RICE RATOONING - IRRI books - International Rice Research Institute

Agronomic principles and practicesof rice ratooningS. K. De Datta and P. C. BernasorInternational Rice Research InstituteP.O. Box 933, Manila, PhilippinesABSTRACTRatooning offers the possibility of economically increasing rice yields where opportunitiesto profitably grow a second rice crop or an upland crop do not exist. Althoughrice ratooning has been practiced in many countries, it has not been widely adoptedbecause of low grain yields and other problems associated with its culture. Screeningtrials identified varieties with good ratoon yield potentials. Thorough and deep tillage inthe main crop enhanced ratoon tillering. More dense main crop planting led to higherratoon tiller populations. Higher cutting height (about 15 cm) increased tillering,shortened crop growth duration, and generally increased yield. Relatively low levels ofN fertilizer application improved ratoon plant growth and grain yield. Delayed flooding(about 10 d after main crop cutting) considerably decreased proportion of missing hills,especially where stubble was cut at ground level. Weeds in the main and ratoon cropcan be controlled by integrating cultural practices with herbicides. Insects and diseasescommon to the main and ratooned crops also can be controlled by using resistantvarieties and appropriate insecticides. Effects of temperature and plant growthregulators were not consistent; further studies should examine growth regulators.Varieties with desirable ratooning ability and resistance to insect pests and diseasesshould be bred. Ratooning should be considered in the context of its economic viabilityin cropping systems.Rice ratooning offers an opportunity to increase cropping intensity per unit ofcultivated area because a ratoon crop has a shorter growth duration than a maincrop (41, 43). In addition, a ratoon crop can be grown with 50-60% less labor. Noland preparation nor planting is needed and the crop uses 60% less water than themain crop (10).Rice ratooning has been practiced to some extent since 1927 (22) in the USA(12,16), India (5, 18, 40), Japan (30), Colombia (42), Swaziland (47), Thailand, andthe Philippines (37). However, ratooning is practiced only in limited areas (4).Although high yields have been recorded in some instances, ratoon crop yieldsare considerably lower than main crop yields (22, 41) or second transplanted ordirect-seeded crop yields (4). Other constraints to adoption are lack of cultivars withgood ratooning ability, lack of appropriate cultural practices, high insect and diseasepressures, and lack of good investment returns because of low grain yield (41).