Vol. 8, Issue 5 (2019)

Author(s):
G Manisankar, T Ramesh, S Rathika, P Janaki and P Balasubramanian

Abstract:
A field experiment was carried out at Department of Agronomy, Anbil Dharmalingam Agricultural College and Research Institute, Trichy during Samba, 2018 to study the effect of sequential application of herbicides on weed dynamics, weed control efficiency, growth, yield and economics of transplanted paddy. The experiment was laid out in split plot design with four main plot and five sub plot treatments. Main plot treatments were pre plant application of herbicides namely glyphosate 2.50 kg/ha, glufosinate ammonium 1.00 kg/ha and halosulfuron methyl 67.5 gm/ha and control. Sub plot treatments consisted of different weed management practices in transplanted paddy namely pre emergence application of bensulfuron methyl + pretilachlor 660 gm/ha on 3 DAT + one hand weeding on 45 DAT, post emergence application of bispyribac sodium 25 gm/ha on 15 DAT + one hand weeding on 45 DAT, application of bensulfuron methyl + pretilachlor 660 gm/ha on 3 DAT + bispyribac sodium 25 gm/ha on 25 DAT, hand weeding twice at 25 and 45 DAT and unweeded control. The pre plant herbicides sprayed 15 days before puddling. These results revealed that pre plant application of glyphosate 2.50 kg/ha recorded significantly lower weed density (18.1 and 16.7 No/m²), weed dry weight (14.5 and 15.0 gm/m²) and higher in weed control efficiency (78.1 and 88.3%) at 40 and 60 DAT respectively, growth characters such as tillers (585 No/m2), dry matter production (11517 kg/ha), yield characters like productive tillers (350 No/m2) and filled grains (153 No/panicle) and grain yield (4232 kg/ha) than halosulfuron methyl and control. These results are on par with glufosinate ammonium 1.00 kg/ha. Highest net return (Rs. 54391/ha) and B:C ratio (2.51) were obtained with application of glyphosate 2.50 kg/ha and this was followed by glufosinate ammonium 1.00 kg/ha which registered net return of Rs. 51198/ha and B:C ratio of 2.39. Among the weed management practices followed in paddy, hand weeding twice at 25 and 45 DAT registered significantly lower weed density (11.8 and 9.4 No/m2), weed dry weight (8.9 and 6.9 gm/m2) and higher weed control efficiency (91.6 and 96.4%), dry matter production (12075 kg/ha) than unweeded control. This was on par with application of bensulfuron methyl + pretilachlor 660 gm/ha on 3 DAT + bispyribac sodium 25 gm/ha on 25 DAT, post emergence application of bispyribac sodium 25 gm/ha on 15 DAT + one hand weeding on 45 DAT. Post emergence application of bispyribac sodium 25 gm/ha on 15 DAT + one hand weeding on 45 DAT registered significantly higher productive tillers (338 No/m²), filled grains (159 No/panicle) and grain yield (4327 kg/ha) than unweeded control. Higher net return (Rs. 53298 /ha) and B:C ratio (2.40) obtained with application bispyribac sodium 25 gm/ha on 15 DAT + one hand weeding on 45 DAT, followed by bensulfuron methyl + pretilachlor 660 gm/ha on 3 DAT + bispyribac sodium 25 gm/ha on 25 DAT.