Rainfed rice - IRRI books - International Rice Research Institute

Cost Effectiveness of
Weed Management for Rice
F
or improved rice varieties, yield loss due to weeds is a major factor
affecting the economics of rice production. Usually, in calculating the
economics of weed management, only the cost of labour and herbicides
is taken into account. But the cost-effectiveness is greatly influenced by
several other factors such as cultural practices, such as crop rotation,
intercropping which has a crop with potential to smother weeds, summer
ploughing, efficient water and nutrient management and use of a weedsuppressing
variety. Indirect long-term gains affecting health and
environmental safety of humans, livestock and other forms of life have to be
considered.
In subsistence farming with
traditional varieties, weed control is
not always beneficial as yields are
otherwise low. Moreover, these
cultivars are naturally competitive
against weeds while comparatively
improved rice cultivars are more
susceptible to weeds. Therefore,
weed control is mandatory and is a
remunerative practice which gives
higher returns.
One has to understand the
economics of weed control before
adopting any weed management
practice. Information is also needed
about the right stage of weed
control, i.e., critical period for weed
control, its necessity and level
required.
Critical period
The crop stage and duration of the
critical period depend on factors
such as weed flora, growth
236
Weeds cause significant yield reduction. The
extent of yield losses ranges between 15-
20% in transplanted rice, 30-35% in direct-
seeded lowland rice and 50-90% in upland
rice.