Soil Science Quiz 2 Tile 5

What is the ideal soil for plant growth

• 50% solid

  • 45% minerals

  • 5% organic matter

• 50% pore space

  • 25% air

  • 25% water

How does the soil moisture change

the moisture changes as soil is saturated and then drains.

Cohesion-Tension Theory

the primary scientific model explaining how water and dissolved minerals travel upward from the roots to the leaves of vascular plants against gravity, without using metabolic energy.

Capillary Mechanism

The upward movement of water from the water table through tiny interconnected pore spaces against the force of gravity.

Gravitational Water

The water lost from a soil following drainage due to the force of gravity, the water held in the macropores.

The soil moisture saturation process

• Saturation: all pores are full of water, and gravitational water is lost.

• Field Capacity: available water for plant growth

• Wilting Point: no more water is available to plants

Field Capacity

The amount of water a soil can hold against the pull of gravity (after 24 hours). Plants can easily extract water from a soil when its moisture is at or near field capacity.

Wilting Point

Water is held tight as a thin film surrounding soil particles, adhesive forces are far greater than gravity.

Hygroscopic Coefficient

Soil water content of air-dried soil, clay colloids are the main agent for holding this water. The removal of the water at this point requires heat above 105 degrees Celsius of extreme pressures.

Plant Available water

The water that the soil will relinquish to the plant.

Wet soils

Water is loosely held and the energy is relatively high.

Dry soils

Water is held tightly by the soil solids lower.

How do soil moisture levels work with soil water potential?

Soil moisture levels are generally correlated with soil water potential.

which pores create a greater amount of suction?

Small pores

Which soils hold less water

Coarse soils

Clay soils

High water holding capacities due to the numerous small pores

Sandy soils

Low water holding capacity due to fewer micropores.

Course Textured Soils

More macropores compared to meso/micro pores, and have a high percentage of soil water is gravitational.

Fine Textured soils

More meso/micro pores compared to macro pores, and has a high percentage of soil water is being held close to the soil particles and is unavailable

Grain production and Plant available water

There is a strong connection between max yields and plant water available water.

Gravimetric Calculation

the direct measurement of soil water content