Effect of weed control practices on weed dynamics, yield and economics of soybean [Glycine max (L.) Merrill]

The experiment was laid out in randomized block design with three replications and eight weed control treatments viz., weedy check, polythene mulching as pre emergence (PE), pendimethalin30EC (PE), chlorimuron ethyl 9g ha-1as post emergence (POE), quizalofop ethyl 50g ha-1 (POE), imazethapyr 100g ha-1 as early post emergence (EPOE), one hand weeding at 40 days after sowing (DAS) and two hand weeding at 20 and 40 DAS. The results showed that polythene mulching had the lowest weed dry matter due to effectively suppression of weed emergence. It was followed by twice hand weeding at 20 and 40 days after sowing. Weed index was found to be the highest with weedy check (42.10%) followed by the pre-emergence application of pendimethalin (19.09%). The effect of herbicide applied as pre-emergence was subdued at this belated stage, which may possibly be on account of longer period after application and restricted effective residual period. Plant height, number of pods per plant and grain yield of soybean was found to be highest in the treatments twice hand weeding at 20 and 40 DAS as well as polythene mulching. However, the net return and B:C ratio was lower in comparison to imazethapyr and quizalofop ethyl due to higher cost of labour and polythene material respectively. On an average, the application of imazethapyr as early post emergence (3.17) and quizalofop ethyl (3.02) gave significantly highest B:C ratio than the other treatments for soybean.