Soil Physics I

Card Set Information

Author:
MRK
ID:
282941
Filename:
Soil Physics I
Updated:
2014-10-07 21:58:48
Tags:
Bulk Density texture sampling
Folders:

Description:
Stuff for examination I
Show Answers:

Home > Flashcards > Print Preview

The flashcards below were created by user MRK on FreezingBlue Flashcards. What would you like to do?


  1. 3 Theories of Sampling
    • 1. Representative
    • 2. Scale appropriate for property
    • 3. Doesn't change with storage
    • 4. Statistics
  2. Diameter (USDA) for sand silt and clay
    • Sand: 2 - 0.05 mm
    • Silt: .05 - .002 mm
    • Clay: < .002 mm
  3. Preparation for texture analysis by dispersal
    • Remove OM with H2O2
    • Remove CaCO3 with HCl
    • Deflocculate clay with Na+ and shake
  4. Assumptions when using Stoke's Law
    • 1. particles are spherical (nope)
    • 2. particles are large enough not to be affected by Brownian motion (nope)
    • 3. All particles have density 2.6-7 (nope Fe is higher)
    • 4. Particles don't interfere with each other
    • 5. Flow is Laminar around particles (turbulence)
  5. Stokes Law
    • Fr + 6πηru
    • Fr = frictional force
    • π = pi
    • η = viscosity
    • r = radius
    • u = velocity
  6. Soil Health
    • capacity for a soil to function:
    • to sustain biological productivity
    • to attenuate environmental contaminates, pathogens and offsite damage
    • to promot plant and animal health
  7. Three Facets of soil:
    • Physical
    • Biological
    • Chemical
  8. Inherent v. Dynamic soil qualities
    • Inherent: can't change, parent material
    • Dynamic: properties that change with use
  9. Biological aggregate formation
    • 1. fungi excreating polysaccarhides
    • 2. earthworm casting and slime
    • 3. Root exudate (helps to feed fungi)
  10. Mechanical aggregate formation
    • Inorganic cementing agents: clay, CaCO3, iron and Al
    • Climate: wetting/drying // freeze/thaw (forms and breaks)
    • Tillage impact: mostly neg. large -> small
  11. brake down of surface aggregates
    • falling rain drops
    • abrasion by water & sediement
    • air entrapment
    • slumping
    • compaction
    • Crusting
  12. Which soil conditions are most susceptable to crusting
    • low OM
    • Silt
    • Smooth surface
    • bare surface
  13. Ways to improve soil structure
    • Biological: keep things growing longer
    • Physical: No till, controlled traffic
    • Chemical: soil conditioners
  14. Types of soil conditioners
    • wetting agent (apply fertilizer)
    • hydrophobic agent (stabilize agregetes)
  15. Soil compression
    • Compaction: in ag
    • Consolidation: in engineering, extruding water
  16. Factors affecting compaction
    • wetness
    • texture (sandy loam is highest)
    • OM
    • -Proctor test water x BD
  17. what is changed by compation
    • BD
    • particle orientation
  18. 4 types of soil structure measurement
    • 1. field agg. shape and size
    • 2. Amount and size of pores
    • 3. Wet agg. size and shape (sieving and stability)
    • 4. Dry Agg. size and shape (wind eroison)
  19. particle density
    mass oven-dry soil/volume of soilds
  20. total porosity
    • volume of pores/total volume bulk soil
    • 1-(BD/PD)
  21. Gravimetric water content
    • mass water/mass oven dry-soil
    • = % water by weight
  22. water content volumetric
    • volume water/total volume bulk soil
    • % water by volume
  23. volumetric water content to gravimetric
    Wv = Wg(BD)/density of water(1)
  24. air filled P.S.
    total porosity - water-filled porosity
  25. Measurements of water eriosion
    • sieving wet
    • rain drop towers
    • rainfall simulators
  26. measurements of wind erioson
    • drop shatter
    • crushing
  27. Measurements of crusting
    • needle penetrometer
    • modulus of rupture (cookies over fulcrum)
    • seedling emergence
    • button test
  28. Cover crops can reduce NO3- out tile drains by
    40-60 % if established well
  29. Air-water Permeability ratio
    • Good for measuring speic tanks
    • larger number = more break down
  30. More earthworms in NT v. CT
    • mulch protection
    • foodsource available for longer
    • Not physically disturbed
  31. Assessing compaction
    • BD but more
    • penetrometer for root growth b/c particle orientation changes- more random
  32. Proctor Test apparatus
    • To determine water content at max BD
    • For engieering strength and ag to avoid
    • gravimetric water content increases then falls off
    • More OM-> shifts curve down and left (density is reduced)
    • peak usally at 85% water filled P.S.
  33. Clod BD often gives higher BD, WHY?
    • saran isn't water proof
    • clods can dry out
    • smashing of clods
  34. Thermal Conductivity
    • amount of heat transfered thru a unit area per time
    • lamda = cal/cm sec ˚C
  35. heat capacity (c)
    • specific heat
    • energy needed to raise 1 g one C
  36. find cm of water in profile with gravimetric water and BD
    • convert to volumetric water content (*BD/1)
    • multiply volumetric water by depth of that layer
    • add up answers
  37. Calc BD from experiment
    • Find volume by using wt & density of saran to calc its volume
    • subtract that from g or cm3 of water displaced
    • then find oven dries wt.
  38. Heat flow equation
    • =-K(∆T/∆Z)
    • K = thermal conductivity (cal/cm sec ˚C)
    • do top minus bottom to get right sign
    • or right minus left
  39. 3 soil properties / processes affected by compaction
    • Bulk density increases
    • Air/water flow reduced
    • Poorer structure
  40. Heat capacity (heat required to raise x)
    the math
    • 1. Determine fractions of each part (solids = BD/PD, H20 by volume)
    • 2. Calc Cvtotal = Faction*heat capacity for each part + => cal/cm3 ˚C
    • 3. Heat req. = Ctotal x Volume x ∆Temp

What would you like to do?

Home > Flashcards > Print Preview