THE EFFECT OF FERTILISATION ON THE CONTENT OF SUCROSE, GLUCOSE AND FRUCTOSE IN ROOTS OF THREE VARIETIES OF BEET

Vliv hnojení na obsah sacharózy, glukózy a fruktózy v bulvách tří odrůd řepy

U. Prośba-Białczyk, P. Regiec

Agricultural University of Wrocław, Poland

Summary: Changes in the content of sucrose, glucose and fructose in roots of three varieties of sugar beet (Atair, Kristall and PN Mono 4) were determined, as dependent on organic fertilisation with stubble catch crops of field bean, phacelia and mustard and with nitrogen at doses 0, 60, 120 and 180 kg/ha. Sugar beets grown after mustard catch crop and without organic fertilisation as well as with nitrogen fertilisation showed a decreased sucrose content, irrespective of variety. Varieties differed in sucrose and simple sugars content. The greatest sucrose content was found with Atair variety, and the lowest simple sugars content had Kristall. The contents of glucose and fructose increased with increasing nitrogen fertilisation doses over 60 kg/ha. Beet roots grown without organic fertilisation contained more glucose and fructose than those grown after catch crops.

Key words: sugar beet, sucrose, glucose, fructose, catch crops, nitrogen, variety

Souhrn: Byly stanoveny změny v obsahu sacharózy, glukózy a fruktózy v bulvách tří odrůd řepy (Atair, Kristall a PN Mono 4) v závislosti na organickém hnojení meziplodinami bobu, hořčice a svazenky a dusíkatém hnojení v dávkách 0, 60, 120 a 180 hg/ha. Cukrovka pěstovaná po hořčici jako meziplodině a bez organického hnojení stejně jako s hnojením dusíkem prokázaly snížený obsah sacharózy bez ohledu na odrůdu. Odrůdy se lišily v obsahu sacharózy a obsahu jednoduchých cukrů. Nejvyšší obsah sacharózy byl zjištěn u odrůdy Atair, nejnižší obsah jednoduchých cukrů měla odrůda Kristall. Obsah glukózy a fruktózy se zvětšoval se zvyšujícím se hnojením dusíkem v dávkách vyšších než 60 kg/ha. Bulvy pěstované bez organického hnojení obsahovaly více glukózy a fruktózy než ty jež byly pěstovány po meziplodinách.

Klíčová slova: cukrovka, sacharóza, glukóza, fruktóza, meziplodiny, dusík, odrůda

Introduction

The most important technological quality factor of sugar beet is the content of sucrose and molassigens. Molassigens are the substances that make the technological process of sugar extraction more difficult and increase sugar losses in the molasses. These are predominantly sodium, potassium and reducing sugars as well as compounds called bad nitrogen (Brunotte and Winner 1986, Dobrzycki 1984, Kalinowska-Zdun and Wyszyński 2000, Prośba-Białczyk at al 2001, Trzebiński and Cieśla 1978). Among reducing compounds are glucose, fructose and galacturic acid which occur in small quantities. Glucose and sucrose, called invert, cause the formation of colour compounds (Maillards reaction), which in turn, by decomposition, form organic acids (mainly lactic acid) that cause smaller alkalinity. Moreover, the invert shows a high negative rotation and raises polarisation at bigger concentrations. Increased concentration of invert is found in beets harvested late and also stored at low temperatures for longer periods.

The aim of the investigation was to determine the changes in the content of sucrose, glucose and fructose as dependent on fertilisation and variety.

Materials and methods

In the investigations on organic fertilisation with stubble catch crops (field bean, phacelia and mustard) and nitrogen at doses 0, 60, 120 and 180 kgN/ha the content of sucrose, glucose and fructose was analysed (Tab. 1, 2 and 3). Sucrose content was determined by the polarimetric method, while that of glucose and fructose by the liquid chromatography (HPLC Pro-Star Varian).

Results

Organic fertilisation with stubble catch crops had a significant effect on the content of sucrose, glucose and fructose (Tab. 1, 2 and 3). Beets grown on ploughed field bean and phacelia had a sucrose content that was significantly higher than those grown after mustard and without a stubble catch crop. The reaction of the varieties to organic fertilisation was, however, differentiated. The varieties PN Mono 4 had the largest content of sucrose just after field bean and phacelia. The Atair variety showed, however, a significantly decreased content of sucrose in reaction to field bean as catch crop, while with the Kristall variety the reaction was positive. Stubble catch crops also affected the glucose and fructose content. With the Atair and Kristall varieties the greatest content of glucose and fructose, significantly higher compared with catch crops, was found in beet roots grown without organic fertilisation. No proven effect of organic fertilisation on glucose and fructose concentration was found with the PN Mono 4 variety.

Table 1: Influence of stubble catch crops on sucrose content

* NIR LSD of catch crops

** NIR LSD of varieties

*** NIR LSD of cooperation

Table 2: Influence of stubble catch crops on glucose content

Table 3: Influence of stubble catch crops on fructose content

The concentration of sucrose and reducing sugars was significantly affected by nitrogen fertilisation (Fig. 1 and 2). The highest content of sucrose was found in roots not fertilised with nitrogen, while the lowest in those fertilised with 180 kg N/ha. No proven differences in sucrose content was found between the nitrogen doses 60, 120 and 180 kg N/ha. The cultivars showed a differentiated sucrose content, dependent on the level of nitrogen fertilisation. No differentiation of the cultivars with respect to sucrose content was found without nitrogen fertilisation, whereas with the other doses of nitrogen significantly more sucrose contained roots of the Atair variety and significantly less the roots of the Kristall variety. The contents of glucose and fructose of roots grown on 0 and 60 kg of nitrogen did not differ significantly. A significant increase in concentration of those sugars was induced by nitrogen fertilisation at 120 and 180 kg N/ha.

Conclusions

1. Growing of sugar beet after a mustard catch crop and without organic and nitrogen fertilisation results in decreased sucrose content irrespective of variety.

2. Varieties differed in the content of sucrose and simple sugars. The greatest sucrose and simple sugars content was found with the Atair variety, the lowest content of simple sugars was in the Kristall variety.

3. The content of glucose and fructose increased with increasing doses of nitrogen fertilisation above 60 kg/ha.

4. Beet roots grown without organic fertilisation contained more glucose and fructose than those grown after catch crops.

References

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KALINOWSKA- ZDUN M., WYSZYŃSKI Z. 2000. Kryteria jakości korzeni i ich zmienność Mat. Konf. “Środowiskowe i agrotechniczne uwarunkowania jakości płodów rolnych”. Warszawa. 151-161.

PROŚBA-BIAŁCZYK U., REGIEC P., MYDLARSKI M.: (2001). Technological value of sugar beet cultivars as dependent on nitrogen fertilization level. EJPAU 2001 v. 4.i. 2 s. Agronomy.

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