Page 8 - Science Class 08

pipe like shape of the funnel is pushed into follow is a natural way of maintaining the
the soil and seeds are dropped through the
upper por on.
Sowing of Seedlings : There are many crop
plants which are not grown directly in the field
like rice, tomato, onion, chilli, etc. They are
grown from the seeds in a small patch of land
called nursery. When the plants in the nursery
have grown to a certain height, they are
carefully rooted out and then they are
transplanted in a prepared field at proper
distance and at a proper depth. It helps in
selec ng healthy plants which finally leads to
good produc on.
Manuring
Manuring means providing nutrients to the
soil. The nutrients include mainly mineral salts
which are required by plants for their proper
growth. However, these mineral salts are
replenished or recycled by natural process. But,
cul va ng in the same field con nuously may
deplete the amount of nutrients. So, to
maintain the amount of nutrients in the soil,
we can add manures or fer lizers to the soil.
Let’s study about some natural and manual
methods of manuring:
Natural Method : It consists of three stages.
v Field Fallow : In this method, par cular
field is le without growing crops for one
or more seasons. During this period, the
field regain nutrients which have been
used of by plants. When we leave the field
uncul vated, small organisms and microor-
ganisms start working on dead and
decomposed material which are collected
on the field. They convert dead and
decomposed materials into simpler
substances, i.e., nutrients. In this way, field
8 Science-8
fer lity of soil.
v Crop Rota on : You already know that soil
contains different types of nutrients in
different propor ons. Besides, different
types of crops use nutrients in different
propor ons. Therefore, if we sow the same
crops con nuously, some par cular nutri-
ents are used up by the crops in excess and
these nutrients get depleted rapidly.
Therefore, we follow crop rota on method
in which different types of crops are
cul vated in the same field to maintain the
amount of nutrients in the soil.
For example, cereal crops like rice and
wheat use up large amount of nitrogen
from the soil. Therefore, a er growing rice
or wheat, farmers should grow legumes in
the same field. Leguminous crops like peas,
gram or groundnut have nodule roots
which convert nitrogen of the air into
nitrates which can be used up by cereal
crops again.
v Mixed Cropping : Mixed cropping means
growing of two or more types of crops in a
par cular field in the same season. In this
method, crops are selected in such a way
that the products and waste materials from
one crop help in the growth of the other.
For example, wheat and mustard or co on
and groundnut can be grown together in
the same field.
Manual Method : It consists of two stages.
v Compos ng : Adding compost to the soil to
increase its fer lity is called compos ng.
Compost is made from waste organic
materials. If waste organic materials like
food wastes, cow dung, fallen leaves, etc.
are dumped into a pit, bacteria and fungi