A field experiment was conducted at privet farm of Demo (29° 17ˋ N, 30° 53ˋ E), Fayoum Governorate, Egypt, during 2018/2019 and 2019/2020 to study the effect of three humic acid treatments, i.e. (0 without humic acid as control, 3.5 and 7 Kg humic acid/fed) on quality and yield traits of eight sugar beet varieties (Santolhne, Pepite, Amina, Beta 401, Dina, Grinta, Sirona and Bts 302). Results indicated that root yield (ton/fed) was increased by increasing the rates of humic acid from 3.5 to 7kg per fed in the first season (27.02 and 29.11 ton/fed, respectively), corresponding (28.08 and 29.72 ton/fed in the second season respectively). Similarly, the content of molasses forming substances showed more reduction in 3.5 than in 7kg/fed treatment. Nevertheless, the trend of increasing content of sucrose and refined sugar was associated with humic acid rates. Results showed that varieties significantly differed among them where, Sirona variety show the superiority over the other seven tested varieties and recorded the highest values of root diameter (14.19 and 15.14 cm, respectively), fresh root weights/plant (1.41 and 1.47 kg, respectively), in both seasons, as well as root yield/fed (29.94) in 2 nd season. While, in first season variety (Bts 302) registered the highest values of root yield (29.42 ton/fed), also this variety recorded the highest sugar yield (4.62 and 5.23 ton/fed, respectively) in both seasons. Highly significant interaction effects between humic acid and varieties root yield and sugar yield and their related traits in both seasons. it could be concluded that fertilization with humic acid at a rate of 7kg /fed as a soil application to get the maximum of root and sugar yields/fed in sandy soil.

Salinity is one of the major abiotic stresses which affected on plant growth and reduces plant productivity. Antioxidants compounds considered as one of the methods and strategies to ameliorate the deleterious effects of salinity stress on plants to reduce the effect of oxidative stress. Field experiment was carried out at Sinnuris District which located mainly adjacent to Lake Qarun (saline soil) at El Fayoum Governorate (latitude 29°20 and 29°30 N and longitude 30°43 and 30°56 E) during 2015/2016 and 2016/2017 growing seasons to study the effect of relation between three application methods (seed soaking, foliar spraying and seed soaking plus foliar spraying together) and four concentrations (without treatment, tap water, 100 ppm and 200 ppm of ascorbic acid) of ascorbic acid on some biochemical and physiological characteristics, antioxidant enzyme activity as well as growth, yield and quality of sugar beet (Beta vulgaris var. saccharifera, L.) under salt stress conditions. The treatments were arranged in a strip-split plot design with three replications. The vertical plots were occupied with three application methods while, the horizontal plots were devoted to four ascorbic acid treatments. Results showed that application of soaking sugar beet seed in ascorbic acid (AsA) plus foliar spraying at 50 and 70 days from sowing significantly increased chlorophyll a, b and carotenoides, LAI, catalase (CAT) and superoxide dismutase (SOD) activities , yield components and sucrose % in both seasons while juice impurities (K, Na and α-Amino-N) were decreased and significantly increased root yield by (9.19, 9.63%) and sugar yield by (13.43, 15.59%) compared to AsA applied as a seed soaking or foliar spray in the 1 st season and the same trend was attained in the 2 nd season. Applying 200 ppm of ascorbic acid was more effective and significantly increased root and sugar yields and sucrose % and caused more reduction in juice impurities in comparison to the control, in both seasons. Higher stomata area, lower stomata density and stomata closure% were recorded by seed soaking plus foliar spraying with 200 ppm AsA treatment for upper and lower surface of sugar beet leaf. Applying seed soaking plus foliar spraying by 200 ppm of ascorbic acid significantly increased root yield by (6.99 and 4.54 ton/fed) and sugar yield by (2.19 and 2.06 ton/fed) over that gained by untreated plants in the 1 st and 2 nd seasons.

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