The present study was undertaken to understand the effects of nitrogen (N) on crop–weed interactions for development of integrated weed management (IWM) systems in onion. The field experiment was conducted in semi-arid conditions at SKN Agriculture University, Jobner (India). Seven IWM practices were tested in main plots and four N doses (0, 50, 100, and 150 kg ha-1) in sub plots. The experiment was laid out in split plot design with three replications using onion cultivar RO 252 during two 2016-17 and 2017-18. It was observed that the interactive use of N doses with IWM practices significantly affected crop dry matter (CDM) and marketable yield. Application of two hand weeding (HW) at 20 and 40 DAT combined with 120 kg Nha-1 was most effective to obtain higher marketable bulb yield of onion followed by pendimethalin (1.0 kg a.i. ha-1) + one HW at 40 DAT in combination with 120 kg Nha-1. The study will be useful to effectively control major weed flora and optimization of nitrogen dose for higher productivity of winter season onion crop in loamy sand soils of semi-arid conditions.