How to control weeds

weeds-fieldWeed control is important to prevent losses in yield and production costs, and to preserve good grain quality. Specifically, weeds

  • decrease yields by direct competition for sunlight, nutrients, and water
  • increase production costs e.g., higher labor or input costs
  • reduce grain quality and price
    For example, weed seeds in grain can cause the buyer price to be reduced.

Weed management should be practiced during specific stages of rice production:

During land preparation

Control of weeds during land preparation is crucial to reduce the amount of weed pressure in the field. Land preparation should start 3−4 weeks before planting. Plowing destroys weeds and remaining stubble from the previous crop. Weeds should be allowed to grow before the next cultivation. In addition, a level field helps retain a constant water level that controls weeds.

list collapse For wet seeded rice

  • Plow and harrow several times before planting. Depending on weed population, three or more operations can be done.
  • Allow weeds to emerge for at least 2 weeks then kill by another shallow tillage. This reduces the number of weed seeds in the soil, and greatly reduces weeds for the subsequent crop.

list collapse For dry seeded rice

  • Allow weeds to emerge within 1−2 weeks, then kill them with either a non-selective herbicide or by light cultivation
  • Spray herbicides, and perform manual and/or mechanical weeding.

Stale seedbed technique

Stale seedbed technique

Stale seedbed technique is a weed control method for land preparation. This technique is effective especially when growing irrigated, dry direct seeded rice.

Herbicides

Herbicides

Using herbicides for weed control is particularly important in places where agricultural labor is scarce and wage rates are high.

Manual and mechanical weeding

Manual and mechanical weeding

Direct control of weeds can be done through manual weeding by hand, and mechanical weeding using implements such as push weeder and interrow cultivation weeders.

The dirty dozen

The dirty dozen

The 12 most troublesome weeds of rice in Asia