Integrated Weed Management in Detail

Definition

Use of a judicial combination of mechanical, cultural, biological and chemical methods to achieve economic and effective weed control. It is a method whereby all economically, ecologically and toxicologically justifiable methods are employed to keep the harmful organisms below the threshold level of economic damage, keeping in the foreground the conscious employment of natural limiting factors. IWM is the rational use of direct and indirect control methods to provide cost-effective weed control. Such an approach is the most attractive alternative from agronomic, economic and ecological point of view. Among the commonly suggested indirect methods are land preparation, water management, plant spacing, seed rate, cultivar use, and fertilizer application.

Direct methods include manual, cultural, mechanical and chemical methods of weed control. The essential factor in any IWM programme is the number of indirect and direct methods that can be combined economically in a given situation. For example, increased frequency of ploughing and harrowing does not eliminate the need for direct weed control. It is, therefore, more cost-effective to use fewer pre-planting harrowing and combine them with direct weed control methods. There is experimental evidence that illustrates that better weed control is achieved if different weed control practices are used in combination rather than if they are applied separately.

Why IWM

• One method of weed control may be effective and economical in a situation and it may not be so in other situation.

• No single herbicide is effective in controlling wide range of weed flora.

• Continuous use of same herbicide creates resistance in escaped weed flora or causes shift in the flora.

• Continuous use of only one practice may result in some undesirable effects. e.g., Rice–wheat cropping system–Philaris minor.

• Only one method of weed control may lead to increase in population of particular weed.

• Indiscriminate herbicide use and its effects on the environment and human health.

Concept

• Uses a variety of technologies in a single weed management with the objective to produce optimum crop yield at a minimum cost taking into consideration ecological and socio-economic constraints under a given agro-ecosystem.

• A system in which two or more methods are used to control a weed. These methods may include cultural practices, natural enemies and selective herbicides.

Good IWM should be

• Flexible enough to incorporate innovations and practical experiences of local farmers.

• Developed for the whole farm and not for just one or two fields and hence it should be extended to irrigation channels, road sides and other non-crop surroundings on the farm from where most weeds find their way into the crop fields.

• Economically viable and practically feasible.

Advantages of IWM

• It shifts the crop-weed competition in favour of crop

• Prevents weed shift towards perennial nature

• Prevents resistance in weeds to herbicides

• No danger of herbicide residue in soil or plant

• Suitable for high cropping intensity