In this study present frequency of several characteristic days as tropical, summer, arctic, frost and ice days and also length of heat waves was compared with modelled future occurrence of these climate extreme indices. Climate-diagrams were used for drought hazard assessment. The main objective of our research was to detect possible changes of frequency of the extreme events toward future. Data from four localities in the Czech Republic (Moravia) were chosen for the evaluation. Each locality represents different climatic, landscape and settlement conditions. Localities are represented by the closest grid points. Future trend was modelled for scenario data (scenario A1B) by regional model ALADIN-Climate/CZ in the Czech Hydrometeorological Institute. The results showed obvious rising tendency of tropical and summer days frequency on all localities, especially in lowland regions. Very strong decreasing trend seemed to be in occurrence of arctic days, which might be very scarce in the future. Frost days and ice days should also decrease. Increase in number of days in heat wave was considerable. Climate-diagrams showed possible rising drought hazard for all localities towards future periods.

To evaluate soil moisture conditions in spring crops sowing term, data of bare soil surface state were used. Analysis included 32 stations throughout the Czech Republic. Number of days with dry soil surface in each year was compared with the average number of those days in the period 1961-2010 for a given station. The limits of the individual categories were then determined for the period 1961-2010. The individual values of the number of days with dry condition of soil in the early spring period were compared with acquired 10th, 25th, 75th and 90th percentile average . More days with dry soil are usually observed in April than in March. In both months there are 11 days with this condition of soil altogether on average. Dry early spring occurred mainly in

352Kvasny prum. / 2013 (12) Výnosy ječmene setého v klimatických podmínkách České republikyKlíčová slova: AVISO, vlhkost půdy, ječmen ■ ■ 1 ÚVOD Mnoho agroklimatologických studií se zaměřuje na vyjádření vztahu mezi růstem či výnosy plodin vzhledem k proměnlivosti klimatu. V souvislosti se stresujícími účinky na výnos a kvalitu produkce má pro pěstitele největší význam případný výskyt tzv. agronomického sucha. To je obecně definováno jako stav, kdy je množství vláhy v půdě nižší, než je potřeba rostlin (Blinka, 2005) a také je často chápáno jako pokles půdní vlhkosti pod bod trvalého vadnutí (tj. cca -1,5 MPa), kdy se zastaví příjem vody a rostliny již nerostou. Stres však nastává již při velmi malých ztrátách vody, kdy turgor klesne jen o 0,1-0,2 MPa. To má za následek zavírání průduchů listů a snížení rychlosti fotosyntézy (Kincl a Krpeš, 2000). Dopady závisí na délce trvání stresu a dalších faktorech.Změny klimatu v Evropě od roku 1990 byly nepříznivé pro výnosy obilovin kvůli tepelnému stresu při plnění zrna a suchu během růstu stonku (Brisson et al., 2010). Výskyt sucha při setí a během vegetativních fází růstu obilnin má vliv na vzcházení porostu a následnou redukci odnoží. Sucho během generativních fází má vliv na redukci počtu založených klásků a zrn. Kritickým obdobím je kvetení, kdy má nedostatek vody horší dopad než v jiných fázích vývoje. Dalším kritickým obdobím je fáze počátku tvorby zrna, kdy se rozhoduje o počtu buněk v endospermu. Ve fázi nalévání zrna vodní stres 1976, 1981, 1985, 1986, 1995, 1996, 2000, 2004, 2007, 2009 Kvasny Prum. 59, 2013, No. 12, p. 352-357 Yields of spring barley and fluctuations in soil water in the critical period in terms of barley yield in the Czech Republic were evaluated for the period 1975-2010. On most sites there was statistically significant relationships between grain yield and soil water in different stages of vegetation; in some locations highly significant relationship. Statistically significant relationship was also found when evaluating average values of soil water and the average income in across stations. When evaluating the season-average soil water and yield a statistically significant (up to highly significant) effect of year 1976, 1981, 1985, 1986, 1995, 1996, 2000, 2004, 2007, 2009 and 2010 was found. In last decade the number of growing seasons with a demonstrable influence of moisture conditions on barley yield increased in different production areas. Kvasny Prum. 59, 2013, Nr. 12, S. 352-357 Es wurden die Erträge der Sommergerstenernte und die Schwankung des Wasserinhalts im Boden in der für die Schöpfung der Gerstenernteerträge kritischen Periode im Zeitraum 1975-2010 ausgewertet. Weiterhin in den meisten Lokalitäten wurde es eine statistisch signifikante Beziehung zwischen dem Kornertrag und der Bodenwassermenge in den verschiedenen Vegetationsphasen, in einigen Lokalitäten sogar einer großen Bedeutung ermittelt. Eine statistisch signifikante Beziehung wurde auch bei der Auswertung der durchschnittlichen Bodenwassermenge und des durc...

Wind erosion in the Czech Republic conditions poses relatively a lot of danger, especially for the most fertile areas, where agricultural land is more vulnerable due to the large pieces of land and inappropriate crop rotation. This process causes damage to agriculture by loss of topsoil, fertilizers, seeds and crop damage as well as sedimentation in water recipients and on roads. It also has negative impacts on human health (airborne dust). Wind erosion is especially affected by climatic elements (wind, temperature, precipitation and evaporation etc.) and soil characteristics (soil type, content of erodible particles, soil moisture). Wind erosion affects mainly light and medium heavy soil. South Moravia is an example of the territories to which this rule does not apply. Although soils in the Carpathian flysch subsoil are mainly heavy, erosion has been causing damage here for many decades. Quite strong dust storms are not rare, especially at the end of winter and in early spring when the soil is not covered by vegetation.Notable cases of dust storms in the area were recorded in local chronicles, and then written in the summary publication by dr. Švehlík. Interest of this publication was focused on the most destructive cases of dust storms in Bílé Karpaty foothills. The aim was to study meteorological conditions during the period before and during the occurrence of dust storms in the area in detail and to find the relationship between weather and the intensity of wind erosion. The data of wind speed and direction, temperature, precipitation and snow were evaluated. In all cases the average daily air temperature and ground air temperature was over the freezing point or closely under it. The temperature generally increased before the dust storm occurrence and it often happened from negative to positive temperature and the soil probably defrosted. Snow cover was very small or there was no snow cover at all. In the course of April wind erosion occurrence there was no snow and the precipitation was inconsiderable. Soil at the station was mostly bare, dry and defrosted.