Page 9 - Science Class 08

start working on them and convert them are nitrogen (N), phosphorus (P) and
into simpler substances or nutrients. This is potassium (K). Fer lizers containing these
called compost. mineral salts are called NPK fer lizers. We

v Addi on of Chemical Fer lizers : Compost can provide the soil with mineral salts just
prepared by organic materials do not by adding fer lizers to the soil. But excessive
contain some other important nutrients like use of mineral salts can destroy the texture
nitrogen, phosphorus and potassium. These of the soil. Besides, it may also lead to the
mineral salts are prepared in fer lizer pollu on of groundwater because it may
industries. The most widely used minerals percolate through soil.

Take moong or gram seeds and germinate them. Select three equal sized seedlings out of these.
Now, take three empty glasses or similar vessels. Mark them A, B and C. To glass A, add li le
amount of soil mixed with a li le cow dung manure. In glass B, put the same amount of soil
mixed with a li le urea. Take the same amount of soil in glass C without adding anything. Now,
pour the same amount of water in each glass and plant the seedlings in them. Keep them in a
safe place and water them daily. A er 7 to 10 days, observe their growth.

Seeds + Seeds +
Cow Dung + Urea + Seeds +
Soil Soil
Soil
A B C
Did all the plants in all the glasses grow at the same pace? Which glass showed be er growth
of plants? In which glass was the growth fastest?

Irriga on s ll depend on rain water. Therefore, some-

Supplying water to the crops in the filed called mes when rain is neither in excess nor in
irriga on. There are many methods of scanty, farmers get good yield. But, some mes
irriga on. It includes sprinkling, making drains, when rain is in excess or in scanty, crops are
etc. Some important sources of water for either ro en or dried up.
irriga on are ponds, lakes, wells and tubewells. Some important points that should be kept in
The water by the ponds, lakes or wells is sent mind while irriga on are as follows:

to the fields manually or by using an electric or v Different types of crops need water in
diesel pump. The water of rivers is sent to far different amounts. Therefore, farmers
off places for irriga on by construc ng canals. should know about the required quan ty
However, a large number of farmers in India of water by different plants.

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