RICE RATOONING - IRRI books - International Rice Research Institute

RICE RATOONING PRACTICES IN INDIA 75CHIKKAMAGALURThe conditions favoring high ratoon yields in the Chikkamagalur area are bettersunlight in the season (December to April); longer daylength than in main cropseason; lower disease and insect pressure; low relative humidity; low wind velocity;and low temperatures during early ratoon growth, favoring high net assimilationand higher yields. More disease and pest problems and high humidity in themonsoon may reduce main crop yields, while the favorable weather in the ratooncrop season (dry season) accounts for ratoon yields in Chikkamagalur area.The photoperiod-sensitive varieties, if planted in the dry season, do not flowerin Bangalore because of long days. But a main crop of photoperiod-sensitive Intanplanted in July and ratooned during December-January normally flowers duringMarch-April. This is an indirect advantage of ratoon cropping.The possible damage by insect pests (leafhoppers and planthoppers, stemborers, leaf roller) and diseases (brown leaf spot, stem rot, mycoplasma-likeorganisms [MLO]) is minimized by following the plant protection schedulerecommended for the main crop. The currently cultivated Intan and Mingolo, whichis in prerelease testing, are resistant to viruses and MLOs. Because birds are activeduring the ratoon crop period (February-May), bird damage has been a majorobstacle to taking ratoon crops in isolated areas where day roosts are available andthe main roosts are nearby (S. Subramanya, pers. comm.).KERALAKerala has a tradition of mixed-cropping rice varieties of different growth durations,where the late variety is harvested in the vegetative stage, along with the earlymaturingcompanion variety. The late variety regenerates and gives normal crops ofboth grain and straw. In 1981, 20 varieties of the Ninth International Rice YieldNursery planted in the wet season and fertilized at 70 kg N/ha, 15 kg P/ha, and 29 kgK/ha was cut at 15 cm stubble height; ratoons were grown without fertilizer orpesticides, with only 625 mm of rainfall spread over 38 rainy days. The averageratoon yield was only 6% (0.225 t/ha) of the main crop yield (3.59 t/ha); ratoonduration was 54 d, nearly 50% of the main crop duration of 110 d. Varietaldifferences were significant (9).ORISSAThe culture CRM 10-3628, a Mahsuri mutant studied at the Central Rice ResearchInstitute, Cuttack, in 1976 produced encouraging ratoon crop grain yield of 3.3 t/ha,or 122% of main crop yield (2.7 t/ha) (2). The ratooning ability is inherited from theparent, Mahsuri, as with the Intan mutant (from Intan) in Karnataka (21).