THE DEVELOPMENT OF THE WINTER RAPESEED VA RIETY STRUCTURE IN THE CZECH-REPUBLIC AND EFFECT OF THE SEED CALIBRATION ON THE YIELD

The time sequence of winter rapeseed yield in the years 1971 to 1994, and from 1984 to 1994, respectively, acquired in the Czech Republic by farmers, based upon the pilot variety trials of the Union of Rapeseed Growers and Processors and official variety trials of the State Insti tute for Agricultural Supervision and Testing (SKZUZ) was compared and analyzed in this paper. The two-years' trials conducted with calibrat ed seed were established within the framework of the pilot variety tri als of the Union of Rapeseed Growers and Processors in 43 localities ( area of one plot was 1 to 2 hectares, winter barley was usually a fore crop, sowing rate of 5 to 6 kg of seed in agrotechnical practice, 150 kg N/ha in two to three spring doses). Certified C1 varieties (1990/19 91 Darmor, 1991/1992 Ceres) served as a standard, out of which two cal ibrated fractions (1.8 to 2.0 mm and 2.0 to 2.2 mm) were chosen. The l evel of winter rapeseed yields can be changed in the period of observa tions - from 1971 to 1994 in the Czech Republic, but from the long-ter m point of view, it had a tendency to increase. Temporary apparent dec rease in the yields in 1990, 1991 and 1992 affected by transformation of the Czech agriculture after 1989 finished in 1993, when yields had again a tendency to grow (Fig. 1). A very strong correlation, particul arly between the yields in the pilot variety trials performed by the U nion of the Rapeseed Growers and Processors, and in conditions of farm ers in 1984 to 1994 (Tab. I) has been found out. Utilization of the va riety-yield potential by farmers was 60 to 70% (the yield of certified varieties tested by SKZUZ was equal to 100%), roughly 35% respectivel y (biological yield of the seeds is based upon the theory - 7.5 t/ha = 100%). The number of the licensed GO-varieties of winter rapeseed is growing fast, but nine of them can be considered as the best one (Fig. 3). The list of licensed varieties included 11 varieties of winter ra peseed in 1994 (Fig. 2) and it is predicted that their number will be higher in the future. The main advantage of the 00-varieties is a low content of glucosinolates (GSL), what allows a utilization of the rape seed-expellers for preparation of feed mixtures for animals. From 1990 /1991 to 1993/1994 the GLS content ranged on an average from 14.25 to 21.96 mu mol/g of seed. The seed calibrated for 2.0 to 2.2 mm, in both years of investigations the yields of rapeseed per 1 hectare increase d (1990/1991 by 80 kg, and in 1991/1992 by 190 kg), but they were not statistically significant (Fig. 4, Tabs IV, V). On average (weight ave rage) of both years of investigations, the profit was + 120 kg/ha, tha t is 672.00 CZK at price of seed 5,600 CZK/t (1 USD = ca 28.00 CZK). T he effect of calibration was reduced by lower yield of seed by their p reparation. It is supposed that seed calibration - with or without che mical treatment - can be one step, moving the growth of winter rapesee d to a higher level and allows to gain even better profitability by gr owing this plant.