To study the response of carrot crop (Daucus carota L.) to foliar application of different potassium fertilizers and some soil amendments i.e., magnetite iron and humic substances (granules or powder) under clay soil conditions, two field experiments were conducted during winter seasons of 2014 and 2015 at the Horticulture Experimental Station of Agriculture Ministry, El-Baramon Experimental Farm, Dakahlia Government, Egypt. The obtained results revealed that humic substances granules or magnetic iron caused marked increases on vegetative growth, yield and NPK uptake in both shoots and roots of carrot plants. Potassium foliar application caused significant increasing on previously mentioned characters as well as carbohydrate and carotenoids content in roots. In addition, potassium foliar application caused significant increasing on previously mentioned characters, which showed a progressive increase in its content with application KNO₃ compared with other sources of potassium. There were statistically significant increases in plant growth, yield, carotenoids, carbohydrate and NPK contents of carrot due to humic substances granules treatment especially under application of potassium nitrate. Finally, the foliar application of potassium nitrate integrated with humic granules or magnetic iron was the best combination and it is recommended for increasing productivity and improving root quality of carrot (cv. Chantenay) under clay soil conditions.