1. WATER-The Substance of Life Limits Kinds and Amounts of Vegetation on Earth Limits Growth of Cities and Kinds of Industry رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

2. EARTH’S WATER SUPPLY  70% of Earth’s Surface covered by water  97% of Earth’s water supply in oceans  Ice at Polar Caps next most abundant supply (>2%)  Groundwater next most abundant supply (~0.5%); approximately 50% of ground water is > 0.5 miles deep  Fresh water in lakes, ponds and streams ~0.008%  Soil and atmospheric water ~ 0.001%  Biological water ~0.0001%  Average annual rainfall on land ~ 30 inches رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

3. Ground water Capillary fringe zone Portion of aquifer where pore spaces are occupied with water and air (unsaturated zone) Precipitation Vadose Zone Soil-Air Interface Soil-Water Interface Evaporation Applications of soil physics are crucial to sustainable use of natural resources for agricultural and other land uses رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

4. نفوذ نزولات جوی آبیاری تبخیر و تعرق روان آب ذخیره در خاک نفوذ عمقی جریان داخلی عمق خاک رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

5. Precipitation/Evaporation P/E>0.75= Humid (Forests) P/E >0.5= Sub-Humid (Mixed Forest and Grasslands) P/E >0.25= Semi-Arid (Mixed Grasslands and Semi-Deserts) P/E <0.25= Arid (Deserts) رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

6. Soil Water Relationships رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

7. Bulk Density (  b )Bulk Density (  b ) –  b = soil bulk density, g/cm 3 –M s = mass of dry soil, g –V b = volume of soil sample, cm 3 Typical values: 1.1 - 1.6 g/cm 3Typical values: 1.1 - 1.6 g/cm 3 Particle Density (  p )Particle Density (  p ) –  P = soil particle density, g/cm 3 –M s = mass of dry soil, g –V s = volume of solids, cm 3 Typical values: 2.6 - 2.7 g/cm 3Typical values: 2.6 - 2.7 g/cm 3 رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

8. Porosity (  ) Typical values: 30 - 60% رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

9. Water in Soils Soil water content –Mass water content (  m ) –  m = mass water content (fraction) –M w = mass of water evaporated, g (  24 hours @ 105 o C) –M s = mass of dry soil, g رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

10. Volumetric water content (  v ) –  V = volumetric water content (fraction) –V w = volume of water –V b = volume of soil sample –At saturation,  V =  –  V = As  m –As = apparent soil specific gravity =  b /  w (  w = density of water = 1 g/cm 3 ) –As =  b numerically when units of g/cm 3 are used Equivalent depth of water (d) –d = volume of water per unit land area = (  v A L) / A =  v L –d = equivalent depth of water in a soil layer –L = depth (thickness) of the soil layer رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

11. Volumetric Water Content & Equivalent Depth (g) (cm 3 ) Equivalent Depth رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

12. Volumetric Water Content & Equivalent Depth Typical Values for Agricultural Soils 1 in. 0.50 in. 0.15 in. 0.20 in. 0.15 in. Soil Solids (Particles): 50% Total Pore Space: 50% Very Large Pores: 15% (Gravitational Water) Medium-sized Pores: 20% (Plant Available Water) Very Small Pores: 15% (Unavailable Water) رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

13. Water-Holding Capacity of Soil Effect of Soil Texture Coarse Sand Silty Clay Loam Gravitational Water Water Holding Capacity Available Water Unavailable Water Dry Soil رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

14. Soil Water Content Soil Moisture Content Water that may be evaporated from soil by heating at 105 0 C to a constant weight Gravimetric moisture content (w) = mass of water evaporated (g) mass of dry soil (g) Volumetric moisture content (  ) = volume of water evaporated (cm 3 ) volume of soil (cm 3 )  = w * bulk density of soil density of water Bulk density of soil (  ) = mass of dry soil (g) volume of soil (cm 3 ) رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

15. Soil Moisture Content: Methods of Measurement 1.Difficulties encountered for accurate moisture measurement in the field: 2.Soils are highly variable 3.Soil moisture is highly dynamic (spatial temporal variability) 4.Plant water uptake is highly variable depending upon the stage of growth 5.State of growth is again dependent upon nutrient application, water availability, pests etc. 6.Chemicals present in the soil can make measurements unreliable 7.Costs involved رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

16. Methods for soil water content Direct method (Gravimetric; Thermogravimetric) Indirect methods Electrical properties Radiation technique Acoustic method Thermal properties Chemical methods Electrical Conductance Dielectric constant -Neutron scattering  - ray attenuation - Gypsum blocks - Nylon blocks - Change in conductance TDR Principles underlying different methods of assessment of soil water content رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology Methods of soil water content determination

17. DIRECT Gravimetric: evaporating water at 105 0 C. Thermogravimetric: Soil sample is weighted and saturated with alcohol and burned several times until a constant dry weight is obtained INDIRECT Electrical Conductance رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

18. DIRECT Gravimetric: evaporating water at 105 0 C. Feel Method: Thermogravimetric: Soil sample is weighted and saturated with alcohol and burned several times until a constant dry weight is obtained There are many classifications for soil types and major differences within each classification Soil management can have a major impact upon these soil properties. Compaction is the major cause of error in bulk density. Advantages: ensures accurate measurements, not dependent on salinity and soil type, easy to calculate Disadvantage: destructive test, time consuming, inapplicable to automatic control, must know dry bulk density to transform data to volume moisture content, inaccurate because of soil variability http://edis.ifas.ufl.edu/ رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

19. Frequency Domain Reflectometry: radio frequency (RF) capacitance techniques Actually measures soil capacitance A pair of electrodes is inserted into the soil Soil acts as the dielectric completing a capacitance circuit, which is part of a feedback loop of a high frequency transistor oscillator As high frequency radio waves (about 150 MHz) are pulsed through the capacitance circuitry, a natural resonant frequency is established which is dependent on the soil capacitance, which is related to the dielectric constant by the geometry of the electric field established around the electrodes Two commercially available instruments using this technique: the Troxler Sentry 200-AP probe and the Aquaterr probe رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

20. The soil bulk dielectric constant (K) is determined by measuring the time it takes for an electromagnetic pulse (wave) to propagate along a transmission line (L) that is surrounded by the soil Since the propagation velocity (v) is a function of K, the latter is therefore proportional to the square of the transit time (t, in seconds) down and back along the L Time Domain Reflectometry (TDR): , 28 s K = (c/v) 2 = ((c.t)/(2.L)) 2 where c is the velocity of electromagnetic waves in a vacuum (310 8 m/s or 186,282 mile/s) and L is the length embedded in the soil (in m or ft) رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

21.  TDR determinations involve measuring the propagation of electromagnetic (EM) waves or signals  Propagation constants for EM waves in soil, such as velocity and attenuation, depend on soil properties, especially  and EC Disadvantage: Costly, not really independent of salt content The propagation of electrical signals in soil is influenced by q and EC The dielectric constant, measured by TDR, provides a good measurement of this soil water content رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

22. Time Domain Transmission (TDT) This method measures the one-way time for an electromagnetic pulse to propagate along a transmission line (L). Thus, it is similar to TDR, but requires an electrical connection at the beginning and ending of the length. Notwithstanding, the circuit is simple compared with TDR instruments. Disadvantages: Reduced precision, because the generated pulse is distorted during transmission; soil disturbance during installation; needs to be permanently installed in the field رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

23. NUCLEAR TECHNIQUES : Neutron Scattering, , 1 to 2 min With this method, fast neutrons emitted from a radioactive source are thermalized or slowed down by hydrogen atoms in the soil Since most hydrogen atoms in the soil are components of water molecules, the proportion of thermalized neutrons is related to  Advantages: can measure a large soil volume, can scan at several depths to obtain a profile of moisture distribution, nondestructive, water can be measured in any phase Disadvantages: high cost of the instrument, salinity, must calibrate for different types of soils, excess tube, radiation hazard, insensitivity near the soil surface, insensitivity to small variations in moisture content at different points within a 30 to 40 cm radius, and variation in readings due to soil density variations (error rate of up to 15 percent) رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

24. Gamma Attenuation: volumetric water content, < 1 min  This method assumes that the scattering and absorption of gamma rays are related to the density of matter in their path  The specific gravity of a soil remains relatively constant as the wet density changes with increases or decreases in moisture  Changes in wet density are measured by the gamma transmission technique and the moisture content is determined from this density change Advantages: can determine mean water content with depth, can be automated for automatic measurements and recording, can measure temporal changes in soil water, nondestructive measurement Disadvantages: restricted to soil thickness of 1 inch or less, but with high resolution, affected by soil bulk density changes, costly and difficult to use, large errors possible when used in highly stratified soils رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

25. evaporation Soil and Water رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

26. WATER CONTENT  LIQUID Gravimetric (Mass/Mass) Volumetric (Volume/Volume) Relative  VAPOR Concentration (Mass/ volume air) Pressure (KPa) Relative Humidity

27. USES of WATER in PLANTS 1. Constituent 2. Solvent 3. Reactant-product 4. Turgidity 5. Temperature Control

28. CONSTITUENT Water constitutes more than 70% of fresh weight of most plants (Seeds are exception) Between 60-90% of the water is contained in the plant cell providing both biological and physical functions. The remaining 10-40% is contained as liquid in cell walls providing a continuum between the soil supply and the living cell.

29. SOLVENT Dissolves both organic and inorganic constituents essential for life Dissolves gases-CO 2

30. REACTANT-PRODUCT Photosynthesis CO 2 + H 2 O = SUGAR Respiration CH 2 O + O 2 = CO 2 + H 2 O

31. ENERGY BALANCE Evaporation dissipates heat Condensation-precipitation releases heat Amount of water passing through plants as transpiration depends on environment and species Wheat 1000 kg H 2 O per kg dry matter Cotton 5000 kg H 2 O per kg lint

32. 1 mole water ~ 18 cm 3 contains 6.02 x 10 23 molecules 1 cm 3 ~ 3.3 x 10 22 (33 thousand billion billion) Consider a beach 1.6 x 10 6 m (1000 miles) long 200 m (656 feet) wide 200 m (656 feet) wide 100 m (328 feet) deep 100 m (328 feet) deep Volume beach = 3.2 x 10 10 m 3 sand Assume that each grain = a sphere 1 mm diameter With loose packing 10 9 (one billion) grains in 1 m 3 Entire beach 3.2 x 10 19 sand grains, 1000 < number of molecules in 1 cm 3 water It would take 1000 beaches to contain as many sand grains as molecules in 1 cm 3 of water Each water molecule is ~ 3 A (3 x 10 -10 m) It would take 33 x 10 6 layers to form a layer of water 1 cm deep. رابطه آب خاك و گیاه تكميلی حاج عباسی

33. UNIQUE PROPERTIES of WATER O HH 105 O -- ++ ++

34. H+H+ H+H+ O -- = + - H2OH2O Hydrogen bond Gives structural strength Bond depends on temperature: Higher is the temperature weaker is bond Positive end attraction with -ve end of other water molecules رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

35. رابطه آب خاك و گیاه تكميلی حاج عباسی

36. 105 0 Oxygen Hydrogen Electro positive Negative Polarity Symmetrical H-O : 0.97 A H-H : 1.54 A angstroms رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

37. O-O- H+H+ H+H+ Polymer type of grouping Cations: Na +, K +, Ca 2+ : become hydrated through their attraction to the Oxygen Anions or negatively charged clay surfaces: attract water through hydrogen رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

38. رابطه آب خاك و گیاه تكميلی حاج عباسی

39. Some definitions Adhesion - the attraction or clinging together of unlike substances Cohesion - the attraction of a substance for itself; the mutual attraction among molecules or particles comprising a substance tat allows it to cling together as a continuous mass. absorption - the process by which one substance is taken into and included within another substance, as the absorption of water by soil or nutrients by plants. adsorption - the increased concentration of molecules or ions at a surface, including exchangeable cations and anions on soil particles. flickering clusters refers to the quasicrystalline state of water molecules while in a liquid state. The molecules associate and dissociate repeatedly in transitory or flickering polymer groups. Water molecules are attracted to one another due to the hydrogen bonding that takes place between the negatively charged end of the oxygen atom in the molecule and the positively charged ends of hydrogen atoms in adjacent water molecules. رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

40. heat of fusion (ice) The amount of energy required to turn a liquid into a solid. heat of vaporization The amount of energy required to turn a liquid to a vapour (to overcome the attractive forces between adjacent molecules in a liquid). dipole moment a measure of the tendency of a polar molecule to be affected by an electrical or magnetic field (i.e., NMR - Nuclear magnetic resonance) Volumetric heat capacity is the change in the heat content of a unit volume per unit change in temperature. Specific heat is the change in the heat content of a unit mass per unit change in temperature. surface tension A molecule at the surface of a liquid is not completely surrounded by other molecules of the liquid. The forces acting upon it are unbalanced, with the result that it experiences a stronger attraction into the body of the liquid (cohesion) rather than into the less dense gaseous phase. This unbalanced force draws the surface molecules inward with and results in the tendency for the surface to contract and the molecules to be slightly denser at the surface. رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

41. sublimation the direct transition from the solid state to the vapor state hydrophobic water repellent capillary attraction - a liquid's movement over or retention by a solid surface due to the interaction of adhesive and cohesive forces. capillary fringe a zone just above the water table that is maintained in an essentially saturated state by capillary forces of lift. viscosity (centipose, cP, N s m-2 x 10-3, kg m-1 s-1). When a fluid is moved in shear (that is to say, when adjacent layers are fluid are made to slide over each other), the force required is proportional to the velocity of shear. Viscosity is the proportionality factor. It is the property of the fluid to resist the rate of shearing and can be visualized as an internal friction. Fluids of lower viscosity flow more readily. Thus oil has a higher viscosity than water. Fluidity is the reciprocal of viscosity. Viscosity is the preferred term. رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

42. Cohesive – forces of attraction between like molecules. molecules. At an air-water interface – surface tension. Adhesion – attraction of one substance for a substance of another kind. substance of another kind. Tensile strength – work that must be done to create or extend a new or create or extend a new or larger surface. larger surface. Viscosity – resistance to flow. رابطه آب خاك و گیاه تكميلی حاج عباسی

43. If water were an ordinary compound whose molecules are subject to weak forces, its boiling and freezing point would fall below hydrogen sulfide Strong hydrogen bonding between water molecules prevents this Water occurs in all three states (solid, liquid, and gaseous) at prevailing temperatures on the earth’s surface Example: Ice cubes in a glass at room temperature رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

44. Why water wets clean glass?  Surface of glass has O and unpaired electrons  Water molecules form hydrogen bond  Force stronger than gravity  Surface of grease has no O and free electrons  Water molecules cannot form hydrogen bond  Therefore, water do not stick Why water does not stick to glass surface coated with grease? رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

45. Forces acting on a water molecules A B Consequently, there is a net downward force on the surface molecules, and result is something like a compressed film at the surface. This phenomenon is called surface tension Air Water Air-water Interface At point B: Forces acting on water molecule are equal in all direction At point A: Attraction of air for water molecules is much less than that of water molecules for each other. رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

46. The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tensioncohesive The molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. This forms a surface "film" which makes it more difficult to move an object through the surface than to move it when it is completely submersed.molecules at the surface Surface Tension  Surface tension is typically measured in dynes/cm. The force in dynes required to break a film of length 1 cm  Equivalently, it can be stated as surface energy in ergs/cm 2  Water at 20°C has a surface tension of 72.8 dynes/cm compared to 22.3 for ethyl alcohol and 465 for mercury رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

47.  Solid  Liquid  Gas Contact Angle Liquid and gas (air) in contact with solid Interface between air and water forms a definite angle “contact angle” Solid Air L  sa >  sw ; cos  = + or  < 90 0 Angle of contact is acute in a liquid that wets the solid Solid Air L Angle of contact is obtuse (between 90 and 180) in a liquid that does not wet the solid Young’s equation رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

48. Hydrophilic Versus Hydrophobic Soils When the adhesive forces between water molecules and an object are weaker than the cohesive forces between water molecules, the surface repels water and is said to be hydrophobic. Hydrophobic soils restrict the entry of water, which 'balls up' or sits on the soil in beads rather than infiltrating the soil. Hydrophobic soils exhibit an obtuse (greater than or equal to 90 o ) wetting angle that causes capillary repulsion, so preventing water from entering soil pores Hydrophilic or normally wettable soils display an acute (less than 90 o ) angle of contact with water, allowing infiltration. adhesive forces between water molecules and an object are stronger than the cohesive forces between water molecules رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

49. By adhesion, solids hold water molecules rigidly at their soil-water surface Gravity Capillary Capillary Fundamentals and Soil Water Cohesion: Attraction of molecules for each other Adhesion: Attraction of water molecules for solid surfaces Together it is possible for soil solids to retain water and control it’s movement By cohesion water molecules hold each other away from solid surfaces رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

50. Dipolar Bonding in Water The dipolar interaction between water molecules represents a large amount of internal energy (the energy associated with the random, disordered motion of molecules) and is a factor in water's large specific heat (the amount of heat per unit mass required to raise the temperature by one degree Celsius). internal energyspecific heat The dipole moment of water provides a "handle" for interaction with microwave electric fields in a microwave oven.dipole moment Microwaves can add energy to the water molecules, whereas molecules with no dipole moment would be unaffected. رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

51. Water rises in the capillary against the force of gravity !!!! What happens if there is no force of gravity !!!!! Water رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

52. Capillary Mechanism Water Rise continues till: Weight of water in the tube (force of gravity) = Total cohesive and adhesive forces 2 r 1 h1h1 h2h2 2 r 2 رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

53. Force of gravity = Mass of water column * Acceleration = (volume of water * density) * g = (  * r 2 * h) *d w * g …………(A) Total cohesive and adhesive forces = (perimeter) * surface tension = 2 *  * r *  …………(B) Water 2 r h At equilibrium: A = B (  * r 2 * h) *d w * g = 2 *  * r *  use  = 72.75 dynes/cm d w = 0.9982 g/cm 3 g = 980 cm/s 2 Show رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

54. This relationship tells us that:  Capillary rise is higher in small pores r = 0.1 cm; h = 1.5 cm r = 1.0 cm; h = 0.15 cm r = 10 cm; h = 0.015 cm Radius Capillary Rise If two principle radii r 1 and r 2 رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

55. The inverse relationship between height of rise of water and radius of soil pores may not be always valid:  Soil pores are not straight uniform openings as a tube  Some soil pores may entrap air and slow down the capillary rise Tortuous flow paths of water Soil solids Entrapped air water رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

56. Adsorbed water Capillary water Enlarged soil particles or aggregates Two forms of water in soil Soil solids tightly absorb water Capillary forces hold water in capillary pores رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

57. Height (cm) Time (days) Clay compacted Loam Sand Brady,1984 رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

58. UNIQUE PROPERTIES of WATER  TEMPERATURE RELATIONS –Heat of Vaporization = 540 cal/g@100C 2.45 MJ/kg –Heat of Fusion = 80 cal/g@0C –Heat Capacity = 1.0 cal/g –Thermal Conductivity = High

59. رابطه آب خاك و گیاه تكميلی حاج عباسی

60. رابطه آب خاك و گیاه تكميلی حاج عباسی

61. UNIQUE PROPERTIES of WATER  DENSITY –0.9998 g/cm 3 at 0 o C –1.0 g/cm 3 at 4 o C –0.9956 g/cm 3 at 30 o C

62. Temperature range in liquid phase for H + compounds 100 50 0 -50 -100 050 Molecular Weight Temperature ( 0 C) 100 H2OH2O H2SH2S H 2 Se H 2 Te Boiling point Freezing point Hydrogen sulfide Hydrogen selenide Hydrogen telluride (2+16=18) (2+32=34) (80) (130) رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

63. Does water swell and shrink with Temperature? 1 0.998 0.996 0.994 0.992 0.990 -100 10 20 304050 Density (g cm -3 ) Temperature ( 0 C) 40C40C رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

64. رابطه آب خاك و گیاه تكميلی حاج عباسی

65. رابطه آب خاك و گیاه تكميلی حاج عباسی

66. UNIQUE PROPERTIES of WATER  SOLVENT –Small Size –Polar characteristics –High Dielectric Constant

67. UNIQUE PROPERTIES of WATER  Transparent to Visible Radiation (400-700nm)  Highly Absorbent in Infra-Red (>1000 nm)

68. UNIQUE PROPERTIES of WATER  HIGH SURFACE TENSION –Adhesion –Cohesion –Tensile Strength ( >30MPa ~4000#/in 2 )

69. UNIQUE PROPERTIES of WATER  IONIZATION –Only 1 molecule out of 55 x 10 7 is ionized pH ~ - Log (H+)

70. CH4 NH3 H20 C2H6 C5H12 C6H16 C4H30 MP5.5 91- 130- 172- 0 78- 184- BP 251 98 36 36- 100 33- 161- MW 198 100 72 30 18 17 16 مقايسه‌ نقطه‌ ذوب‌ (MP) نقطه‌ جوش‌ (BP ) ووزن‌ ملكولي‌ (MW ) چندين‌ ماده‌ با آب‌ رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

71. Fig. 1. Temperature range of various hydride groups. Properties of Water رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

72. باوجوداينكه‌ وزن‌ ملكولي‌ آب‌ نسبتا كم‌ است‌ ولي‌ مقاومت‌ پيوند هيدروژني‌ وساختمان‌ دروني‌ آن‌ باعث‌ شده ‌تا دردرجه‌ حرارت‌ طبيعي‌ بصورت‌ مايع‌ باشد نه‌ بصورت‌ بخاربدين‌ معني‌ كه‌عناصري‌ با وزن‌ ملكولي‌ تقريبا شبيه ‌به‌ آب‌ در درجه‌ حرارتهاي‌ بسيارپايين‌ ذوب‌ مي‌ شوند ويابجوش‌ مي‌ آيند از طرف‌ ديگر عناصرديگربايد وزن‌ ملكولي‌ بسياربالايي‌ داشته ‌باشند تا بتوانند دردرجه‌ حرارتهاي‌ ذوب‌ ياجوش‌ آب‌ ذوب‌ يا بحالت‌ جوش‌ درآيند يعني‌ آب‌ درحالت ‌مايع‌ مانند ملكولهاي‌ بسيارسنگين‌ عمل‌ مي‌ كند. رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

73. COLLIGATIVE PROPERTIES of AQUEOUS SOLUTIONS PROPERTYPURE WATER1.O M SOLUTION 1. Vapor Pressure 0.61 KPa@O o Decreased according 101.3 KPa@100 o to Raoult’s Law 2. Boiling Point 100 o C 100.52 o C 3. Freezing Point 0 o C -1.86 o C 4. Osmotic Potential 0 -2.27 MPa 5. Chemical Potential 0 Decreased

74. WATER VAPOR TEMP o C CONCENTRATION G M -3 MOLE FRACTIONPRESSURE kPa -102.3580.002560.260 04.8470.006030.611 109.3990.012111.227 2017.300.023072.337 3030.380.041874.234 4051.190.072817.378 5083.060.121812.34

75. Vapor pressure=4.62 x10 -4 v d T DRY AIR = 1. 205 Kg m -3 SATURATED AIR = 1.194 Kg m -3

76. Wet bulb Dew Point

77. RAUOLT’S LAW e = e o N w N w +N s e= Vapor Pressure of solution e o = Vapor Pressure of pure water N w = moles of solvent N s = moles of solute

78. OSMOTIC PRESSURE Van’t Hoff equation  = N s RT V  = osmotic pressure in Mega Pascals N s = moles of solute R= gas constant (0.0083 L MPa /mol @273 o ) T= absolute temperature V= volume of solvent in Liters (RT= 2.272 @) 0 o C &2.437 @ 20 o C literMPamol -1)

79. CHEMICAL POTENTIAL of WATER in a SOLUTION A measure of the ability of WATER to do work  G o = partial molal Gibb’s free energy  G o = -RTlnK (K = equilibrium constant) A B  G Negative = Spontaneous  G Positive = Additional Energy Required

80. CHEMICAL POTENTIAL of WATER µ w -µ w o = RT lnN w µ w = chemical potential of water in solution (Jmol -1 ) µ w o = chemical potential of pure water R= Gas constant = 8.314 J mol -1 K -1 T= Absolute temperature N w = mole fraction of water in solution-can be replaced by ln e/e o

81. WATER POTENTIAL (PRESSURE UNITS)  w = RT ln e/e o V w The water potential of a solution is decreased by those factors which reduce the vapor pressure 1. Addition of solutes (Osmotic) 2. Matric forces ( Interfacial Adhesive Forces) 3. Reduction in Temperature 4. Tension

82. WATER MOVEMENT Flux J w (moles per meter 2 per second) = Concentration Gradient ( -  mols  Distance   * Diffusion Coefficient (D W )  LIQUID STATE Potential Gradient Hydraulic Conductivity (Cells 7 x 10 -13 ms -1 ) (Soil 10 -2 – 10 -10 m 2 sec -1 ) VAPOR STATE Vapor Pressure Gradient Diffusion Coefficient (2.4 x 10 -5 m -2 s -1 ) Resistance

83. Forces that affect movement of water into the soil Gravity: a constant force that pulls the water downward Cohesion: attraction of water molecules for each other. It is the force that holds a droplet of water together Adhesion: attraction of water molecules to other substances. This force causes water molecules to adhere to other objects, such as soil particles Placing a drop of water on a piece of newsprint paper Force of adhesion between the water molecules and the paper molecules is greater than the force of cohesion that holds the water molecules together The water droplet spreads out and soaks into the paper Placing a drop of water on a piece of waxed paper Force of adhesion between the water molecules and the paper molecules is lower than the force of cohesion that holds the water molecules together The water droplet remains intact رابطه آب خاك و گیاه تكميلی حاج عباسی Isfahan University of Technology

84. TOTAL WATER POTENTIAL  W =  p – (   +  m +  g )  W = Total Water Potential  p = Pressure Potential   = Osmotic Potential  m = Matric Potential  g = Gravitational Potential

85. WATER POTENTIAL  SOIL SYSTEM Matric Forces Surface Tension Electrostatic Association Osmotic  PLANT SYSTEM Surface Tension Cohesion Osmotic Pressure

86. DIFFUSION COEFFICIENTS (10 -5 M 2 S -1 ) TEMPERATURE o C H 2 O VAPORCO 2 02.131.33 102.271.42 202.421.51 302.571.60 402.721.70

87. Physical Properties of Water Liquid phases in soil and plant are similar Liquid phases in soil and plant are similar In both systems the liquid is a solution of In both systems the liquid is a solution of water and dissolved substances water and dissolved substances Physical properties of water Physical properties of water رابطه آب خاك و گیاه تكميلی حاج عباسی