Definitions:
- Weed is a plant that originated under a natural environment and in response to imposed and natural environments, evolved and continues to do so as an interfering associate with our desired plant and activities.
- Weed is a plant growing out of place and time. They are unwanted not useful, persistent and prolific, effectively competing with the beneficial and desirable crop plants for space, nutrients, sunlight and water, interfere with agricultural operations and thereby reducing the yield and quality of produce.
- Weeds are unwanted and undeserved plants that interfere with the utilization of the land and water resources and thus adversely affect crop production and human welfare. Thus a plant out of its place or a plant growing where it is not desired at that time is a weed. This definition was given by Buchholtz in 1967.e.g. Bajra is a weed in pulse; Pulse is a weed in Bajra, Tomato is a weed in Brinjal field.
- Weeds are all types of undesirable plants i.e. sedges, grasses, broad leaved weeds, aquatic plants, trees and parasitic flowering plants (Striga, Orobanche) affecting crop area and non- crop area (industrial side, road side, railway line, water tank, irrigation channel etc.).
- Weeds are unwanted, pernicious and harmful plants which interfere with agricultural operations, increase labour, add to the cost of cultivation and reduce yield of crops. Weed has no species, but name was suggested as a useless and harmful plant that persistently grows where it is quite unwanted.
- Weed is defined as the unwanted, undesirable plant, growing out of their proper place, which interfere with the utilization of natural resources, prolific, persistent, competitive, harmful and even poisonous in nature and can grow in adverse climatic conditions. (Jethro Tull: father of weed Science)
- Weediness: Weediness is defined as the state or condition of a field, flower bed, lawn and so forth in which there is an abundance of weeds.
Characteristics of weeds:
- Weeds have rapid seedling growth and ability to reproduce when young e.g. Redroot Pigweed can flower and reproduce when it is less than eight inches tall.
- Weeds have quick maturation period or take only a short time in the vegetative phase e.g. Canada thistle can produce mature seeds in two weeks after flowering and Russian thistle seeds can germinate very quickly between 280 -110 0 F in late spring.
- Weeds may have dual mode of reproduction. Most weeds are angiosperms & reproduce by seeds and vegetatively too.
- Weeds have environmental plasticity. Many weeds are capable of tolerating and growing under a wide range of climatic and edaphic conditions.
- Weeds are often self-compatible but self-pollination is not obligatory.
- If a weed is cross pollinated, this is accomplished by non- specified flower visitors or by wind.
- Weeds resist detrimental environmental factors. Most crop seed rot, if they do not germinate shortly after planting whereas, and weed seeds resist decay for long periods in soil and remain dormant for longer duration.
- Weed seeds exhibit several kinds of dormancy and escape the rigors of environment and germinate when conditions are more favourable for their survival. Many weeds have no special environment requirements for germination.
- Weeds often produce seeds of same size and shape as the crop seeds, making physical separation difficult and facilitating spread by men.
- Some annual weeds produce more than one seed flush per year and seed is produced as long as growing conditions permit.
- Each weed plant is capable of producing large number of seeds per plant and seed is produced over a wide range of environmental conditions.
- Many weeds have specially adapted long and short range seed dispersal mechanisms.
- Roots of some weeds are able to penetrate and emerge from deep in the soil, while most roots are in the upper foot of the soil Canada thistle roots routinely penetrate 3-6 feet and field bindweed roots upto 10 feet deep. Roots and rhizomes are capable of growing many feet per year.
- Roots and other vegetative parts of perennial weeds are vigorous with large food reserves, enabling them to withstand environmental stress.
- Perennials have bitterness in the lower stem nodes or in rhizomes and roots and, if severed vegetative organs will quickly regenerate in to whole plant.
- Many weeds have adaptation mechanism that repels grazing, such as spines, odd taste or odour.
- Weeds have great competitive ability for nutrients, light and water and can compete by special means (e.g. Rosette formation, climbing growth and allelopathy)
- Weeds are ubiquitous (present everywhere). They exist everywhere, where we practice agriculture.
- Weeds resist control, including herbicides.
|
Participants