The improved varieties of field crop are although very responsive to the higher inputs but it deplete soil fertility. The Integration of green manuring crops along with inorganic fertilizers in the existing cropping system can help to sustain soil fertility and crop productivity. The main objective of the experiment was to assess the effect of green manuring crops on soil fertility and crop productivity. A two years long field experiment was conducted at the Agricultural Research Institute Tarnab, Peshawar-Pakistan. The experiments were laid out in randomized complete block design (RCBD) with split plot arrangement using three replications. A combination of crop species (guar and millet) and crop age at green manuring (40,70 and 100 days after sowing, DAS) were allocated to main plots while the combination of plant parts (whole plant and stubbles) used as green manuring and nitrogen levels (0, 75 and 100 kg ha-1) were applied to sub plots. The two years average data showed that as compared to millet, guar as preceding green manuring crop had significantly improved canola growth, seed yield, oil yield and qualitative traits. Furthermore, based on soil tests, the soil N contents in guar sown plots was significantly higher when tested prior to canola sowing and after canola harvest. The data also revealed that soil C contents in guar sown plots after canola harvest was also significantly higher. Canola sown on the guar green manuring plots had delayed flowering as compared to those green manuring of millet sown plots. Whole plants green manuring as compared to stubbles had significantly enhanced canola growth, yield and yield components and qualitative traits. Based on soil test the soil N contents before canola sowing and after canola harvest and soil C contents after canola harvest were significantly higher in guar incorporated plots as compared to millet plots. Plants that were incorporated at the age of 100 DAS had significantly lower canola growth, yield and yield components, seed N and protein contents as compared with 40 and 70 DAS green manuring. However, the soil C contents of 100 DAS were significantly higher than 40 and 70 DAS green manuring. Although the green manuring at the age of 40 DAS had significantly lower leaf area plant-1 and leaf area index of canola, the other attributes of canola due to age of incorporations (40 DAS) were at par with those of green manuring at the age of 70 DAS. Nitrogen application had significantly affected all the parameters except emergence m-2, seed pod-1 and glucosinolates content. Increasing N level from 0 to 100 kg ha-1 had significantly enhanced growth, yield and yield components and qualitative traits of canola. Nitrogen application at the rate of 75 kg N ha-1 had significantly delayed maturity, having taller plants, more branches plant-1, harvest index, oil yield, and seed protein content as compared with 100 kg N ha-1. Significant Improvement in yield and yield xiii components, quality of canola having taller plants with delayed flowering and maturity were recorded in second year of the experiment as compared with first year. Data on the interaction effect showed significant increase in seed and oil yield of canola with the increase in N levels in both guar and millet sown as preceding green manuring crops irrespective of their age of incorporation. Guar as a green manuring crop had significantly improved yield and quality of canola as compared with millet crop, whole plant green manuring of the crop species at 40 DAS had enhanced seed, oil yield and quality traits followed by 70 DAS. Application of 100 kg N ha-1 along with the green mannuring management had significantly increased all the parameters except oil contents of canola. Data on economic returns showed that guar at 40 DAS incorporation along with 100 kg N ha-1 gave maximum value cost ratio. Our study indicated that green manuring provides an opportunity to improve quantitative and qualitative yield of canola in addition to improving soil health without disturbing the existing cropping system. Hence, it is concluded that green manuring preferably legumes incorporation as whole plant up to the age of 40-70 DAS coupled with 100 kg N ha-1 is recommended for enhancing overall productivity and net economic returns of canola in agro-ecological zones of Khyber Pakhtunkhwa Province, Pakistan and areas alike.