Better Farming Series 04 - The Soil: How the Soil is Made up (FAO - INADES, 1976, 37 p.) Water in the soil (introduction...) Circulation of water in the soil Practical advice

Better Farming Series 04 - The Soil: How the Soil is Made up (FAO - INADES, 1976, 37 p.)

Water in the soil

· To live, a plant needs water
(see Booklet No. 2, page 26).
When plenty of rain falls, the harvest may be good.
But when very little rain falls, the harvest is bad.
To get a good harvest, there must be enough water.

· A plant needs water every day.

But it does not rain every day.
When it does not rain, the plant must be able to find water in the soil.
Thus the soil must build up reserves of water.
Good soil builds up reserves of water and gives it back to the plant when necessary.

Good soil builds up reserves of water and gives it back to the plant when neccesarry

Circulation of water in the soil

· Water goes from above downward during the rainy season.

Water enters easily into soil which has a good structure.
It also enters easily into light soils.
Water enters badly into a soil which has a bad structure, into soil which is too dense.

· Water goes from below upward during the dry season.

Let us make an experiment.
Put a little water in a plate.
Take some lumps of earth from three different fields.
Put these lumps in the plate.

What do we see?

In each of the lumps the water rises higher than it is in the plate.
In the same way, the water rises from the wet subsoil up to the roots.
In some lumps the water rises more quickly.
In clay soils the water rises more quickly than in silty soils.

· In soils with a good structure, water rises more quickly than in soils with a bad structure.

If the structure of the soil is good, the water goes in better and stays there; the earth builds up reserves.
A clay soil holds water better than a sandy soil.
When it rains a lot the water may sink very deep into the earth.
If it meets an impermeable layer of soil, it remains there.
When we dig a well, we may find this water.

In the dry season; In the rainy season

· Water goes sideways.

Let us make a hole in the earth and then pour water into the hole.
The water goes into the hole from above downward, but it also makes the sides of the hole wet.
In the soil water also goes sideways.

Practical advice

Practical advice

To get good reserves of water in the soil, it is necessary to:

· improve the soil structure, by adding organic matter such as manure and the remains of plants.

The organic matter becomes humus.

· work the soil, since water does not go into soil that is too dense.

Working the soil at the beginning of the rainy season enables the soil to put a lot of water into reserve.