RICE RATOONING - IRRI books - International Rice Research Institute

160 RICE RATOONINGTable 5. Effect of N level before main crop harvest on tillers, panicles, and ratooncrop yield of Aiyou 2, cut 40 cm above ground, 1981.N level(kg/ha)69.034.50TillersPanicles(no./m 2 ) (no./m 2 )435 a360 b230 c306 a277 a192 bYield(t/ha) a2.9 a2.7 a1.9 ba Av of 3 replications. Means in a column followed by the same letter are not significantlydifferent at 5% level.Table 6. Effect of cutting height on plant characters of ratoon crops of varieties Aiyou 2 (1981)and Zaishengyou (1983).CharacterAiyou 2Zaishengyou26 cm 33 cm 40cm 43cm 23cm 33cm 43cmPercent of 2d node cutHeading date 26 AugPanicles/m 2 244Spikelets/panicle 54Filled spikelets (%) 791000-grain wt (g) 22Yield (t/ha) 2.4(%) 10021 Aug2745476232.610819 Aug3045180232.911919 Aug3015087223.01266310 Sep2836585212.910046 Sep3915686213.211402 Sep4835887214.1148than those at T1 and T3. The yield of T2 was 4.4% higher than T1 and 5.2% higherthan T3, but yield did not differ significantly.In production trials, N rate and application time varied with soil fertility andmain crop status. Generally, quick-acting N fertilizer at 35-70 kg N/ha wastopdressed 2 wk before main crop harvest. No additional N fertilizer was necessary.Cutting heightCutting height determines the origin of the ratoon tiller and the growth duration ofthe ratoon crop. Most ratoon tillers of hybrid rice sprouted from the 2d, 3d, and 4thnodes of the main crop stubble and headed before low temperature in autumn.When cutting height of the main crop ranged from 23 to 43 cm, the ratooncrop formed more panicles, matured earlier, had a higher percentage of filled grains,and higher yield (Table 6). The maximum yield increase from a 23 cm cutting heightto 43 cm was 48%.Height of the 2d node of variety Zaishengyou was 18-34 cm above ground;average height was 24.9 ± 3.9 cm. Furthermore, most of the 2d node remained bycutting above 33 cm (Table 6), which means that the optimum cutting height rangesfrom 30 to 40 cm.PRODUCTION DEMONSTRATIONSFrom 1983 to 1985, ratoon crops were obtained with hybrid rice on 1,346 ha, inJiangjin, Yongchuan county, Sichuan. The average main crop yield was 7.9 t/ha