Soil Water

Question 1

3 properties of water

Answer 1

1. Polar molecules
2. Hydrogen bonding
3. Surface tension

Question 2

Polarity

Answer 2

Has an electronegative and an electropositive side

Question 3

Hydrogen Bonding

Answer 3

H atoms attracted to O atom on another water molecule

Question 4

Cohesion

Answer 4

Water molecules attraction to each other

Question 5

Adhesion

Answer 5

Water molecules attraction to solid surfaces

Question 6

Surface tension

Answer 6

Cohesive forces of water molecules are greater than the attraction forces between water and air

Question 7

Capillary Movement

Answer 7

Adhesion Water will climb the tube and form a meniscus

Question 8

Capillary rise equation

Answer 8

H=0.15/pore radius

Question 9

How is capillary movement dependent on pore size distribution

Answer 9

smaller the pore size the greater the movement

Question 11

Which capillary rise is quickest but the shortest

Answer 11

Sand

Question 12

affects of soil water energy

Answer 12

-water retention and movement in soil
-uptake and movement within plants
- loss of water in atmosphere

Question 13

Basic types of energy

Answer 13

kinetic and potential

Question 14

Which energy is more important in soil

Answer 14

potential

Question 15

All substances want to move from a ______ energy state to a ______ energy state

Answer 15

Higher and lower

Question 16

Matric Force

Answer 16

Force of attraction between water and soil

Question 17

Osmotic Force

Answer 17

Attraction of water to ions or other solutes

Question 18

Gravity

Answer 18

Always pulling water downward

Question 19

Equations for potential energy

Answer 19

Pt= Pg+Pm+Po

Question 20

The _____ the potential the more energy is needed to move water

Answer 20

Lower or more negative

Question 21

Clay soils water potential and content

Answer 21

Will hold more water. but have lower water potentials

Question 22

Well structured soils have ______ water content at _____ potentials (have larger pores)

Answer 22

Higher and higher

Question 23

Gravimetric water content

Answer 23

• Mass of water per mass of dry soil
• g water/ g dry soil
• Loss of weight after oven frying (105C for 24 hours)

Question 24

volumetric water content

Answer 24

-Volume of water per given volume of dry soil
- cm^3 water / cm^3 soil

Question 25

Tensiometers

Answer 25

-measures the tension in soil
-filled with water in a porous cup
- Used in irrigation management
- Based on pressure changes
- if soil is dry water will be pulled in lowering the pressure
- if soil is wet water will pull in and increase the pressure

Question 26

Primary tool for measuring soil water potential

Answer 26

Tensiometers

Question 27

Primary methods for measuring volumetric water content

Answer 27

• Time domain reflectometry
• Electrical capacitance