Weed control measures
There are several methods used in weed control. They can be classified into:
(a) Mechanical or physical method of weed control
(b) Cultural method of weed control
(c) Biological method of weed control
(d) Chemical method of weed control
(a) Mechanical or physical method of weed control
Cultural method of weed control
(i) Hand pulling:
this is the pulling of weeds
by hand in the farm. Though it is efficient, but only useful in small gardens and not large farms.
The short or small hoe is very useful in weeding
. It is used to cut the weed below the crown of the plant which gives, complete destruction of the shoot system. It is effective in the control of weeds
either in pasture,
home garden or row crops. Hoe
can be used to weed from the furrow to the top of a ridge. Its use is however on a limited and it requires plenty of labour.
(iii) Mowing of the soil
This method helps to prevent seed production in till of weeds. It removes all unsightly weed growth especially where weeds are too much for effective cultivation to take place. The method can be used to control weeds in lawns, plantation or fields. The mower is normally attached to a tractor
or pulled by hand to move over the area to be cleared.
(iv) Flooding: This is done by keeping the area to be weeded Hooded up to 20 cm of water for 3 to 8 weeks. This practice kill, the weeds because they can no longer receive air for a-.piration.
(v) Heat treatment of the soil: Heal can be used in controlling weeds. For instance nursery soil is sterilized to kill all weed parts and seeds. Fire ran be used to burn dry weeds on cultivated land before cultivation starts
(vi) Smothering with non-Living materials: to control the spread of weeds
Weeds can be Followed by the use of mulch materials such, as papers, hulls from rice, manure, plastic materials or cellophane. These materials help to exclude sunlight and prevent shoot growth. The weeds then become etiolated (lose chlorophyll) and die off.
(vii) Cultural method of weed control:
This involves the use of cultural practices of crop production to reduce the growth of weeds on the farm. Such cultural practices include
i. Burning of farmland
: This kills weed parts, seeds and fruits
both in the soil
and on the surface.
ii. Tillage system
helps to expose weed parts for destruction by sun or herbicides. They can also be hand picked and destroyed.
iii. Early planting: This ensures that crops are well established before the weeds start growing.
iv. Using Good spacing to control weed:
Proper spacing of crops helps in the reduction of weeds along the crop rows. It also makes it easy for weeding to he done.
v. Mixed cropping of controlling the spread of weeds
Planting or two or more crops, together oil the same farmland can help to reduce the intensity of weeds on the farm
(c) Biological method of controlling the spread of weeds
This involves the use of living plants and animals to control weeds. They include:
(i) Use of suppressive plants: Crops that grow fast and large too can be used to overshadow weeds thereby reducing their growth, Also, cover crops
such as melon and legumes like groundnut
can be used to control weeds on the farm.
(ii) Use of insects to control weed spread:
This involves the use of identified insect pests weeds in controlling weeds on the farm. Insects which have been found to feed on a particular weed can be multiplied and introduced to the area to feed and destroy such weed species.
(iii) Pasturing system of controlling weeds
involves the grazing of farm animals on weeds
usually in plantations such as rubber
and oil palm
. Animals like i cattle
, sheep or goat
are commonly used in this method.
(d) Chemical method for controlling weed
This is the method that is used on a large scale. It makes use of chemicals in the control of weeds. These chemicals are known as herbicides. They are sprayed either on the leaves of weeds or applied to the soil.
Types of herbicide for controlling spread of weeds
They are classified into:
(i) Selective herbicides: These are chemicals that can kill certain groups or species of plants. Example is 2, 4 -D (Dichlorophen-oxyacetic acid). They can be used in cereals, sugar cane and soya beans farms to reduce weeds.
(ii) Non-selective herbicides:
These arelthe herbicides that can kill any plant which they come in contact with. Examples are arsenicals chlorates, petroleum oils and carbon
Herbicides can also be classified as contact herbicides, systemic or translocation herbicides.
The contact herbicides are applied as foliage sprays (that is on the leaves), dust or granules: They scotch the tissues of the plants
already growing on the farm. Examples are sodium chlorate and arsertates.
The systemic or in trans-located herbicides are carried in the tissues of the plants after the ingredients have been absorbed by the roots in the soil.
These chemicals must first enter the soil and then absorbed the roots of the weeds into their tissues. They are applied as dust or granules onto the plants or used as soil treatments
. When used as soil treatments, they control all weeds that are still to emerge from the soil, hence, they are sometimes called pre-lltrgencc herbicides. Examples are 2,4,5-T(2,4,5-Trichlorophen-oxyyacetic acid), Atrazine and others.
Quality of good herbicide
Quality of good herbicide used to control weed spread
A good herbicide recommended for use should have the flowing qualities:
1. It should be able to kill the weeds easily and at a small dosage rate. That is, it should be phytotoxic.
2. It should kill the weeds and not the growing crops. That is, it should be selective in its action.
3. It should have low toxicity on animals that use weeds as food and on man.
4. It should be easy to compound or formulate.
5. It should be easy to use.
6. It should be cheap and easy to get.
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