Page 10 - Science Class 08
P. 10
For example, rice crops need heavy amount Weeds are also controlled by using certain
of water while wheat crops need moderate chemicals called weedicides, like 2,4-D. These
amount of water at specific me intervals. are sprayed in the fields to kill the weeds. They
v The flow of water supply or water-logging do not damage the crops. The weedicides are
in the field may reduce the supply of air to diluted with water to the extent required and
the roots. Besides, it may also increase the sprayed in the fields with a sprayer.
amount of salts in the soil which is not
good for crops.
Weeding
In a field, many other undesirable plants may
grow naturally along with the crops. These
undesirable plants are called weeds.
The removal of weeds is called weeding.
Weeding is necessary since weeds compete Weeds
with the crop plants for water, nutrients, space Weeding is done by two ways:
and light. Thus, they affect the growth of the v Weeding is generally done manually. In this
crop. Some weeds interfere even in harves ng method, farmers pull the weeds out by
and may be poisonous for animals and human hand or by using trowel or a harrow to
beings. uproot them.
Farmers adopt many ways to remove weeds v Weeding is also done by using special
and control their growth. Tilling before sowing chemicals called herbicides or weedicides.
of crops helps in uproo ng and killing of These chemicals are sprayed on the
weeds, which may then dry up and get mixed unwanted plants. These chemicals destroy
with the soil. The best me for the removal of the weeds. But these chemicals do not
weeds is before they produce flowers and cause any harm to the main crops. Some
seeds. The manual removal includes physical commonly used weedicides are dalapon,
removal of weeds by uproo ng or cu ng them metachlor and siniazine.
close to the ground, from me to me. This is Since these chemicals are poisonous, people
done with the help of a khurpi. A seed drill is should use food grains only a er washing them
also used to uproot weeds. properly in running water.
Protec ng a Crop
Crops do not remain under any shelter. They
are exposed to several dangers. Extremes of
climate, stray animals, pests and diseases are
chief dangers for the crops.
Extremes of weather require the sensi ve crops
to be provided with protec on from the
scorching sun and the icy cold. Stray animals
Tilling can be kept away by erec ng fences.
10 Science-8
