Two field experiments were carried out during the two successive seasons of 2009 and 2010 at south El-Tahrir Research Station, (Ali Moubarak) Horticulture Research Institute to study the response of cassava plants to the combination between three rates of water requirements and compost manure at three rates of application. Obtained results were as follows: 1- The longest plants, highest leaves and largest length and diameter of branches as well as the heaviest total cassava yield and its best physical (tuber length and diameter) and chemical characters expresed as N,P and K contents of tuber tissues were recorded with cassava plants received 35 ton/fed. of compost followed in descending order by the addition of compost manure at 30 ton/fed. and the finally the application of 25 ton/fed. of compost manure. 2- The medium and high level of irrigation water (100 and 120%) encouraged the vegetative growth of cassava plants expresed as number of leaves, stem length, number of later branches and branches diameter and total tuber yield and the highest values of physical and chemical tuber quality i.e. tuber length and diameter as well as N,P and K contents of tuber tissues. 3- In spite of the non significant effect of the interaction of water requirements and the levels of compost manure application in the two seasons.