A field experiment was carried out during winter seasons of 1996–97 and 1997–98 and the weed population, growth and the mustard seed yield were studied. Four main plot treatments with 50 and 100% recommended NPK dose with or without sulphur and six weed management practices viz., weedy check, weed-free, hoeing 20 DAS, 40 DAS and pre-emergence alachlor @ 1.0 kg ha with or without hoeing at 40 DAS were studied in a split plot design. Density of different groups of weeds was not affected much due to fertility levels but weed dry matter was increased significantly due to increase in NPK level, however, the effect of sulphur was not significant. In unweeded plot, sedge population decreased and broad leaved weed population was increased with advancement of cropping season, however, grass population did not show any definite trend. Pre-emergence alachlor with one hoeing at 40 DAS maintained comparatively lower weed density and dry matter throughout the crop season which was 73.5 and 73.8% less dense and 85.0 and 81.7% less heavy compared to unweeded control in 1996–97 and 1997–98, respectively, and recorded seed yield at par with weed-free.
