In the course of vegetation in the years 1997-1999 changes in chlorophyll content in leaves of 21 select sugar beet varieties in small-plot trials at Sedlec u Prahy were measured by chlorophyllmeter. Chlorophyllmeter determines chlorophyll in leaves of plants directly in field, without damaging them. The measured chlorophyll units show the relative amount of chlorophyll present in leaves of plants. The assessment of individual values of chlorophyll content showed a correlation between individual times of measurements and between the total average chlorophyll content. The assessment of relationship between yield and chlorophyll content showed no stronger correlation. The statistical assessment showed no correlation between chlorophyll content and the efficiency type (sugar, normal and yield type) of variety. The trials confirmed different chlorophyll content in the surveyed varieties and, accordingly, the need for their classification into groups. The varieties were classified into groups by the index of chlorophyll content in sugar beet leaves in the whole course of vegetation. The values of percentage of index of chlorophyll content greater than or equal to 102.5%, 97.5-102.5% and less than or equal to 97.5% were considered high, average and low, respectively. The overall highest chlorophyll content was found in Domino, Orion, Fox and Kaweduca varieties. The medium chlorophyll content group is most numerous. The low chlorophyll content group included four varieties, namely Madeira, Melina, Petra and Amelie. The low and high chlorophyll content groups were assessed as statistically significant, with 95% probability rate. The above mentioned findings may be used for the creation of methodics for optimisation of nitrogen nutrition of sugar beet.
