What affects water movement in unsaturated soil?

Water movement in unsaturated soil is mainly affected by the attraction of solid surfaces and not gravitation.

What happens when the soil becomes saturated?

When soil becomes saturated, gravitational forces predominate.

Why doesn't water move readily into coarse sand?

Water doesn't move readily into coarse sand because the pores are larger than those in the soil above, which hold water due to greater adhesive and cohesive forces.

How do sand layers act in water movement through soil?

Sand layers act like a check valve, holding back water until the soil becomes very wet, then allowing excess water to pass through.

What is the water holding capacity of soil with coarse sand and gravel layers compared to fine sandy loam?

Soil with coarse sand and gravel layers can retain more than double the amount of water usually held in a fine sandy loam.

Ch 2. of Water Movement in Soils, Capillary Barriers and Water Movement

00:02:40

https://www.youtube.com/watch?v=eBJEP_wQSa8

Zusammenfassung

TLDRWater movement in soil during irrigation is influenced primarily by the attraction of solid surfaces rather than gravity, especially in unsaturated conditions. As soil becomes saturated, gravity takes a more dominant role. The video demonstrates how water moves horizontally and vertically, highlighting that finer soil pores hold water more effectively than coarser sandy layers due to adhesive and cohesive forces. Such sand layers act like a check valve, eventually allowing water passage as the soil wets up. An example is provided from the Columbia Basin, where fine sandy loam over coarse sand and gravel demonstrates increased water retention, supporting better plant growth.

Mitbringsel

💧 Water moves due to solid surface attraction.
🏞️ Gravity dominates in saturated soils.
🪨 Sand acts as a water check valve.
🌾 Fine sandy loam retains more water.
📈 Coarse layers improve soil water holding capacity.

Zeitleiste

00:00:00 - 00:02:40
The movement of water from an irrigation source is influenced more by the attraction to solid surfaces than by gravity, though gravity becomes more significant as the soil gets wetter. Water moves less readily into coarse sand layers due to larger pores, acting as a check valve. This principle explains water flow in filled soils, crucial for agricultural land, such as in Washington State's Columbia Basin, where fine sandy loam retains more water due to underlying coarse sand, enhancing plant growth.

Mind Map

Häufig gestellte Fragen

What affects water movement in unsaturated soil?
Water movement in unsaturated soil is mainly affected by the attraction of solid surfaces and not gravitation.
What happens when the soil becomes saturated?
When soil becomes saturated, gravitational forces predominate.
Why doesn't water move readily into coarse sand?
Water doesn't move readily into coarse sand because the pores are larger than those in the soil above, which hold water due to greater adhesive and cohesive forces.
How do sand layers act in water movement through soil?
Sand layers act like a check valve, holding back water until the soil becomes very wet, then allowing excess water to pass through.
What is the water holding capacity of soil with coarse sand and gravel layers compared to fine sandy loam?
Soil with coarse sand and gravel layers can retain more than double the amount of water usually held in a fine sandy loam.

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Untertitel

Automatisches Blättern:

00:00:12
watch as the water moves out from an
00:00:15
irrigation pearl
00:00:16
note that the movement awkward is almost
00:00:18
as great as that downward this is added
00:00:21
evident water movement is mainly due not
00:00:24
to gravitation but to the attraction of
00:00:27
solid surfaces as the soil becomes
00:00:30
wetter and wetter however gravitation
00:00:32
plays a stronger role and if the soil
00:00:35
becomes completely saturated then
00:00:38
gravitational forces predominate the
00:00:41
horizontal layer you see is coarse sand
00:00:44
one of the important principles of
00:00:46
unsaturated flow is described as you
00:00:49
witness what happens as the wedding
00:00:50
front encounters this layer of coarse
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sand the pores in the soil are many
00:00:56
times smaller than those between sand
00:00:58
grains water is held in these small
00:01:00
pores by large adhesive and cohesive
00:01:03
forces the pores in the soil are like
00:01:06
the pores in a piece of blotting paper
00:01:08
used to soak up ink the huge pores in
00:01:12
the sand cannot hold water at the
00:01:14
tensions which exist in the wetted soil
00:01:16
above so water does not move readily
00:01:20
into the sand
00:01:21
however as the soil above the sand
00:01:23
becomes very wet the water eventually
00:01:26
moves into the sand just as ink would
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drip from a blotter which is swept
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excessively the sand layers us to act
00:01:33
something like a check valve holding the
00:01:35
water back until the soil becomes very
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wet and then letting the excess pass
00:01:40
through what happens to water in soil
00:01:43
containing a sand layer is typical in
00:01:46
principle of what happens to water in
00:01:49
filled soils for sands and gravels occur
00:01:51
as layers in finer soil material a great
00:01:55
deal of agricultural land is
00:01:57
in this fashion in Washington State's
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Columbia Basin there exists a quarter of
00:02:02
a million acres of soil composed of one
00:02:04
to two feet of a fine sandy loam
00:02:06
overlying coarse sand and gravel the
00:02:10
ability of this soil to support plant
00:02:12
growth is greatly affected by the
00:02:14
presence of course fans and gravel
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because of these course materials the
00:02:19
overlying soil can retain more than
00:02:21
double the amount of water usually held
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in a fine sandy loam this is one of the
00:02:27
best soils in the Columbia Basin