Improvement in Food Resources — Science STD 9 — Question

1. Mechanical Methods The process of removing the weeds from crop fields is called weeding.It is done by following methods.

1. Weeds may be pulled out by hand. Ploughing helps in removing large number of the weeds.
2. Before sowing or transplantation weeds are removed by using a big comb called Harrowcannot be used in standing crops because it will also uproot the crop plants.

The weeds which appear during the growth of crop plants are removed manually by using a trowel (Khurpa).

2. Cultural Methods: They include the following methods, proper bed preparation timely sowing of crops, inter cropping and crop rotation.

3. Chemical Methods: Chemical weed killers, called herbicides or weedicides, are sprayed on weeds to destroy (kill) them. This is called chemical control of weeds. Some common examples of weedicides are:

1. 24-D (2, 4-Dichlorophenoxy acetic acid)
2. Atraxine.
3. Fluchloralin.
4. Isoproturon.

4. Biological Control: Biological control of weeds involves the deliberate use of insects or some other organism which consume and specifically destroy the weed plants. The best Indian example of biological control is eradication of prickly pear cactus (Opuntia) by using the cochineal insects in Maharashtra and Tamil Nadu.

Generally, a combination of one or more of these weed control methods are employed to get good results. Aquatic weeds are controlled by the fish grass carp.