A field experiments were conducted to study the seed production and shattering pattern of barnyardgrass (BYG) in response to its emergence and transplanted rice geometry. A split-plot design with four replications was used with transplanted rice geometry (M1- 15×15 cm, M2- 25×25 cm) in main-plots and BYG emergence timings [S1- 0 days after transplanting (DAT), S2- 20 DAT, S3- 40 DAT] as sub-plot treatments.  The increase in crop spacing by 10 cm in each row and column (M2) increased the BYG seed production by 20% over M1. The wider crop geometry (M2) also recorded significantly higher density (17.2%), dry matter production (39.6%), leaf length (11.6%) and panicle count (24.7%) than M1. With respect to time of emergence, the maximum number of seeds per BYG plant was produced (31987) by S1 (BYG emergence at 0 DAT) while S3 (BYG emergence from 40 DAT) recorded the lowest (5641) number of seeds. The delay in BYG emergence by 40 days leads to 82% reduction in BYG seed production/plant. With respect to seed shattering, the maximum seed (152/panicle) shattering was recorded in crop geometry M1 (15×15 cm) which is 18% higher over M2 (25×25 cm) at 20 days after installation (DAI) of weed seed trap, while at harvest the difference was non-significant. However, seed shattering was significantly more with M2 (25×25 cm) compared to M1 (15×15 cm) and with S1 (BGY emergence from 1st DAT), which was higher by 46% and 50% at 20 DAI and at harvest, respectively, over S3. The seed shattering percentage of BYG was 22 to 26% while around 75% of the seeds produced by BYG remained intact at the time of harvest making BYG a suitable candidate for harvest weed seed control (HWSC). Management techniques need to be developed to control escaped or late emerged BYG in order to prevent its soil weed seedbank enrichment and to ensure sustainable weed management.