INFLUENCE OF GENOTYPE AND NITROGEN NUTRITION ON GRAIN SIZE VARIABILITY IN SPRING MALTING BARLEY

Grain size is an important quality parameter of malting barley, which depends on genotypes, environmental factors and their interactions. Also, grain size is governed by the efficiency of assimilation and translocation of mineral nutrients (mainly nitrogen) during grain endosperm development, which affects grain yield. The aim of this study was to evaluate variability in the percentage of three different grain size classes: class I (thickness. 2.5 mm), class II (2.2-2.5 mm) and class III (< 2.2 mm) in spring malting barley genotypes ('Novosadski 448', 'Novosadski 456', 'Dunavac' and 'Jadran'). The experiment was conducted during three years (2012-2014) in a randomized complete block design with three replications at different rates of nitrogen fertilization (N-1=45, N-2=75, N-3=105 and N-4=135 kg ha(-1)). The presence of different grain sizes in barley cultivars in all N fertilization treatments after harvest was investigated. The proportion of the three grain classes was dependent upon year, cultivar and nitrogen fertilization rate. The highest percentage of class I grains was recorded in 'Novosadski 456', and that of class II and class III grains in 'Dunavac'. The percentage of class I grains increased significantly with increasing nitrogen rates up to 75 kg ha(-1), stagnated at 105 kg ha(-1), and decreased significantly as the nitrogen level was further increased to 135 kg ha(-1). Class II and class III grain contents decreased at nitrogen rates up to 105 kg ha(-1), but increased significantly at 135 kg ha(-1). The best response to favorable environmental conditions and the highest percentage of class I grain in all years were recorded in 'Novosadski 456'. The most favorable effect on grain size in the studied spring malting barley genotypes was exhibited by the nitrogen rate of 75 kg ha(-1).