Water in The Soil-Plant System

Question 1

Imports and exports of soil water

Answer 1

Rainfall, precipitation, evapotranspiration, groundwater flow…

Question 2

What does water movement depend on?

Answer 2

Conc grad, gravitational, pressure, solute and matric

Question 3

Porosity as a water store…

Answer 3

Adhesion/Cohesion properties of clay/colloidal material

Question 4

Clay and humus in storage…

Answer 4

Determine surface are for which soil can be held

Question 5

Pore in storage…

Answer 5

Amount/proportions/continuity

Question 6

Water Potential

Answer 6

Relative energy level of water in a volume of soil, being 0 when saturated, water potential decreasing as soils dry

Question 7

Modes of water movement…

Answer 7

Evapotranspiration
Soils gradients

Question 8

What does soil water flow rate depend on?

Answer 8

Gradients in height, pressure, solutes and soil wetness, surface friction or poor constriction

Question 9

Hydraulic Conductivity

Answer 9

Ease of water movement through pores

Question 10

Saturated FLOW

Answer 10

Stronger capillary/surface forces in small pores, little flow until pressure forces movement, improving water holding capacity, impeding drainage

Question 11

Darcy’s Law

Answer 11

This says flow of a liquid at any point is given by fluid pressure gradient, viscosity of the fluid and effective permeability

Question 12

What is total water potential a sum of?

Answer 12

Gravity, pressure, matric and solutes

Question 13

Importance of gravity/pressure?

Answer 13

Drives water movement, osmotic effect, suction or tension on water surfaces

Question 14

Matric Potential

Answer 14

Binding of water to materials and enclosure in capillaries/other fine pores

Question 15

Relationship of water potential and water content…

Answer 15

Proportional

Question 16

Where are water vapor gradients most common?

Answer 16

Leaf/Soil surface
roots

Question 17

Where is saturated flow?

Answer 17

Dominates beneath water table, flooding soils, and irrigation/heavy rain infiltration

Question 18

Where is unsaturated flow?

Answer 18

Air obstructs it in largest pores, thus flows through the smallest pores remaining filled with water

Question 19

What does field capacity?

Answer 19

Upper limit of which water is useful to plants: permanent wilting point with further drying

Question 20

Where does transpiration dominate?

Answer 20

Drying soils, low evaporation due to uncoductivity and dryness, with large surface area allowing dominant transpiration