RICE RATOONING - IRRI books - International Rice Research Institute

PRODUCTION PRACTICES IN TUNGABHADRA RIVER PROJECT 101Table 3. Effect of weedicide application on main and ratoon crops of Tellahamsa.TreatmentMain cropRatoon cropWeed Weed Yield Weed Weed Regenerated Stem Yieldno. wt (kg) (t/ha) no. wt (kg) tillers (no.) girth (t/ha)(cm)1. Pendimethalin2. Pendimethalin3. Pendimethalin4. Oxadiazon5. Oxadiazon6. Oxadiazon7. Butachlor8. Butachlor9. Butachlor10. Amilophos11. Amilophos12. Amilophos13. Oxifluorfen14, Oxifluorfen15. Oxifluorfen16. Unweeded17. Hand weeded twice18. Weed freeSE±CD (0.05)0.751.01.50.250.500.751.001.251.50.400.500.600.080.100.12128.0127.0133.0121.3133.6148.6142.3152.3150.0144.0147.7126.6130.3131.6156.7185.7116.725.675.6716.40.1080.1040.1180.1190.1330.1200.1230.1270.170.1200.1250.1200.1420.1250.1220.3240.0560.0200.0080.054.564.364.144.463.974.264.184.03.413.923.664.044.294.053.883.625.848.250.140.4837.345.062.150.6106.6226.0207.3235.8179.0119.0159.3156.7148.3117.0115.756.752.351.310.925.40.30.930.640.30.991.331.30.870.671.641.371.510.930.820.950.890.280.030.080.249.79.2014.37.47.510.26.410.19.61.810.410.98.08.19.76.56.608.60.42.60.360.350.340.360.300.340.350.320.320.320.350.360.340.350.320.370.360.340.010.041 .861.762.041.141.041.440.941.151.021.251.441.151.421.321.530.951.561.750.100.39regeneration was suppressed in the unweeded plot. The yield levels were higher in theplots treated with pendimethalin at three concentrations and in weed-free plots.Pendimethalin suppressed some of the perennial monocot weeds, which became aproblem in the ratoon crop treated with other herbicides and in the unweeded plot(Table 3).In another weedicide experiment on a ratoon crop of Sona Mahsuri(Appendix 3), hand weeding and pendimethalin at 3 liters/ha effectively controlledweeds and increased ratoon regeneration and shoot and root weights. The herbicidecontrolled dicot plants, annual grasses, and some perennial weeds. As Table 4shows, number of weeds and weed weight were less in the hand weeding treatment.Tillers/plant, panicles/plant, and grain yield were significantly higher in handweeding and pendimethalin treatments than in the other treatments. We concludethat pendimethalin is suitable for ratoon rice crops.CONCLUSIONFertilizer nitrogen applied at 50 kg/ha immediately after ratooning increased tillernumber and dry matter accumulation in roots. Higher nitrogen levels may benefitthe ratoon crop, and effects of various levels of mineral nitrogen must be studied. Ifwe are to use Azolla as a nitrogen source for the ratoon crop, we should start byapplying it to the main crop. Applying Azolla long before ratooning allows it todecompose in time to benefit the ratoon crop. It may not, however, replace mineralnitrogen and its complementarity with mineral nitrogen must be investigated. Handweeding is a more efficient method of weed control and should be used wherever