The present experiment conducted during kharif season of 2008 and 2010 at AICRP on Water Management field, R.A.U, Pusa, Samastipur, (Bihar) with the rice variety Proagro (Arize) 6444 (hybrid) to find out the effect of irrigation and mechanical weeding on growth, yield and quality of rice under system of rice intensification. Irrigating with submergence to 2.5 cm 3 days after disappearance of ponded water and rotary weeding at 20, 30 and 40 DAT were found to be most congenial for the rice crop grown under system of rice intensification. 1.Water use efficiency and water productivity were optimum with irrigation level of submergence to 2.5 cm 3 days after disappearance of ponded water and rotary weeding at 20, 30 and 40 DAT. 2.Weed population and weed dry weight were increased with decrease in number of irrigation and mechanical weeding and were found minimum with irrigation level of continuous submergence and four rotary weeding at 10, 20, 30 and 40 DAT. 3.N, P and K uptake were increased with increase in number of irrigation and mechanical weeding which were found to be maximum with irrigation level continuous submergence to 2.5 cm and rotary weeding at 10, 20, 30 and 40 DAT.