Chapter 5, 6 - Soil water

Question 1

soil water

Answer 1

water in the soil; a solution, includes nutrients, etc.

Question 2

atom

Answer 2

smallest unit of an element that retains the properties of the element

Question 3

molecule

Answer 3

two or more atoms together (H2O)

Question 4

ionic bonds

Answer 4

attraction between oppositely charged ions

Question 5

covalent bonds

Answer 5

sharing of electrons between atoms

Question 6

ion

Answer 6

a charged atom (+ or -)

Question 7

polar molecule

Answer 7

molecule with unequal charge distribution which creates slightly positive and negative sites on a molecule

Question 8

hydrogen bonds

Answer 8

H in one molecule will adhere to on O in a different molecule; a weak bond

Question 9

cohesion

Answer 9

likes adhered to likes (water to water)

Question 10

adhesion

Answer 10

likes adhered to unlikes (water to solid surfaces, like sand, silt, clay)

Question 11

surface tension

Answer 11

more attraction of water to water than water to air; water loves to be w/ water; creates a small skin of tension; causes water to boil at ta higher temp than alcohol

Question 12

capillary movement

Answer 12

movement of water through pores or tubes (capillaries) due to adhesion and cohesion

Question 13

influences on capillary movement

Answer 13

• pore size (the bigger the size, the slower going up, the faster going down)
• quantity of pores
• distribution of pores (lined up or more random)

Question 14

kinetic energy

Answer 14

energy being used

Question 15

potential energy

Answer 15

energy stored, not being used

Question 16

wet soil potential vs. dry soil potential

Answer 16

wet = high potential; dry = low potential
low because water molecules are held tightly by dry soil, wet soils hold less tightly because it’s already full, so water moves through

Question 17

soil water potential

Answer 17

the amount of H2O movement that will occur in the soil, how much water can move from one place to another; pure water is baseline for calculation

Question 18

energy of water is influenced by 3 factors (3 types of water potential)

Answer 18

• gravitational potential
• matric potential
• osmotic potential

Question 19

gravitational potential

Answer 19

• makes water move
• positive energy potential
• the force of gravity on water

Question 20

matric potential

Answer 20

• effects of attractive forces betwene water and soil solids (SSC,OM)
• soil solids tend to be a negatively-charged material, so water clings and slows its movement
• always a negative potential, reducing potential energy (water movement)

Question 21

osmotic potential

Answer 21

• presence and quantity of solutes in the soil water
• solutes in the form of ions (usually)
• reduces movement of water (negative energy, slows it down)

Question 22

gravitational water

Answer 22

Excess water from rain or irrigation that temporarily fills the macropores, then drains. Considered unavailable to plants.

Question 23

field capacity

Answer 23

Remaining water after gravitational water has drained away.

Question 24

permanent wilting point/percentage

Answer 24

When plants are unable to recover at night from daytime wilting. Plant is unable to pull enough water from colloids because it is held too tightly. Remaining water in soil is considered unavailable to plants.

Question 25

Plant available water

Answer 25

between the field capacity and permanent wilting point

Question 26

hygroscopic coefficient

Answer 26

last portion of water that holds so tightly it resists evaporation

Question 27

osmosis

Answer 27

movement of water through a semi-permeable membrane, from a high concentration to a lower concentration

Question 28

saturated flow

Answer 28

• all pores are full of soil water
• important in recharging ground water
• high potential energy
• influenced by:
• • gravity
• • size/arrangement of macropores
• • soil texture and structure
• • water pressure (amt of h2o above)

Question 29

preferential flow

Answer 29

easy/fast movement through cracks, biopores, large macropores
* bad aspect - can lead to moving chemicals to the ground water (not getting filtered)

Question 30

unsaturated flow

Answer 30

at field capacity

• micropores have water, macros have air/gasses
• after saturated flow is over
• soil water will move due to matric potential
• water moves from moister micropores to drier micropores
• water can move in any direction due to capillary action

Question 31

water vapor movement

Answer 31

water vapor moves from more moist soil to drier soils (high energy to lower energy)
* influenced by temperature

Question 32

hardpan

Answer 32

layer of soil that inhibits root growth and water movement, usually a compacted layer

Question 33

perched water table

Answer 33

saturated layer of soil sitting on a different textured (or structured) layer

Question 34

infiltration

Answer 34

process of water entering the soil becoming soil water

• initially fast, then slows as pores fill up
• influences:
• • texture type of soil
• • soil covering: mulch, turf, ground covers
• • topography

Question 35

percolation

Answer 35

movement of water downward through the soil (after enters the soil and becomes soil water/solution)

• influences:
• • porosity
• • texture/structure
• • amount of water (water weight)

Question 36

evaporation

Answer 36

water lost as vapor