Soil and what it is made of
Soil is the soft top layer of the Earth’s crust. It is made of sand, clay, humus, mineral salts, water and air. Humus is a dark, nourishing material formed when plant and animal remains rot; many tiny creatures and worms make it. Sandy soil lets water drain quickly, so it dries fast. Clay soil holds water but lets little air through. The best soil is a mix of sand and clay with plenty of humus. The ability of soil to grow plants is called fertility. Black soil (chernozem) is very fertile; grey soil (bo‘z) is common over wide areas of Uzbekistan and gives a good harvest when irrigated; in salty soil there is a lot of salt, so plants grow with difficulty.
Experiment: put the same amount of sand and clay soil into two containers. Pour a glass of water over each and compare how many seconds the water takes to drain. Record the result in a table. Wash your hands afterwards.