A field experiment has taken place in Wahet El-Nagah farm, Khatatba village, Menoufia governorate, Egypt in the year 2005, in order to use the ability of rice-straw mulching as cheap farm residue, to reduce the effect of deficit irrigation on highly sensitive crop for water deficit. Split plot design consisted of soil surface covering case (rice straw mulching (500g/m2) and no-mulch) as main plot with four amounts of applied water 70, 80, 90, and 100% of ETc as sub-plot. Cucumber crop was irrigated by drip irrigation system under sandy soil conditions. Using rice straw mulch led to decrease the soil moisture reduction by 66, 57, 48.9, and 38 % compared with no-mulch treatments for the 70, 80, 90, and 100% of ETc respectively. All rice straw mulch treatments showed a productivity increase compared to no-mulch. The maximum crop yield 8.24 Mg/fed was obtained under rice straw mulching and 100% of ETc percentage causing a 29.6% increase in productivity compared with the crop productivity obtained at the treatment of same amount of applied water under traditional conditions. Rice straw mulch led to increase water use efficiency (WUE) the maximum value of WUE under rice straw mulch was 6.55 kg/m3 with 90% of ETc while it was 4.37 kg/m3 under the same conditions with no-mulch. Maximum benefit-cost ratio, 2.92 was obtained under rice straw mulch with 90% while it was 2.86 for no-mulch with 100%. The study recommended using rice straw mulch with 90% of ETc to obtain the maximum product of unit of water and maximum economic benefit.