Soil - Plant / Water Relations

Question 1

Saturation

Field Capacity

Permanent Wilting Point

Answer 1

• saturation
  
  • soil water content when all soil pores afre full
• Field Capacity
  
  • soil water content after free drainage has essentially ceased
• Permanent Wilting Point
  
  • soil water content where plants will not recover when soil is moistened or plants placed in humid chamber

Question 2

Gravitational Water

Plant Avail Water

Answer 2

• GW
  
  • water that moves in response to gravity
• Plant Avail
  
  • water that can be extracted from soil from plants
  • maximum value
    
    • field capacity minus permanent wilting point

Question 3

Evapotranspiration

Answer 3

• the evaporation of water from soil surface plus transpiration of water from plant surfaces

Question 4

Evapotranspiration Rate

(ET)

Answer 4

• ET
  
  • the relative humidity gradient from a leaf or soil surface to some point in the atmosphere
  • and the resistance to water moving from surface to the atmosphere
• Any factor that increases the gradient or decreases the resistance, increases ET
  
  • increase in gradient
    
    • wind (hot air across leaves)
    • low humidity increases ET
  • Temperature increases ET increases
  • Solar Radiation increases ET
• Plant Avail Water - as soil dries, transpiration will start to decrease.

Question 5

ET with maturing Plants

Answer 5

• as plants mature, canopy increases, root volume increases
  
  • transpiration higher percentage of ET
  • after maturity, ET declines

Question 6

Excessive Moisture Plant Nutrient Uptake

Answer 6

• generally cuses a decrease in nutrient uptake (except for rice)
  
  • plant root metabolism declines dur to lack of O₂
    
    • some nutrients are leached (NO₃-) (SO₄²)
    • NO₃^-

Question 7

Moisture Deficiency Plant Nutrient Uptake

Answer 7

• moisture deficiencies cause declines in nutrient uptake
  
  • root growth low
  • movement of nutrients low
  • nutrients left out of solution