IMPACT OF HUMIC ACID AND MINERAL NITROGEN FERTILIZATION ON SOIL CHEMICAL PROPERTIES AND YIELD AND QUALITY OF SUGAR BEET UNDER SALINE SOIL.

Two field experiments were conducted at Gelbana district Sahl–El Tina plain (North Sinai) laying between longitudes 32 ^o 20 and 32^o 33 east and latitudes 30 ⁰ 57 and 31⁰ 04 North during two successive seasons 2011/2012 and 2012/2013 to study the effect of soil application of inorganic nitrogen fertilization at rates of 50, 75 and 100 kg N fed ^-1 and organic humic acid fertilizer at rates of (0- 10 kg fed^-1)and its impact on some chemical soil properties, growth, chemical composition, yield and quality of some sugar beet varieties (Mirador, Panther and Athospoly). A split- split plot design with three replicates was used in the two seasons.
                                                The highest values of available K content in soil in both seasons and available N content in the 1^st season were recorded by Panther variety.
Panther variety occurred a significant superiority over the other varieties in vegetative traits i.e. diameter, weight, dry matter %, of root, photosynthetic pigments i.e. chlorophyll a, b and carotenoides and proline as will as root and sugar yields in the two season. All quality parameters (total soluble solids %, sucrose% and juice purity %) were insignificantly affected by the tested varieties in the two seasons.
Soil application of humic acid exhibited significant increase in available K-content in the soil in both seasons and available N in the 2^nd season as will as N, P and K- percentages in sugar beet root in both seasons. Also application of humic acid significantly increased proline concentration in leaves beet by (15.73 and 13.97%), sucrose% by (0.41 and 0.61%), as will as root yield by (22.80 and 28.38 %) and sugaryield by (26.56 and 32.44%) in the 1^st and 2^nd seasons compare with untreated one.
Increasing mineral N-rate significantly increased root and sugar yields/fed in both seasons. Also application of 100 kg N fed ^-1 recorded the highest values of root yield ( 29.91 and 27.27 ton fed ^-1) and sugar yield ( 5.53 and 4.71 ton fed ^-1) in the 1^st  and 2^nd  seasons. 
The interaction between mineral nitrogen fertilizer rates and humic acid (NXH) had a significant effect on root and sugar yields, sucrose%, and proline concentration in both seasons as will as on available K in the soil in the 1^st season. However, the interaction between sugar beet varieties and nitrogen fertilizer (VxN) and between sugar beet varieties and humic acid (VxH) had a significant effect on root length, LA, chlorophyll a and carotenoides, proline concentration and root and sugar yields in both season. Meantime, the interactions effects between the three variables under study (sugar beet varieties, humic acid and mineral nitrogen fertilizer rates) insignificantly effected on all traits under studies.