Two field experiments were carried out at EI-Serw Agricultural Research
Station, Damietta Governorate, Egypt, in 2003/2004 and 2004/2005 seasons, to study
the effect of three nitrogen fertilizer rates Le. (30, 60 and 90 kg N/fad) and two
potassium fertilizer rates i.e. (0 and 24 kg K20/fed), in two forms Le. Potassium
sulphate (SOP) and Potassium chloride (MOP), on growth and yield of sugar beet
plant, as well as, its resistance against Cercospora Leaf Spot disease, under three
different levels of natural soil salinity i.e. (2.8-5, 6-10 and 11-12 dS/m at 25°c). The obtained results of the combined analysis of the three levels of soil salinity in the
two growing seasons, showed the following trends: 1-Significant negative effect between sugar beet yield and raising soil salinity levels
has been established in both seasons. 2- The highest and best optimum beet root yield and quality were obtained at the soil
salinity level of 2.8-5 dS/m, compared to the other soil salinity levels. 3-Soil salinity level more than 10 dS/m indicated the hazard and deteriorating effect,
on growth and yield of sugar beet, in eastnorthern Delta region. 4- The average root length, fresh root weight and yield of top, root and sugar (ton/fed)
of sugar beet plant, significantly increased with increasing N fertilizer rate from 30 to
90 kg N/fed, under each soil salinity level, while it gave opposite effect on sucrose
percentage in both seasons. Application of 90 kg N/fed increased root yield
(ton/fed) by 15.76 and 13.96%, and sugar yield (ton/fed) by 14.96 and 10.7% as
compared with the control treatment (30 kg N/fed) in 2003/2004 and 2004/2005
seasons, respectively. 5- Results also showed that fertilizing sugar beet plants, with 24 kg K20 in the form of
potassium sulphate (SOP), or potassium chloride (MOP), gave the highest values of
all studied characters without significant differences between them, as compared
with the control (no K addition). 6-AII the interaction effects between soil salinity levels, nitrogen rates and potassium
forms, were significant on all studied characters in both seasons. The highest
values of all studied characters were recorded with soil salinity level, up to 5.0
dS/m, 90 kg N/fed + 24 kg K20/fed, in the form of MOP or SOP, as compared with
all the other treatments in both seasons. 7-Potassium fertilization in the form of both MOP and SOP, obviously increased the
resistance of sugar beet to leaf spot disease, caused by Cercospora beticola Sacco
Comparably no potassium additions under all the three soil salinity levels and the
three N fertilizer rates. 8- Soil salinity level more than 10 dS/m, achieved higher Na, and CI% and lower K% in
beet roots, while increasing N levels caused lower Na and CI% in beet roots. Also,
both MOP and SOP caused lower Na% in beet roots, while SOP caused lower CI%
in beet roots.