Rainfed rice - IRRI books - International Rice Research Institute

RAINFED RICE A SOURCEBOOK OF BEST PRACTICES AND STRATEGIES IN EASTERN INDIA
Prepared by:
G.N. Mishra
230
Using weed-free seeds
Rice seed is one of the major sources of dissemination of weed seed and
infestation of new areas by weeds.
Strict vigil through quarantine and seed certification can help. As far as
practicable, seed should be free from weed seed. But in any case, 50 g of rice
seed should not have more than one seed of problem weeds.
Morpho-physiological traits useful for
better competitive ability of rice
Rapid and uniform germination
Faster growth rate at the seedling stage
Early prolific root growth near the soil
surface and a deep main root system
High nitrogen absorption at an early
stage
Good vegetative vigour
Tall height and more canopy, especially
during the early stages
of rice
Using varieties with better
competitiveness against
weeds
Some rice varieties either suppress
weed growth or compete with
weeds without sacrificing yield.
Vandana is one such variety for upland
rice farming.
Proper schedule of fertiliser application
To prevent weed proliferation without sacrificing yield, do not apply
nitrogen fertilisers until weed control is adequate. In acidic uplands, use a rock-
phosphate at the time of sowing in place of a single super-phosphate to help
reduce weed growth. Weed control is mandatory when fertiliser is applied.
Otherwise, fertiliser will favour weeds over rice.
Water management
In lowland rice ecosystems, water can minimise weed problems by 52%-
85%. Weed growth is directly influenced by the depth and duration of their
submergence, particularly during the early stage of the crop. Grasses are com-
pletely eliminated in continuous submergence of 16 cm depth throughout the
crop period. A 3-5 cm submergence depth also gives substantial control of
grasses, followed by sedges.