by soil The water is retained in the soil by following ways 1.Cohesion and adhesion 2.Surface tension 3. Polarity or dipole character Facture affecting soil water Texture Structure Organic matter Density of soil Temperature Salt content Depth soil Types of clay

57. Classification of soil water Physical classification Biological classification I. Physical classification Gravitational water Capillary water Hygroscopic water a)Gravitational water It moves downwards by gravity It is excess of field capacity It affects texture and structure b) Capillary water Water held between capillary pores

58. Capillary water is retained on the soil Factor affecting capillary water Surface tension Soil texture Soil structure Organic matter c) Hygroscopic water The water that held tightly on the surface of colloidal substances. It is a non-liquid state. Primarily in vapour form Some microorganism may utilize hygroscopic water This water cannot be separated from the soil unless it is heated.

59. Factors affecting hygroscopic water Size of the soil particle Fine textured soil II Biological Classification of soil water There is a relation between moisture r ention and its utilization by plants. Soil moisture can be divided into three parts Available water: The water lies between wilting coefficient and field capacity. Unavailable water : This includes the whole of the hygroscopic water plus a part of the capillary water below the wilting point. Super available or superfluous water: The water beyond the field capacity stage is said to be super available.

60. Movement of soil water The soil water move under different ways Saturated flow Unsaturated flow Water vapour movement 1.Saturated flow This occurs when the soil pores are completely filled with water This water moves at water potentials larger than-33lPa This flow is caused by gravity ‘s pull It begins with Infiltration Movement of excess water flowing through the wetted soil is termed percolation The rat at which soil absorbs rain wate.r o r irrigation water

61. Vertical water flow The vertical water flow rate through soil is given by Darcy’s law The rater at which groundwater flows is equal to the product of the hydraulic conductivity multiplied by the hydraulic gradient V=K(G) V=Groundwater velocity K= hydraulic conductivity G= Hydraulic gradient 2. Unsaturated It is flow water held with water potential slower than 1/3 bar. Water will move toward the region of lower potential The rate of flow is greater as the water potential gradient increases and the size of water filled pores also increases.

62. Factors affecting the unsaturated flow Amount of moisture in the soil affects the unsturated flow 3.Water Vapour movement Two types a)Internal moment – Liquid to vapour within soil face b) External moment – Water s lost to atmosphere by diffusion Factor affecting water vapour movement Soil regimes Thermal regimes Entry of water into soil Infiltration It refers to the downwards entry ormovement of water into the soil surfaces

63. Factors affecting infiltration Clay minerals Soil texture Soil structure Moisture content Vegetative cover Topography Percolation The movement of water through a column of soil is called percolation. It is important for two reasons This is the only source of recharge of ground water which can be used through wells for irrigation Percolating waters carry plant nutrients down and often out of reach of plants roots

64. Permeability The relative ease of movement of water within the soil, the characteristics d etermine how fast air and water move through the soil is known as permeability. Drainage The frequency and duration of periods when the soil is free from saturation with water It controls the soil cum water relationship and supply of nutrients to the plants. Drainage class Very poorly drained poorly drained Imperfect Moderately well Well Excessive

65. Hysterisis The moisture content at different tensions during wetting if soil varies from the moisture content at same tensions during drying. This effect is called as hysteresis. This due to the presence of capillary and non capillary pores The moisture content is always low during sorption and high during desorption Hysteresis exists in soil minerals as a consequence of shrinking and swelling Shrinking and swelling affect pore size on a microbasis as well as on the basis of overall bulk density. The most important factor affecting hysteresis is the entrapment of air in the soil under rewetting condition. The clogs some pores and prevents effective contact between others

66. Soil Colloids The soil colloids are most active portion of the soil and largely determine the physical and chemical properties of a soil The clay fraction of the soil contain particles less than 0.002 mm in size. Particles less than 0.001 mm size posses colloidal properties and are known as soil colloids The organic colloids include highly decomposed organic matter generally called humus. General properties of soil colloids Size Surface area Surface charges – i) Ionizable hydrogen ion II) Isomorphous substitution

67. 4.Adsorption of cations 5.Adsorption of water 6.Cohesion 7.Adheson 8. Swelling and shrinkage 9. Dispersion and flocculation 10.Non permeability Types of soil colloids There are four major of colloids present in soil Layer silicate clays Iron and aluminum oxide Allophane and associated amorphous clays Humus

68. 1.Layer silicates It is important silicate clays known as phyllosilicates (phyllon –leaf) Because of their leaf-like or plate like structure There are comprised two kind of horizontal sheets One dominated by silicon and other by aluminum or magnesium. layer silicate clay 1:1 type clay Eg.Keolinite 2:1 type caly (Expanding) Eg . Montorillonite ( smectitic clay)

69. 2:1 type clay (Non expanding) Eg.mica , illite 2:2 typeclay Eg . chloide 2.Iron and aluminum oxide( sesquioxide clays) Sesquioxides ( metal oxides ) are mixtures of aluminum hydroxide. Examples of iron and aluminum oxides common in soils are gibbsite (Al 2 O 3 .3H 2 O) and geothite (Fe 2 O 3 .H 2 O )

70. 3.Allophane and associated amorphous clays These silicates clays are mixtures of silica and alumina Clay are common in soils forming from volcanic as ( e.g. Allophane) It is soil acidity 4.Humus It is amorphous dark brown to black nearly in water but mostly soluble in dilute alkali. It is an organic colloidal and consists of various chains and loops of linked carbon atoms. The negative charge of humus are associated with partially dissociated enolic ,carboxylic and phenolic groups These groups in turn are associated with central unit varying size and complexity.

71. Soil organic matter Substances containing carbon are organic matter. Soil organic matter consists of decomposing plant and animal residues It also includes substances of organic origin either leaving ordead Factor affecting organic matter Climate Natural vegetation Texture –fine texture high organc production Drainage –power water Cropping and tillage Crop rotation and plant residues Organic content i) moisture content

72. 8. Plant residue Cellulose, legnin , starch Sugar, fat protein hemicellulose 9.Dry matter Carbon ,oxygen, hydrogen, nitrogen, and some micro nutrients Water soluble minerals Ammonium and nitrate Water insoluble minerals Protein, sulphur, peptides Classification of organic matter Based of decomposition 1.Rapidly decomposed Starch, sugar

73. 2.Less rapidly decomposed 3. Very slowly decomposed- fat , legnin 4.Aerobic decomposition products Co 2 , Ammonium, nitrate, sulphate, water Minerals – Ca, Mg,Fe , Cu,Zn 5.Anaerobic products Metane , hydrogen sulphide , ethyl alcohol,propionic acid

74. Decomposition of soluble substances Ammonification Nitrifiation Denitrification The conversion of organic nitrogen into ammonia is called ammonification. Nitrification process

75. Denitrification process 1.Converson of nitrate into gaseous nitrogen 2.Decompostion of insoluble substances i) Breakdown of protein Conversion of protein into amino acid ii ) Breakdown of cellulose iii) Breakdown of starch Decomposition of ether soluble substances Iv) Decomposition of lignin Legnin to sulphate Legnin to posphate V) Breakdown of Hemicellulose

76. Mineralization Biological conversion of organic forms of carbon ,nitrogen , sulphur into inorganic minerals. Immobilization:The conveson of inporganic forms of C.N,P and S by the soil organism into organic forms is called immobilization. Factor affecting decompostion Temperature Soil mosture Nutrients Soil pH<4.8 or>8.5 not suitable Soil texture increased decomposition Other factors like toxic level elements

77. Role of organic matter in plant growth It creates granular structure It increases the water holding capacity of soil It can be used as a mulching material It is a reservoir of nutrient It is helpful in soil reclamation Store house of exchangeable ion

78. Ion Exchange The process by which ions are exchanged between solid and liquid phase or between solid p hase if in close contact with each other is called ion exchange The common exchangeable cations are Ca 2+ ,Mg 2+ ,H + ,K + . The common are SO 4 2- , Cl - & PO 4 2- . Exchange of cation is called cation exchange and exchange of anion is called anion exchange. Mechanism of cation exchange Calcium is added to an acid soil the following reaction takes place

79. Similarly when H + is added to the soil solution through the decomposition of organic matter or through acidic martials Ca 2+ is replaced from the exchange complex by H + . Cation exchange capacity (CEC) The sum total of the exchangeable cations that a soil can adsorb is called as cation exchange capacity Itisalso defined as theamountofcationic speciesbound at p H 7.0. Some author consider p H 4.0 as the appropriate point. Unit is centi mole/Kg Anion exchange process OH >H 2 PO 4 >Sulphate>Nitrate>Chloride

80. Anion exchange capacity The capacity ofsoil to hold anion is called aniom exchnage capacity Microcell Cation heldonsmall particles of clay andorganicmatterisknown as microcell The sum of exchange cation that the soil can absorb Sand :Capacity 0-5 Lumy soil :10-10.5 Acidoids (acid forming minerlas ) Aluminium and hydrogen basoids (base forming minerals) Ca,Mg,Na

81. Monovalent Lithium Sodium<potassium< Rubium<hydrogen Divalent Mg<Ca<Ba Mixtureof of monovalent & divalent Na<Potassium< Aluminium <Mg<Ca<Hydrogen

82. Factors influencing CEC Soil Texture Organic matter Nature of clay Soil reaction Significance or important of ion exchange Effect on soil fertility Availability of applied nutrients Effect of adsorbed cations Toxic ions Effect on soil p H Correction of soil problems Very helpful for soil reclamation process

83. Soil reaction (p H) The important characteristic of the soil solution is its reaction The soil reaction describes the degree of acidity or alkalinity The acidity or alkalinity is expressed in terms of concentration of H ions or OH ions the p H are used to express the concentration of Hand OH ion The term p H was introduced by Sorenson (1909) p H = -Log [H + ], based on dissociation of water where [ H + ]× [OH - ]= 10 -14 pH sale and range in soil pH Acidity Alkalinity Extreme acidity Very strongly acidic strongly acidic Moderately acidic Slightly acidic Slightly alkalinity Moderately strongly Very strongly Extreme

84. To measure soil pH – pH meter Soil water suspension ratio 1:25 In order to avoid soluble salt problems and add potassium chloride Factor affecting soil pH Presence of H 2 and aluminum ions Presence of base saturation (<80 %soil acidity ,80-905 neutral, > 90% alkaline) Nature of clay & native vegetation Exchange of ions& hydrogen fertilizers Nature of soil collids & climate Parent material and Precipitation Decomposition of organic matter& soil depth

85. Plant Nutrients Chemical elements that are essential for the proper development and growth of plants are typically referred to as plant nutrients There are 14 essential plant nutrients The primary macronutrients : nitrogen, phosphorous, potassium Secondary macronutrients: Calcium, sulfur, magnesium Micronutrients/trace minerals : boron, chlorine, manganese, iron, zinc, copper, molybdenum, nickel Macro Nutrients are consumed in plant tissue from 0.2 % to 4% on a dry matter weight basis Micro Nutrients are consumed in plant tissue from 5 to 200 ppm or less than 0.02% dry weight.

86. Process Plants take up essential elements from through their roots and from the air through leaf. Nutrient uptake in the soil is achieved by cation exchange wherein root hairs pump hydrogen ions(H+) in to the soil through proton pump. Hydrogen ion displae cation attached to negatively charged soil particles . So cation uptake by the root In the leaves stomata open to take in carbon dioxide and expel oxygen.

87. Function of nutrients Soil supplies macro and micro nutrient Macronutrients(Derived from air and water) Carbon Hydrogen Oxygen Macronutrients(Primary) Nitrogen Phosphorous Potassium Macronutrients(secondary and Tertiary) S,C,Mg Micro nutrients Iron Molybdenum Boron Copper Manganese Sodium Essential of sodium Zinc Nickel Chlorine Cobalt Aluminium Silion Photosynthesis

88. Availability of Nutrients At low pH Al,Fe , Mn (Available) Ca,N 2 ,Phosphate (Unavailable) At high PH Na ,Phosphate .Fe , Mn , ( Unavailable) Nitrogen pH (6.5-7.5) Phosphorous PH (6.5-7.5) Potassium Not affected by soil pH Alkaline –Non exchangeable condition

89. Calcium and magnesium Unavailable in soil condition Alkaline is not > than8.5 Ferrous ,Aluminium Manganese Acid soil –High ( availlable ) pH > 7.5 unavilable Sulphur Not affected soil conditions Micronutrients Soil alkaline- Cu,Zn (( unavilable ) Acid soil – molybdenum9unavilable)

90. Factors affecting nutrient availability Soil pH Organic matter Soil texture Climate Crop removal Nutrient interactions Soil mobility Plant mobility High performance varieties Manure applications Light & Temperature

91. Symptoms of nutrients deficiencies Nitrogen – Leavs are small and light green Phosphourous – Darkgreen foliage Potassium – lower leaves may be mottled calcium - young leaves die Mg - Lower leaves are yellow between veins Sulphu r- light green upper leaves Iron –new upper leaves turn yellow between vein Mn - new upper leaves have dead spots over surface Boron - Stems and petiols are britlle Nitrogen - Iight green leaf if excess darkgreen Ammonium toxicity – from ferticlizers reducedplant growth Phosphorous - plant growth will be slow if excess direct effect in plant

92. Potassium – older leaved edge will look burn called as scorch Calcium – roots and leaves turn brown Mg- Plant growth will be slow Sulphur - leaves light green to yellow Boron – Abnormal development of the growing point Chlorine – young leaves will be wilt Copper – plant growth will be slow Iron –young leaves will bleaching Mn - plants green wil be stunted Mo - Flower formation are restricted Zinc- Affected leaves

93. Chemical used for correcting nutrient deficiencies Nitrogen – green colour P- Hardly growth K- biochemical plants Ca- Activate enzymes Mg- Photosysthesis Crop nutrition and fertilizer requirement Supplied from soil and fertilizer sources of Macro and miro nutrients

94. Types of fertilizers 1.Nitrgen fertilizers Urea Ammonium nitrate Ammonium sulphate urea Ammonium sulphate Anhydrous ammona Urea –ammonium nitate solution 2.Phosphate fertilizers Mono – ammonium phosphate Ammonium polyphosphate

95. 3.Ntrogen Phosphate 4.Potash Fertilizers 5.Sulphur fertilizers Nutrient availability and mobility Precipitation – Dissolved substance form solid and drop out of solution called precipitation Distillation – the opposite process where by solidn go into solution phase and become solutes. Fixation: Elements or certain ions such as NH4 become physically and chemically bound in a nonexchangeable.

96. Thank you