Field experiments were conducted during winter seasons of 1996–97 and 1997–98 at Jabalpur. Treatments comprised combinations of four N levels (0, 40, 60 and 120 kg/ha) and two planting geometry (uni-and bi-direction) in main plots; two herbicides viz., isoproturon 1.0 kg and oxadiazon 0.75 kg/ha as pre-emergence were compared with hand weeding at 30 DAS and weedy check in sub-plots. Weed population at 25 DAS was not influenced due to increasing levels of N; however, weed dry weight at harvest was reduced drastically at 120 kg N/ha as compared to no nitrogen. Planting geometry failed to affect population and dry matter of weeds. Both the herbicides significantly reduced population as well as dry matter of weeds over weedy check. Increasing levels of N upto 120 kg/ha significantly increased the mustard yield. Bi-directional sowing resulted in slightly higher seed yield than uni-directional sowing but differences were not significant. Weeds caused 26.5% reduction in seed yield of mustard as compared to isoproturon treated plot. Isoproturon produced the highest seed yield but was at par with oxadiazon. The interaction of nitrogen levels x weed control methods was not significant during both the years. However, results revealed that with increase in nitrogen levels from 0 to 120 kg/ha there was substantial increase in seed yield under herbicide treated and hand weeded plots as compared to weedy plots.
