|Better Farming Series 04 - The Soil: How the Soil is Made up (FAO - INADES, 1976, 37 p.)|
|What is soil made of ?|
Sand is found everywhere.
Rain carries sand into hollows and streams. It is then white- or yellow and shining because it is clean.
In the soil, sand is grey and does not shine, because it is mixed with earth.
Let us take a closer look at some sand.
It is made up of little grains.
These grains are not all alike.
They are very hard. If you rub a piece of iron with them, they scratch the iron because sand is harder than iron.
Grains of sand
· Sand is permeable.
Take a can.
Make a hole in the bottom of it.
Fill the can with sand.
If you pour water on to the sand, it goes through.
If you pour water on to the sand, it goes through
We say sand is permeable because it lets water through.
· Sand is unstable.
Take some dry sand in your hand and let it run gently.
The grains slide over each other; you cannot make a ball of sand.
Sand runs like water
· Sand in the soil.
Almost all soils contain sand.
Soils that contain a lot of sand are called sandy veils.