Soil water, potential and flow

Question 1

What ate 7 things determined by soil-water interactions?

Answer 1

1. Balance between air and water in soil pores.
2. The rate of water loss by leaching, runoff, and evaporation.
3. The capacity of soil to store and provide water for plant growth and other biological activities.
4. The rate and kind of metabolism for soil organisms.
5. The rate of change in temperature.
6. The continuity of soil formation and development
7. The ability of the soil to withstand mechanical stresses

Question 2

What is energy in terms of soil water content?

Answer 2

Energy is the capacity to do work.

Question 3

What is potential energy and how is it calculated?

Answer 3

Energy a body contains due to its position.
Potential Energy = mass x energy x height.

Question 3

What is kinetic energy =

Answer 3

Energy a body contains due to it’s motion.

Kinetic Energy =
1/2 (mass x velocity^2)

Question 4

Is the total energy state of water defined by its potential or kinetic energy?

Answer 4

potential energy

Question 5

What is water in a standard state?

Answer 5

Water in a standard state in pure (no solutes), free water, (no external forces other than gravity) at some reference pressure (usually atmospheric pressure), reference temperature and reference elevation.

Question 6

Is water hydrostatic under saturated or unsaturated conditions?

Answer 6

Saturated conditions.

Question 7

What is soil water retention?

Answer 7

It is the ability of the soil to retain water against the pull of gravity.

Question 8

What is the saturated soil water retention condition?

Answer 8

It is when the soil retains water above the gravitational pull due to flow impediment thereby creating water lodging effects.

Question 9

What is the unsaturated water retention condition dependent on?

Answer 9

Matric potential

Question 10

What are capillary and adsorptive forces?

Answer 10

Capillary forces draw water up and adsorptive forces bind water to clay mineral surfaces and to cations in solution.

Question 11

What is the formula to determine Plant Available Water (PAW)?

Answer 11

Filed capacity (FC) - Permanent wilting point (PWP)

Question 12

What is Field capacity (FC)?

Answer 12

FC is soil water content after 2- 3 days of draining without the influence of evaporation.

Question 13

What is Permanent Wilting point (PWP)?

Answer 13

It is soil water content at which 50% of the plants will permanently wilt.

Question 14

What does water infiltration determine?

Answer 14

It determines how much water from rainfall, snowmelt, irrigation, or a spill will enter the soil and how much becomes runoff.

Question 15

What is the soil’s infiltrability or infiltration capacity?

Answer 15

It is the rate of water infiltration at the surface of the soil.

Question 16

What is the steady infiltration rate?

Answer 16

Infiltrability reaches a constant rate after a prolonged period known as steady infiltration rate.

Question 17

What is the preferential flow of water movement?

Answer 17

It describes the rapid flow of water through large pores in the soil via direct pathways that constitute only a fraction of the soil’s total volume. Ex: Big cracks in the soil due to the swelling and shrinking of clay, burrowing animals, and human activity.