How to increase sugar quality in sugar beets

Sugar-beet quality is increased by increasing the concentration of sucrose reducing the concentration of impurities such as amino acids, potassium and sodium.

These impurities often cause a reduction in extractable sugar.

This chart shows the effect of impurities on the overall sugar yield.

Nitrogen excess can reduce sugar content

An adequate supply of nitrogen is essential for optimum yield, while excessive use may result in an increase in roots with lower sucrose content and juice purity.

Yield increases with the amount of applied nitrogen, but sucrose purity and recoverable sugar yield / ha significantly decrease as the nitrogen level increases.

The optimum supply of nitrogen depends on the growing conditions, soil type, previous crop residues, nitrogen from organic manure etc. Under most conditions a supply of 120 kg N per ha is appropriate, but in some growing areas the optimum is higher.

This study from Germany shows the relationship between nitrogen rate and both sugar-beet yield and sugar content.

This study shows the effect of increasing nitrogen rate on amino-n content leading to a reduction in sugar yield.

These data based on a large number of trials shows the relationship between fertilizer nitrogen rate, amino-n content and extractable sugar yield.

These data also show that the optimum nitrogen rate for extractable sugar is lower than the optimum rate for beet yield

These data also show that the optimum nitrogen rate for extractable sugar is lower than the optimum rate for beet yield.

Phosphorus deficiency can impact juice purity

Phosphorus fertiliser does not have a direct influence on sugar content or juice purity. However, indirectly it plays an important role in the growth and establishment of the plants. Deficiency limits the growth which leads to excessive uptake of other nutrients, leading to impurities in the juice and low quality.

Potassium and sodium do not influence juice quality

This study shows the effect of sodium fertilisation on the concentration in the molases of amino-N, sodium and potassium levels.

Buyers of sugar beet prefer low levels of potassium and sodium in the juice because both elements decrease the extraction of crystalline sugar. It could be expected that the supply of potassium and sodium in the fertiliser would have a negative influence of the purity of the juice. This seems not to be the case either in trials or in practice. This is perhaps due to the beneficial effect of potassium and sodium. Nonetheless accurate recommendations should be calculated to avoid the likelihood of excess nutrients causing problems.