- For designing any weed control programme in a given area, one must know the nature u0026amp; habitat of the weeds in that area, how they react to environmental changes u0026amp; how they respond to herbicides.
- Before selecting a method of weed control one, much have information on the number of viable seeds nature of dispersal of seeds, dormancy of seeds, longevity of buried seeds u0026amp; ability to survive under adverse conditions, life span of the weed, soil textures moisture and the area to be controlled.
Principles of weed control are;
Preventive weed control
It encompasses all measures taken to prevent the introduction and/or establishment and spread of weeds. Such areas may be local, regional or national in size. No weed control programme is successful if adequate preventive measures are not taken to reduce weed infestation. It is a long-term planning so that the weeds could be controlled or managed more effectively and economically than is possible where these are allowed to disperse freely.
Following preventive control measures are suggested
- Avoid using crop that are infested with weed seeds for sowing
- Avoid feeding screenings and other material containing weed seeds to the farm animals.
- Avoid adding weeds to the manure pits.
- Clean the farm machinery thoroughly before moving it from one field to another. This is particularly important for seed drills
- Avoid the use of gravel sand and soil from weed-infested
- Inspect nursery stock for the presence of weed seedlings, tubers, rhizomes, etc.
- Keep irrigation channels, fence-lines, and un-cropped areas clean
- Use vigilance. Inspect your farm frequently for any strange looking weed seedlings. Destroy such patches of a new weed by digging deep and burning the weed along with its roots. Sterilize the spot with suitable chemical.
- Quarantine regulations are available in almost all countries to deny the entry of weed seeds and other propagules into a country through airports and shipyards.
Weed-free crop seeds
It may be produced by following the pre-cautionary measures.
- Separating crop seeds from admixture of crop u0026amp; weed seeds using physical differences like size, shape, colour, weight/texture u0026amp; electrical properties.
- Using air-screen cleaners u0026amp; specific gravity separators, which differentiate seeds based on seed size, shape, surface area u0026amp; specific gravity.
- Through means of Seed certification we can get certified seeds and can be used safely because the certified seeds contain no contaminant weed seeds
- Weed laws are helpful in reducing the spread of weed species u0026amp; in the use of well-adapted high-quality seeds. They help in protecting the farmers from using mislabeled or contaminated seed and legally prohibiting seeds of noxious weeds from entering the country.
- Quarantine laws enforce isolation of an area in which a severe weed has become established u0026amp; prevent the movement of the weed into an uninfected area.
- Use of pre-emergence herbicides also helpful in prevention because herbicides will not allow the germination of weeds.
Eradication: (ideal weed control rarely achieved)
- It infers that a given weed species, its seed u0026amp; vegetative part has been killed or completely removed from a given area u0026amp; that weed will not reappear unless reintroduced to the area.
- Because of its difficulty u0026amp; high cost, eradication is usually attempted only in smaller areas such as few hectares or few thousand m2 or less.
- Eradication is often used in high-value areas such as greenhouses, ornamental plant beds u0026amp; containers.
- This may be desirable and economical when the weed species is extremely noxious and persistent as to make cropping difficult and economical.
- It encompasses those processes where by weed infestations are reduced but not necessarily eliminated.
- It is a matter of degree ranging from poor to excellent. In control methods, the weeds are seldom killed but their growth is severely restricted, the crop makes a normal yield.
- In general, the degree of weed control obtained is dependent on the characters of weeds involved and the effectiveness of the control method used.
- Weed control aims at only putting down the weeds present by some kind of physical or chemical means while weed management is a system approach whereby whole land-use planning is done in advance to minimize the very invasion of weeds in aggressive forms and give crop plants a strong competitive advantage over the weeds.
- Weed control methods are grouped into cultural, physical, chemical and biological. Every method of weed control has its own advantages and disadvantages.
- No single method is successful under all weed situations.
- Many a time, a combination of these methods gives effective and economic control than a single method.