In the decisive production conditions of maize, beet, potato growing regions and potato-oats production subtype the results of the trials performed at the Cereal Research Institute, Kromeriz (1976 to 1985) we analysed for the relationships of yield-forming components to the spring barley yields. An analysis was carried out with a differentiation for the whole period, for the set of years with higher and lower yields. The yield values and yield-forming components found in absolute values as well as in relative expression am recorded on the basis of different production types in Tab I. The relative level of the effect expressed in percent is derived from the values of partial coefficients which am summed in Tab. II. The paper contributes to the enrichment of the knowledge from the biological intesification by means of regulating the different yield-forming components in spring barley. The highest yields were obtained in the beet-growing region. Another most productive type was found to be the potato-growing one, followed by potato-oats production subtype. The lowest average yields were found in thc maize-growing type. The degree of the effect of different factors on the yield (group I) TKW (group II) and kernel number per m2 (group III) may be characterized as follows: The group I is evaluated for the effect of yield-forming components on the yield. The number of ears per m2 was a decisive yield component in each production type (except potato production type which exhibited the second highest influence). TKW was less significantly affected by the grain yield - except potato production type where it had a decisive effect. TKW participated in the yield in all production types by lowest degree. The evaluation of these relationships in the years of highest and lowest yields indicates some difference. A decisive effect of number of spikes per m2 was clearly demonstrated in higher yield. The values of yield components, grain number and TKW were lower while in more productive types -beet and potato, the effect of number of grains per spike was greater, in return, under the condition of maize production type and potato-oats production subtypes, the effect of TKW was greater. The sequence of effects of yield-forming components remained the same in lower yields in a yield as total, however, the degree of effect varied very much in different production types. In the group of relations II, the effect of spike number per m2 and grain number per spike per TKW were evaluated. In thc years with higher yields in all production types, the TKW value was significantly influenced by spike number per m2. In the group III the effect of spike number per m2 and grain number per spike to the grain number per m2 were evaluated, too. The decisive yield characteristics - grain number per m2 was evidently affected by spike number per m2 except the potato production type in the years with lower and mean yields and the maize production type with higher yields. A dispersion of the yield and the yield-forming components values were studied at different yields in the relative expressions of limited sets of the years. The results are given in Figs 1 and 2. Average grain yields in the set of the years fluctuated from 3.42 t per ha in the maize -production type to 7.66 t per ha in beet production type. In the sugar beet production type, not only highest yields were obtained, but at the same time it was with the lowest dispersion. It was confirmed that the best production conditions reflected in the highest stability of the yields. In the dispersion of the yields of all their components participated spike number per 1 m2 in this production type. The proportion of the grain number per spike was low, thc proportion of TKW was even zero. On the contrary, the highest yield dispersion was found in the maize production type which was caused by thc variability of moisture conditions. In the maize production type, the main proportion on the yield dispersion has the variability in the spike number per m2; the peculiarity of this production type consists in the shift of grain number values per spike and TKW towards the lower values. It maybe concluded that in these production conditions it is less effective to compensate the lower spike number per m2 by increased grain number per spike or higher TKW value. This fact strongly emphasizes the need for optimum stand establishment in these conditions. In the potato production type, the highest yield dispersion has been found out. In contrast to the previous production types not the spike number per m2 shared the most in the highest yield dispersion, but the grain number per spike. In the conditions with lower yielding capacity of the potato production type and of the potato-oats subtype, other yield components become more important, that is the grain number per spike and TKW. In the years with the optimum weather conditions when the productivity increased by earlier sowing in these production conditions, on the other side, the spike number per m2 has also here a decisive effect.
