FORMATION AND COMPENSATION OF YIELD COMPONENTS IN CHOSEN SPRING BARLEY GENOTYPES

In 1989, 1990 and 1991, formation, reduction and compensation of yield components in chosen spring barley genotypes (Galan, Akcent, Ladik, H eran) were quantitatively analysed at decisive stages of organogenesis and under different environmental conditions: weather conditions of t he year and N-fertilization (60 and 90 kg of pure nutrients per 1 ha). A basic method used for statistical estimation was analysis of varian ce of two-fold classification with replications. The Tukey test was us ed to verify differences between individual mean values of variants. T he objective of the study was to characterize formation, reduction and compensation of yield components in different spring barley genotypes , and to determine effects of increased N-rates on formation and utili zation of yield potential. Data on characteristics of investigated gen otypes are given in Tabs I and II. The genotype Galan showed lower til ler formation, however, a high percentage of their fertility. It had b oth high potential and actual spike productivity. The genotype Akcent developed a high number of tillers, however, intensity of their format ion was lower at the earliest growth stages and tillers were considera bly reduced. It produced an average number of florets and kernels per spike and reached a low kernel weight. The genotype Ladik exhibited lo wer intensity of tiller formation and a number of the tillers was less reduced. It produced a high number of florets per spike which was, ho wever, strongly lowered. It was characteristic by a high kernel weight . The genotype Heran showed intensive tillering and developed tillers were considerably reduced. It had a low number of both florets and ker nels per spike. A spike weight was higher. These results prove that wi th regard to breeding for production potential genotypes with both hig h yield potential and its realization are suitable. Weather conditions of the years influenced the plant growth and development, and associa ted processes of formation and reduction of yield components (Tabs III and IV). The early growth stages were very important; they influenced a number of tillers and, based on the intensity of their formation, a lso productive density of the stand. At higher intensity of tiller for mation till stage V of organogenesis a spike number per unit area incr eased. The increase was, however, insignificant. Not only a number of founded florets but as well as their reduction was decisive for a kern el number per spike. There was no relationship between a number of dev eloped florets and a final kernel number per spike. Yield differences were caused by spike productivity, and especially by kernel weight. Ef fects of nitrogen on formation and reduction of yield components are p resented in Tabs V and VI. Under intensive conditions of the sugarbeet growing region, after sugarbeet as a forecrop, an increased N-rate (9 0 kg.ha(-1)) improved potential stand productivity (tiller and floret formation), but did not significantly affect its sink. It significantl y decreased kernel weight and thus spike productivity and grain yield.