Climate change is affecting all sectors of human activities worldwide, including crop production. The aim of the paper was to evaluate the average daily air temperatures measured at one hundred meteorological stations across Slovakia in 1961–2010 and calculate the maximum length of the vegetation period for Solanum lycopersicum L., Brassica oleracea L. var. capitata and Daucus carota L. Future trends predictions of the temporal and spatial development across the duration of the vegetation period in Slovakia were elaborated for decades 2011–2020, 2041–2050, 2071–2080 and 2091–2100. Our results show that there was an earlier start to the vegetation period in spring and a later termination in autumn for past 30 years. There is a predicted trend of prolongation of the maximum duration of the vegetation period up to 20 days (Solanum lycopersicum L., Brassica oleracea L. var. capitata) and 15 days (Daucus carota L.) in comparison with the refence decade 2001–2010. The maximum vegetation period duration will extend from the south of Slovakia towards the north of the country. The predicted potential increase in crop vegetation periods will be limited by other constraints such as the availability of arable land and soil water availability.

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The Water Framework Directive requires as an obligatory goal to achieve and to keep "good water quality" status within the defined period (for Slovakia-up to the year 2015). For surface waters, the main criterion is the ecological and chemical status of the water. Mathematical and numerical modelling allows evaluating various situations of contaminants spreading in rivers (from everyday wastewater disposal through fatal accidents and discharges of the toxic substances) without immediate destructive impact to the environment. Determination of longitudinal and transverse dispersion coefficient values, as the main hydrodynamic characteristics of the dispersion, has the highest extent of uncertainty for hydrodynamic models simulating pollutant transport in streams. This paper deals with the determination of dispersion coefficients based on field tracer experiments performed in a small modified stream (basic hydrodynamic parameters during the experiments were: discharge Q = 0.138-0.553 m 3 .s −1 , depth h=0.29-0.48 m, width B=5.2-5.9 m). During the experiments, various conditions and situations were taken into account, e.g., continuous and instantaneous pollution source, as well as various positions of pollution source along the river width, among others. Field measurements were evaluated using three different methods for dispersion coefficient determination: based on statistical evaluation, based on analytical solutions of advection-dispersion equation, and using numerical models. The dimensionless dispersion coefficients values were determined, which can be used for numerical simulation of pollutant transport in similar types of streams.

Hens of the laying hybrid Shaver Starcross 288 were used in two consequential experiments. The first experiment (for 10 months) was conducted on hens at the age from 18 to 60 weeks (1^st cycle; <i>n</i> = 50) and moulted hens after 10 months laying from 70 to 110 weeks of age (2^nd cycle; <i>n</i> = 50). For the second experiment (for 8 months) in the 1^st cycle 18 weeks old hens were bought (<i>n</i> = 60) and hens from the first experiment after moulting were used in the 2^nd and 3^rd cycle (<i>n</i> = 32 and <i>n</i> = 28). During the experiments eggshell qualitative parameters and calcium utilisation (%) were determined. The results indicate that the percentage of eggshell decreased with the increasing number of cycles. The significant correlation of the eggshell proportion and the age of hens was higher in long, advanced cycles (<i>P</i> < 0.05). The shell strength in both experiments decreased slightly in relation to the age of hens and repeated laying cycles. The shell deformation had an opposite trend to the shell strength, i.e. it increased with the increasing laying. The average shell thickness showed a decrease in the repeated laying cycles, more significant in shorter cycles (<i>P</i> < 0.01). The specific shell gravity maintained balanced values both in cycles and by the age of hens. The shell density in all cycles in both experiments showed a decreasing tendency in relation to the age of hens. In dietary calcium utilization for the shell formation a significant decrease was recorded in the second cycles after moulting (<i>P</i> < 0.05).

abstract. The development of the computer technologies enables us to solve the ecological problems in water management practice very efficiently. Hydrodynamical models which simulating transport of pollution in surface water are very demanding on input data and calculation time, but on the other side, they are able to simulate detailed effect of dispersion in surface waters. The paper deals with 1-dimensional numerical model HEC-RAS and its response on various values of dispersion coefficient. This parameter is one of the most important input data for simulation of pollution spreading in streams. Getting fair value, however, is in practice very difficult. One option is the most accurate simulation of tracer experiments carried out on the ground on the natural surface flow. For the pilot application was selected flow Small Nitra. Of longitudinal dispersion coefficient in the flow, or the flow of a similar nature (with and limit the rate of flow), were in the range 0.05 to 2.5 m 2 · s -1. The next task was carrying out the model sensitivity analysis, which means to evaluate input data influences, especially longitudinal dispersion coefficient, on outputs computed by 1-dimensional simulation model HEC-RAS. Sensitivity analysis model HEC-RAS also showed its adequate response to changes of the input parameter. Given the present results it can be stated that the HEC-RAS model responds to changes in the values of the longitudinal dispersion coefficient appropriately. HEC-RAS model has demonstrated its applicability to simulation of pollution in streams, and therefore is an appropriate tool for decision making related to the quality of water resources.