Average yield of Rice, Wheat, Maize and Pea crop is very low in Pakistan as compared to world. In present studies the possible role of sunflower allelopathy in decreasing the economic produce of these crops was evaluated. During early growth bioassays, all the test crops were subjected to different concentration of fresh and dry root, stem and leaf aqueous extracts of sunflower variety Hysun 33. Leaf extracts especially in higher concentrations, followed by stem and root, significantly inhibited the studied parameters of all test crops. During field trials sunflower was grown to maturity twice a year and was then mixed in field plots to be used for the cultivation of test crops after sunflower mulching (class A) and harvesting the crops of class A (class B), under various treatments. In both the classes the growth and mycorrhizal colonization of these crops was inhibited significantly under sunflower mulching. Seven allelochemicals were identified through thin layer chromatography in this sunflower variety. The present study concludes that residual sunflower allelopathy could be responsible for low produce of test crops when grown in rotation with sunflower.