In field trials conducted at Borovce (Trnava district) on warm and dry stand with average precipitation of 625 mm and average temperature of 9,2 degrees C and on colder and wetter stand - 822 mm and 7,5 degrees C at Bystricka (Martin district) in 1990 to 1993 the effect of growth regulators Relan PGR (rate of 0.1 l.ha(-1) in bud setting stage + early anthesis), Atonik (rate of 0.1 l.h(-1) in bud setting stage + early anthesis), Nevirol 60 WP (rate of 0,4 kg.ha(-1) in full flowering stage) on seed yields and thousand-seed weight of white clover, the Dubrava variety was assessed. The stands were established into green fodder oat cover crop at seeding rate of 7.0 mil. seedlings.ha(-1) at row spacing of 250 mm. Efficiency of growth regulators was different as from the point of view of years, so according to individual stands. At Bystricka, significantly increased seed yields were found out with Nevirol 60 WP, compared with the untreated control, as well as with other preparations. Its positive influence - 29 kg.ha(-1) (6.1%) on average for years was manifested in each year of examination. Other preparations had no significant effect on seed yields (Tab. I). In opposite to Borovce, on this stand the average stand yield of 0.485 t.ha(-1) was obtained (under conditions of premature cutting), significantly higher, compared to the non-cutting stands with average yield of 0.465 t.ha(-1) (LSD-p-0.01 = 0.009 t.ha(-1)). At all growth regulators, as well as the control, the reaction in yield on additional cutting was the same, it means, the higher yield was reached in all variants after additional cutting. On the stand established at Borovce none of estimated growth regulators significantly influenced the seed yield on average for estimated years, although some increase in the yield appeared with all growth regulators, mostly with Atonik (control - 0.506 t.ha(-1), Atonik - 0.563 t.ha-1; LSD-p-0.01 - 0.072 t.ha-1). Minimum differences among preparations were found (Tab. I). No significant differences were found out among methods of stand preparation for seed cutting (without additional cutting - 0.554 t.ha(-1); with additional cutting - 0.538 t.ha-1; LSD-p-0.01 = 0.042 t.ha(-1)), it means, the additional cutting moderately decreased seed yields. From the view of reaction of used growth regulators, the above-mentioned cutting had no significant effect on the yield, with exception of Relan, the yields without additional cutting were always higher than with it. The average seed yield at Borovce (0.546 t.ha-1) was higher than at Bystricka (0.475 t.ha(-1)). Values of thousand-seed weight (Tab. II) did not nearly differ in individual stands (Bystricka - 0.717 g and Borovce - 0.713 g) and were not significantly influenced by the growth regulators applied, at Borovce, insignificantly lower values were found after growth regulators applied and higher ones at Bystricka, where the values of thousand-seed weight were not significantly affected by additional cutting (without additional cutting - 0.715; after additional cutting - 0.719 g), whereas at Borovce additional cutting significantly decreased the value of thousand-seed weight (without cutting - 0.718 g; after cutting - 0.707 g; LSD-p-0.01 = 0.012 g). Values of thousand-seed weight were mostly influenced by years of cultivation.
