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Abstract - This work represents a research of non-sugar matter (the content of alpha amino nitrogen, potassium and sodium) in the root, and their effect on the recoverable sucrose quantity of several genotypes of sugar beet on vegetation areas of different sizes. Those are Esprit, Belinda and Chiara. They had been grown by standard agrotechnical measures for sugar beet in the densities of 80.000, 100.000 and 120.000 plants per hectare.
The minimal content of non-sugar matter in the juice was found in the roots coming from the highest crop density. This amount rose with the enlargement of vegetation area of plants, which also caused significant decrease in the content of recoverable sucrose. The genotypes did not considerably influence the changes in the content of non-sugar matter by their production characteristics, but the weather conditions displayed the influence on the technological value of the root. In the third year, when the meteorological conditions were the most favourable, the content of non-sugar matter was the lowest, and the overall sugar content was the highest. The decreased quantity of non-sugar matter positively influenced the crystallization of the sugar from the juice, so that the content of recoverable sucrose was the highest in the third year, and totaled 13.68%. Of all the examined genotypes, Belinda had the highest technological value in the total average.
Key words: sucrose content, recoverable sucrose, alpha amino nitrogen, potassium, sodium, cultivar, sugar beet.
Sugar beet technological value is determined by sucrose and non-sugar matter content in the storage root. Non-sugar components (Î±-amino-nitrogen or harmful nitrogen, potassium, sodium, magnesium, calcium) in the root reduce sugar crystallization from molasses during sugar beet processing (Sinobad and Brdar, 1996; Sklenar et al., 2000; RadivojeviÄ‡ and KabiÄ‡, 2000; Leilah et al., 2005; Pytlarz-Kozicka, 2005; JaÄ‡imoviÄ‡ et al., 2006; FilipoviÄ‡, 2009). The percentage of crystallized sugar from molasses is calculated on Reinefeld's formula. The obtained value is the percentage of total sugar content utilization from the storage root. The percentage of crystal sugar content is affected by a multitude of factors. Significant differences between total and crystal sugar content are caused by the size of plant's vegetative site as well as by sugar beet genotypes (FilipoviÄ‡, 2009).
Therefore, the selection of the best suited cultivar should involve the testing of as large number of genotypes as possible, differing in sugar synthesis intensity and sugar accumulation in the storage root. Genotypes of a shorter vegetative period have faster initial growth and earlier sugar synthesis, hence they achieve earlier technological maturity i.e. the period of sugar optimal utilization from the root starts earlier. These genotypes are referred to as sugary genotypes or Z-type genotypes, and they are suitable for early harvest dates. E-type genotypes, on the other hand, have the longest sugar accumulation period and they are suitable for late harvest dates (Ramadan, 1999). Total sugar content in the root and percentage of sugar utilization is considerably affected by nitrogen rates and arrangement of fertilizer application and plant nutrition (Halvorson and Hartman, 1975).
This paper presents, firstly, the studies of non-sugar matter content in the root of three sugar beet genotypes (Belinda Z-type, Esprit N-type and Chiara E-type) grown at different crop densities and, secondly, the effect of non-sugar matter on percentage of crystal sugar sucrose.
MATERIAL AND METHODS
Three-year trials were conducted during the 2005-2007 period on the experimental field of the Institute "TamiÅ¡" PanÄevo as a randomized complete block design with four replications. The size of vegetative site for individual plants was 0.125 m2, 0.1 m2 0.083 m2. It was formed by crop hand thinning during a sprouting stage. The studies comprised genotypes Belinda (KWS - 2004. Z-type), Esprit (Strube Dieckmann - 2004. N-type) and Chiara (KWS - 2004. E-type). Sugar beet was hand harvested and analysis was conducted on the sugar beet roots from middle rows of the elementary site.
Non-sugar components (potassium, sodium and harmful nitrogen) in the root were determined in automatic laboratory analyzer for the root, Betasyler. The values of potassium, sodium and harmful nitrogen are expressed in mmol/100 g of sugar beet, while content of total sugar sucrose and crystal sugar content are given in percentages (%). Based on the results obtained, computations were done for crystal sugar percentage on Reinefeld formula (Reinefeld, 1974):
SU = S0 - [0.343 x (K + Na) + 0.094 x Î±-amino-N + 0.29] âˆ™ %
SU - sugar utilization and S0 - sugar content
The obtained data were analyzed by mathematical-statistic methods (Snedecor and Kohran, 1971). Analysis of variance was applied to estimate significance derived by F-test and LSD-test for 5% significance.
RESULTS AND DISCUSSION
In the first study year the analyzed factors had significant influence on non-sugar matter content and percentage of sugar utilization from juice (Table 1).
The highest content of total sugar was found in cultivar Esprit grown on the vegetative site of 0.083 m2 (13.25%) and the lowest in cultivar Chiara, vegetative site equaling 0.1 m2 (12.54%). In cultivar Esprit the content of harmful nitrogen was highest in the crop of the lowest density (2.69 mmol/100 g of sugar beet) and lowest when the size of vegetative site was 0.1 m2 (2.40 mmol/100 g of sugar beet). Cultivar Chiara had the highest potassium and sodium content in the root. On the vegetative site of 0.125 m2 the content of potassium was 3.38 mmol/100 g of sugar beet and in cultivar Belinda (0.1 m2) it amounted to 3.03 mmol/100 g of sugar beet. The highest difference in sodium content per cultivar was found between cultivar Chiara (1.80 mmol/100 g of sugar beet) and cultivar Esprit (1.14 mmol/100 g of sugar beet) with identical size of the vegetative site (0.1 m2). The amounts of non-sugar matter that varied per cultivar and crop density influenced the percentage of crystal sugar sucrose too. The lowest content of crystal sugar was in cultivar Chiara on the vegetative site of 0.1. m2 (12.23%) and it was the highest in cultivar Esprit on the vegetative site of 0.083 m2 (12.94%). These results conform to the reports by RadivojeviÄ‡ & KabiÄ‡ (2000).
Change in the size of vegetative site produced very significant effects on difference in potassium (P<0.01), while effects on the percentage of crystal sugar were significant (P<0.05). Variations per cultivar were not significant. In the second study year individual variations in total sugar and non-sugar matter content as well as sugar utilization from juice were not significant (Table 2).
The analysis of effects of the studied factors on sugar beet technological value demonstrated that the interaction between the size of vegetative site and cultivar had significant effects on sodium and potassium content in the root. Compared to the first study year, sugar beet had significantly higher total sugar content, but also increased non-sugar matter content.
However, the coefficient of sugar utilization was at the same level, over 97.6%. According to the results reported by Sinobad and Brdar (1996) non-sugar components significantly reduce total sucrose content in the root but did not significantly reduce the coefficient of sugar utilization. Sklenar et al. (2000), on the other hand, point out that non-sugar matter content significantly influences the coefficient of sugar utilization. Technological value of sugar beet roots, at total average, was highest in the third study year (Table 3).
The size of vegetative site influenced total sugar content in the root. As crop density was increased, total sugar content was decreased, 14.09%-13.89%. This difference is significant. The coefficient of nitrogen utilization in the soil depends on the number of plants per unit area. In more dense crops the competition is great, which causes reduced crop nitrogen supply and lesser production of sugar (Winter, 1990). Variations in total sugar content per cultivar were not significant. Non-sugar matter content was significantly influenced by crop densities. As vegetative site was increased, sodium content was also increased, 1.25 mmol/100 g of sugar beet - 1.42 mmol/100 g of sugar beet, the obtained difference being very significant. Sugar utilization from juice was higher in the roots that were developing on a larger vegetative site, and variations from crops of highest density to crops of lowest density were very significant. Increased content of non-sugar matter did not significantly influence sugar crystallization, so in the third study year its coefficient of utilization was very high, over 97.7%. Variations in the amount of total sugar and non-sugar matter per cultivar were not significant and depended individually on the size of vegetative site and environmental conditions throughout vegetative period in sugar beet.
During three-year average the size of vegetative site (I, II, III) did not significantly influence technological value of sugar beet root (Fig. 1). Among genotypes, at three-year average, there were significant variations in root technological value (Fig. 2). Weather conditions influenced significantly crystal sugar digestion and content, but also non-sugar matter content in sugar beet root (Fig. 3).
The results of studies on effects of "non-sugar" matter on sugar utilization in genotypes of different technological value at different crop densities lead to the conclusion that:
The size of crop vegetative site influenced significantly the content of non-sugar matter in each study year but not at three-year average. A higher number of plants per unit area influenced the coefficient of sugar utilization in each study year. The highest technological value was determined in the roots of cultivar Belinda (Z type). The most favorable weather conditions were in the third study year when digestion was highest, which resulted in the highest percentage of crystal sugar amounting to 13.68%.