RICE RATOONING - IRRI books - International Rice Research Institute

156 RICE RATOONINGVARIETIES AND CULTURAL PRACTICESCoordinated trials of rice ratooning were conducted from 1981 to 1985 in southeastSichuan. Through varietal screening and multilocation yield tests, the hybridsZaishengyou, Aiyou 1, Aiyou 2, and Shanyou 63 were identified as having goodratooning ability. Ratoon crop growth and development, yield, planting time, Nfertilizer application, and cutting height were studied at five sites; productiondemonstrations with hybrid rice ratooning were conducted using test results.VarietiesMultilocation ratooning yield trials were conducted in 1981-85. Some hybrid ricesare not only high grain yielding but also have high ratooning ability (Table 1).Zaishengyou (Chaoyang IA/Taiguodaoxuan) was the best among the entries.Its main crop yield was comparable to that of the popular hybrid Shanyou 2, and itmatured 4 d earlier. Yield components of the ratoon crop were 300 panicles/m 2 ,60 spikelets/panicle, and about 80% filled grain. Its ratoon yield was higher andmore stable than the others.Aiyou 1 had wide adaptability, relatively high main crop yield, and ratherstrong ratooning ability. It has been adopted by many farmers.Aiyou 2 ranked third in ratoon yield, but the main crop yield was low becauseof its low tolerance for high temperature at flowering. It seems unsuitable for ratooncropping.Shanyou 63, a hybrid rice resistant to blast disease, showed rather highratooning ability. It yielded 7.6 t/ha in the main crop and 2.5 t/ha in the ratoon crop.It is extensively grown and we are promoting its use for rice ratooning.Yield componentsIn 1981, Ren (3) analyzed ratoon grain yield of the hybrid Aiyou 2 in relation to theyield components: number of mature panicles, spikelets per panicle, filled spikeletpercentage, and 1,000-grain weight. Mature panicles and percentage of filledspikelets were the principal factors affecting ratoon crop output. The correlationcoefficients were 0.93** for number of panicles and 0.71** for percentage of filledTable 1. Grain yields of main and ratoon crops of some rice varieties in Jiangjin,Sichuan, 1983.TypeVarietyGrain yield (t/ha) aMain crop Ratoon crop TotalHybridHybridHybridHybridHybridConventionalConventionalZaishengyouAiyou 1Aiyou 2Shanyou 63Shanyou 2ZaishengaiLuke 38.0 a6.8 b6.7 b7.6 a7.6 a5.2 c6.3 b3.0 a1.7 bc2.6 ab2.51.3 c2.7 ab2.0 bc11.0 a8.5 bc9.3 b10.18.9 bc7.9 c8.3 bca Av of 3 replications. Means in a column followed by the same letter are notsignificantly different at the 5% level.