الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Presently, finding an effective alternative to mineral N-fertilizers is the biggest challenge in sustainable development especially after some research has proven that synthetic nitrogen fertilization is related to the increase of impurities in sugar beet. A field trial was executed in a split plot design during the 2020/21 growing season to study the possibility of using titanium dioxide as a substitute for mineral N-fertilizers with sugar beet plants grown on salt-affected soil (EC=6.25 dSm-1) and irrigated simultaneously with water having an EC value of 4.86 dSm-1. Treatments were N-fertilization (applied or not) as main plots and ten Ti treatments represented subplots, where the Ti was added as titanium dioxide (TiO2) at rates of 5.0,10.0 and 15.0 mgL-1 using different application methods i.e., foliar application, soil addition and combination of both methods (foliar+ soil) in addition to control treatment (without titanium dioxide). Plant performance at period of 90 days from sowing i.e., plant height and chlorophyll content as well as top and roots yield, juice quality and soil available N, P and K at harvest stage were evaluated. The results obtained could be summarized as follows:- 1. Performance at a period of 90 days from sowing. The N-fertilization significantly affected both plant height and chlorophyll content values, where the values of these traits for plants treated with N fertilizer were more than that of corresponding plants grown without N-fertilization. On the other hand, the titanium, under all application methods, was beneficial at low concentrations (5.0 mg Ti L-1) but it possessed a toxic effect at high concentrations (10.0 and 15.0 mg Ti L-1), where the values of plant height and chlorophyll content under each studied application method significantly increased with raising added Ti concentration from 0.0 mg L-1 to 5.0 mg L-1 and then significantly decreased as the Ti rate increased. Also, it can be noticed that application of Ti as foliar and soil addition together (as application combined method) was the most effective method followed by the foliar application method alone then the soil addition method alone. In fact, the performance of sugar beet plants treated with N-fertilization was better than that grown without N-fertilization under each Ti studied rate. Meantime, sugar beet plants treated with N fertilizer and sprayed with Ti at rate of 5.0 mg L-1 under combined method of application recorded the highest values of plant height and chlorophyll content, while the lowest values were realized with sugar beet plants untreated with N fertilizer and sprayed simultaneously with 15.0 mg Ti L-1 under application combined method. 2Performance at a maturity stage (180 days from planting). N-fertilization and Ti treatments significantly affected performance, root yield and juice quality of sugar beet expressed in top and root fresh weights (g plant-1 & Mg fed-1) as well as root length and diameter (cm), N and P content (%) in root as well as impurity components i.e., K, Na and -amino N (%)and juice quality i.e., sucrose, TSS, purity, impurity, sugar loss, sugar recovery (%), recoverable sugar yield, sugar loss yield (Mg fed-1) and quality index (%)during growing season of 2020/21. All aforementioned traits could be considered as the main factors affecting sugar beet production. It is quite obvious that the plants treated with N fertilizer possessed the highest values of all aforementioned traits, except purity and quality index (%),compared to corresponding plants grown without N-fertilization. On the other hand, the titanium was beneficial for performance, root yield and juice quality of sugar beet plants at low concentrations (5.0 mg Ti L-1) but it possessed a toxic effect at high concentrations (10.0 and 15.0 mg Ti L-1) under all application methods, where the values of all aforementioned traits under each studied application method, except purity and quality index (%) which took another trend, significantly increased with raising added Ti concentration from 0.0 mg L-1 to 5.0 mg L-1 and then significantly decreased as the Ti rate increased. Concerning purity and quality index (%), the data shows that their highest values were recorded when plants were treated with Ti at rate of 15 mg L-1 under combined application method. Under all application methods, it could be noticed that the values of purity and quality index (%) increased as added Ti rate increased. These results confirmed that Ti has an important role in N-fixation and simultaneously increasing purity. Also, the application of Ti as foliar and soil addition together (as combined treatment) was the most effective method for performance, root yield and juice quality of sugar beet plants followed by the foliar application method alone then the soil addition method alone.. Post-harvest soil analyses. All Ti treatments (all rates under both addition methods) enhanced the N-fixation process and this was reflected in the mean values of soil available N at the harvest stage.Regarding available soil P and K at the harvest stage, the values for soil cultivated with sugar beet plants fertilized with N were less than that unfertilized with N. the application combined method was the superior application method, therefore improving sugar beet plants’ status under this method and decreasing residues of N, P and K in soil compared to the other methods (foliar and soil addition). CONCLUSION The current investigation confirms some facts as follows; 1. Although mineral N fertilization is so important for plants including sugar beet, it has a negative effect of quality parameters of sugar beet..Mineral N- fertilization causes the impurity in sugar beet to rise, where impurity could be considered as one of the major factors affecting on quality of sugar beet root.3.Ti has a vital role in non-biological nitrogen fixation with sugar beet plants grown under salinity conditions, where it can fix atmospheric nitrogen either on plant foliage or soil surface. 4. Ti can fix atmospheric nitrogen whether its application method for agricultural purposes is foliar or soil addition, but the combination of both methods is the most effective compared to each method alone due to raising Ti ability to non-biological nitrogen fixation under the combined application method. 5. Ti application to sugar beet plants at a low concentration (5 mg L-1) is beneficial, but the Ti toxicity starts to appear at high concentrations i.e., 10 and 15 mg L-1. Generally, it can be concluded that Ti may be a good substitute for mineral N-fertilizers in sustainable development.