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In areas where adequate water is available after the first
crop season, rice ratooning could be practised as an alternative
to raising of the second crop in rice double cropping. The
ratoon crop matures earlier and requires less labour and water
inputs. Water use efficiency is high. Early maturing, high
yielding first crop varieties like No.11 and Barket are suitable
for ratooning.
The success of a good ratoon crop depends on the care with
which the first crop is cultivated in the growing season.
Agronomic practices for the first crop determine the success
of ratooning and grain yields of ratoonable varieties. Variations
in soil, water, light and temperature influence ratooning
ability. Tiller development is highly influenced by the carbohydrates
that remain in the stubbles and roots after harvest and the
level of nitrogen in the soil. Varieties with thick culms/stems
store more carbohydrates and are more suitable for ratooning.
AGRONOMIC PRACTICES
Time of harvest
The best time to harvest the main crop for raising a good
ratoon crop is when its culms or stems are still green. Stalks
should be cut before the main crop is fully matured and dried
up so that the stems are physiologically viable for ratoon
tillering.
Spacing
The effect of spacing on grain yield of the main and ratoon
crops is different from one variety to another. In general,
the optimum spacing for good ratoon yield is 20 x 20 cm.
Cutting height
Interactions between varieties and cutting height exist; some
varieties tiller better when cut high, while others produce
better tillers when cut at lower levels. For short-statured
varieties like No.11 and Barket, a cutting height of 15-20
cm is optimum. Further reducing the cutting height increases
the number of missing hills in the ratoon crop.
Water management
Excess flooding immediately after main crop harvest can cause
rotting of stubbles and can retard tiller formation. Keep
the field drained but moist for about 10 days after harvest
to promote sprouting and tillering. Thereafter, irrigate the
field as in the main crop.
Fertilizer management
Studies on fertilizer requirements show that a ratoon crop
needs nitrogen at the rate of 75% of the main crop. P and
K are usually adequate and do not respond upon application.
For Wangdi-Punakha valley, topdress N at the rate of 50 kg/ha
after 20-30 days of harvesting the main crop.
Weed control
Weed intensity in a ratoon crop depends very much on the control
measures applied to the main crop. A thorough handweeding
should be carried out 20-30 days after harvesting of the main
crop during the time of topdressing.
HARVESTING
Harvest the ratoon crop when over 80% of the grains are matured
and turn straw-coloured.
YIELD
On an average, ratoon rice can give a yield roughly equivalent
to 40% that of the main crop, with 40% reduction in crop duration.
For further information contact
Mahesh Ghimiray, Field Crops Sector, RNR-RC, Bajo
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