Weeds infestation is one of the major constraints in limiting the crop productivity particularly when the organic manures are applied. Therefore an experiment was designed to study the weeds dynamics with respect to addition of different forms of dairy manure with nitrogen (N) management for improved economic yield of maize. The experiment was comprised of two forms of dairy manure, i.e. fresh and composted and their respective levels (3, 4 and 5 tons ha^-1) with supplemental nitrogen application method (single split and two splits). The results of the experiment indicated that different forms and levels of manure significantly affected weeds density m^-2, weeds fresh weight, weeds dry weight and grain yield whereas nitrogen application timing had no significant effect on weeds density, weeds fresh and dry weight but considerably varied the grain yield of maize. The weeds density, fresh and dry weights of the weeds were higher with the addition of fresh dairy manure as compared to composted manure. In contrast, the grain yield was higher with the addition of composted dairy manure as compared to fresh manure. Among different levels dairy manure addition at the rate of 5 tons ha^-1 significantly increased the weeds density, weeds fresh and dry weights. The grain yield of maize was also higher with the addition of 5 tons manure ha^-1. The grain yield was higher with the addition of supplemental nitrogen at the rate of 100 kg ha^-1 in two equal splits half each at sowing and V6 stage. It was concluded that composted dairy manure at higher level of (5 t ha^-1) increased the yield of maize and declined the weeds infestation.