Greenhouse experiments has been conducted during 2006 and 2007 season at Sakha Greenhouse Station, Kafr El-Sheikh to study the impact of different compost levels (crop residuals) on damping-off caused by Pythium ultimum, Fusarium solani and Sclerotinia sclerotiorum  on growth productivity and quality of cucumber as well as their effect on powdery and downy mildew diseases .The applied compost levels were 0.68, 1.36, 2.05, 2.73 and 3.41 kg/m²  while the control treatment was cattle manure fertilizers . Application of 0.68 and 1.36 kg/m² compost gave maximum protection against post emergence damping-off and reduced the disease incidence to 7.5 and 11.25%, respectively compared with the fungicide Topsin M₇₀(1.25%). While, the compost levels of 2.73 & 3.41 kg/m² gave less effect in this respect. The levels of compost 0.68 &1.36 kg /m² were most effective in controlling powdery and downy mildew and  1.36 kg/m² recorded the best results of the plant growth, i.e. stem length, leaf area, number of branches and leaves, total chlorophyll as well as fresh and dry weight followed by the compost levels of 0.68, 2.73 and 3.41 kg/m^2, respectively. Data also showed that the highest increased in cucumber yield , number of fruits, diameter and length of fruits had been achieved when compost at the rate  of 2.05 and1.36 kg/m² were applied.