A field experiment was conducted on a sandy soil for winter season 2004 at the Agricultural Experimental Station, Kalapshoo, Dakahlia governorate, to study the combined effects of different types of organic materials (Corn straw, FYM and Mix) with three levels of them i.e. without addition, 14 and 28 ton /fed and three levels of mineral nitrogen fertilizers were used in this study i.e. without addition, 300 and 600 kg (NH₄)₂SO₄/fed. While potassium and phosphorus were added in two levels, P₁K₁=150 kg Ca (H₂PO₄)₂/fed + 50 kg K₂SO₄/fed and P₂K₂=300 kg Ca (H₂PO₄)₂/fed + 100 kg K₂SO₄/fed on plant content of nitrate and crop productivity. The treatments were arranged in a split split split plot design. The results obtained were as follows: The individual and combined treatments of organic matter and inorganic fertilizers gave significant increase in shoot, root, yields and fruit of squash plant.  Concerning individual traits, there was significant increase in dry weight of shoot, root and fruit with adding FYM at the harvest. Whereas with organic levels it was noticeable that increase in dry weight of shoot, root and fruit with adding 28 ton.fed^-1 organic manure. With increasing nitrogen fertilizer till double recommended doses. The combined effect of results show that, the combination of double recommended dose of N + 28 ton.fed^-1 of FYM fertilization treatments gave significant increase in dry weight, and nitrate content. Concerning combined traits, there was a significant increase in fruit dry weight with adding 28 ton.fed^-1 of organic manure + double recommended dose of nitrogen (N₂). Organic manure and inorganic fertilizers gave significant increases in nitrate and nitrite contents, the highest value of plant NO₃^- content with adding 28 ton.fed^-1 with double recommended doses of nitrogen fertilizer, the same influence of the farmer treatments was found with NO₂^- content. So, it is recommended to add great amounts of organic and inorganic fertilizers to sandy soil for two benefits, firstly to give the plants their nutrients requirements, secondly to easies releasing nutrients in available forms through activating the decomposition process of organic matter. Also, we must be attentioned for vegetable crops and their contents of nitrate to prevent health hazard for human.