Monday, May 20, 2024
General Agriculture

Methods of Weed Management and Control

A weed management system is a functional unit of integrated weed control or methods. Weed control refers to those actions that seek to restrict the spreads of weeds, destroy and reduce their population so that they do minimum harm in a given location.

On the other hand, weed eradication refers to the complete removal or elimination of all weeds and propagation of single species from an area. This is a very difficult task. This is difficult to achieve on a large scale, and it is uneconomical in most cases.

Except in serious cases of noxious weeds menace, weed eradication is not a major objective in arable and permanent crop production.

Four weed management systems have been identified. They are as follows:

  • Cultural system
  • Biological system
  • Chemical system
  • Preventive systems

1. Cultural system

Cultural methods are those practices adopted by farmers to minimize weed problem without being necessarily directed toward weed control. Some involve mechanical weed control methods and these include hand pulling, hoeing, slashing and cultivation. In all cases, the aim is to destroy established weed stands.

For it to be effective, operations must be carried out regularly and it is labour intensive and very expensive. The cultural methods of weed control include the following practices:

Manipulation of seeding rate: sparse plant population gives room for weed development. It is better to plant at optimum plant populations.

Crop rotation: certain weeds with similar physiological requirements as the crop plants tend to get associated with them. Growing these particular crops yearly creates favourable conditions for such weeds, but there will be reduction in this weed population with the planting of another crop of different requirements e.g. Striga are more associated with sorghum.

Mulching: involves the use of dead mulch or plastic sheet. This prevents sunlight from reaching the germinating weed seeds, but it is only possible on a small scale and not very important to field or tree crops. It also creates some inconveniences in farm operations like fertilizer application.

Hand weeding: this involves hand pulling of weeds, hand slashing with cutlass and hand hoeing.

Flooding of farmlands.

2. Biological method

This involves the use of living organisms or biological agents (live mulch or insect) to control weeds. It also implies using natural enemies of the weeds such as man, parasites, pathogens or predators to destroy the weeds.

It must be ensured that these enemies will not be enemies of the crop. Under agronomic conditions, this approach has not found much use, but on national bases e.g use of Cactoblastis esctorum to control Opuntia species in Australia.

Biological system of weeds control includes the following weed control methods:

  • Use of live mulch
  • Use of insects
  • Microbial control
  • Plant canopy manipulation
  • Allelopathy.

3. Chemical system

The chemical system involves the use of chemicals to eradicate the weeds. The chemicals are called herbicides. Herbicides can be systemic i.e. stops the normal function of plant system. The action is gradual and total control is achieved with the use of “round up” and Atrazine.

Contact herbicides on the other hand destroy weeds on contact. E.g. gramazone. Herbicides can also be very selective in destroying either grass or broad leaves e.g. Gramozone.

4. Preventive system

These are measures to prevent the introduction of weeds that are not common to an area e.g. Siam weed – Chromolaenaodoratacan be introduced to a new area by using it as packaging material.

In the preventive weed management system, the following weed control methods are used:

Sanitation measures especially non – crop area on the farm.

Read Also : Effects of Weeds in Crop Production and their Control Measures

Use of clean seed lots as planting material. Such seed lots must be free from weed seeds and other propagules.

Quarantine of animals.

Screening of irrigation water.

Roughing of isolated weeds.

Methods of Weed Management and Control

Enforcement of laws designed to prevent the seed or propagules of certain plants from entering a country.

Perennial weeds tend to be more under permanent crops. Annual weeds tend to be more frequent in arable crop fields.

There is no water – light distribution of perennial and annual crops. Weeds like chromolaenaodorataand Imperatacylindricalwhich are problems under tree crops are also found in arable fields.

Perennial weeds like cyperus spp. and Cynodon dactylon are also highly associated with arable crops, irrigated and wetland vegetable production.

Striga species are clearly in association with arable crops. It should therefore be understood that both agro – ecological effect and nature of crop influence the weed types.

For maximum yields, crops need to germinate and become established in a weed – free environment. Crops face competition from weeds after establishment and early growth.

In weed management, the goal is to focus on the limited weed management resources on the crop growth stages at which weed interference is most critical.

Subsistence farmers in Africa, depend mainly on the cultural system, followed by chemical and biological systems for weed management in arable crops. Specifically the practice is mainly hand weeding followed by the use of herbicides, live mulch and canopy effect.

A minimum of 2–3 hand weeding are carried out in arable crops production, usually between the 2nd and 8th week after planting. In farming systems involving crop mixtures, the weeding recommendation for the base crop shall be applied to the mixture.

Vegetable and food legumes may be grown along the alley ways during the early years of tree crop establishment. Thereafter, cover crop or grass leys may be maintained.

5. Herbicides in weed control

Herbicides are highly crop specific. The rates of these specific herbicides to be use in any given situation vary with the soil type and growth stage of the weeds. Herbicides are either soil or foliar applied.

Soil acting herbicides help crops to establish and begin early growth in weed free environment. Foliar acting herbicides on the other hand, help to reduce the vigor and population of growing weeds, thus placing the crop at an advantage with respect to resource use.

In summary, weeds have both harmful and beneficial effects. When and where the harmful effects of weeds are greater than the usefulness, there is a need to reduce their population and growth through management practices to such an extent that the nature and extent of damage they cause are within permissible limits.

The understanding of the life cycle of weeds determines the effective method and optimum time of their management.

Read Also : How To Generate Money From Inert Wastes


Benadine Nonye is an agricultural consultant and a writer with over 12 years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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