RICE RATOONING - IRRI books - International Rice Research Institute

84 RICE RATOONINGTable 3. Yield trial a of varieties for ratoon (17).TypeVarietyYield (t/ha) bMain crop Ratoon crop TotalHybrid riceHybrid riceHybrid riceHybrid riceConventionalConventionalZaisheng YouAi You 1Ai You 1Shan You 2ZaisheigaiLuke 38.0 a6.8 b6.7 b7.6 a5.2 c6.3 b3.0 a1.7 bc2.6 ab1.3 c2.7 ab2.0 bc11.0 a8.5 bc9.3 b8.9 bc7.9 c8.3 bca Randomized complete block design, three replications. b Figures within a columnfollowed by the same letter(s) show no significant difference at the 5% level (LSRmethod).2. Growth stages of medium-duration midseason hybrid-ratoon rice in relation to temperature.4. Sow and transplant early. Early sowing and transplanting of the main cropensures safe heading of the ratoon (16). The safe growing season insoutheast Sichuan is about 190-195 d. (The critical low temperatures are13 °C for sowing and 23°C for heading [Fig.2]). That is long enough forsome medium-duration hybrids, such as Zai Sheng You, and the ratooncrops.Thus, hybrid vigor can be exploited twice to produce high yields from the mainand ratoon crops.In southeast Sichuan, an area of 533,000 ha consists of rainfed fields, wherewater has to be reserved after the rice season every year to avoid drought in the nextgrowing season. Generally, these winter waterlogged fields are fertile; however,because of the limited duration of the growing season, only one rice crop can begrown. Farmers used to grow a single crop of medium-duration varieties. Now amedium-duration hybrid and its ratoon may take its place, and higher total grainyields obtained.