International Journal of Agriculture and Crop Sciences. Available online at www.ijagcs.com IJACS/2014/7-3/136-141 ISSN 2227-670X ©2014 IJACS Journal Influence of Irrigation Method, Weed, and Splitting Nitrogen Fertilizers on Water Use Efficiency and Productivity of Sunflower M Mubarak A. Abdyl-Razak 1 , Ibrahim A. Hamzah 2 , Makkiyah K. Alag 3 , Shatha A.H. Ahmed 4 *Dept of Field Crops, College of Agriculture, University of Baghdad Corresponding author email:**drmmubarak@gmail.com ABSTRACT: Two field experiments were conducted at the experimental farm, Department of Field Crop Science, College of Agriculture, University of Baghdad during two successive growth seasons of 2010 and 2011to study the influence of three irrigation methods Sprinkler(S), Flood(F) and Drip(D); weed(W)(with weeds)(W 1 ) and( with no weeds)(W 0 ); and splitting Nitrogen fertilizers treatment(N)( 50% at planting + 50% at Budding)(N 1 ),(50% at planting+25% at Budding + 25% at Flowering)(N 2 ),and(25% at planting +50% at Budding + 25% at Flowering)(N 3 )on yield and yield components of sunflowers. The results indicate that using Drip irrigation increases Water Use Efficiency by two to three folds comparing with Flood and Sprinkler irrigation;and reduces water consumption by 74%. Weed growth reduces WUE, Yield, weight of 100 seeds, seeds per head, head radius by 9-33%,13-25%,9-14%, 27%,and 27% respectively in one or both seasons of study. Furthermore,splitting nitrogen fertilizers in three parts during growth season, improved sunflower seed yield, weight of 100 seeds, head radius, and oil content significantly in one season by11-16%,13-16%, 6-10%, and 2% respectively. All interaction combinations between studied factors were statistically significant at 5% probability level. Keywords: Drip, Flood, Sprinklers, WUE, Yield, Yield components, N splitting, weeds. INTRODUCTION After the reduction in the national rainfall rates during the last few decades, and the resulting decline in the water level of the Tigress and Euphrates,it became crucial for Iraqi scientists to find better ways of managing irrigation water and improving water use efficiency for all cultivated crops (Taha and, Abbass 2008).In dry land agriculture of semi- arid regions,water availability to plantsis the most limiting factor to yield potential( Bednarz et al.,2002). Therefore,water is often the primary factor the influence the management and crop selection decisions (Stone et al., 2002).Using surface irrigation, in most cases, leads to long intervals between irrigations, which requires the need to compensate by applying all the water intendedforuse. This leads to substantial water waste through evaporation and percolation (Mavi and Tupper, 2004); however, it leads to other problems such as water logging and salinity buildups. Sprinklers and micro irrigation systems are definitely better and much more efficient than surface irrigation systems (Ramalan and Hill, 2000).Drip irrigation improves yield and WUE by 18-42% and 35-103% respectively (Ibragimov,2007). Sinclaire et al (1984) described WUE on various scales from leaf to the field. In its simplest terms, it is characterized as crop yield per unit of water use.At a more biological level, it is the carbohydrates formed through photosynthesis from CO2, sun light, and water per unit of transpiration.These definitions are attractive but difficult to apply because many management factors such as fertility, variety, pest management, sawing date, soil water content at planting, planting density,and row spacing, could affect yield or differ substantially between irrigated and dry land agriculture. Sunflower is one of the major oil seed crops in the world, grown on some 22 million hectares (skoric et al., 2008). The oil type is distinguished with small seeds, high oil content, with various fatty acids compositions and is used as high quality edible vegetable oil for human consumption, or for biodiesel production (Arkansas Biofuel Enterprises, 2007; National Sunflower Association, 2009). Sunflower is a drought tolerant crop with a deep explorative root system (Stone et al., 2002). The superior performance of sunflower under dry land conditions is