HOW WATER MOVES THROUGH SOIL When Rainfall Hits

HOW WATER MOVES THROUGH SOIL

When Rainfall Hits the Earth It can either:

1) Runoff the Land

2) Move through the Soil

Infiltration – the downward entry of water into the surface of soil or other materials.

How does water infiltrate into the soil? Through the pore space in the soils. Soil Particle Pore Space

About ½ of the soil volume is solid particles About ½ of the soil volume is pore space

The amount and size of pore space affected by: 1. Texture 2. Structure 3. Activity of Beneficial Soil Organisms

TEXTURE

The quantities of large and small spaces directly affect plant growth.

STRUCTURE Soil structure describes the arrangement of the individual soil particles, and therefore, the arrangement of soil pores between them.

Paths of water flow through soils with granular, prismatic, subangular blocky, and platy structure, respectively

Compacted Soils Lost pore volume

BIOLOGICAL ORGANISMS � The burrowing activity of earthworms and other invertebrates creates channels (large spaces) that allow rapid flow of water into or through soil.

� Organic matter acts as the “glue” to hold the frame work of soil particles and pores together in place, allowing the infiltration of air and water, and may hold as much as twice its weight in water. � Fungi and bacteria also produce substances that help bind soil particles together; keeping them in place.

Vegetative Cover

Once in the soil, the water movement is affected by one of two forces: � Gravity � Capillary Action

Gravity � � Pulls the water downwards. Largely occurring in the large pore spaces. � Primary force once the soil becomes saturated (all the pore spaces full of water). � Relatively rapid

Capillary Action � Refers to the attraction of water to: � Itself (cohesion) � Other solid surfaces (adhesion) � Can move in all directions � Occurs in the small pores � Primary force when soil unsaturated (all the pore spaces are not full of water). � Relatively Slow

QUESTIONS?