Weeds compete directly with the rice plants and reduce rice yield. Each 1 kg dry matter of weeds is equivalent to 1kg grain loss. Weeds cause most yield loss within the first 20- 50 days after crop establishment. Weeding after panicle initiation may also be important to prevent weeds shedding seeds in future crops.
Effective weed management
• Plowing and harrowing in fallow should be undertaken at least 10-14 days apart or after rain.
• Good land leveling reduces weed growth because most weeds have trouble germinating under water
• Select varieties which have early vigor
• Use clean rice seed which is free of weed seeds.
• Apply permanent water early - weeds cannot germinate under water.
• First weeding begun within 2-3 weeks after establishment and the second in another 2-3 weeks. Weed before fertilizer application.
• Using herbicides. Identify the weed correctly and use the appropriate herbicide as recommended on the label.
• Spray when the weeds are small
• Pre-emergent herbicides apply after planting prior to establishment
• Post emergent herbicides apply after emergence being careful of crop damage
• Herbicides are poisonous; if they are not used properly they can cause health and environment problems. Label them clearly and keep them out of children’s reach.
• Always use protective clothing when spraying.
• Do not wear raincoats as this increases sweating.