DRÁPAL KAREL, JŮZL MIROSLAV, ELZNER PETR, MAREČEK VÍT:The eff ect of urea with urease inhibitors and urea on yield and nitrate content in potato tubers. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 6, pp. 1613-1619 The three-year fi eld trial was established on two localities -Žabčice and Valečov in 2010-2012. Seven variants of nitrogen fertilization in four replications have been involved in this experiment -100% of urea (U), 80% of urea, 60% of urea, 100% of UreaStabil (US), 80% of UreaStabil and 60% of UreaStabil, whilst 100% corresponded to 90 kg N.ha −1 a er subtracting the content of Nmin in the soil, and the control variant without fertilization by mineral nitrogen. The two varieties with diff erent lengths of vegetation periods have been chosen for the experiment -the early variety Karin and the mid-early variety Red Anna. In all cases, samples for the yield and qualitative analyses have been taken according to the phenological phase -the beginning of physiological maturity. The obtained results show that the highest average yield has been achieved in the variant of 100% of urea -40.95 t. ha −1 , the yield of this variant was statistically signifi cantly higher than the yield of the other variants of fertilization (P < 0.05). Variants treated by urea without the urease inhibitor reached an average yield of 37.62 t.ha −1 . However, this yield was not statistically signifi cantly higher when comparing to the urea with the urease inhibitor (P > 0.05). In regard to localities, a relatively high average yield (44.58 t.ha −1 ) has been achieved on a characteristically potato-growing locality Valečov. This yield was statistically signifi cantly higher than the one attained on the Žabčice locality (P < 0.05). In respect to varieties, the mid-early variety Red Anna attained a higher average yield (39.65 t. ha −1 ). Likewise, this yield was statistically signifi cantly higher than the one of the early variety Karin (P < 0.05). The best year was 2012, in which the average yield of 38.73 t.ha −1 was achieved. This yield was statistically signifi cantly higher than the yield of the year 2010 (P < 0.05). As far as nitrates are concerned, the lowest average nitrate content has been found in the control variant -184.1 mg.kg −1 of moisture content. Nevertheless, the diff erences of the nitrate content among all the varieties were statistically inconclusive (P > 0.05). When using the fertilizer consisting of urea without the urease inhibitor, a lower average content of nitrates was found -207.8 mg.kg −1 of moisture content, but there was no statistically signifi cant diff erence in comparison to the urea with the urease inhibitor variants (P > 0.05). In respect to localities, lower average nitrate content was established on the Žabčice locality -177 mg.kg −1 of moisture content. A statistical signifi cance in comparison to the Valečov locality was found (P < 0.05). The mid-early variety Red Anna had a lower average nitrate content -167.7 mg.kg −1 of moisture content. When...

AL-MOSANIF, E., VEJRAŽKA, K., JŮZL, M., DRÁPAL, K.: Root system size of alfalfa varieties under diff erent plant densities. Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 1, pp. 9-16 The fi eld experiment was established from pre-grown alfalfa sprouts in 2008. In 2009 and 2010, the harvest was carried out. The yield and the root size system (RSS) were evaluated in the total of fi ve cuts. Two localities of diverse soil and weather conditions were selected. Žabčice is a dry location with a highly permeable sandy soil layer, but at the same time, with a considerable fl uctuation of the underground water level; Troubsko, on the other hand, represented a location with a higher content of clay in soil suitable for growing alfalfa. The trial was established in two types of plant spacing -25 × 25 cm (16 plants per m 2 ) and 50 × 50 cm (4 plants per m 2 ). Two alfalfa varieties were used -Hodonínka (an old variety) and Oslava (a new variety). The following factors were evaluated by statistical means: location, variety, plant spacing, and cut number. The eff ect of location on the above ground phytomass and the RSS value proved highly statistically decisive. The higher average values of above ground phytomass as well as RSS were achieved on the Troubsko location where the above ground phytomass was 19.57 t.ha −1 and RSS was 2.71 nanofarad (nF). The impact of the variety was highly statistically signifi cant only in respect to RSS. The eff ect of variety on the alfalfa above ground phytomass was not proven. The higher average RSS values were reached by the Hodonínka variety (2.59 nF). The eff ect of the plant spacing on both the above ground phytomass and the RSS values was highly statistically signifi cant. The higher average above ground phytomass was achieved when the 25 × 25 cm plant spacing was employed (18.64 t.ha −1 ). As for the RSS value, the case was exactly opposite -the higher average value was reached when the plant spacing was 50 × 50 cm (2.99 nF). The impact of the cut number on both the above ground phytomass and the RSS was highly statistically signifi cant. The highest average above ground phytomass and root system size were measured in the third cut. The above ground phytomass was 30.36 t.ha -1 and RSS was 3.86 nF.