Conservation agriculture (CA) can promote sustainable crop intensification. However, weeds are the major constraints under CA, in the initial years. Nitrogen (N) management under CA is also crucial. A field experiment was undertaken to study the effect of conventional tillage (CT) and CA with and without residue using 75 and 100% recommended N dose on weed dynamics and crop productivity during 2018-19 and 2019-20 in maize (Zea mays L.) under maize - wheat (Triticum aestivum L.) - greengram (Vigna radiata (L.) Wilczek) cropping system at ICAR-Indian Agricultural Research Institute, New Delhi. Nine CA-based treatments and one conventional tillage were laid out in a randomized complete block design with three replications. CA-based zero till (ZT) bed planting systems with residue retention resulted in significant reductions in total weed density and biomass compared to CT. Permanent broad bed with residue using 75% N resulted in 34% lesser weed density than CT. Among the CA-based treatments, the permanent broad bed with residue using 100% N resulted in 22% higher maize grain yield than CT (5.72 t/ha) with 36% higher net returns than CT. However, the permanent broad bed with residue using 75% N was found comparable in this regard and may be recommended for sustainable maize production under the maize-wheat-greengram system in north-western Indo Gangetic Plains of India.