الفهرس 
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Abstract
Field experiment was carried out on sweet potato cv. Abees in clay soil during the summer seasons of 2013 and 2014 in the Farm of Faculty of Agriculture, Kafrelsheikh University, Egypt. The aim of this study was to study the possibility of replacing furrow irrigation with drip irrigation system under the North River Nile Delta conditions. The effect of drip irrigation, mulch treatments and their combined interaction on vegetative growth, yield, quality, chemical composition and storability were studied. The treatments were three drip irrigation rates at 50, 60 and 70% of the field capacity (F.C.) with two mulching treatments comparing with surface irrigation (control). The soil was covered with organic mulch (rice straw) or left uncovered. The results indicated that, the drip irrigation rates at 60 or 70% of F.C. with soil mulch led to a positive increase in most vegetative traits (plant length, number of branches /plant, vin fresh and dry weight, stem fresh and dry weight, chlorophyll content (SPAD) and leaf area compared to the bare soil (without mulching) in most sampling dates. Also, tuberous roots yield with high percentage of marketable one and quality were higher in both growing seasons. The highest water use efficiency (WUE) with lower water consumption was recorded with drip irrigation under soil mulch comparing to the surface irrigation without soil mulch. Furthermore, the percentage of weight loss and decay were decreased during storage period. The anatomical features of stem the results showed that, the higher irrigation levels at 60 and 70 % F.C. of drip and surface irrigation gave the highest values of xylem vessel diameter, phloem and cortex thickness and section diameter. Mulching treatment increased vegetative growth parameters, yield components, absolute growth rate, water use efficiency and decreased weight loss % during storage period. Therefore, it is recommended by using drip irrigation under clay soil conditions to replacing furrow irrigation especially by the rate of 60 or 70% F.C. with soil mulch by rice straw to improve the growth and productivity of sweet potato plants and increase the water use efficiency.