Pre-plant and pre-emergence herbicides for weed management in transplanted rice

摘要

The study on pre-plant and pre-emergence herbicide weed management in transplanted rice during Rabi 2011-12 at Tamil Nadu Agricultural University, Coimbatore revealed that pre-plant application of glyphosate 0.75 kg a.i. ha~(-1) recorded higher mean grain yield (5766 kg ha~(-1)), lower weed density (3.2, 6.7 and 5.6 m~(-2) at 20,40 and 60 DAT), dry weight (2.0, 3.7 and 4.1 g m~(-2) at 20,40 and 60 DAT) and weed control efficiency (71,5, 69.5 and 69.2 % at 20,40 and 60 DAT) compared to non applicationof glyphosate. The application of pre-plant glyphosate eliminated most existing vegetation and prevented weed establishment. In main field among the different treatments early post emergence (EPOE) application of Bensulfuron methyl+ pretilachloar (6.6 GR) at 0.06+0.60 kg /ha recorded significantly higher grain yield (6450 kg ha~(-1)), straw yield (8614 kg ha~(-1)) through better weed control efficiency as indicated by lower weed density (4.3,5.5 and 4.6 m~(-2) at 20,40 and 60 DAT), reduced weed dry matter (2.2,3.4 and 3.0 g m~(-2) at 20,40 and 60 DAT) and higher weed control efficiency (80.6,83.2 and 85.0% at 20,40 and 60 DAT) followed by PE application of Pretilachlor at 0.75 a.i.Kg ha~(-1) + HW at 40 DAT other treatments. This is due to better control of pre emerged weeds and as well as emerging weeds as it has a high level of activity against broad leaved weeds and sedges. Pre-plant application of glyphosate 0.75 kg a.i ha~(-1) recorded highest net return (X25,l88/ha) compared to non glyphosate application (%/ha 22,579). Among the different herbicides, EPOE Bensulfuron methyl + pretilachlor (6.6 GR) at 10 DAT registered higher gross returns ft/ha. 59,318 ha~(-1)), net return (?/ha. 33, 120 ha~(-1)) andB: C ratio (2.19).