Field experiments were conducted during Rabi 2014, at Paddy Breeding Station, Tamil Nadu Agricultural University, Coimbatore to study the effect of pre-emergence / early post emergence herbicides along with hand weeding options on weed control in transplanted rice. The soil of the experimental field was clay loam in texture with pH 8.23. The performance of different pre-emergence application of butachlor 50% EC 1.5 kg a.i. ha-1, flucetosulfuron 10% WG in two doses at 20 g a.i ha-1 and 25 g a.i ha-1, pyrazosulfuron-ethyl 10% WB 75 g a.i ha-1, early post emergence application of penoxsulam + cyhalofop-butyl in two doses at 120 g a.i ha-1 and 135 g a.i. ha-1, bispyribac sodium 10% SC 35 g a.i ha-1 were evaluated along with pre-emergence application of pretilachlor 50% EC 1.0 kg a.i ha-1 + HW at 45 DAT, butachlor 50% EC 1.0 kg a.i ha-1 + HW at 45 DAT in comparison with hand weeding twice at 20 and 40 DAT, unweeded control and weed free check. The test variety used in this experiment was Co (R) 50. The experimental results revealed that weed free check had 100% weed control efficiency (WCE) in all the stages of crop growth. Among the various treatments tested, At 90 DAT, weed control efficiency (WCE) was maximum with early post emergence application of penoxsulam + cyhalofop-butyl135 g a.i. ha-1 (T5 ) recorded the maximum weed control efficiency of 85.78%. The number of productive tillers m-2 recorded ranged between 441 in T5 and 295 in unweeded control (T11). Grain yield ranged between 7717 kg ha-1 in weed free check (T12) and 5194 kg ha-1 in unweeded control (T11). The maximum straw yield of 9277 kg ha-1 was recorded in weed free check (T12). This was on par with early post emergence application of penoxsulam+ cyhalofop-butyl 135 g a.i. ha-1 (T5 ) and hand weeding twice at 20 and 40 DAT (T10) with 9206 kg ha-1 and 9019 kg ha-1.
Deiveegan et al. (Sun,) studied this question.