In the paper presented, 99 single seed descent barley lines as well as their parental forms Roland and Apex were studied. The grain weight components and their interrelations were analyzed using simple coefficients of correlation. The direct and indirect effects of such components on grain weight per plant and 1 000-grain weight were estimated using path analysis. In the 2006 and 2007, the spike length and number of spikelets per spike were the determinants of grain weight. Genetic parameters as additive and epistasis effects were estimated for all studied traits. The results indicate the importance of both additive and epistasis gene effects of number of spikes per plant, grain weight per spike, grain number per plant and grain weight per plant in this study.

    Field experiments (2009–2011) were conducted at the Department of Agronomy at Poznań University of Life Sciences on the fields of the Research Institute in Swadzim. We evaluated the health of maize plants of two types, depending on the variations in mineral fertilization. The conducted research recorded the occurrence of pests such as oscinella frit (Oscinella frit L.) and the European corn borer (Pyrausta nubilalis Hbn.). Diseases recorded during the research included two pathogenes: Fusarium (Fusarium ssp.) and corn smut (Ustilago maydis Corda). It was shown that the meteorological conditions during the maize vegetation had a significant influence on the occurrence of pests. Adding potassium to mineral fertilizers increased the maize resistance to Fusarium. Cultivation of “stay-green” cultivar shall be considered as an element of integrated maize protection. The occurrence of oscinella frit was correlated with the occurrence of Fusarium as well as the occurrence of the European corn borer for both examined cultivars.  

The parallel coordinate plot is proposed as an efficient tool for visualization of 13 traits of “stay-green” maize (Zea mays L.) cultivar exposed to different methods of magnesium application. The field experiment was conducted in the Department of Agronomy, Poznań University of Life Sciences, on the fields of the Department of Teaching and Experimental Station in Swadzim in 2006–2008. Experiment was conducted as a single-factor experiment with seven applications of magnesium in a randomized complete block design with four replicates. The highest mean values of grain yield and 1 000-grain weight were obtained after application of variant T3 of magnesium (10 kg MgO ha–1 soil) in the all three years of study.