The polyfactorial field trials established on the experimental base UBRP-EPAX in thc plots owned by Agrokomplex were conducted on heavy-textured stagno-gleyic to gleyic Luvisol in warm climatic region in Nitra, where, among other things, the effect of various ways of the basic soil cultivation and of direct seeding into untreated soil was studied as affected the winter wheat grain yield, the Kosutka cultivar, after seed pea. The tillage to the depth of 0.20 to 0.22 m was used as a control, done immediately after a forecrop harvest. Moreover, tillage to the depth of 0.20 to 0.22 m was studied, performed two to three weeks after forecrop harvest, though not later than four weeks before planned seeding date, discing to the depth of 0.10 to 0.12 m close to the forecrop harvest, discing to the depth of 0.10 to 0.12 m two to three weeks after forecrop harvest, at least four weeks before planned seeding date and discing to 0.10 to 0.12 m close to the winter wheat seeding. A direct seeding into untreated soil was accomplished after Gramoxone application. The trials were conducted in the years 1986 to 1987 over 1988 to 1989 on fertilized and unfertilized soil. The basic soil preparation was performed on the treatments with the dates two to three weeks after harvest, at least weeks before planned seeding date-in each year of the first decade of September in order to leave minimum four weeks to the seeding date. In the first year, it was seeded on 7 October 1986, in the second year on 14 October 1987 and on 4 October 1988 in the third year. Grain yields were evaluated by the analysis of dispersion in particular years together with the whole three-year period. On an average for three-year period, the effect of particular years was manifested the most on the grain yield, followed by the effect of fertilizing and that of cultivation, all these highly significantly. The highest average grain yield for thc whole trial without respect to fertilizing and treatments of cultivation was gained in the year 1988/1989 good for climate, that is 9.09 t per 1 ha (Tabs III and IV). An average grain yield was higher by 0.80 t per 1 ha on the treated soil in comparison with untreated one.The average lowest grain yield for the whole trial irrespectively to fertilizing and cultivation treatments was obtained in climatically bad year 1987/1988 (Tabs II and IV), that is 6.81 t per 1 ha, this being affected mainly by low grain weight (cereal plants dried). The difference in the grain yield on fertilized soil was only 0.11 per 1 ha in comparison with untreated one for the benefit of fertilizing. An average grain yield was 8.02 t per 1 ha for the whole trial, irrespectively to fertilizing and cultivation treatments (this being 8.38 t per 1 ha on treated soil and 7.67 t per 1 ha on untreated soil), on an average for three-year period (Tab. IV). In view of cultivation dates, those cultivation practices were found to be the best which were conducted about four weeks before planned seeding date. In comparison of the cultivation dates close to the forecrop harvest with the date of cultivation close before seeding, better grain yields were obtained with earlier dates. The depth of cultivation, however, had no significant effect on the grain yield, it was found that a shallow cultivation accomplished in earlier dates exceeded the deep cultivation as far as the yields are concerned, while in dates of cultivation close to the seeding exhibited an adverse trend. Out of tested cultivation practices, the best seemed to be the shallow soil cultivation (discing to 0.10 to 0.12 m) performed about four weeks before planned date of seeding. A direct seeding into untreated soil under the given conditions, seemed to be less favourable, in particular on untreated soil.
