Weed Control

Weed control and weed management are the two terms used in weed science. Weed control is the process of limiting infestation of the weed plant so that crops can be grown profitably.

Weed management includes prevention, eradication and control by regulated use, restricting invasion, suppression of growth, prevention of seed production and complete destruction. Thus weed control is one of the aspects of weed management.

CULTURAL METHODS OF WEED CONTROL

Several cultural practices like tillage, planting, fertilizer application, irrigation etc., are employed for creating favourable condition for the crop. These practices if used properly, help in controlling weeds. Cultural methods, alone cannot control weeds, but help in reducing weed population.

Field Preparation

1. The field has to be kept weed free. Flowering of weeds should not be allowed. This helps in prevention of build up of weed seed population in the fields
2. Irrigation channels are the important sources of spreading weed seeds. It is essential, therefore, to keep irrigation channels clean.
3. Deep ploughing in summer, exposes underground parts like rhizomes and tubers of perennial and abnoxious weeds to scorching summer sun and kills them.
4. Conventional tillage which includes 2 to 3 ploughings followed by harrowing decreases the weed problem.
5. Running blade harrows cuts weeds and kills them.
6. In lowland rice, puddling operation incorporates all the weeds in the soil which would decompose in course of time.

Planting Method

1. Sowing of clean crop seeds without weed seeds should be done. It is a preventive method against introduction of weeds.
2. Sowings are taken up one to three days after rainfall or irrigation depending on soil type. Weeds already present in the soil start geminating within two or three days.
3. Sowing operation with seed drill removes some of the germinating weeds.
4. Transplanting is another operation which reduces weed population. Since, the crop has an additional advantage due to its age.

Varieties

1. Short statured, erect leaved varieties permit more light compared to tall and leafy traditional varieties.
2. Weeds continue to germinate for long time in 'dwarf varieties resulting in high weed growth.

Planting Density

1. Plants of one type do not generally allow germination of other plants near their vicinity. Closer planting of crops suppresses germination and growth of weeds.
2. Wider planting should be avoided

Fertiliser Application

1. Plants differ in their capacity to respond to fertiliser application.
2. Crops like sorghum, maize, pearl millet and rice grow at a faster rate when nitrogenous fertilisers are applied and cover the soil earlier.
3. Weeds like Cynodon dactylon, Cyperus rotundus do not respond to nitrogen application and they are suppressed by fast growing crops.

Irrigation and Drainage

1. Depending on the method of irrigation, weed infestation may be increased or decreased.
2. Frequent irrigation or rain during initial stage of crop growth induces several flushes of weeds.
3. In lowland rice, where standing water is present most of the time, germination of weeds is less.
4. Continuous submergence with 5 cm water results in reducing weed population whereas under upland situation, weed population and weed dry matter is very high

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