RICE RATOONING - IRRI books - International Rice Research Institute

126 RICE RATOONINGTable 3. Effect of stubble height of main rice crop (CH10) on the yield of itsratoon, Sabour (Bihar), India, 1952.TreatmentHarvested close to groundHarvested at 15 cm aboveground (height at whichcrop is ordinarily harvested)Harvested at half the crop heightabout 36 cm above ground)The panicles were pickedOnly panicles were harvestedMain crop1.831.791.811.82Grain yield (t/ha)Ratoon crop0.070.270.570.50Table 4. Normal mean daily maximum and minimum temperatures and meandaily relative humidity at 0830 h on the Bihar plains, India.MonthMaxTemperature (°C)MinRelative humidity (%)JanFebMarAprMayJunJulAugSepOctNovDec23.225.632.137.137.134.832.531.932.031.327.924.29.311.616.121.524.726.126.226.025.521.614.59.8757257525375828381726869The high-yielding varieties of medium- and long-duration (130-150 d) rice aregenerally harvested by 15 Nov. Tillers do regenerate but die out with a fall intemperature.However, early-maturing varieties (100-115 d), transplanted in July andharvested the first week of October (autumn rice), have produced ratoon tillerswhich yielded around 31% of the main crop yield (Table 4). It might be possible totake a ratoon crop (40-45 d) of transplanted early rice varieties under irrigationbefore wheat sowing. The rice varieties, however, should possess some cold toleranceat heading.Experimental results indicate that ratoon cropping after summer rice has goodpromise (Table 1, 2), because temperatures remain favorable for crop growth(Table 4). Irrigation costs on the ratoon crop would be reduced substantially bymonsoon rain. Such a ratoon cropping would also relieve pressure on labor duringthe peak transplanting period in July and permit timely transplanting of theremaining rice area with the limited manpower available.Unfortunately, the area under summer rice is hardly 2-4% (or even less) of thetotal rice area. With improvement in power supply and canal water supply, the areaunder summer rice would increase and this in turn may brighten the prospects forrice ratooning.