INFLUENCE OF FERTILIZATION AND NITRATE-NITROGEN POSITION IN SOIL PROFILE ON THE SUGAR BEET ROOT YIELD AND QUALITY

Researches, which have lasted for two years, were carried out on long-term trial field at Rimski Ãanåevi, Novi Sad, Serbia. In this trial, the eight fertilization variants of N, P 2 O 5 and K 2 O increased amounts were studied. Sugar beet root and tops yields were determined, as well as the elements of technological sugar beet root quality. Based on these results, percentage of sugar utilization and refined sugar yield was defined. In the spring, before applying of N fertilizer, amount of nitrate nitrogen in the soil and its influence on yield and quality was determined. The highest root yield in 2002 was produced at the variant N 100 P 150 K 150 , and in 2003 at the variant N 150 P 150 K 150 . However, in both years, referring to the variant N 100 P 100 K 100, the differences were not statistically significant. Increasing of nitrogen amounts had negative effects on refined sugar yield. Amounts of NO 3 -N in the soil in spring, before sugar beet sowing, in 2002 had significant influence on root yield and refined sugar yield. In the year 2003, which was highly dry, high correlation ratio were gained between amounts of NO 3 -N in the soil and root quality parameters, but it wasn't significant between nitrogen amounts and root and refined sugar yield.

beside the high root yield, the technological quality of root must be good as well.Between all elements of mineral nutrition, the highest influence on yield and qualitative beet properties has nitrogen.Negative effects, especially on sugar yield which can have nitrogen surplus, can be avoided by following and determining its amounts and dynamics in soil.At the same time herewith the economical and ecological fertilization aspects will be respected.
The main cause of these investigations was to explore the influence of NPK mineral nutrition at root yield and underground biomass as well as the influence on technological root properties.
Also, based on the amounts of soil nitrate-nitrogen before sowing and its distribution in soil profiles we will try to determine its correlation dependency with root yield and quality.

Material and Methods
Researches have lasted for two years and they were conducted at stationary field trial at Institute of Field and Vegetable Crops -Novi Sad.The trial was designed by split-plot plan, in four repetitions.The main plots were 150 m 2 , with eight fertilization variants by different amounts of N, P 2 O 5 and K 2 O: Ø (control), N 2 P 2, N 2 K 2, N 1 P 2 K 2, N 2 P 2 K 2, N 2 P 3 K 3, N 3 P 2 K 2, N 3 P 3 K 3 (where 1 =50, 2 =100, 3 =150 kg active matter of each nutrition element per hectare).
After extraction of a root, root samples were taken from all fertilization variants to the end that determine technological root quality properties and next parameters were determined: sugar percentage, content of harmful nitrogen, K and Na, and based on these properties sugar utilization and refined sugar yield were valuated.Determination of technological root quality was done by standard methods in automatic beet laboratory "WENEMA", in Institute for Field and Vegetable Crops at Rimski Ãanåevi, Novi Sad.
In the spring, before nitrogen fertilizers' application, the content and distribution of soil mineral nitrogen was monitored.The soil samples were taken in layers from 30 cm, till the depth of 120 cm.The samples were analyzed on NO 3 -N content by standard methods.Weather conditions in investigated years: Sugar beet yield and quality and seeded areas in our county are very variable from year to year.Besides the applied practical measures and economical reasons, the huge influences on the like fluctuations have the mutable weather conditions.By comparing the water balance elements (Bioclimatic method , Vu å i ñ ; 1971 ) in observed years with average values from Rimski Ãanåevi site, we can mark the very high values of potentially evapotranspiration (ETP) and higher precipitation deficit in a both years, in relation to a long-term period average.
The year 2002 was very dry.Percentage of real evapotranspiration (ETR) in relation to potentially (ETP) was only 50 %, and totally water deficit in relation to plants requirements was 311 lm -2 .Year 2003 was climatic more unfavorable.Totally, during the vegetation period there was less precipitations for 125 lm -2 and at the same time the temperature was higher for 2.1 0 C regarding to the multi-annual average.Plant water requirement (= ETP) in 2003 was 648 lm -2 , and real ET was only 272 lm -2 , while precipitation deficit was 376 lm -2 .The highest water deficit during vegetative period was in June and August.

Results and Discussion
All fertilization variants have positive effects on root yield (tab. 1) with the exception of variant N 100 K 100 during the year 2000.Average yield increasing for all variants was 39% in relation to control in 2002, and 60% in 2003, respectively.The highest amounts of mineral fertilization didn't produce significant increasing of fresh root yield.So in the 2002 year the highest yield was accomplished with applying of 100 kgha -1 N, 150 kgha -1 P 2 O 5 and 150 kgha -1 K 2 O.However, the root yield at this fertilization variant in relation to variant with by 100 kgha -1 N, P 2 O 5 and K 2 O, was higher, but that difference was not statistically significant.The highest NPK fertilizer amounts (by 150 kgha -1 ) in relation to medium (100 kgha -1 NPK) even now produced lower root yield for 4.6 %.During the 2003 year the highest yield was accomplished at variant N 150 P 150 K 150 and root yield differences were significant in relation to the all fertilization variants except N 100 P 100 K 100 .According to our results S a r i ñ and J o c i ñ (1977) refers that the yield increasing with the fertilizer amounts bigger than 100kg ha -1 N, P 2 O 5 and K 2 O is minimal.

Tab. 1. -Influence of different amounts of mineral fertilizers on root, tops and sugar yield
In 2002 year increasing of the nitrogen amounts from 50 to 100 kgha -1 , at the same level of P and K (P 100 K 100 ), increased root yield for 14.5 % (increasing in relation to control was 62 %) which is statistically significant.The further increasing for 50 kgha -1 N decreased yield for 15.6 %, which is also statistically very significant.With the lowest nitrogen amounts (N 50 ) in 2003, the root yield increased for 57 % in relation to control, which was high significant.By increasing nitrogen dose to 100 kgha -1 (variant N 100 P 100 K 100 ) in relation to the previous variant the yield was increased for 6.97 tha -1 (11 %), however the difference wasn't statistically significant.Additionally 50 kgha -1 of nitrogen (at variant N 150 P 100 K 100 ) decreased root yield for 1.85 tha -1 (2.6 %), that also wasn't statistically significant.The results of these investigations are in accordance with the results referred by L a w i n s k i and G r z e b i s z (2000), N e n a d i ñ et al. (2003), M a r i n k o v i ñ et al. (2004).
The highest sugar beet tops' yields were accomplished at variants with the average or high nitrogen amounts and with the higher doses of P and K, accordingly at variants N 100 P 150 K 150 in 2002, and N 150 P 150 K 150 in 2003, respectively.
Against positive nitrogen effects on root and tops yield, its influence at technological root properties was negative (tab.2).With increasing of nitrogen amounts, -amino-nitrogen and the other no-sugar matter amounts increased, which has negative effects on sugar utilization during root processing.A large number of authors quote results that indicated that by increasing of nitrogen amounts decreased the sugar content and get worse root quality traits for beet processing (R e i n i e f e l d , B a u m g a r t e n (1975), M a r i n k o v i ñ et al. (2004).

Tab. 2. -Influence of different amounts of mineral fertilizers on root technological quality
The highest sugar content (16.6 %) in 2002 year was accomplished by fertilizing variant with the smallest nitrogen amount (N 50 P 100 K 100 ), and at control variant in 2003.The smallest sugar content was gained at variants N 100 K 100 and N 100 P 100 , while follows variants with the highest nitrogen amounts.Ã o l t y so v a (2003) also quoted that the highest nitrogen amounts significantly decreased digestion (0,33 % averaged), and the refined sugar yield (for 0,38 %) in relation to unfertilized variant.
Intensively nitrogen fertilizing significantly influenced on increment of harmful nitrogen content in root: the highest content in 2002 have variants with the highest nitrogen amounts.In 2003 year the highest content of harmful nitrogen was obtained at variant N 100 K 100 , but higher content had fertilizing variants by the highest nitrogen doses.As we expect, the smallest amount of harmful nitrogen has control variant and variant with the smallest N amount (50 kgNha 1 ).
In both years the highest percentage of sugar utilization was accomplished at the variant fertilized with the smallest nitrogen dose (N 50 P 100 K 100 ) and at control variant.Increasing of nitrogen dose from 50 to 100, in other words using of 150 kgha -1 , causes significant decrease of sugar utilization.
Refined sugar yield in 2002 year was the highest at variant N 50 P 100 K 100 .Variants with the smallest refined sugar yield were control variant and N 100 K 100.Increasing of nitrogen amount had negative effect on refined sugar yield.The smallest N dose gave the sugar yield for 700 kgha -1 higher than the medium and 630kg ha -1 higher yield than the highest N dose.The highest sugar yield in 2003 year was accomplished at the variants with the medium amounts of all three nutrition (N 100 P 100 K 100 ).
In the spring, before nitrogen application, the amount of soil nitrate-nitrogen was monitored at all variants, as well as its influence on root yield and quality was determined by correlative analysis.The amount of NO 3 -N in the soil before sugar beet sowing in 2002 significantly influenced on root and refined sugar yield (tab. 3).

Tab. 3. -Correlation coefficients between nitrat-nitrogen in soil and yield and some indices of technological quality of sugar beet
The biggest influence at root yield had the amount of NO 3 -N in the soil layer from 30-60 cm, (high significant correlation; r=0.83**), then in the layer 60-90 cm (r=0.72*).H a n a å k o v a (2003) obtained the high correlation between the amount of mineral nitrogen in soil layer 0-60 cm and root yield.At sugar beet tops yield significant correlation obtained with the amount of NO 3 -N in layer 30-60 cm, while at refined sugar yield the biggest influence had NO 3 -N from soil layer 60-90 cm (r=0.72*).These results are in accordance with the results of M a r i n k o v i ñ et al. (1994).According to them, root yield is depending from NO 3 -N which is situated in the layer 30-60 cm, while the correlation with the NO 3 -N amount in the layer 0-30 cm was negative.
During the spring 2003, the amount of NO 3 -N in soil layer from 90-120 cm had significant positive effect at beet tops yield (r=0.73*) and at -amino nitrogen content (r=0.83**).Effect at sugar content (r=-0.71*)and percentage of sugar utilization (r=-0.75*)were negative.The total amount of NO 3 -N (in the layer 0-120 cm) significantly influenced at increasing of -amino nitrogen.That plant alimentation isn't dependent only by sum of available N aspects, but and of their distribution in soil profile, quote M a l e ã e v i ñ et al (1990).

C o n c l u s i o n
The highest amounts of mineral fertilizers didn't produce at the same time the highest increase of root yield.The high dosage of all three mineral nutrients didn't statistically sustainable.Intensively nitrogen fertilizing significantly influenced on increment of harmful nitrogen content in root as well as on decreasing sugar content.