RICE RATOONING - IRRI books - International Rice Research Institute

AGRONOMIC PRINCIPLES AND PRACTICES OF RATOONING 171Table 9. The effect of cutting height and flooding time on missing hills and grain yield oflR2061-632-3-1 ratoon a (4).Cutting heightFlooding time(d after Missing hills (%) Grain yield (t/ha)harvest)Ground level 15 cm Difference Ground level 15 cm Difference048121679 c3.3 b25 ab18 ab16 a3 a2 a2 a1 a1 a76** 0.0 c31** 1.7 b23* 1.9 ab17*2.4 a15 ns 2.3 a2.5 a2.4 a2.4 a2.3 a2.6 a–2.5**–0.7 ns–0.5 ns0.1 ns–0.3 nsaAV of 4 replications. In a column, means followed by a common letter are not significantly differentat the 5% level. *, **Significant at the 5 and 1% levels, respectively.3. Percentage of sprouted bud of IR42 as affected by plant growthregulator (22).Quddus (39) reported that GA3, indole acetic acid (IAA), naphthalic aceticacid (NAA), and 2,4-D also increased panicle number but had no pronounced effecton grain yield and other yield components.The use of PGR in improving ratoon crops is a relatively new research topic.Preliminary results have not clearly defined their effects on yield, much less on totalperformance of the ratoon crop. More studies on this aspect are needed to arrive atdefinite conclusions.PESTS OF RATOON CROPSInsects and diseasesOne of the many risks associated with rice ratooning is the buildup of insects hostingon cut stubble left on unplowed ground (11). Insects that are likely to heavily infestrice ratoons are stem borers and leaf beetles.