DIFFERENT SYSTEMS OF SOIL CULTIVATION WITHIN THE CROP-ROTATION IN RELATION TO THE CEREAL AND SUGAR-BEET YIELDS

Different soil cultivations (traditional and reduced) with various manuring (manure, green manuring, straw plough-in, trash plough-in) and gradated nitrogen application rates were studied within the crop rotations in field polyfactorial trials conducted at the Research Institute of Crop Production in Praha-Ruzyne. (clay loam Luvisol). The use of commercial nitrogen had a significant effect on grain yields of winter wheat only after omitted soil cultivation. On the treatments after beets a forecrop with traditional soil cultivation, manuring (trash ploughed in), nitrogen application rate above 40 kg per 1 ha exhibited an adverse effect on winter wheat grain yields, at nitrogen application rates above 120 kg per 1 ha, the adverse effect was statistically significant. When 80 to 120 kg per 1 ha of nitrogen was applied, the winter wheat grain yields on the treatment without soil cultivation were completely comparable with the treament with traditional soil cultivation. Elimination of omitted soil cultivation and bad forecrop, however, required more nitrogen application rates amounting to 40 to 80 kg per 1 ha. Winter wheat grain yields without using fertilizers were reduced much more on Luvisol due to long-term cultivation by 7 to 13 % (Tab, III), only in the crop rotation M III, where organic matter has been ploughed-in into the soil, grain yields were not lower for the period under study. When higher nitrogen rates were applied, winter wheat yields were higher with the length of the period (in next rotation). In reduced soil cultivation, the sugar beet root yield was lower by 12 %, trash by 15 % in comparison with the traditional way of soil cultivation. The results indicate statistically insignificant effect of nitrogen applied from fertilizers (except the crop rotation M I) on the sugar beet root, that is also in crop rotation with reduced soil cultivation (crop rotation A). A high sugar beet concentration (33 %) in the crop rotation resulted in the fall of the yield by about 10 % (Tab. V) in all crop rotations under study. Dry matter yield of plant phytomass in the studied crop rotations with different soil cultivation and fertilizing showed that as reduced soil cultivation, as crop growing without manure, require an increased nitrogen rates. An omitted manuring in the crop rotation M required nitrogen application rate od 90 kg per 1 ha within the whole crop rotation to balance the production of plant phytomass output to the level of crop rotation with manuring. Reduced soil cultivation (crop rotations A and M I) within the crop rotation required nitrogen application rates about 80 kg per 1 ha for obtaining the comparable output of plant phytomass with traditional soil cultivation. In economic and energy-relating considerations, higher nitrogen rates are to be applied in reduced soil cultivation and to balance them by savings of fuels, in crop rotations without manures by the need to replace industrial nitrogen with organic manuring.