Nitrogen addition and weeds controlling are important practices for a successful plant growth and maximizing yield. However, excessive nitrogen and herbicides application may pose a potential threat for soils, water and human health. This study was performed to investigate the effect of increasing nitrogen fertilization in combination with different weed controlling practices on the growth and yield of onion. Also, the potential risk due to residual nitrate and herbicides was a matter of concern. To achieve these goals, field experiments were performed for two successive growing seasons 2014/2015 and 2015/2016. Nitrogen fertilizer was added at different rates of 0.0, 178.6, 357.14 and 535.71 kg N ha^-1. In addition, weeds were controlled through hand weeding and chemical herbicides addition. The obtained results showed that, increasing the rate of applied nitrogen in combination with hand weeding practice enhanced plant growth in terms of plant height, fresh weight, dry weight and bulbing ratio. Furthermore, nitrate levels in both soils and onion bulbs increased due to high nitrogen addition. However, the levels of P and K in bulbs decreased due to the increased biomass of the growing plants. For Hazard Index (HI) analysis, the HI of nitrate and bentazon didn't exceed the safe level of 1. However, increasing the rate of applied nitrogen and using chemical herbicides elevated the values of HI. We concluded that, high nitrogen addition enhanced the plant growth and yield, and there was no potential risk from nitrate. Therefore, additional studies are needed to investigate the feasibility of increasing nitrogen fertilization through foliar application and using hand weeding in the newly reclaimed soils to maximize yield and prevent the environment and human health deterioration.