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Abstract
Two field experiments were conducted at Wadi El-Natrun, Egypt (30{u00B0}23’19.89{u02DD} N latitude and 30{u00B0}21’41.06{u02DD} E longitude) during 2011/2012 and 2012/2013 seasons to study the effect of water stress (100%, 75% and 50% of irrigation water requirements), two organic fertilization levels (zero and 5 ton compost/fed) and three nitrogen fertilization rates (60, 90 and 120 kg N/fed) on growth, yield and quality of sugar beet plants grown under conditions of drip and sprinkler irrigation systems. Results revealed that drip irrigated sugar beet plants with 75% of irrigation water requirements (IWR) recorded the highest significant leaf area index, sucrose%, purity% and extractable sugar% in both seasons and white sugar yield in the second season only, while application of sprinkler irrigation at 100% of IWR gave the heaviest root weight, root number/fed, purity%, root yield in both seasons. Applying of 5 ton/fed compost with sprinkler irrigation significantly increased root weight, root number and root yield in both seasons. Also, application of compost at 5 ton/fed with drip irrigation system increased root yield. Increasing N level up to 120 kg N/fed significantly increased LAI, root weight, root number/fed and impurities% as well as root yield in both seasons and white sugar yield only in the first one. Excessive N application lowered beet quality in terms of sucrose, purity and extractable sugar percentages in both seasons. In order to maximize water use efficiency, it is recommended to use drip irrigation system with 1322 m3 water/fed (50% of the calculated water requirements) + 5 ton/fed compost + 120 kg N/fed of ammonium nitrate (33.5%). The maximum value of net profit was L.E. 7688.10/fed resulted from drip irrigation system with 75% water regime, 5 ton/fed compost and 90 kg N/fed during 2012/13 season, while the minimum value of net profit was L.E. 2231.88/fed resulted from sprinkler irrigation with 50% water regime, 5 ton/fed compost and 90 kg N/fed during 2012/13 season