The experiment consisted of five planting geometry viz., sole maize, sole blackgram, maize + blackgram (1:1), maize + blackgram (2:1) and maize + blackgram (2:2) and four weed management practices viz., weedy check, hand weeding (HW) at 30 DAS, alachlor 2.0 kg/ha as pre emergence (PRE) and alachlor 1.5 kg/ha as PRE + HW at 40 DAS. These treatments were evaluated under split plot design with three replications. At harvest of maize (105 DAS), weed population and nitrogen removals of all species of weeds were significantly highest under sole maize. However, the highest nitrogen removal by weeds was recorded under weedy check by all the weed species, while the lowest removal of nitrogen was in alachlor 1.5 kg/ha + HW at 40 DAS. Among the planting geometry, the grain yield, productivity rating index (PRE), production efficiency (PE) and weed control efficiency (WCE) were highest under maize + blackgram (2:1) for maize, however weed smothering efficiency of maize was highest under maize + blackgram (1:1). The same parameters were highest under sole blackgram. At harvest stages of blackgram (75 DAS) and maize (105 DAS), dry weight of weeds was lowest with the application of alachlor 1.5 kg/ha + HW at 40 DAS. This treatment produced maximum grain yield, PRI and PE of maize and blackgram, along with higher WCE.