The influence of harvest date and crop treatment on the production of two different sugar beet variety types

In a four-year trial, the effect was evaluated of the harvest time on the production of two different sugar beet variety types (the Z-type variety Elan and the NE-type variety Epos) grown in three patterns - 1. check pattern, 2. fertilisation with50 kgN/ha, 3. fertilisation with50 kgN/ha + fungicide treatment. Sugar beet was harvested in two terms: at the beginning of the beet processing season, and four weeks later. The differences between the varieties became apparent mainly at the later harvest time. The root yields of the NE-type variety Epos were higher at the later harvest by the average 4.35 t/ha (statistically significant, α = 0.01) while its sugar content was lower by 0.3% (α = 0.05) than in the Z-type variety Elan. The postponement of the harvest time increased the root yields of both varieties by the average 10.47 t/ha (i.e. by 17.9%, α = 0.01). The effect of the harvest time on the sugar content was dependent on the year. Due to retrovegetation following the rainfalls after a prolonged dry period in the year 2000, the sugar content decreased at the later harvest time by 1.68% in absolute figures (or by 8.35% rel., α = 0.01). The content of molassigenic substances in sugar beet roots varied according to the year rather than to the factors followed. The white sugar yields increased at the later harvest by the average 1.57 t/ha (or by 16.9%, α = 0.01). The average increment of sugar for each day of the postponed harvest was 58.2 kg/ha (or 0.63%). The effect of nitrogen fertilisation and fungicide treatment on the sugar beet production became apparent at the later harvest time. Fertilisation with50 kgN/ha + fungicide treatment increased the root yields by 1.07 t/ha (or by 10.32%, α = 0.01) in comparison with the pattern without nitrogen fertilisation and fungicide treatment. Spraying with fungicide itself increased the sugar yields by 0.81 t/ha (or by 7.81%, α = 0.01) in comparison with the pattern equally fertilised but not treated with fungicide.