Methods of weed control
Weed control by pesticide
The weeds multiply and spread very fast because they produce a large quantity of seeds.
When we grow a food crop in the field, then in addition to the crop plants, many small, unwanted plants also germinate and grow in the field. The unwanted plants (or wild plants) which grow along with a cultivated crop are called weeds. The growth of weeds in the fields is harmful because they consume a lot of fertiliser, water, sunlight and space, meant for the crop plants and reduce the crop yield, and lower the quality of food – grains. Another harmful effect is that the weeds spread crop pests and diseases by acting as alternate host to insects and micro – organisms. And sometimes the weeds produce toxic substances (poisonous substances) which may interfere with crop growth or which may poison crop produce. Since the presence of weeds in the fields will reduce the crop – yield, therefore, it is necessary to remove them from time to time. Through most of the weeds get uprooted during the ploughing of fields but they reappear when the crop grows. The weeds multiply and spread very fast because they produce a large quantity of seeds.
Some common weeds
The type of weeds vary from field to field, from crop to crop, and also from season to season. Some of the common weeds (unwanted plants) found in wheat and rice fields are-
a) wild oat (javi). b) grass (ghaas). c) amaranthus (chaulai). d) chenopodium (bathua). e) convolvulus (hirankhuri).
The most common weed which grows along with almost every crop is amaranthus (chaulai). Some of the weeds have broad leaves whereas others have narrow leaves.
Methods of control
The process of removing weeds (unwanted plants) from a crop field is called weeding. Weeding is done by hand or with help of implements like trowel (khurpa) or harrow. Weeds can also be destroyed by spraying special chemicals called weedicides or by biological methods. Thus, the various methods of controlling weeds (or eradicating weeds) in the fields are -
A) removal of weeds by pulling them out with hand. B) removal of weeds by using a trowel (khurpa). C) destroying the weeds by spraying special chemicals called weedicides like 2, 4 D, MCPA and Butachlor (This is called chemical control of weeds). D) weeds can also be controlled by biological methods. In the biological control of weeds, some appropriate insects or some other organisms are deliberately put into the crop field having weeds. These insects or other organisms selectively destroy the weed plants but do not harm the crop plants. Foe example, cochineal insects are used to eradicate the weed called opuntia. In actual practice, a combination of one or more of these methods is used.
The removal of weeds by using a big comb – like implement called harrow can be done by only before sowing or transplanting. Harrow cannot be used in standing crops because it will also up – root the crop plants.
The chemical substances which are used to kill weeds (unwanted plants present in a crop are called weedicides. Some of the common weedicides are – a) 2,4 -D (2,4 dichlorophenoxy -acetic acid). b) MCPA (2- methyl 4- chloro 1- phenoxy acetic acid). c) butchlor.
A solution of the weedicide is approved on the standing crops in the fields. The weedicides kill (destroy) the weeds (unwanted plants) but do not damage the main crop. Since weedicides are poisonous substances, so the grains must be well washed before use. Weedicides are also called herbicides. From the above discussion we conclude that the implements or tools used for weeding are trowel (khurpa) and harrow. Sprayers are used for spraying weedicides.