RICE RATOONING - IRRI books - International Rice Research Institute

174 RICE RATOONINGTable 12. Weed biomass of selected species in transplanted IR42 as affected byweed control method a (22).TreatmentBiomass b (g/m 2 )Rate(kg ai/ha) Paspalum Echinochloa Monochoriadistichum glabrescens vaginalis2,4-DBentaronButachlorThiobencarb/2,4-DHand weedingNo weeding0.82.01.51.0/0.5––70 ab10 ab2 a10 ab3 a33 b2 a8 a0 a1 a2 a30 b1 e3 a1 a5 a6 a30 ba Av of 4 replications. In a column, means followed by a common letter are notsignificantly different at the 5% level. b Sampled at 70 d after transplanting.shifted from annuals to perennials (29). For example, a change from conventional tozero tillage in lowland rice shifted weed species from the annuals Echinochloa sp.and Monochoria vaginalis to the perennials Paspalum distichum and Scirpusmaritimus (7). Because rice ratooning is a no-till culture, the same weed shift couldalso occur.Hou (22) reported that of the 10 weed species present in the main crop, M.vaginalis comprised 37%, P. distichum 21%, and Echinochloa glabrescens 7%. In theratoon crop, however, M. vaginalis decreased to 3%, P. distichum increased to 63%,E. glabrescens to 18% (Fig. 4). The weed shift could be partly due to the weed controlmeasures used (Table 12). E. glabrescens and M. vaginalis, but not P. distichum,were significantly reduced by all herbicides. The tolerance of P. distichum for theherbicides used and the absence of tillage contributed to its increase in the ratooncrop.These data suggest that weed control, particularly of perennial weeds, whichare tolerant of herbicides, should be done on the main crop to minimize theirproliferation in the ratoon crop. Annual weeds in the ratoon crop can easily becontrolled with supplemental manual or mechanical weeding or with chemicaltreatment.REFERENCES CITED1. Altamarino, L. 1959. The influence of spacing on the development, yield and agronomic characters ofrice ratoon crop. BS thesis, University of the Philippines at Los Baños, Laguna, Philippines. 20 p.2. Anonymous. 1963. Second rice crop: a signifcant factor on total rice production in Texas. Rice J.66(5):10-12, 43.3. Bahar, F. A. 1976. Prospects of raising productivity of rice by ratooning. MS thesis, University of thePhilippines at Los Baños, Laguna, Philippines.4. Bahar, F. A., and S. K. De Datta. 1977. Prospects of increasing total rice production throughratooning. Agron. J. 69:536-540.5. Balasubramanian, B., Y. B. Morachan, and R. Kaliappa. 1970. Studies on ratooning in rice. I.Growth attributes and yield. Madras Agric. J. 57(11):565-570.6. Beachell, H. M., J. E. Scott, N. S. Evatt, J. G. Atkins, and J. V. Halick. 1961. Belle Patna. Rice J.84(6):24.7. Bernasor, P. C., and S. K. De Datta. 1981. Long-term effects of reduced tillage on weed shift inwetland rice. Paper presented at the 12th Annual Conference of the Pest Control Council of thePhilippines, 13-15 May 1981, University of the Philippines at Los Baños, Laguna, Philippines.