Field Crops> Maize> Weed Control

The abundant rainfall in Kharif encourages rapid weed growth. Weeds emerge with the germination of maize seeds and grow along with plants till the early growth period. This causes severe crop weed competition. Failure of timely weed control would not only offer direct competition to the maize plant but also indirectly through reduction in fertiliser use efficiency. Losses through weed competition in early stages cannot be offset by keeping the field weed free later. In case the weeds are not brought under control at right time, there is 50-60 per cent reduction in yield. Maize crop is infested with grassy and broad-leaved annual weeds. Among grassy weeds, Echinochloa colonum, Enhinochloa crusgulli (sawan), Dactyloctenium aegypticum(makra), Elusine indica (kodo), Setaria glauca (banra), Cynodon dactylon (doob), Phragmites karka (narkul), Cyperus rotundus (motha), Sorghum halepanse (banchari) are common.

The broad-leaved weeds are Celosia argentia (chilimil), Commelina benghalensis (kankoua), Phylanthus niruri (hulhul), Solanum nigrum (makoi), Amaranthus viridis (chaulai) and Podrtulaca oleraceae (naunia).

It is very difficult and economically not feasible to keep the crop weed free throughout the growing season. The maize crop kept weed free for 30 to 45 days after planting is almost similar in yield as that kept weed free for entire crop season. Two to three manual weedings would be needed for this purpose. Generally khurpi, hand hoe and spades are used for weed control in maize. At many places, people use cultivator or country plough in between the rows of maize. Sometimes due to continuous rains during the early period of maize growth, it becomes impossible to enter in the field. In such a situation the only effective way to control weeds is the use of pre-emergence herbicides. The following herbicids can be used in maize crop.

Atrazine and Simazine

Either of these herbicides may be applied immediately after planting maize. The rate of application varies from 1.0 to 1.25 kg of active ingredient in light soils and 1.25 to 1.50 kg of active ingredient in heavy soils per hectare. The weedicide should be mixed in 1000 litres of water and evenly sprayed on the soil surface just after sowing. There should be enough moisture in the soil at the time of spraying. Care should be taken that the seedbed is well prepared and does not contain any emerging weed. Field should not be disturbed for initial three to four weeks.

Alachlor (Lasso)

This herbicide needs to be used immediately after planting the crop. It helps in controlling weeds for initial 30 to 45 days after planting. Afterwards the crop cover provides necessary check on the growth of weeds. The field should be well prepared and free of clods at the time of spraying. This weedicide if available should be used at the rate of 5 litres per hectare. The weedicide should be mix-ed in 1000 litres of water and evenly sprayed in one hectare. This herbicide controls grassy weeds better than Atrazine.